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["필드선택","검색값"]
["권호","40권2호","☜ 필드선택 - 검색값 입력 후 Enter (첫 글자 대소문자 구분)"]
[]
["시트","권호","제목","토픽","초록","키워드","저자","DOI"]

{"sheet":"2022년","index":1,"n_rows":41,"n_cols":7,"rows_kept":41,"cut":false,"hidden":false,"merged":[]}
["권호","제목","토픽","초록","키워드","저자","DOI"]
["38권1호\npp.1-7","패드 마모 균일성 향상을 위한 CMP 컨디셔닝 시스템설계 변수 연구\n(Design Variables of Chemical-Mechanical Polishing Conditioning System to Improve Pad Wear Uniformity)","Chemical Mechanical Polishing","Chemical-mechanical polishing (CMP) process is a semiconductor process that planarizes a wafer surface using mechanical friction between a polishing pad and a substrate surface during a specific chemical reaction. During the CMP process, polishing pad conditioning is applied to prevent the rapid degradation of the polishing quality caused by polishing pad glazing through repeated material removal processes. However, during the conditioning process, uneven wear on the polishing pad is inevitable because the disk on which diamond particles are electrodeposited is used. Therefore, the abrasion of the polishing pad should be considered not only for the variables during the conditioning process but also when designing the CMP conditioning system. In this study, three design variables of the conditioning system were analyzed, and the effect on the pad wear profile during conditioning was investigated. The three design variables considered in this study were the length of the conditioner arm, diameter of the conditioner disk, and distance between centers. The Taguchi method was used for the experimental design. The effect of the three design variables on pad wear and uniformity was assessed, and new variables used in conditioning system design were proposed.","Chemical mechanical planarization(화학적 기계 평탄화), Pad conditioning(패드 컨디셔닝), Design variables(설계 변수), Conditioning simulation(컨디셔닝 시뮬레이션), Pad wear profile(패드 마모 프로파일)","박병훈1ㆍ박범영2ㆍ전언찬3ㆍ이현섭4†\n1동아대학교 대학원 기계공학과 박사과정생, 2부산대학교 대학원 기계공학부 박사, 3동아대학교 기계공학과 특임교수, 4동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.1.1"]
["38권1호\npp.8-14","컴프레서 부품의 DLC코팅 적용에 따른 트라이볼로지적 특성 연구\n(Tribological Characteristics of DLC-Coated Part in Compressor)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Amorphous carbon (a-C) has excellent wear resistance and, therefore is used as a coating to protect numerous mechanical components to prolong their lifetimes. Among the a-C coatings, diamond-like carbon (DLC) and DLC-containing silicon (Si-DLC) receive extensive attention owing to their enhanced wear resistance and low frictional characteristics. In this study, the friction and wear characteristics of DLC and Si-DLC coatings are analyzed. For comparative analysis, DLC-coated and Si-DLC-coated vanes are utilized with the counterpart of a roller for the friction tests. Since the lubricated mechanical components are generally vulnerable to wear when a lubricant film does not form properly, friction tests are conducted under boundary lubrication conditions to promote wear. A cylinder-on-cylinder type tribometer is used to perform the friction tests with various normal load conditions. After the friction test, a 3D laser confocal microscope is used for quantifying the wear volume to calculate the wear rate of each specimen. Consequently, the DLC-coated specimen shows a lower coefficient of friction (COF) and wear rate than the specimen without the coating, while the Si-DLC coating shows a higher COF than the bare specimen. The results of this study are expected to contribute to improving the efficiency and reliability of compressors.","Coating hardness(코팅 경도), Compressor(압축기), DLC coating(DLC 코팅), Surface topography(표면 형상), Vane(베인)","윤주용1ㆍ서국진2ㆍ한재호2ㆍ전지환3ㆍ송지영3ㆍ고영덕4ㆍ남자현3ㆍ김선교4ㆍ김대은5†\n1연세대학교 대학원 기계공학과 석사과정생, 2연세대학교 대학원 기계공학과 박사과정생, 3삼성전자 생활가전사업부 책임연구원, 4삼성전자 생활가전사업부 수석연구원, 5†연세대학교 기계공학과 교수","https://doi.org/10.9725/kts.2022.38.1.8"]
["38권1호\npp.15-21","다이아몬드 강화 Cr 기반 소재의 정량적 마모 특성 평가\n(Quantitative Assessment of Wear Characteristics of Cr-based Coating Reinforced with Diamond)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials)","Diamond reinforced Cr-based coating has been proposed as wear-resistant materials. In this study, the friction and wear characteristics of diamond reinforced Cr-based coating are experimentally assessed. The experiments are performed using a pin-on-reciprocating plate tribo-tester under various normal forces with boundary lubrication. The stainless-steel ball is used as a counter material. Prior to the experiments, mechanical properties such as elastic modulus and hardness are determined using nanoscale instrumented indentation. The hardness of the specimen is further determined using a Vickers hardness tester. The specimens before and after the experiments are carefully observed using a confocal microscope to understand the wear characteristics. In addition, the wear volume and wear rate of the specimens are determined based on the confocal microscope data. The results show that the friction coefficients are 0.096–0.100 under 20–40 N normal forces. Furthermore, the wear rates of the diamond reinforced Cr-based coating and the stainless steel ball under 20–40 N normal forces are found to be 12.8 × 10-8 mm3/(Nm)–15.5 × 10-8 mm3/(Nm) and 1.9 × 10-8 mm3/(Nm)–3.9 × 10-8 mm3/(Nm), respectively. However, the effect of the normal force on wear rates is not clearly observed, which may be associated with the flattening of the ball. The results of the study may be useful for the tribological applicability of diamond reinforced Cr-based coating as wear-resistant materials.","Diamond reinforced Cr-based coating(다이아몬드 강화 Cr 기반 코팅), Friction(마찰), Wear rate(마모율)","후인 옥-팟1ㆍ부 아 린2ㆍ정구현3†\n1울산대학교 대학원 기계공학과 박사과정생, 2울산대학교 대학원 기계공학과 석사졸업생, 3울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.1.15"]
["38권1호\npp.22-26","1.7톤급 소형 굴착기용 주행 감속기의 복합 유성기어류에대한 강도 평가\n(Strength Evaluation of Complex Planetary Gear Train ofTraveling Reducer for 1.7-Ton Grade Small Excavator)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","A 1.7-ton grade small excavator is a construction equipment that can perform various functions in limited spaces where heavy equipment cannot enter easily. Owing to the recent acceleration of urbanization, it has been used increasingly in drainage and gas pipes, as well as for road repair works in urban areas. The power train of a traveling reducer for a 1.7-ton grade small excavator utilizes a complex planetary gear system. Complex planetary gears are vital to the power train of a traveling reducer as it mitigates the fatigue strength problem. In the present study, the specifications of a complex planetary gear train are calculated; furthermore, the gear bending and compressive stresses of the complex planetary gears are analyzed to achieve an optimal design of the latter in terms of cost and reliability. In this study, the actual gear bending and compressive stresses of a planetary gear system are analyzed using a self-developed gear design program based on the Lewes and Hertz equation. Subsequently, the calculated specifications of the complex planetary gears are verified by evaluating the results with the data of allowable bending and compressive stress based on curves of stress vs. number of cycles of the gears.","Excavator(굴착기), Travelling reducer(주행 감속기), Complex planetary gear train(복합 유성기어 트레인), Gear bending stress(기어 굽힘 응력), Gear compressive stress(기어 면압 응력)","남석주1ㆍ배명호2ㆍ조연상3†\n1(주)델릭스 대표이사, 2창원문성대학교 항공정비학부 교수, 3동아대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2022.38.1.22"]
["38권1호\npp.27-31","3D 프린팅 기법을 이용한 하모닉 드라이브(Harmonic Drive) 설계 및 응용 분석\n(Design of a Novel 3D Printed Harmonic Drive and Analysis of its Application)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Harmonic drives have attracted increasing attention with the development of materials, parts, and related equipment. Harmonic drives exhibit high deceleration, high accuracy, and light weight. The stiffness of flexible splines according to the radial load is studied using a commercial FEM program to design the structure of the flexible spline and finite element to improve the weight and price competitiveness of harmonic drives. In addition, several studies have measured and compared friction coefficients based on 3D printed tread patterns. However, owing to the characteristics of plastic materials, a decrease in stiffness in the radial direction is inevitable. To prevent a decrease in stiffness in the radial direction, we designed and manufactured flex splines with a wrinkle shape. Through structural analysis, the reaction force and stiffness in the radial direction were determined. In addition, the maximum angle of the mound was derived by theoretical calculations, and the performance of the harmonic drive was compared with the results obtained in the mound experiment. Structural analysis shows that the shape of wrinkles decreased the stress and reaction force and increased the safety factor in comparison with that of the circular shape. During performance verification through continuous experiments, the developed harmonic drive showed continuous performance similar to that of an actual tank model. It is expected that the flex spline with a compliant spring and wrinkle shape will prevent a decrease in the radial stiffness.","Harmonic drive(하모닉 드라이브), Flex spline(플렉스 스플라인), Compliant spring(컴플라이언트 스프링), Wrinkle shape(주름 형상), Static analysis(정적 해석)","김상현1ㆍ변창섭2ㆍ이철희3†\n1인하대학교 건설기계공학과 석사과정생, 2인하대학교 기계공학과 학부생, 3인하대학교 기계공학과 교수","https://doi.org/10.9725/kts.2022.38.1.27"]
["38권2호\npp.33-40","정압베어링을 적용한 터보팽창기의 회전체 동역학 해석 및 구동시험\n(Rotordynamic Analysis and Operation Test of Turbo Expander with Hydrostatic Bearing)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","In this study, we present rotor dynamic analysis and operation test of a turbo expander for a hydrogen liquefaction plant. The turbo expander consists of a turbine and compressor wheel connected to a shaft supported by two hydrostatic radial and thrust bearings. In rotor dynamic analysis, the shaft is modeled as a rigid body, and the equations of motion for the shaft are solved using the unsteady Reynolds equation. Additionally, the operating test of the turbo expander has been performed in the test rig. Pressurized helium is supplied to the bearings at 8.5 bar. Furthermore, we monitor the shaft vibration and flow rate of the helium supplied to the bearings. The rotor dynamic analysis result shows that there are two critical speeds related with the rigid body mode under 40,000 rpm. At the first critical speed of 36,000 rpm, the vibration at the compressor side is maximum, whereas that of the turbine is maximum at the second critical speed of 40,000 rpm. The predicted maximum shaft vibration is 3 μm, whereas sub-synchronous vibration is not presented. The operation test results show that there are two critical speeds under the rated speed, and the measured vibration value agrees well with predicted value. The measured flow rate of the helium supplied to the bearing is 2.0 g/s, which also agrees well with the predicted data.","Hydrostatic bearing(정압베어링), Turbo expander(터보팽창기), Orifice(오리피스), Hydrogen liquefaction(수소액화)","이동현1†ㆍ김병옥1ㆍ정준하2ㆍ임형수3\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2한국기계연구원 시스템다이나믹스연구실 선임연구원, 3한국기계연구원 에너지변환기계연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.2.33"]
["38권2호\npp.41-52","전력분야의 바이오 기반 친환경 전기 절연유 적용에 관한 개발 동향 분석\n(Analysis of Development Trends on Bio-based Environmental Transformers Oils in Power Sector)","Eco/Green Tribology (Renewable / Alternative Energies) ","Mineral electrical insulating oil, which is widely used in transformers, exhibits excellent cooling performance and transformer efficiency. However, given that it is composed of petroleum-based components, it is weak in terms of biodegradability. This causes environmental problems in case of leakage and a low flash point, which is a factor that would cause great damage in the event of a fire in a substation. In this context, the use of eco-friendly electric insulating oil composed of bio-based vegetable oil and synthetic ester, which has excellent biodegradability and flame retardancy performance, has recently been expanded to the field of electric power, and various research and development (R&D) studies are in progress. According to different research results, vegetable oil and synthetic ester manufacturing technology, thermal stability, oxidation stability, property change, and quality control, which are characteristics of eco-friendly electrical insulating oils, are major factors affecting the maintenance of insulating oil properties. In addition, power companies have established and operated quality control standards according to the use of eco-friendly electrical insulating oil as they expand the exploitatoin of renewable energy in electricity production. In particular, deterioration and oxidation characteristics were jointly identified in R&D as an important influencing factor according to the content of saturated and unsaturated fatty acids present in vegetable oils and synthetic esters in power transformer applications.","Vegetable oil(식물성 오일), Synthetic ester(합성 에스테르), Transformer(절연유), Biodegradable oil(생분해성 오일), Thermal stability(열안정성), Oxidation stability(산화안정성)","김재곤1†ㆍ민영제2ㆍ김목연3ㆍ곽병섭4ㆍ박현주5\n1한국석유관리원 미래기술연구소 팀장, 2한국석유관리원 미래기술연구소 선임연구원, 3한국석유관리원 미래기술연구소 책임연구원, 4한전 전력연구원 일반연구원, 5한전 전력연구원 책임연구원","https://doi.org/10.9725/kts.2022.38.2.41"]
["38권2호\npp.53-62","무급유 포일 베어링으로 지지되는 소형 전동 압축기의회전체동역학 성능 측정 및 예측\n(Measurements and Predictions of Rotodynamic Performance ofa Motor-Driven Small Turbocompressor Supportedon Oil-Free Foil Bearings)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study presents experimental measurements of the rotordynamic performance of a motor-driven small turbocompressor supported by gas beam foil journal bearings (GBFJBs) and compares the test results with the predictions of a computational model. The experiments confirmed that the rotational synchronous frequency component dominates the behavior of the overall rotor vibrations, whereas the nonsynchronous components are insignificant, indicating the rotor-bearing system remains stable up to 100 krpm. The undamped natural frequency and imbalanced response of the rotor-bearing system are predicted when integrating the finite element model of the rotor-bearing system with the predictions of the bearing dynamic coefficients. The results are in good agreement with the experimental results. In addition, base excitation test results show that the small turbocompressor can endure large external forces and demonstrate limited rotor amplitudes. A simple single degree-of-freedom rotor model using the nonlinear stiffness of the GBFJBs can effectively predict the test results.","High speed motor(고속 전동기), Beam foil(빔포일), Gas foil bearing(가스 포일 베어링), Rotordynamics(회전체동역학), Base excitation(바닥 가진)","백두산1ㆍ황성호2ㆍ김태호3†ㆍ이종성4ㆍ김태영5\n1국민대학교 대학원 기계설계학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3국민대학교 기계공학부 교수, 4한온시스템 연료전지부품팀 전임연구원, 5현대자동차 연료전지운전장치설계팀 책임연구원","https://doi.org/10.9725/kts.2022.38.2.53"]
["38권2호\npp.63-69","스월 브레이크가 장착된 래버린스 씰의 동특성 해석\n(Rotordynamic Analysis of Labyrinth Seal with Swirl Brake)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","In this research, the rotordynamic characteristics of the labyrinth seal with and without swirl brake were predicted using the computational fluid dynamic (CFD) model. Based on previous studies, a simple swirl brake consisting of square vanes without stagger angle is designed and placed in front of the seal inlet. The rotating frame of reference is utilized to consider the whirling motion of the rotor in the steady-state analysis since the whirling motion is transient behavior in nature. CFD analysis was performed in the range of -1 to 1 pre-swirl ratio for a given seal and swirl brake design and operating conditions. The CFD analysis result shows that the swirl brake effectively reduces the pre-swirl since the circumferential fluid velocity of labyrinth seal with swirl brake was lower than that without swirl brake. The cross-coupled stiffness coefficient, which is greatly affected by the circumferential fluid velocity, increased with an increasing pre-swirl ratio in a seal without a swirl brake but showed a low value in a seal with a swirl brake. The change in the damping coefficient was relatively small. The effective damping coefficient of the labyrinth seal with swirl brake was generally constant and showed a higher value than the labyrinth seal without swirl brake.","Labyrinth seal(래버린스 씰), Swirl brake(스월 브레이크), Pre-swirl(프리스월), Rotordynamic coefficient(동특성 계수), Effective damping coefficient(유효감쇠계수)","이정인1ㆍ서준호2†\n1부산대학교 대학원 기계시스템설계전공 석박사통합과정생, 2부산대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2022.38.2.63"]
["38권2호\npp.70-72","구동 모듈 감속기 윤활 특성에 관한 연구\n(Research on the Lubrication Characteristics of Driving Modules)","Eco/Green Tribology (Renewable / Alternative Energies) ","In this study, we report on a power system developed as a decelerator for a driving module in an electric vehicle. The system is to be mounted in a limited space. The research focus was on development of miniaturization, light weight, and high power density. In particular, we aimed to minimize the layout of existing external components as integrated or built-in, and to maximize the power density by applying optimal cooling technology to increased requirements for developing modular power systems applicable to various OEM models. South Korean automakers ranked fourth in global electric-vehicle sales in 2020, but domestic sales are relatively slow. Despite government's expansion in subsidies for eco-friendly cars, consumers are delaying purchases after 2021 considering the cost-effectiveness of electric vehicles. In major European markets, the demand for electric vehicles exceeded the demand for diesel cars, and sales of hybrid cars, which used to represent eco-friendly cars, are slowing down as Toyota, started selling electric vehicles. In this study, the internal lubrication characteristics of a decelerator installed in an electric vehicle were analyzed in terms of the deceleration time while driving. By selecting the proper oil and oil viscosity, it was confirmed that there is no problem in lubricating the bearings and gears of the decelerator.","Driving module(구동 모듈)","김은겸1ㆍ김현찬2ㆍ박준영3†\n1삼보모터스 책임연구원, 2삼보모터스 수석연구원, 3삼보모터스 연구소장","https://doi.org/10.9725/kts.2022.38.2.70"]
["38권3호\npp.73-83","직각 쐐기와 응착접촉 하는 반무한 평판 내 전위: 제1부 - 보정 함수 유도\n(Dislocation in Semi-infinite Half Plane Subject to Adhesive Complete Contact with Square Wedge: Part I - Derivationof Corrective Functions)","Contact Mechanics & Friction","This paper is concerned with an analysis of a surface edge crack emanated from a sharp contact edge. For a geometrical model, a square wedge is in contact with a half plane whose materials are identical, and a surface perpendicular crack initiated from the contact edge exists in the half plane. To analyze this crack problem, it is necessary to evaluate the stress field on the crack line which are induced by the contact tractions and pseudo-dislocations that simulate the crack, using the Bueckner principle. In this Part I, the stress filed in the half plane due to the contact is re-summarized using an asymptotic analysis method, which has been published before by the author. Further focus is given to the stress field in the half plane due to a pseudo-edge dislocation, which will provide a stress solution due to a crack (i.e. a continuous distribution of edge dislocations) later, using the Burgers vector. Essential result of the present work is the corrective functions which modify the stress field of an infinite domain to apply for the present one which has free surfaces, and thus the infiniteness is no longer preserved. Numerical methods and coordinate normalization are used, which was developed for an edge crack problem, using the Gauss-Jacobi integration formula. The convergence of the corrective functions are investigated here. Features of the corrective functions and their application to a crack problem will be given in Part II.","Adhesive complete contact(응착 완전접촉), Perpendicular crack(수직 균열), Dislocation density function method(전위밀도함수법), Corrective function(보정 함수), Stress intensity factor(응력확대계수)","김형규1,2†\n1한국원자력연구원 핵연료안전연구부 책임연구원, 2과학기술연합대학원대학교 원자력 및 방사선안전전공 교수","https://doi.org/10.9725/kts.2022.38.3.73"]
["38권3호\npp.84-92","직각 쐐기와 응착접촉 하는 반무한 평판 내 전위: 제2부 - 보정 함수의 근사 및 응용\n(Dislocation in Semi-infinite Half Plane Subject to Adhesive Complete Contact with Square Wedge: Part II - Approximation and Application of Corrective Functions)","Contact Mechanics & Friction","In Part I, developed was a method to obtain the stress field due to an edge dislocation that locates in an elastic half plane beneath the contact edge of an elastically similar square wedge. Essential result was the corrective functions which incorporate a traction free condition of the free surfaces. In the sequel to Part I, features of the corrective functions, Fkij,(k = x, y;i,j = x,y) are investigated in this Part II at first. It is found that Fxxx() = Fyxy() where = y/η and η being the location of an edge dislocation on the y axis. When compared with the corrective functions derived for the case of an edge dislocation at x = ξ, analogy is found when the indices of y and x are exchanged with each other as can be readily expected. The corrective functions are curve fitted by using the scatter data generated using a numerical technique. The algebraic form for the curve fitting is designed\nas Fkij() = where λI = 0.5445, the eigenvalue of the adhesive complete contact problem\nintroduced in Part I. To investigate the exponent of Fkij, i.e.(1 − λI) and p, Log|Fkij|()-Log|()| is plotted and investigated. All the coefficients and powers in the algebraic form of the corrective functions are obtained using Mathematica. Method of analyzing a surface perpendicular crack emanated from the complete contact edge is explained as an application of the curve-fitted corrective functions.","Dislocation density function method(전위밀도함수법), Corrective function(보정 함수), Crack problem(균열 문제), Numerical approximation(수치적 근사)","김형규1,2†\n1한국원자력연구원 핵연료안전연구부 책임연구원, 2과학기술연합대학원대학교 원자력 및 방사선안전전공 교수","https://doi.org/10.9725/kts.2022.38.3.84"]
["38권3호\npp.93-100","마이크로 스탬프를 이용한 Micro-LED 개별 전사 및 리플로우 공정에 관한 연구\n(A Study on Selective Transfer and Reflow Process of Micro-LED using Micro Stamp)","Micro/Nano-Tribology","Micro-light emitting diode (micro-LED) displays offer numerous advantages such as high brightness, fast response, and low power consumption. Hence, they are spotlighted as the next-generation display. However, defective LEDs may be created due to non-uniform contact loads or LED alignment errors. Therefore, a repair process involving the replacement of defective LEDs with favorable ones is necessitated. The general repair process involves the removal of defective micro-LEDs, interconnection material transfer, as well as new micro-LED transfer and bonding. However, micro-LEDs are difficult to repair since their size decreases to a few tens of micron in width and less than 10 μm in thickness. The conventional nozzle-type dispenser for fluxes and the conventional vacuum chuck for LEDs are not applicable to the micro-LED repair process. In this study, transfer conditions are determined using a micro stamp for repairing micro-LEDs. Results show that the aging time should be set to within 60 min, based on measuring the aging time of the flux. Additionally, the micro-LEDs are subjected to a compression test, and the result shows that they should be transferred under 18.4 MPa. Finally, the I-V curves of micro-LEDs processed by the laser and hot plate reflows are measured to compare the electrical properties of the micro-LEDs based on the reflow methods. It was confirmed that the micro-LEDs processed by the laser reflow show similar electrical performance with that processed by the hot plate reflow. The results can provide guidance for the repair of micro-LEDs using micro stamps.","Micro-LED(마이크로 엘이디), Micro stamp(마이크로 스탬프), Repair process(수리 공정), Selective transfer process(선택적 전사 공정), Laser reflow(레이저 리플로우)","한승1,3ㆍ윤민아2,3ㆍ김 찬4ㆍ김재현5,6ㆍ김광섭5,6†\n1과학기술연합대학원대학교 나노메카트로닉스학과 석사과정생, 2과학기술연합대학원대학교 융합기계시스템 박사과정생, 3한국기계연구원 나노융합장비연구부 학생연구원, 4한국기계연구원 나노융합장비연구부 박사후 연구원, 5과학기술연합대학원대학교 융합기계시스템 교수, 6한국기계연구원 나노융합장비연구부 책임연구원","https://doi.org/10.9725/kts.2022.38.3.93"]
["38권3호\npp.101-108","자장여과아크소스의 자장필터 꺾임 각도와 아크방전전류에따라 증착된 ta-C 코팅의 마모 거동 연구\n(A Study on the Wear Behavior of Tetrahedral Amorphous Carbon Coatings Based on Bending Angles of the Filtered Cathodic Vacuum Arc with Different Arc Discharge Currents)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","The structure and properties of tetrahedral amorphous carbon (ta-C) coatings depend on the main process parameters and bending angles of the magnetic field filter used in the filtered cathodic vacuum arc (FCVA). During the process, it is possible to effectively control the plasma flux of carbon ions incident on the substrate by controlling the arc discharge current, thereby influencing the mechanical properties of the coating film. Furthermore, we can control the size and amount of large particles mixed during carbon film formation while conforming with the bending angle of the mechanical filter mounted on the FCVA; therefore, it also influences the mechanical properties. In this study, we consider tribological characteristics for filtered bending angles of 45° and 90° as a function of arc discharge currents of 60 and 100 A, respectively. Experiment results indicate that the frictional behavior of the ta-C coating film is independent of the bending angle of the filter. However, its sliding wear behavior significantly changes according to the bending angle of the FCVA filter, unlike the effect of the discharge current. Further, upon changing the bending angle from 45° to 90°, abrasive wear gets accelerated, thereby changing the size and mixing amount of macro particles inside the coating film.","Filtered cathodic vacuum arc(자장여과아크플라즈마), Arc discharge current(아크방전전류), Hardness(경도), Surface roughness(표면거칠기), Wear(마모), Macro particle(거대입자)","김원석1,3ㆍ김송길2ㆍ장영준3†ㆍ김종국3‡\n1부산대학교 대학원 기계공학부 석사과정생, 2부산대학교 기계공학부 부교수, 3한국재료연구원 극한소재연구소 극한환경코팅연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.3.101"]
["38권3호\npp.109-114","마이크로 버블 발생장치와 결합된 오일 플러싱 장치 개발\n(Development of Oil Flushing System with Microbubble Generator)","Condition Monitoring & Maintenance System (System Reliability)","This paper reports the development of an oil flushing system combined with a microbubble generator. Oil flushing plays a crucial role in regulating the lubricant’s performance during the lubricant replacement process. Moreover, harmful contaminants, such as sludge, wear particles, and rust, from piping systems or lubrication system can be removed by oil flushing. Oil flushing aims to increase the system’s efficiency using a dedicated flushing oil, increasing of the supply pressure and generating a vortex. In addition, it helps the mechanical system or equipment achieve peak performance and reduces the potential for premature failure. However, the contaminant-removal applications of existing oil flushing system are limited. In this research, we aim to improve the performance of oil flushing system by incorporating a microbubble generator, which uses the venture effect to generate microbubbles and mixes them with lubricant. The microbubbles in the blended lubricant remove contaminants from the lubrication system more effectively. Structural mechanics and fluid dynamics are analyzed through fluid-structure interaction (FSI) analysis, and the numerical analysis results are used for the designing the system. The magnitude of the maximum stress is investigated based on the pressure results obtained by the CFD analysis; through the CFD analysis, the mixing ratio of air (bubble) and lubricant is evaluated using the volume of fluid (VOF) model according to the working conditions.","Fluid-structure interaction analysis(유동-구조 연성 해석), Lubricant(윤활유), Microbubble generator(마이크로 버블 발생기), Oil flushing(오일 플러싱)","홍성호1†ㆍ이경희2ㆍ정남화3\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2삼영필텍 대표, 3삼영필텍 전무","https://doi.org/10.9725/kts.2022.38.3.109"]
["38권3호\npp.115-119","Influence of Grease Consistency on the Wear of Gear Surfaces","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","This paper selected three kinds of grease with the same type but different consistency for the experiment. The purpose of the experiment is tested the effect of different consistency of grease on the wear of the gear surface. Different torque test groups were selected in the test, and the lubrication effect of different greases was tested in the test groups with the same torque. After each set of tests, the wear of the gear surfaces was observed and recorded. The data recorded in the experiment included the area of the wear area on the gear surface, the type of wear and the volume of wear. After the test, the gear surface roughness was measured. By calculating the wear volume, the effects of different concentrations of grease on the gear surface wear were compared. The experimental results show that under different stress conditions, the consistency of the grease has a great influence on the lubricating effect of the gear surface and the gear wear. Under the condition with low speed and high torque, different grease consistency affect the gear surface wear, the high consistency grease can reduce the wear of the gear surface, so that the gear can get better lubrication effect during the work.","Consistency, Gear, Grease, Pitting, Surface wear","Chen-Xiao Li1, Haneum Park2 and Chul-Hee Lee3†\n1Ph.D. Student, Graduate School, Dept. of Mechanical Engineering, Inha University, 2Researcher, R&D Team, CALS Corporation, 3Professor, Dept. of Mechanical Engineering, Inha University","https://doi.org/10.9725/kts.2022.38.3.115"]
["38권4호\npp.121-127","통합형 오일 정제 시스템의 개발\n(Development of an Integrated Oil Purification System)","Condition Monitoring & Maintenance System (System Reliability)","This study presents the development of an integrated oil purification system consisting of moisture removal, oil flushing, and oil filtering devices. In this system, the oil flushing device is combined with a microbubble generator. Oil purification is necessary for ensuring the high performance of the lubricant through the efficient removal of contaminants and thus enables good maintenance of mechanical systems. The developed purification system removes moisture, varnish, and solid particles. Moreover, during oil purification, the oil flushing device separates foreign materials and contaminants remaining in the lubricating oil piping or mechanical systems. The microbubble generator, which is combined with the oil flushing device, can separate harmful contaminants, such as sludge, wear particles, and rust, from piping or lubrication systems through the cavitation effect. Moisture is removed using a double high-vacuum chamber, while sludge and varnish are removed via electro-absorption using a high-voltage generator. Additionally, the total maintenance cost of the system is reduced through the use of domestically fabricated cartridge filters composed of glass fiber and cellulose. The heater, which maintains the temperature of the lubricant at 60oC, can process 41,000 L of lubricant simultaneously. Multiple tests confirmed that the proposed integrated purification system exhibits good performance in oil flushing and removal of water and varnish.","Lubricant(윤활유), Oil filter(오일 필터), Oil flushing(오일 플러싱), Oil purification(오일 정제), Vacuum chamber(진공 챔버)","홍성호1†ㆍ이경희2ㆍ정남화3\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2삼영필텍 대표, 3삼영필텍 전무","https://doi.org/10.9725/kts.2022.38.4.121"]
["38권4호\npp.128-135","가속내구시험 마모영역 판별에 대한 이미지 분석 연구\n(A Study on Image Analysis for Determination of Wear Areain Accelerated Durability Test)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements), Tribology Applications (Industrial Case Studies)","In the product development process, the reliability of the product can be secured through durability tests. However, since the durability test method is expensive and time consuming, a method to save time and money by utilizing virtual product development (VPD) is required. However, research on the accuracy of the results of virtual product development is required. In this paper, an accelerated durability test was designed and conducted using a planetary gear decelerator. And an analysis model under the same conditions was created and simulated. To correlate the results of the experiment with the results of the analytical model, created a model that can discriminate the wear region using one of the data mining methods, the k-means algorithm method and HSV (Hue, Saturation, Value). The wear area is compared by counting the number of pixels defined as wear through a discrimination model. A similar ratio was calculated by comparing the pixel ratio of the area determined as wear in the entire area. It showed a similar ratio of about 70%, and it is necessary to improve the discrimination method.","Accelerated durability test(가속내구시험), CAE(컴퓨터 응용해석), Wear area(마모 영역), Planetary gear(유성기어), Virtual product development(가상제품개발)","천민우1ㆍ이철희2†\n1인하대학교 대학원 기계공학과 박사과정생, 2인하대학교 기계공학과 정교수","https://doi.org/10.9725/kts.2022.38.4.128"]
["38권4호\npp.136-142","공정 개선에 따른 사고저항성 CrAl 코팅 피복관의 내마모성 향상\n(Improved Coating Process for Enhanced Wear Resistance of CrAl Coated Claddings for Accident Tolerant Fuel)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ,Wear Phenomena & Mechanisms","This paper investigates the enhanced wear performance of a CrAl coated accident tolerant fuel (ATF) cladding. In the wake of the Fukushima accident, extensive research on ATF with respect to improving the oxidation resistance of cladding materials is ongoing. Since coated Zr claddings can be applied without major changes to the criteria for reactor core design, many researchers are studying coatings for claddings. To improve the quality of the CrAl coating layer, optimization of the manufacturing process is imperative. This study employs arc ion plating to obtain improved CrAl coated claddings using CrAl binary alloy targets through an improved coating method. Surface roughness and adhesion are improved, and droplets are reduced. Furthermore, the coated layer has a dense and fine microstructure. In scratch tests, all the tested CrAl coated claddings exhibit a superior resistance compared to the Zr cladding. In a fretting wear test, the wear volume of the CrAl coated claddings is smaller compared to the Zr cladding. Furthermore, the coated cladding manufactured through the improved process exhibits better wear resistance than other CrAl coated claddings. Based on these results, we suggest that fine microstructure is attributed to a mechanically and microstructurally robust CrAl coating layer, which enhances wear resistance.","Fretting wear(프레팅 마모), Accident tolerant fuel cladding/ATF cladding(사고저항성핵연료 피복관), Arc Ion Process(아크 이온 플레이팅), CrAl coating(CrAl 코팅), Scratch test(스크래치 시험)","김성은1†ㆍ이영호 2ㆍ김대호2ㆍ김현길2\n1한국원자력연구원 핵연료안전연구부 박사후 연구원, 2한국원자력연구원 핵연료안전연구부 책임연구원","https://doi.org/10.9725/kts.2022.38.4.136"]
["38권4호\npp.143-151","건설기계의 오일진단 관련 특허 분석\n(Analysis of Patents Related to Oil Diagnosis of Construction Equipment)","Condition Monitoring & Maintenance System (System Reliability)","This study analyzes patents related to oil diagnosis of construction equipment. Oil diagnosis is extremely important for maintaining construction equipment properly. Through the evaluation of existing patents, a patent strategy for the future construction equipment market is presented. The related patents are classified and selected in several steps. Finally, 16 valid patents are selected and analyzed in detail. In the classification process, patents are classified by country, year, and company. A market analysis shows that the top 10 companies have a market share of more than 50. In addition to patents related to the oil analysis of construction equipment, patents related to automobile oil analysis and development of oil sensors are investigated to identify the contents of patents in other fields that can be applied to oil diagnosis technology for construction equipment. Moreover, not only the contents of research articles of two Korean construction companies, but also the research trends in the literature in this field are used in the analysis. The related patents of the two Korean companies are few. Companies with a high market share, including Caterpillar, hold many patents, and patents for diagnosis algorithms using such technologies as artificial intelligence and artificial neural networks, along with oil sensor-based condition monitoring technology, are gradually expanding.","Construction equipment(건설기계), Lubricant(윤활유), Oil diagnosis(오일진단), Patent(특허)","홍성호1†ㆍ장범석2\n1동국대학교 창의융합공학부 기계시스템공학전공 조교수, 2동국대학교 창의융합공학부 기계시스템공학전공 학부생","https://doi.org/10.9725/kts.2022.38.4.143"]
["38권4호\npp.152-161","인공신경망을 활용한 CMP 컨디셔닝 시스템 설계 변수에 따른 컨디셔닝 밀도의 불균일도 분석\n(Nonuniformity of Conditioning Density According to CMP Conditioning System Design Variables Using Artificial Neural Network)","Chemical Mechanical Polishing","Chemical mechanical planarization (CMP) is a technology that planarizes the surfaces of semiconductor devices using chemical reaction and mechanical material removal, and it is an essential process in manufacturing highly integrated semiconductors. In the CMP process, a conditioning process using a diamond conditioner is applied to remove by-products generated during processing and ensure the surface roughness of the CMP pad. In previous studies, prediction of pad wear by CMP conditioning has depended on numerical analysis studies based on mathematical simulation. In this study, using an artificial neural network, the ratio of conditioner coverage to the distance between centers in the conditioning system is input, and the average conditioning density, standard deviation, nonuniformity (NU), and conditioning density distribution are trained as targets. The result of training seems to predict the target data well, although the average conditioning density, standard deviation, and NU in the contact area of wafer and pad and all areas of the pad have some errors. In addition, in the case of NU, the prediction calculated from the training results of the average conditioning density and standard deviation can reduce the error of training compared with the results predicted through training. The results of training on the conditioning density profile generally follow the target data well, confirming that the shape of the conditioning density profile can be predicted.","Chemical mechanical planarization(화학적기계적 평탄화), Pad conditioning(패드 컨디셔닝), Design ariables(설계 변수), Conditioning simulation(컨디셔닝 시뮬레이션), Artificial neural network(인공신경망)","박병훈1ㆍ이현섭2†\n1동아대학교 대학원 기계공학과 박사과정생, 2동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.4.152"]
["38권4호\npp.162-169","CoCrW와 CoCrMo 합금의 트라이볼로지 특성 평가\n(Assessment of Tribological Characteristics of CoCrW and CoCrMo Alloys)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials)","Cobalt–chromium (CoCr)-based alloys have been used for wear applications because of their excellent mechanical properties and wear resistance. With growing concern over environmental problems, CoCr alloys are expected to be used for various tribological applications in degraded lubrication states. To expand the applicability of the materials, data should be accumulated across a broad spectrum of experimental parameters. In this work, the friction and wear characteristics of cobalt–chromium–tungsten (CoCrW) and cobalt–chromium–molybdenum (CoCrMo) alloys are investigated experimentally. The tests are conducted using a pin-on-reciprocating-plate tribo-tester in dry lubrication. CoCrW and CoCrMo are used as pin and plate materials to investigate the effect of the counter material. The results show that the friction coefficients between CoCrW and CoCrMo generally range from 0.4 to 0.5. The friction coefficient between the CoCrW pin and plate is found to be slightly small. However, the total wear between the CoCrW pin and plate is found to be the largest. In contrast, the total wear between the CoCrW pin and plate is relatively small. Furthermore, CoCrW may cause a faster wear progression of CoCrMo, especially for the case in which CoCrMo is used as the pin material. The results of this work provide a better understanding of the tribological properties of CoCrW and CoCrMo alloys. In addition, this work provides a practical guideline for the use of CoCrW and CoCrMo from the tribological design viewpoint.","CoCrMo alloy(CoCrMo 합금), CoCrW alloy(CoCrW 합금), Friction(마찰), Wear rate(마모율)","권동균1ㆍ오세진2ㆍ정구현3†\n1울산대학교 기계공학부 학사과정생, 2울산대학교 기계공학부 석사과정생, 3울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.4.162"]
["38권4호\npp.170-178","SUJ2 베어링 강의 트라이볼로지 특성에 대한 초음파나노표면개질 (UNSM) 및 원더프로세스크래프트 (WPC) 처리 효과 연구\n(A Study on the Effects of Ultrasonic Nanocrystal SurfaceModification (UNSM) and Wonder Process Craft (WPC)Treatments on Tribological Properties of SUJ2 Bearing Steel)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Mechanical surface treatment is an excellent approach widely used to modulate and improve the performance and service life of bearings, gears, and frictional joints. The main purpose of this study is to investigate and compare the effect of ultrasonic nanocrystal surface modification (UNSM) and wonder process craft (WPC) on the surface and tribological properties of SUJ2 bearing steel. The surface roughness and hardness of the untreated and treated (UNSM- and WPC-treated) specimens were measured and compared. Their tribological properties were evaluated using a micro-tribometer under grease-lubricated and dry conditions against itself. Surface hardness measurement results revealed that both the UNSM- and WPC-treated specimens had a higher hardness than that of the untreated specimen. The surface roughness of the untreated specimen was reduced after UNSM and WPC treatments. Abrasive wear mode was observed on the surface of the specimens worn under grease-lubricated conditions, while adhesive wear mode was found on the surface of the specimens worn in dry conditions. According to the tribological test results, the friction coefficient and wear rate of the untreated specimens were reduced by the application of both the UNSM and WPC treatments under grease-lubricated and dry conditions.","SUJ2 bearing steel(SUJ2 베어링 강), Sliding friction(미끄럼 마찰), Sliding wear behavior(미끄럼 마모거동), UNSM(초음파나노표면개질), WPC(원더프로세스크래프트)","아마노프 아웨즈한1†ㆍ카림바예프 루슬란2ㆍ조인호3ㆍ김응주4\n1선문대학교 기계공학과/융합과학기술학과 부교수, 2선문대학교 대학원 융합과학기술학과 박사과정생, 3(주)디자인메카 대표이사, 4(주)포휴먼사이언스 대표이사","https://doi.org/10.9725/kts.2022.38.4.170"]
["38권5호\npp.179-184","21톤급 휠 굴착기용 트랜스미션의 기어 트레인에 대한 강도 해석\n(Strength Analysis of Complex Gear Train for Transmission of 21-Ton Grade Wheel Excavator)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","The power train of transmission for 21-ton grade wheel excavator makes use of a complex gear train composed of a planetary and helical gear system to drive the wheel excavator by transmitting power to the axle. The complex gear train with a shift mode is an important part of the transmission because of strength problems in an extreme environment. To calculate the specifications of the complex gear train and analyze the gear bending and compressive stresses of the complex gear train, this study analyzes gear bending and compressive stresses accurately for the optimal design of the complex gear train with respect to cost and reliability. In this article, the gear bending and compressive stresses of the complex gear train are calculated using the Lewes and Hertz equation. Evaluating the results with the data of the allowable bending and compressive stress from the stress and number of cycles curves of the gears verified the calculated specifications of the complex gear train. A computer structure analysis is performed with the 3D model of the planetary and helical gears to analyze the structure strength of the complex gear train. The results demonstrate that the durability and strength of the complex gear train are safe, because the safety factors of the bending and compressive stresses are more than 1.0.","Wheel excavator(휠 굴착기), Transmission(변속기), Complex gear Train(복합 기어 트레인), Gear bending stress(기어 굽힘 응력), Gear compressive stress(기어 면압 응력), Computer structure analysis(컴퓨터 구조 해석)","이준희1ㆍ배명호2ㆍ조연상3†\n1(주)디아이씨 기술연구소 부장, 2창원문성대학교 항공정비학부 교수, 3동아대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2022.38.5.179"]
["38권5호\npp.185-190","히트파이프 모세관 성능 개선을 위한 스크린-메쉬 윅의 표면 개질\n(Surface Modification of Screen-Mesh Wicks to Improve Capillary Performance for Heat Pipes)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Among the operating limits of a heat pipe, the capillary limit is significantly affected by the characteristics of the wick, which is determined by the capillary performance. The major parameters for determining capillary performance are the maximum capillary pressure and the spreading characteristics that can be expected through the wick. A well-designed wick structure improves capillary performance and helps improve the stability of the heat pipe by enhancing the capillary limit. The capillary performance can be improved by forming a porous microstructure on the surface of the wick structure through surface modification techniques. In this study, a microstructure is formed on the surface of the wick by using a surface modification method (i.e., an electrochemical etching process). In the experiment, specimens are prepared using stainless-steel screen mesh wicks with various fabrication conditions. In addition, the spreading and capillary rise performances are observed with low-surface-tension fluid to quantify the capillary performance. In the experiments, the capillary performance, such as spreading characteristics, maximum capillary pressure, and capillary rise rate, improves in the specimens with microstructures formed through surface modification compared with the specimens without microstructures on the surface. The improved capillary performance can have a positive effect on the capillary limit of the heat pipe. It is believed that the surface microstructures can enhance the operational stability of heat pipes.","Capillary performance(모세관 성능), Capillary rise height(모세관 상승 높이), Micro(마이크로 구조), Screen-mesh wick(스크린-메쉬 윅), Surface modification(표면 개질)","정지윤1ㆍ임혜원1ㆍ김혜원1ㆍ이상민2ㆍ김형모3†\n1경상국립대학교 기계공학부 학부연구생, 2동의대학교 기계자동차로봇부품공학부 조교수, 3경상국립대학교 기계공학부 조교수","https://doi.org/10.9725/kts.2022.38.5.185"]
["38권5호\npp.191-198","사각형 딤플로 Surface Texturing한 경사진 Slider 베어링의 윤활해석\n(Lubrication Analysis of Surface-Textured Inclined Slider Bearing with Rectangular Dimples)","Lubrication (Lubricants & Additives) ,Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","With the world's fast expanding energy usage comes a slew of new issues. Because one-third of energy is lost in overcoming friction, tremendous effort is being directed into minimizing friction. Surface texturing is the latest surface treatment technology that uses grooves and dimples on the friction surface of the machine to significantly reduce friction and improve wear resistance. Despite the fact that many studies on this issue have been conducted, most of them focused on parallel surfaces, with relatively few cases of converging films, as in most sliding bearings. This study investigated the lubrication performance of surface-textured inclined slider bearings. We analyzed the continuity and Navier–Stokes equations using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and velocity distributions and the lubrication performance according to the number and orientation of rectangular dimples. Partial texturing somewhat improves the lubrication performance of inclined slider bearings. The number of dimples with the maximum load-carrying capacity (LCC) and minimum friction is determined. When the major axis of the dimple is arranged in the sliding direction, the LCC and friction reduction are maximized. However, full texturing significantly reduces the LCC of the slider bearing and increases the flow rate. The results have the potential to improve the lubrication performance of various sliding bearings, but further research is required.","Slider bearing(슬라이더 베어링), Surface texturing(표면조직가공), Hydrodynamic lubrication(유체윤활), Computational fluid dynamics(CFD, 전산유체역학), Numerical analysis(수치해석)","박태조1†ㆍ장인규2\n1경상국립대학교 기계공학부 교수·공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2022.38.5.191"]
["38권5호\npp.199-204","물 분자막의 두께와 윤활특성의 상관관계에 대한 분자시뮬레이션 연구\n(Molecular Simulation Study on Influence of Water Film Thickness on Lubrication Characteristics)","Modeling & Simulation in Tribology ","This paper presents a numerical investigation of the influence of water molecule thickness on frictional behavior at the nanoscale using molecular dynamics simulation. Three different models, comprising water thin films of various thicknesses, were built, and indentation and sliding simulations were performed using the models. Various normal loads were applied by indenting the Si tip on the water film for the sliding simulation to evaluate the interplay between the water thin film thickness and the normal load. The results of the simulations showed that the friction force generally increased with respect to the normal load and thickness of the water thin film. The friction coefficient varied with respect to the normal load and the water film thickness. The friction coefficient was the smallest under a moderate normal force and increased with decreasing or increasing normal loads. As the water film became thicker, the contact area between the tip and water film became larger. Under well-lubricated conditions, the friction force was proportional to the contact area regardless of the water film thickness. As the normal force increased above a critical condition, the water molecules beneath the Si tip spread out; thus, the film could not provide lubrication. Consequently, the substrate was permanently deformed by direct contact with the Si tip, while the friction force and friction coefficient significantly increased. The results suggest that a thin water film can effectively reduce friction under relatively low normal load and contact pressure conditions. In addition, the contact area between the contacting surfaces dominates the friction force.","Contact area(접촉면적), Film thickness(유막 두께), Lubrication(윤활), Molecular simulation(분자 시뮬레이션), Water molecule(물분자)","김현준1,2†ㆍ허세곤3\n1경북대학교 정밀기계공학과 부교수, 2경북대학교 미래과학기술융합학과 부교수, 3한국기계연구원 3D프린팅장비연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.5.199"]
["38권5호\npp.205-212","고속 전동기용 2 패드 빔 타입 가스 포일 저널 베어링의 회전체동역학 성능 측정\n(Rotordynamic Performance Measurements of a Two-PadBeam-Type Gas Foil Journal Bearing for High Speed Motors)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper presents experimental measurements of the structural characteristics of a two-pad beam-type gas foil journal bearing and its rotordynamic performance for a high-speed motor-driven turbocompressor. The test bearing had two top foils and two beam foils, each with an arc length of ~180°. Each beam foil was etched to obtain 40 beams with six geometries of different lengths and widths. The insertion of beam foils into the bearing housing produces equivalent beam heights. The structural tests of the bearing with a non-rotating journal revealed a smaller bearing clearance and larger structural stiffness for the load-on-pad configuration than for the load-between-pads configuration. Rotordynamic performance measurements during driving tests up to 100 krpm demonstrated synchronous vibrations and subsynchronous vibrations with large amplitudes. The test was repeated after inserting the shim between the top foil and beam foil to reduce the bearing radial clearance. The reduced bearing clearance resulted in a reduction in the peak amplitude of the synchronous vibrations and an increase in the speed at which the peak amplitude occurred. In addition, the onset speed and amplitude of the subsynchronous vibrations were dramatically increased and diminished, respectively. The rotor coast-down tests at 100 krpm show that the reduction in the bearing clearance extends the time to rotor stop, thus implying an improvement in hydrodynamic pressure generation and a reduction in bearing frictional torque.","High speed motor(고속 전동기), Bam foil(빔 포일), Gas foil bearing(가스 포일 베어링), Rotordynamics(회전체동역학), Bearing clearance(베어링 간극)","정권종1ㆍ황성호2ㆍ백두산3ㆍ김태영4ㆍ김태호5†\n1국민대학교 대학원 기계시스템공학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3현대모비스 연료전지시스템개발셀 연구원, 4현대자동차 연료전지운전장치설계팀 책임연구원, 5국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.5.205"]
["38권5호\npp.213-221","경사 그루브를 갖는 평판 실의 압력 강하 및 누설 성능\n(Pressure Drop and Leakage Performances of Flat Seals with Inclined Grooves)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper presents performance measurements of pressure drop and leakage flow rate of test flat seals with asymmetric inclined grooves. This study aims to reveal the influence of groove shapes, often machined in radial film riding-face seals, in forming a hydrodynamic wedge on leakage performance. A test facility was developed, and test seals were manufactured to study the effects of the inlet pressure level, ratio of inlet to outlet pressure, seal groove length, and seal groove height on the steady-state pressure drop and leakage performance. A series of tests were conducted, and the test data were compared to the predictions from a simple and efficient mathematical model using a one-dimensional Reynolds equation. The test results revealed that an increase in the inlet pressure increased the pressure drop through the test seals. The leakage flow rate increased significantly as the inlet pressure and ratio of the inlet to outlet pressure increased. The groove shape also affects seal performance. An increase in the groove length and height resulted in an evident increase in the leakage flow rate. The simple model predictions underestimated the leakage flow rates but showed good agreement with the trend in the measurements for all test operating conditions and changes in the groove shape.","Seal(실), Leakage flow rate(누설 유량), Pressure drop(압력 강하), Groove(그루브), Pressure ratio(압력비)","정진우1ㆍ정권종1ㆍ황성호2ㆍ김태호3†ㆍ김어진4\n1국민대학교 대학원 기계시스템공학과 석사과정생, 2국민대학교 대학원 기계설계학과 박사수료, 3국민대학교 기계공학부 교수, 4두산에너빌리티 주임연구원","https://doi.org/10.9725/kts.2022.38.5.213"]
["38권5호\npp.222-226","압축기 부품소재 표면 적용을 위한 탄소 기반 고체 윤활막의 마찰 및 마모 특성 평가\n(Evaluation of Friction and Wear Characteristics of Carbon-based Solid Lubricant Films for Surface Application of Compressor Parts)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Between diaphragms made of stainless steel (SUS), which is the main component of a hydrogen gas compressor, micro-slip occurs owing to repeated bending, resulting in scratches on the surface. The surface scratch of the compressor part is a problem with airtightness, which reduces the efficiency of the compressor; in severe cases, damage is a possibility. In this study, the changes in friction and wear characteristics due to the surface polishing of SUS and carbon-based solid lubricant films (graphene and CNT) were analyzed. Bare SUS, polished SUS, graphene film, and CNT film specimens were prepared. The surface roughness of the SUS was significantly reduced by surface polishing but increased by carbon-based solid lubricating films. In contrast, the friction coefficient maintained a similar value after surface polishing but was significantly reduced by the carbon-based solid lubricant films. In particular, the graphene film exhibited the lowest initial friction coefficient, while the CNT film exhibited the lowest overall average friction coefficient. Regarding the wear rate, polished SUS exhibited the lowest value, but the surface condition of the wear track showed that the carbon-based solid lubricating films were relatively less damaged. Although the wear rate measured was largely attributed to the solid lubricating film peeling off, the SUS surface under the film was considered protected.","Carbon nanotube(탄소나노튜브), Friction/wear(마찰/마모), Graphene(그래핀), Solid lubricant(고체 윤활제), Surface polishing(표면 연마)","이성준1ㆍ김창래2†\n1조선대학교 대학원 기계공학과 박사과정생, 2조선대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.5.222"]
["38권6호\npp.227-234","선박엔진 부품의 성능 향상을 위한 초기 마모 및 윤활 해석 연구\n(Simulation of the Initial Wear and Lubrication Performance of Marine Engine Components)","Tribology in Transportation (Railway / Road) ","Recently, the demand for improving energy efficiency has rapidly increased because of the growing concerns over environmental issues. In this work, the tribo-test and simulation for the initial wear and lubrication performance were performed for the piston pin in the small end system of the connecting rod of a marine engine, to obtain useful data for improving the efficiency of marine engine systems. In addition, a diamond-like carbon (DLC) coating was applied to the piston pin to explore feasibility of eliminating the bush used in the system. The initial wear and lubrication characteristics between the uncoated piston pin and bush were compared with that between the DLC-coated piston pin and connecting rod in the tribo-test. The simulation for the wear and lubrication performance according to the wear progression was conducted based on the data obtained from the test. The wear characteristics were quantitatively assessed by the wear depth and wear volume, and the lubrication performance was characterized with the change of pressure and minimum oil film thickness with respect to the crank angle. It was found that the DLC-coated piston pin may provide better initial wear characteristics and lubrication performance. The results of this work may provide fundamental information for marine engines with improved efficiency.","DLC coating(DLC 코팅), Friction(마찰), Piston pin(피스톤 핀), Wear(마모)","차수빈1ㆍ이 향2ㆍ정구현3†\n1울산대학교 대학원 기계공학부 석사과정생, 2현대중공업㈜ 엔진기계사업본부 엔진기계연구소 책임연구원, 3울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2022.38.6.227"]
["38권6호\npp.235-240","Frictional Anisotropy of CVD Bi-Layer Graphene Correlated with Surface Corrugated Structures","Micro/Nano-Tribology","Atomically-thin 2D nanomaterials can be easily deformed and have surface corrugations which can influence the frictional characteristics of the 2D nanomaterials. Chemical vapor deposition (CVD) graphene can be grown in a wafer scale, which is suitable as a large-area surface coating film. The CVD growth involves cooling process to room temperature, and the thermal expansion coefficients mismatch between graphene and the metallic substrate induces a compressive strain in graphene, resulting in the surface corrugations such as wrinkles and atomic ripples. Such corrugations can induce the friction anisotropy of graphene, and therefore, accurate imaging of the surface corrugation is significant for better understanding about the friction anisotropy of CVD graphene. In this work, the combinatorial analysis using friction force microscopy (FFM) and transverse shear microscopy (TSM) was implemented to unveil the friction anisotropy of CVD bi-layer graphene. The periodic friction anisotropy of the wrinkles was measured following a sinusoidal curve depending on the angles between the wrinkles and the scanning tip, and the two domains were observed to have the different friction signals due to the different directions of the atomic ripples, which was confirmed by the high-resolution FFM and TSM imaging. In addition, we revealed that the atomic ripples can be easily suppressed by ironing the surface during AFM scans with an appropriate normal force. This work demonstrates that the friction anisotropy of CVD bi-layer graphene is well-correlated with the corrugated structures and the local friction anisotropy induced by the atomic ripples can be controllably removed by simple AFM scans.","CVD graphene, Frictional anisotropy, Friction force microscopy(FFM), Transverse shear microscopy(TSM)","Seonha Park1, Mingi Choi2, , Seokjun Kim3 and Songkil Kim4†\n1M. S. Student, Graduate School, School of Mechanical Engineering, Pusan National University, 2Ph.D. Student, Graduate School, School of Mechanical Engineering, Pusan National University, 3Student Researcher, School of Mechanical Engineering, Pusan National University, 4Associate Professor, School of Mechanical Engineering, Pusan National University","https://doi.org/10.9725/kts.2022.38.6.235"]
["38권6호\npp.241-246","극저온이 22MnB5강의 냉간 스탬핑 마모에 미치는 영향\n(Effects of Cryogenic Temperature on Wear Behavior of 22MnB5 Under Cold Stamping)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials) ,Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ,Wear Phenomena & Mechanisms ","This paper presents the effects of cryogenic temperature on the wear behavior of 22MnB5 blank under cold stamping. After immersing the blank in liquid nitrogen (LN2) for 10 min, a strip drawing test was performed within 10 s. The hardness was measured using the Rockwell hardness test, which increased from 165 HV at 20oC to 192 HV at cryogenic temperature. The strip drawing test with 22MnB5 blank and SKD61 tool steel shows that for the different wear mechanisms on the tool surface with respect to temperature; adhesive wear is dominant at 20oC, but abrasive wear is the main mechanism at cryogenic temperature. As the friction test is repeated, sticking gradually increases on the tool surface at 20oC, whereas the scratch increases at cryogenic temperature. For the friction behavior, the friction coefficient rapidly increases when adhesive wear occurs, and it occurs more frequently at 20oC. The results for nanoindentation near the worn blank surface indicate a difference of 1.3 GPa at 20oC and 0.8 GPa at cryogenic temperature compared to the existing hardness, indicating increased deformation by friction at 20oC. This occurs because thermally activated energy available to move the dislocation decreases with decreasing temperature.","Cold stamping(냉간 스탬핑), Cryogenic(극저온), Adhesive wear(접착 마모), Abrasive wear(연마 마모)","지민기1ㆍ노연주2ㆍ강현학3ㆍ전태성4†\n1인천대학교 기계공학과 박사과정생, 2인천대학교 기계공학과 석사과정생, 3인천대학교 기계공학과 학부생, 4인천대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.6.241"]
["38권6호\npp.247-254","자외선 광을 활용하는 화학기계적 연마에 관한 연구 동향\n(Research Trends on Chemical Mechanical Polishing Using Ultraviolet Light)","Chemical Mechanical Polishing","Chemical mechanical polishing (CMP) is a hybrid surface-polishing process that utilizes both mechanical and chemical energy. However, the recently emerging semiconductor substrate and thin film materials are challenging to process using the existing CMP. Therefore, previous researchers have conducted studies to increase the material removal rate (MRR) of CMP. Most materials studied to improve MRR have high hardness and chemical stability. Methods for enhancing the material removal efficiency of CMP include additional provision of electric, thermal, light, mechanical, and chemical energies. This study aims to introduce research trends on CMP using ultraviolet (UV) light to these methods to improve the material removal efficiency of CMP. This method, photocatalysis-assisted chemical mechanical polishing (PCMP), utilizes photocatalytic oxidation using UV light. In this study, the target materials of the PCMP application include SiC, GaN, GaAs, and Ru. This study explains the photocatalytic reaction, which is the basic principle of PCMP, and reviews studies on PCMP according to materials. Additionally, the researchers classified the PCMP system used in existing studies and presented the course for further investigation of PCMP. This study aims to aid in understanding PCMP and set the direction of future research. Lastly, since there have not been many studies on the tribology characteristics in PCMP, research on this is expected to be required.","Chemical mechanical polishing(화학-기계적 연마), Ultraviolet(UV) light(자외선 광), Photocatalyst(광촉매), Research trend(연구 동향)","이현섭†\n동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2022.38.6.247"]
["38권6호\npp.255-260","의료용 폴리머 소재를 활용한 3D 프린팅 인공치아용 사면체 비정질 카본 코팅 기술 연구\n(A Study on the Tetrahedral Amorphous Carbon (ta-C) Coating on Medical Polymer Materials for 3D Printing Artificial Teeth)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","This research presents tetrahedral amorphous (ta-C) coating on the artificial tooth for improving the durability and functionality (esthtics, foreign body of tooth) by filtered cathodic vacuum arc (FCVA). A differentiated coating method is required for a ta-C coating on polymer owing to the low melting point of the polymer, inter-facial adhesion, low friction, and non-conductivity. Herein, ta-C coating is applied below 50oC, and the potential difference of the carbon plasma drawn to the substrate was controlled by applying a positive duct bias voltage without using a substrate bias voltage. Consequently, the ta-C coating with a thickness of 70nm using the duct bias condition of 20V with the highest plasma intensity satisfies the esthetics of the artificial tooth and had a 5B level of inter-facial adhesion. In addition, the composite hardness of ta-C/polymer is 380 MPa, and correlations with esthetics, sp3 bonding, and mechanical properties. The friction coefficient (CoF) of the ta-C coating in a water-lubricated environment is 0.07, showing a six-fold reduction in CoF compared with that of a polymer.","3D Printing(3D 프린팅), Medical polymer resin(의료용 폴리머 레진), Artificial teeth(인공치아), ta-C(사면체 비정질 카본), Composite hardness(복합 경도)","장영준1ㆍ김종국1ㆍ신창희2ㆍ유성미3†\n1한국재료연구원 극한소재연구소 극한환경코팅연구실 책임연구원, 2제이머티리얼즈 부설연구소 상무, 3광주보건대학교 간호학과 교수","https://doi.org/10.9725/kts.2022.38.6.255"]
["38권6호\npp.261-266","그리스 윤활하에서 레이저 표면 텍스쳐링된 그루브 빗살무늬 패턴의 사잇각에 따른 미끄럼 마찰특성 평가\n(Dependence of Sliding Friction Properties on the Angle of Laser Surface Texturing for a Grooved Crosshatch Pattern Under Grease Lubrication)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","Notably, laser surface patterning facilitates tribological applications under lubricated sliding contacts. Consequently, a special pattern that can reduce the coefficient of friction under contact is considered necessary for improved machine efficiency. However, inappropriate pattern designs produce higher friction coefficients and cannot reduce friction. In this study, we use cast iron pins as specimens to investigate their friction and wear characteristics. Moreover, we experimentally investigate the correlation between the friction reduction effect and the design of groove crosshatch patterns fabricated with various angles and widths. We conduct a friction test using a pin-on-disc type tribometer under grease lubrication to study the friction reduction effect of the specimens, and we observe that the average coefficient of friction changes with the crosshatch angle and width. The experiment reveals that grooved crosshatch specimens with a crosshatch angle of 135°maximize friction reduction. The coefficient of friction of the groove specimens with a width of 120 μm is lower than that of the specimens with a width of 200?. The friction reduction effect of the width of the groove is attributed to the density of the groove pattern. Thus, grooved crosshatch patterns can be designed to maximize friction reduction, and the friction property of a grooved crosshatch pattern is found to be related to its width and angle.","Groove crosshatch pattern(그루브 빗살무늬 패턴), Laser surface texturing(레이저 표면 텍스쳐링), Grease(그리스), Sliding friction(미끄럼 마찰)","공민선1ㆍ채영훈2†\n1경북대학교 금속신소재공학과 학부생, 2경북대학교 기계연구소 연구교수","https://doi.org/10.9725/kts.2022.38.6.261"]
["38권6호\npp.267-273","사각형 그루브로 Surface Texturing한 평행 스러스트 베어링의 열유체윤활 해석: 제1보 − 유막온도경계조건의 영향\n(THD Lubrication Analysis of a Surface-Textured Parallel Thrust Bearing with Rectangular Grooves:Part 1 − Effect of Film-Temperature Boundary Condition)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Surface texturing is the latest technology for processing grooves or dimples on the friction surface of a machine. When appropriately applied, it can reduce friction and significantly increase durability. Despite many studies over the past 20 years, most are isothermal (ISO) analyses in which the viscosity of the lubricant is constant. In practice, the viscosity changes significantly owing to the heat generated by the viscous shear of the lubricant and film-temperature boundary condition (FTBC). Although many thermohydrodynamic (THD) analyses have been performed on various sliding bearings, only few results for surface-textured bearings have been reported. This study investigates the effects of the FTBC and groove number on the THD lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves. The continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations are numerically analyzed using a commercial computational fluid dynamics code, FLUENT. The results show the pressure and temperature distributions, variations of load-carrying capacity (LCC), and friction force with four FTBCs. The FTBCs greatly influence the lubrication characteristics of surface-textured parallel thrust bearings. A groove number that maximizes the LCC exists, which depends on the FTBC. ISO analysis overestimates the LCC but underestimates friction reduction. Additional analysis of various temperature boundary conditions is required for practical applications.","Computational fluid dynamics(CFD / 전산유체역학), Film-temperature boundary condition(유막 온도경계조건), Parallel thrust bearing(평행 스러스트 베어링), Surface texturing(표면 텍스쳐링), Thermohydrodynamic lubrication(THD / 열유체 윤활)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2022.38.6.267"]
["38권6호\npp.274-280","다구찌 강건 설계를 통한 반도체 Probe상 Ti 도핑된 DLC(ta-C:Ti) 코팅 막의 전도성 및 기계적 물성 연구\n(Conductive and Mechanical Properties Study of Ti-doped DLC (ta-C:Ti) Film on Semiconductor Probe through Taguchi Bobust Design)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","There is a problem that semiconductor probe pin has a short lifespan. In order to solve this problem, Ti having excellent conductivity was doped to tetrahedral amorphous carbon (ta-C) having excellent hardness and abrasion resistance. This experiment was planned through the Taguchi robust design to determine the effect of the control factor of the ta-C:Ti coating film. The effect and contribution of control factors such as Unbalanced Magnetron Sputter(UBM) discharge current, arc discharge current, temperature, and bias voltage on ta-C:Ti characteristics were analyzed from the perspective of electrical and mechanical characteristics. The UBM discharge current was set to 4, 6, and 8 A. The main control factor of thickness and resistance is the UBM discharge current, and the thickness increased and the resistance decreased as the current increased. The decrease in resistance is due to the increase in the Ti content of the ta-C:Ti coating film. The arc discharge current was set to 60, 80, and 100 A. The main control factor of hardness and wear is the arc discharge current, and as the current rises, the hardness increases and the wear area decreases. This is due to the increased ta-C content of the ta-C:Ti coating film. Since resistance and wear are important for Probe Pin, the optimal level is set from the perspective of resistance and wear and a confirmation experiment is conducted.","Taguchi robust design(다구찌 강건 설계), ta-C:Ti(Ti 도핑 ta-C), Conductive(전도성), Hardness(경도), wear(마모)","김도영1ㆍ신준기2ㆍ장영준3ㆍ김종국3†\n1한국기술교육대학교 에너지신소재화학공학부 학부생, 2부산대학교 바이오산업기계공학과 학부생, 3한국재료연구원 극한소재연구소 극한환경코팅연구실 책임연구원","https://doi.org/10.9725/kts.2022.38.6.274"]
["38권6호\npp.281-286","Critical Shoulder Height of Raceway in Ball Bearing Considering Elastohydrodynamic Lubrication","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","In this study, the effects of Elasto-hydrodynamic lubrication pressure on the critical shoulder height of raceway in an angular contact ball bearing were investigated. Both 3D contact analyses using an influence function and the EHL analysis were conducted for the contact geometry between the ball and raceways. The pressure distributions by 3D contact analysis and EHL analysis for an example bearing were compared. The effect of ellipse truncation on the minimum film thickness also investigated from EHL analysis. The critical shoulder height in the dry contact and the EHL state were compared for various applied loads. It is shown that when the ellipse truncation occurs, the pressure spike for the EHL conjunction is higher than that for the dry contact, and its location moves more inward of the contact center. The steep pressure gradients would increase the flow rate, so in order to maintain flow continuity a significant reduction in film thickness and an abrupt rise in pressure occurs in the edge of shoulder. Significant reduction of the minimum film thickness occurs near the edge of shoulder. The critical shoulder heights in the EHL state are calculated as higher values compared with in the dry contact. This results shows that the determination of critical shoulder height by the EHL analysis is more proper.","Ball bearing, Shoulder height, EHL(Elastohydrodynamic lubrication), Minimum film thickness","Kyeongsoo Kim1 and Taewan Kim2†\n1Ph.D. Student, Special Ship Advanced Technology Center, Research Institute of Medium & Small Shipbuilding, 2Professor, Dept. of Mechanical Engineering, Pukyong National University","https://doi.org/10.9725/kts.2022.38.6.281"]
["38권6호\npp.287-290","압축수 방식 사출장치 내부 과도압력파 모의를 위한 간이 식\n(Simplified Formula for Simulating Overpressure Waves in Compressed-Water-Type Launching Device)","Marine Tribology ","Compressed-water-type launching devices convert the force from compressed water into force-launching underwater structures, such as torpedos and autonomous underwater vehicles. In particular, the overpressure wave in the launching tube is a critical design factor for the launching device. This paper presents a simplified formula for simulating overpressure waves in the launching tube of a compressed-water-type launching device. Scaled model experiments were performed to obtain actual measurement data of overpressure waves in a launching tube with varying piston speeds to examine the practical applicability of the simplified formula. The main factor of the simplified formula was estimated using an optimization technique. The time history of the overpressure waves was satisfactorily simulated using the estimated factor values and showed consistency with the measurement data. In addition, the trend of change by the piston speed of the estimated factors was reviewed, and the practical applicability was demonstrated. A systematic study of the factors influencing the overpressure waves in launching tubes will be possible using experimental data for more various conditions and the proposed simplified formula.","Compressed-water-type launching device(압축수방식 사출장치), Overpressure wave(과도압력파), Simplified formula(간이 식), Scaled model experiment(축소모형 실험)","김국현†\n동명대학교 조선해양공학과 교수","https://doi.org/10.9725/kts.2022.38.6.287"]

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["권호","제목","토픽","초록","키워드","저자","DOI"]
["39권1호\npp.1-7","화학공정용 전동기에 사용된 3D 프린팅 플라스틱 볼베어링의 내화학성 평가 및 현장적용 연구\n(Chemical Resistance and Field Trial of 3D-Printed Plastic Ball Bearing Used in Electric Motors for Chemical Processes)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Fluid pumps in chemical processes are typically driven by electric motors. Even if the motor is separated from the pump with seals, wear resulting from friction and misalignment can lead to leakage of chemical fluid, causing corrosion in the bearing supporting the motor, and, eventually, failure of the motor. It is thus a standard procedure to replace bearings at regular intervals. In this article, we propose 3D-printed plastic ball bearings for use as an alternative to commercial stainless-steel ball bearings. The plastic bearings are easy to manufacture, require less time to replace, and are chemically resistant. To validate the applicability of the plastic bearings, we first conducted chemical resistance tests. Bearings were immersed in 30 caustic acid and 30 nitric acid for 30 min and 24 h, respectively. The test results showed no corrosive damage to the bearings. A test rig was set up to compare the performance of the plastic bearings with that of the commercially equivalent deep-groove ball bearings. Loading test results showed that the plastic bearings performed as well as the commercial bearing in terms of vibration level and load-handling capability. Finally, a plastic bearing was subjected to a clean-in-place process for three months. It actually outperformed the commercial bearing in terms of chemical resistance. Thus, 3D-printed plastic bearings are a viable alternative to stainless-steel ball bearings.","3D printing(3D 프린팅), Plastic bearing(플라스틱 베어링), Chemical process(화학공정), Chemical resistance(내화학성), Field applicability(현장 적용성)","권영준1ㆍ노명규2†\n1충남대학교 대학원 메카트로닉스공학과 석사과정생, 2충남대학교 메카트로닉스공학과 교수","https://doi.org/10.9725/kts.2023.39.1.1"]
["39권1호\npp.8-12","Thermal wetting 현상이 탄소나노튜브-금속박막 계면의응착력에 미치는 영향에 관한 분자 시뮬레이션 연구\n(A Molecular Simulation on the Adhesion Control of Metal Thin Film-Carbon Nanotube Interface based on Thermal Wetting)","Modeling & Simulation in Tribology","This study presents a molecular simulation of adhesion control between carbon nanotube (CNT) and Ag thin film deposited on silicon substrate. Rough and flat Ag thin film models were prepared to investigate the effect of surface roughness on adhesion force. Heat treatment was applied to the models to modify the adhesion characteristics of the Ag/CNT interface based on thermal wetting. Simulation results showed that the heat treatment altered the Ag thin film morphology by thermal wetting, causing an increase in contact area of Ag/CNT interface and the adhesion force for both the flat and rough models changed. Despite the increase in contact area, the adhesion force of flat Ag/CNT interface decreased after the heat treatment because of plastic deformation of the Ag thin film. The result suggests that internal stress of the CNT induced by the substrate deformation contributes in reduction of adhesion. Contrarily, heat treatment to the rough model increases adhesion force because of the expanded contact area. The contact area is speculated to be more influential to the adhesion force rather than the internal stress of the CNT on the rough Ag thin film, because the CNT on the rough model contains internal stress regardless of the heat treatment. Therefore, as demonstrated by simulation results, the heat treatment can prevent delamination or wear of CNT coating on a rough metallic substrate by thermal wetting phenomena.","Adhesion(점착), Contact area(접촉 면적), Heat treatment(열처리), Molecular simulation(분자 시뮬레이션), Surface roughness(표면 거칠기)","이상훈1ㆍ김현준2,3†\n1경북대학교 대학원 미래과학기술융합학과 석사과정생, 2경북대학교 미래과학기술융합학과 부교수, 3경북대학교 정밀기계공학과 부교수","https://doi.org/10.9725/kts.2022.39.1.8"]
["39권1호\npp.13-20","Enhancement of Wear Resistance of CoCrNiAlTi Plasma Sprayed Coatings Using Titanium Carbide","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Large drill bits may face high hardness ore and high working pressure when working. To optimize the use effect of large drill bits and prolong the use time, it is necessary to add a layer of pressure-resistant, wear-resistant, and low-friction coating on the surface of the drill bit. In this study, CoCrNiAlTi high-entropy alloy coatings and CoCrNiAlTi (70 wt%)-TiC (30 wt%) composite coatings are successfully prepared on Q235 steel by plasma spraying. The CoCrNiAlTi (70 wt%)-TiC (30 wt%) coating consists of FCC solid solution and a small amount of TiC phase. The effect of TiC on the composition phase, microhardness, and elastic modulus of HEA coating is studied by X-ray diffractometer (XRD) and microhardness tester. The effect of TiC on the friction and wear properties of HEA coatings is investigated using a wear tester. By improving the process parameters, the metallurgical bonding between the coating and the substrate is well combined, and a coating without pores and cracks is obtained. The experimental results confirm that the microhardness, elastic modulus, and wear resistance of CoCrNiAlTi-TiC composite coating are better, and the friction coefficient is lower.","High-entropy alloy, Coating, Composite, Plasma spray, Wear","De-Yong Li1 and Chul-Hee Lee2†\n1Master student, Dept. of Mechanical Engineering, Inha University, 2Professor, Dept. of Mechanical Engineering, Inha University","https://doi.org/10.9725/kts.2023.39.1.13"]
["39권1호\npp.21-27","사각형 그루브로 Surface Texturing한 평행 스러스트 베어링의 열유체윤활 해석: 제2보 - 그루브 깊이의 영향\n(THD Lubrication Analysis of a Surface-Textured Parallel Thrust Bearing with Rectangular Grooves: Part 2 - Effect of Groove Depth)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","Surface texturing is widely applied to friction surfaces of various machine elements. Most of the theoretical studies have focused on isothermal (ISO) analyses which consider constant lubricant viscosity. However, there have been limited studies on the effect of oil temperature increase owing to viscous shear. Following the first part of the present study that investigated the effects of film-temperature boundary condition (FTBC) and groove number on the thermohydrodynamic (THD) lubrication characteristics of a surface-textured parallel thrust bearing with multiple rectangular grooves, this study focuses on the effect of groove depths. Current study numerically analyzes the continuity, Navier-Stokes, and energy equations with temperature-viscosity-density relations using a commercial computational fluid dynamics (CFD) software, FLUENT. The results of variation in temperature, velocity, and pressure distributions as well as load-carrying capacity (LCC) and friction force indicate that groove depth and FTBC significantly influence the temperature distribution and pressure generation. The LCC is maximum near the groove depth at which the vortex starts, smaller than the ISO result. For intense grooves, the LCC of THD may be larger than that from ISO. The frictional force decreases as the groove becomes deeper, and decreases more significantly in the case of THD. The study shows that groove depth significantly influences the THD lubrication characteristics of surface-textured parallel thrust bearings.","Computational fluid dynamics(CFD/전산유체역학), Film-temperature boundary condition(유막온도경계조건), Parallel thrust bearing(평행 스러스트 베어링), Thermohydrodynamic lubrication(THD)(열유체 윤활), Surface texturing(표면 텍스쳐링)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2023.39.1.21"]
["39권1호\npp.28-34","다공질 공기 베어링을 적용한 반도체 웨이퍼 연마용 스핀들 개발\n(Development of Wafer Grinding Spindle with Porous Air Bearings)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Because of their cleanliness, low friction, and high stiffness, aerostatic bearings are used in numerous applications. Aerostic bearings that use porous materials as means of flow restriction have higher stiffness than other types of bearings and have been successfully applied as guide bearings, which have high motion accuracy requirements. However, the performances of porous bearings exhibit strong nonlinearity and can vary considerably depending on design parameters. Therefore, accurate prediction of the performance characteristics of porous bearings is necessary or their successful application. This study presents a porous bearing design and performance analysis for a spindle used in wafer polishing. The Reynolds and Darcy flow equations are solved to calculate the pressures in the lubrication film and porous busing, respectively. To verify the validity of the proposed analytical model, the calculated pressure distribution in the designed bearing is compared with that derived from previous research. Additional parametric studies are performed to determine the optimal design parameters. Analytical results show that optimal design parameters that obtain the maximum stiffness can be derived. In addition, the results show that cross-coupled stiffness increases with rotating speed. Thus, issues related to stability should be investigated at the design stage.","Aerostatic bearing(공기 베어링), Porous bearing(다공질 베어링), Spindle(스핀들)","이동현1†ㆍ김병옥1ㆍ전병찬2ㆍ허균철3ㆍ김기수4\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2한국기계연구원 시스템다이나믹스연구실 선임기술원, 3한국기계연구원 시스템다이나믹스연구실 선임연구원, 4카스윈㈜ 기술연구소 이사","https://doi.org/10.9725/kts.2023.39.1.28"]
["39권2호\npp.35-42","시간에 따른 회전 및 하중을 고려한 강체 동역학 해석에기반한 베어링 성능 평가\n(Bearing Performance Evaluation Based on Rigid Body Dynamic Analysis Considering Rotation and Loads Over Time)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Bearing is a mechanical component that supports loads and transmits rotation. As the application of high-value-added products such as semiconductors, aviation, and robots have recently become diverse and more precise, an accurate bearing performance prediction and evaluation technology is required. Bearing performance evaluation can be divided into evaluations based on bearing theory and on numerical analysis. An evaluation based on numerical analysis is a technique that has been highlighted because the problems that remained unsolved owing to time problems can be solved through recent developments in computers. However, current studies have the disadvantage of not considering the essential changes over time and bearing rotation. In this study, bearing performance evaluation based on rigid body dynamic analysis considering rotation and load over time is performed. Rigid body dynamic analysis is performed for deep groove ball bearing to calculate the load applied by the ball. The reliability of the analysis is verified by comparing it with the results calculated using bearing theory. In addition, rigid body dynamic analysis is performed for automotive wheel bearings to calculate the contact angle and load applied by the ball for cases where axial load and radial load are applied, respectively. The effect of rotation and load over time is evaluated from these results.","Bearing(베어링), Dynamic analysis(동역학 해석), Rotation(회전), Rigid body(강체), Numerical analysis(수치해석)","이승표†\n㈜일진글로벌 기술연구소 이사","https://doi.org/10.9725/kts.2023.39.2.35"]
["39권2호\npp.43-48","Lubricating Effect of Water-soluble Hexagonal Boron Nitride Nanolubricants on AISI 304 Steel Sliding Pair","Lubrication (Lubricants & Additives) ,Wear Phenomena & Mechanisms ","In this study, we investigate the tribological behavior of AISI 304 stainless steel pairs under deionized water and hexagonal boron nitride (h-BN) water dispersion lubrication. The specimen friction and wear properties are evaluated using a reciprocating ball-on-flat tribometer. The coefficient of friction remains nearly constant throughout the test under both lubricant conditions. The wear depth of the specimens under h-BN lubrication is smaller than that under deionized water lubrication, indicating the inhibition behavior of h-BN nanolubricants on direct metal–metal contacts. Optical micrographs and stylus profilometer measurements are performed to evaluate the severity of damage caused by the sliding motion and to determine the wear morphology of the specimens, respectively. The results show that h-BN nanolubricants does not have a significant effect on the friction behavior but demonstrates reduced wear owing to their trapping effect between the sliding interfaces. Moreover, scanning electron microscopy and energy-dispersive X-ray spectroscopy images of the specimens were acquired to confirm the trapping effect of h-BN between the sliding interfaces. The results also suggest that the trapped lubricants can distribute the contact pressure, reducing the wear damage caused by the metal–metal contact at the interface. In conclusion, h-BN nanolubricants have potential as an anti-wear additive for lubrication applications. Further investigation is needed to provide direct evidence of the trapping effect of h-BN nanoparticles between the sliding interfaces. These findings could lead to the development of more efficient and effective lubricants for various industrial applications.","Reciprocating sliding, Aqueous additive, Nanolubricant, AISI 304 steel","Gowtham Balasubramaniam1 and Dae-Hyun Cho2,3†\n1Ph.D. Student, Department of Computer Mechatronics Engineering, Gyeongsang National University, 2Associate Professor, Department of Mechatronics Enigneering, Gyeongsang National University, 3Associate Professor, Department of Energy System Engineering, Gyeongsang National University","https://doi.org/10.9725/kts.2023.39.2.43"]
["39권2호\npp.49-55","메탄올 첨가에 따른 Ni 기반 합금의 트라이볼로지 특성 변화에 대한 실험적 연구\n(Experimental Assessment of the Methanol Addition Effect on the Tribological Characteristics of Ni-based Alloy)","Wear Phenomena & Mechanisms","Currently, the demand for green technologies toward a sustainable future is rapidly increasing due to growing concern over environmental issues. Methanol is biodegradable and can provide clean combustion to reduce sulfur oxide and nitrogen oxide emissions, and therefore it is a candidate fuel for marine engines. However, the effect of methanol on tribological characteristic degradation should be addressed for methanol-fueled engines. In this study, the methanol addition effects on tribological characteristic degradation is experimentally assessed using a pin-on-disk tribo-tester. Ni-based alloy is used as a target material due to its broad applicability as an engine component material. For a lubricant, engine oil with and without methanol are used. The tests are conducted for up to 10,000 cycles under boundary lubrication while the change in friction force is monitored. Additionally, the wear rate is determined based on laser scanning confocal microscope data. An additional test in which methanol is added at regular intervals is performed with an aim to directly observe its effect on friction. Overall, the friction coefficient increases slightly with increasing methanol concentration. Furthermore, the wear rate of the pin and disk increase significantly with methanol addition. The results also indicate that the friction increases instantaneously with methanol addition at the contacting interface. These findings may be useful for better understanding the methanol effect on the tribological characteristics of Ni-based alloys for methanol-fueled engines with improved performance.","Friction(마찰), Methanol(메탄올), Ni-based alloy(Ni 기반 합금), Wear rate(마모율)","최준민1*ㆍ박상문1*ㆍ김영준1ㆍ김성훈1ㆍ김혜민1ㆍ박정언1ㆍ유정원1ㆍ이명규1ㆍ이현우1ㆍ정구현2†\n1울산대학교 기계공학부 학사과정생, 2울산대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.49"]
["39권2호\npp.56-60","경사 돌기 표면의 젖음 특성 평가\n(Hydrophobicity Evaluation of Oblique Micro-asperities Structures)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","In this study, we evaluate the anisotropic flow of droplets according to the directionality of asperities. We manufacture a mold with an inclined hole by adjusting the jig angle using a high-power diode laser. Using the manufactured mold, we prepare specimens for wettability studies by the micro molding technique. We fabricate twelve kinds of surfaces with micro-asperities inclined at 0°, 15°, 30°, and 45° for asperity pitches of 100 μm, 200 μm, and 300 μm. We evaluate the static and dynamic behaviors of the droplets as a function of the asperities pitch and inclination angles. The anisotropic effect increases as the pitch increases between asperities, and the anisotropic flow characteristics increase as the inclination angle of the asperities increases. On the surface with hole pitches of 100 μm and 200 μm, the contact angle of the droplet shows high hydrophobicity at approximately 160°, but on the surface with the 300-μm hole pitch, the contact angle is approximately 110°, indicating that the hydrophobic effect rapidly reduces. Additionally, when the inclination angle of the asperities is approximately 30°, the left and right contact angle deviations of the droplet are the lowest, showing that the roll-off angle is relatively low.","Hydrophobic surface(소수성 표면), Anisotropic flow(이방성 흐름), Asperity(돌기)","백승익1ㆍ김태완2†\n1부경대학교 대학원 지능로봇공학과 석사과정생, 2부경대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.56"]
["39권2호\npp.61-71","누설유량과 회전체동역학적 성능을 고려한 래버린스 씰 설계\n(Labyrinth Seal Design Considering Leakage Flow Rate and Rotordynamic Performance)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study proposes a procedure for designing a labyrinth seal that meets both leakage flow rate and rotordynamic performance criteria (effective damping, amplification factor, separation margin, logarithmic decrement, and vibration amplitude). The seal is modeled using a one control volume (1CV) bulk flow approach to predict the leakage flow rate and rotordynamic coefficients. The rotating shaft is modeled with the finite element (FE) method and is assumed to be supported by two linearized bearings. Geometry, material and operating conditions of the rotating shaft, and the supporting characteristics of the bearings were fixed. A single labyrinth seal is placed at the center of the rotor, and the linearized dynamic coefficients predicted by the seal numerical model are inserted as linear springs and dampers at the seal position. Seal designs that satisfy both leakage and rotordynamic performance are searched by modifying five seal design parameters using the multi-grid method. The five design parameters include pre-swirl ratio, number of teeth, tooth pitch, tooth height and tooth tip width. In total, 12500 seal models are examined and the optimal seal design is selected. Finally, normalization was performed to select the optimal labyrinth seal designs that satisfy the system performance requirements.","Labyrinth seal(래버린스 씰), Dynamic coefficient(동특성 계수), Leakage flow(누설유량), Bulkflow model(벌크플로우 모델), FE model(유한요소 모델)","문민주1ㆍ이정인2ㆍ서준호3†\n1부산대학교 대학원 기계공학부 기계시스템설계전공 석사과정생, 2부산대학교 대학원 기계공학부 기계시스템설계전공 박사과정생, 3부산대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2023.39.2.61"]
["39권2호\npp.72-75","SiO2/TiO2 혼합입자 슬러리 SiC CMP의 재료제거율 모델링\n(Material Removal Rate Modeling of SiO2/TiO2 Mixed-Abrasive Slurry CMP for SiC)","Chemical Mechanical Polishing ","Silicon carbide (SiC) is used as a substrate material for power semiconductors; however, SiC chemical mechanical polishing (CMP) requires considerable time owing to its chemical stability and high hardness. Therefore, researchers are attempting to increase the material removal rate (MRR) of SiC CMP using various methods. Mixed-abrasive CMP (MAS CMP) is one method of increasing the material removal efficiency of CMP by mixing two or more particles. The aim of this research is to study the mathematical modeling of the MRR of MAS CMP of SiC with SiO2 and TiO2 particles. With a total particle concentration of 32 wt, using 80-nm SiO2particles and 25-nm TiO2 particles maximizes the MRR at 8 wt of the TiO2 particle concentration. In the case of 5 nm TiO2 particles, the MRR tends to increase with an increase in TiO2 concentration. In the case of particle size 10-25 nm TiO2, as the particle concentration increases, the MRR increases to a certain level and then decreases again. TiO2 particles of 25 nm or more continuously decreased MRR as the particle concentration increased. In the model proposed in this study, the MRR of MAS CMP of SiC increases linearly with changes in pressure and relative speed, which shows the same result as the Preston's equation. These results can contribute to the future design of MAS; however, the model needs to be verified and improved in future experiments.","Chemical mechanical polishing(CMP), Mixed-abrasive slurry(MAS), Silicon dioxide(SiO2), Titanium oxide(TiO2), Silicon carbide(SiC)","이현섭†\n동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2023.39.2.72"]
["39권2호\npp.76-80","냉각 유량이 가스 포일 스러스트 베어링의 성능에 미치는 영향\n(Effects of Cooling Flow Rate on Gas Foil Thrust Bearing Performance)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper describes an experimental investigation of the effect of cooling flow rate on gas foil thrust bearing (GFTB) performance. In a newly developed GFTB test rig, a non-contact type pneumatic cylinder provides static loads to the test GFTB and a high-speed motor rotates a thrust runner up to the maximum speed of 80 krpm. Force sensor, torque arm connected to another force sensor, and thermocouples measures the applied static load, drag torque, and bearing temperature, respectively, for cooling flow rates of 0, 25, and 50 LPM at static loads of 50, 100, and 150 N. The test GFTB with the outer radius of 31.5 mm has six top foils supported on bump foil structures. During the series of tests, the transient responses of the bearing drag torque and bearing temperature are recorded until the bearing temperature converges with time for each cooling flow rate and static load. The test data show that the converged temperature decreases with increasing cooling flow rate and increases with increasing static load. The drag torque and friction coefficient decrease with increasing cooling flow rate, which may be attributed to the decrease in viscosity and lubricant (air) temperature. These test results suggest that an increase in cooling flow rate improves GFTB performance.","Cooling flow rate(냉각 유량), Drag torque(마찰 토크), Friction coefficient(마찰 계수), Gas foil thrust bearing(가스 포일 스러스트 베어링)","황성호1ㆍ김대연2ㆍ김태호3†\n1국민대학교 기계공학부 박사후연구원, 2LG이노텍 Actuator 선행개발팀 사원, 3국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.76"]
["39권2호\npp.81-85","표면 거칠기가 가스 포일 스러스트 베어링의 성능에 미치는 영향\n(Effects of Surface Roughness on the Performance of a Gas Foil Thrust Bearing)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study presents an experimental investigation of the effects of surface roughness on gas foil thrust bearing (GFTB) performance. A high-speed motor with the maximum speed of 80 krpm rotates a thrust runner and a pneumatic cylinder applies static loads to the test GFTB. When the motor speed increases and reaches a specific speed at which a hydrodynamic film pressure generated within the gap between the thrust runner and test GFTB is enough to support the applied static load, the thrust runner lifts off from the test GFTB and the friction mechanism changes from the boundary lubrication to the hydrodynamic lubrication. The experiment shows a series of lift-off test and load-carrying capacity test for two thrust runners with different surface roughnesses. For a constant static load of 15 N, thrust runner A with its lower surface roughness exhibits a higher start-up torque but lower lift-off torque than thrust runner B with a higher surface roughness. The load capacity test at a rotor speed of 60 krpm reveals that runner A results in a higher maximum load capacity than runner B. Runner A also shows a lower drag torque, friction coefficient, and bearing temperature than runner B at constant static loads. The results imply that maintaining a consistent surface roughness for a thrust runner may improve its static GFTB performance.","Gas foil thrust bearing(가스 포일 스러스트 베어링), Surface roughness(표면 조도), Load capacity(하중지지력), Friction coefficient(마찰 계수)","황성호1ㆍ김대연2ㆍ김태호3†\n1국민대학교 기계공학부 박사후연구원, 2LG이노텍 Actuator 선행개발팀 사원, 3국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.2.81"]
["39권3호\npp.87-93","나노윤활유를 사용하는 평행 슬라이더 베어링의 윤활해석\n(Lubrication Analysis of Parallel Slider Bearing with Nanolubricant)","Lubrication (Lubricants & Additives), Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","Nanofluids are dispersions of particles smaller than 100 nm (nanoparticles) in base fluids. They exhibit high thermal conductivity and are mainly applied in cooling applications. Nanolubricants use nanoparticles in base oils as lubricant additives, and have recently started gathering increased attention owing to their potential to improve the tribological and thermal performances of various machinery. Nanolubricants reduce friction and wear, mainly by the action of nanoparticles; however, only a few studies have considered the rheological properties of lubricants. In this study, we adopt a parallel slider bearing model that does not generate geometrical wedge effects, and conduct thermohydrodynamic (THD) analyses to evaluate the effect of higher thermal conductivity and viscosity, which are the main rheological properties of nanolubricants, on the lubrication performances. We use a commercial computational fluid dynamics code, FLUENT, to numerically analyze the continuity, Navier-Stokes, energy equations with temperature-viscosity-density relations, and thermal conductivity and viscosity models of the nanolubricant. The results show the temperature and pressure distributions, load-carrying capacity (LCC), and friction force for three film-temperature boundary conditions (FTBCs). The effects of the higher thermal conductivity and viscosity of the nanolubricant on the LCC and friction force differ significantly, according to the FTBC. The thermal conductivity increases with temperature, improving the cooling performance, reducing LCC, and slightly increasing the friction. The increase in viscosity increases both the LCC and friction. The analysis method in this study can be applied to develop nanolubricants that can improve the tribological and cooling performances of various equipment; however, additional research is required on this topic.","Nanolubricant(나노윤활유), Slider bearing(슬라이더 베어링), Thermohydrodynamic lubrication(THD/열유체윤활), Thermal wedge effect(열쐐기효과), Computational fluid dynamics (CFD/전산유체역학)","박태조1†ㆍ강정국2\n1경상국립대학교 기계공학부 교수 · 공학연구원, 2경상국립대학교 대학원 기계항공공학부 석사과정","https://doi.org/10.9725/kts.2023.39.3.87"]
["39권3호\npp.94-101","수명과 강성을 고려한 자동차용 휠 베어링의 설계 최적화\n(Design Optimization for Automotive Wheel Bearings Considering Life and Stiffness)","Automotive Tribology","Automotive wheel bearings are a critical component of vehicles that support their weight and facilitate rotation. Life and stiffness are significant performance characteristics of wheel bearings. Designing wheel bearings involves finding optimal design variables that satisfy both performances. CO2 emission reduction and fuel efficiency regulations attribute to the recent increase in design requirements for lightweight and compact automotive parts while maintaining performance. However, achieving a design that maintains performance while reducing weight poses challenges, as performance and weight are generally inversely proportional. In this study, we perform design optimization of automotive wheel bearings considering life and stiffness. We develop a program that calculates the basic rated life and modified rated life based on international standards for evaluating the life of wheel bearings. We develop a regression equation using regression analysis to address the time-consuming stiffness analysis during repetitive analysis. We perform ANOVA and main effect analyses to understand the statistical characteristics of the developed regression equation. Furthermore, we verify its reliability by comparing the predicted and test results. We perform design optimization using the developed life prediction program, stiffness regression equation and weight regression equation. We select bearing specifications and geometry as design variables, weight as the cost function, and life and stiffness as constraints. Through design optimization, we investigate the influence of design variables on the cost function and constraints by comparing the initial and optimal design values.","Automotive wheel bearing(자동차용 휠 베어링), Optimization(최적설계), Bearing design(베어링 설계), Bearing life(베어링 수명), Bearing stiffness(베어링 강성)","이승표†\n(주)일진글로벌 기술연구소 이사","https://doi.org/10.9725/kts.2023.39.3.94"]
["39권3호\npp.102-110","탄성변형으로 인한 틸팅패드 저널베어링의 예압 변화\n(Elastic Deformation Induced Preload Change in Tilting Pad Journal Bearing)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study aims to quantify the variation in the performance of a tilting pad journal bearing (TPJB) owing to the elastic deformation of its pad. To this end, we first defined a parameter, “elastic preload”, and predicted the changes in the performance of the TPJB, as a function of the preload amount. We used the iso-viscosity Reynolds equation, which ignores the temperature rise due to viscous shear in thin films, and the resultant thermal deformation of the bearing structure. We employed a three-dimensional finite element model to predict the elastic deformation of the bearing pad, and a transient analysis, to converge to a static equilibrium condition of the flexible pads and journal. Conducting a modal coordinate transformation helped us avoid heavy computational issues arising from a mesh refinement in the three-dimensional finite element pad model. Moreover, we adopted the Hertzian contact model to predict the elastic deformation at the pivot location. With the aforementioned overall strategy, we predicted the performance changes owing to the elastic deformation of the pad under varying load conditions. From the results, we observed an increase in the preload due to the pad elastic deformation.","Dynamic performance(동적 성능), Elastic preload(탄성 예압), Elastic deformation(탄성 변형), Static performance(정적 성능), Tilting pad journal bearings(틸팅패드 저널 베어링)","이동현1ㆍ서준호2†\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2부산대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2023.39.3.102"]
["39권3호\npp.111-117","나노 CuO입자로 충진된 PTFE 나노복합소재의 저속 및 하중 조건에서의 트라이볼로지 특성에 관한 연구\n(A Study on the Tribological Characteristics of PTFE Composites-filled with Nano CuO Particles Under a Slow Sliding Speed and Low Load Condition)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","This paper presents an experimental investigation of the tribological characteristics of PTFE composites filled with nano CuO particles under low sliding speed and load. All the specimens were prepared by sintering. Before sintering, the mixture of PTFE powder and CuO particles were mixed by a high-speed mixer using CuO volume fractions of 0.2 vol. % and 5 vol. %. Each mixture was sintered at 350 °C for 30 min on the steel disk. We conducted ball-on-disk sliding test an hour using a steel ball against PTFE composites, including pure PTFE. The load and sliding speed used was 2 N and 0.01 m/s, respectively. Adding nano CuO particles increases the friction coefficient because of the abrasiveness of hard nano CuO particles. The highest coefficient of frictions was obtained from 5 vol. % CuO. Conversely, the lowest wear of the composites was obtained from the 5 vol. % CuO nanocomposite. This study reveals that the addition of nano CuO particles can lower the wear of PTFE, despite an increase in the coefficient of friction. However, the coefficient friction is still moderate compared to other engineering polymers. In addition, the amount of CuO nano particles has to be optimized to reduce friction and wear at the same time.","PTFE(테플론), Nanocomposite(나노복합재료), Nano particles(나노 입자), Nano CuO filler(나노 산화구리 충진재), Sintering(소결)","조민행1†ㆍ김정환2\n1중앙대학교 기계공학부 교수, 2중앙대학교 대학원 기계공학과 석사과정생","https://doi.org/10.9725/kts.2023.39.3.111"]
["39권3호\npp.118-122","Finite Element Model for Wear Analysis of Conventional Friction Stir Welding Tool","Tribology Applications (Industrial Case Studies)","In our study, we develop a finite element model based on Archard's wear law to predict the cumulative wear and the evolution of the tool profile in friction stir welding (FSW) applications. Our model considers the rotational and translational behaviors of the tool, providing a comprehensive description of the wear process. We validate the accuracy of our model by comparing it against experimental results, examining both the predicted cumulative wear and the resulting changes to the tool profile caused by wear. We perform a detailed comparison between the predictions of the model and experimental data by manipulating non-dimensional coefficients comprising model parameters, such as element sizes and time increments. This comparison facilitates the identification of a specific non-dimensional coefficient condition that best replicates the experimentally observed cumulative wear. We also directly compare the worn tool profiles predicted by the model using this specific non-dimensional coefficient condition with the profiles obtained from wear experiments. Through this process, we identify the model settings that yield a tool wear profile closely aligning with the experimental results. Our research demonstrates that carefully selecting non-dimensional coefficients can significantly enhance the predictive accuracy of finite element models for tool wear in FSW processes. The results from our study hold potential implications for enhancing tool longevity and welding quality in industrial applications.","Frictional stir welding, Finite element analysis, Tool wear, Archard’s wear law, Experiment valida","Hyeonggeun Jo1, Ilkwang Jang2, Yeong Gil Jo3, Dae Ha Kim4 and Yong Hoon Jang5†\n1Ph.D. Student, Graduate School, Dept. of Mechanical Engineering, Yonsei University, 2Research Professor, Dept. of Mechanical Engineering, Yonsei University, 3Researcher, Advanced Welding & Joining R&D Group, Korea Institute of Industrial Technology, 4Managing Director, KONASOL R&D Center, KONASOL, 5Professor, Dept. of Mechanical Engineering, Yonsei University","https://doi.org/10.9725/kts.2023.39.3.118"]
["39권4호\npp.123-132","항공용 고속 롤러베어링의 냉각 방식에 따른 작동간극 변화\n(Variation of Operating Clearance Depending on Cooling Methods of High-Speed Roller Bearings for Aerospace Applications)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","In this study, the expansion, stress, and operating clearance of bearing elements during operation are observed using the inner/outer ring temperature test data of a 3.0×106 DN-class roller bearing. The operating clearance characteristics of inner-/outer-ring cooling (IORC) bearings are compared to those of inner-ring cooling (IRC) bearings. For IRC bearings, the thermal expansion of the outer ring is the most important factor in clearance variation. As a result, the operating clearance is less than the initial clearance of 61 μm, and the operating clearance decreases to 0.5 μm at 25,500 rpm. Conversely, the temperature of the outer ring of IORC bearings is lower than that of IRC bearings, so the operating clearance is kept smaller. When the coolant flow rate to the outer ring is approximately 1.5 to 2.0 L/min, the temperature difference between the inner and outer rings is minimized and the operating clearance is maintained at a significantly lower level than IRC bearings. Small operating clearances are expected to be effective in reducing cage slip and skid damage in roller bearings. The results and analysis procedures of this study can be utilized to design of bearing clearance, lubricant flow rate, and assembled interference in the early design stage of aerospace roller bearings.","Rolling element bearings(구름요소 베어링), Bearing clearance(베어링 간극), Bearing cooling(베어링 냉각)","박지수†\n국방과학연구소 항공기술연구원 연구원","https://doi.org/10.9725/kts.2023.39.4.123"]
["39권4호\npp.133-138","윤활유 필터의 종류 및 특징\n(Types and Characteristics of Lubricant Filters)","Tribo-Testing / Measurement & Instruments","This paper presents a discussion on lubricating oil filters. The maintenance of lubricating oil filters can improve the performance of mechanical systems and extend the service life of the lubricating oil. Therefore, the effective management of the lubricating oil can extend the service life of the machine and reduce maintenance costs. A representative method for managing lubricating oil is filtering the lubricating oil using a lubricant filter. However, effectively managing a lubricating oil using a lubricant filter requires an understanding of the related knowledge. In this paper, we present the definition, classification, characteristics, specifications, performance, and self-cleaning function of lubricating oil filters. The lubricant filters are classified based on the filter material, filtering method, filtering location, and amount of filtered fluid. Cellulose and glass fiber materials are conventionally used as materials for lubricant filters, and recently, metal materials, which show excellent durability, are being increasingly adopted. The filtering methods can be classified into physical, chemical, magnetic, and electric field methods, and the lubricant filters can be classified according to their location in the lubrication system. The beta ratio and efficiency of the lubricant filter can be determined based on the performance of the filter. Finally, there are many products or technologies that add a self-cleaning function to the filter to remove foreign substances or contaminants for efficient management.","Lubricant filter(윤활유 필터), Filtering(필터링), Self-cleaning(자가 세정), Efficiency(포집효율)","홍성호1†ㆍ신주용2ㆍ박태성2ㆍ이상후2\n1동국대학교 창의융합공학부 기계시스템공학전공 부교수, 2동국대학교 창의융합공학부 기계시스템공학전공 학부생","https://doi.org/10.9725/kts.2023.39.4.133"]
["39권4호\npp.139-147","공동현상 모델에 따른 침수형 평면 저널베어링의 동특성 및 회전 안정성에 대한 연구\n(Dynamic Characteristics and Instability of Submerged PlainJournal Bearings in accordance with the Cavitation Model)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","Cavitation phenomena observed during the operation of a submerged plain journal bearing (PJB) can affect bearing performance parameters such as dynamic coefficients, whirl frequency ratio, and critical mass. This study presents numerical solutions of the Reynolds equation for steadily and dynamically loaded submerged PJBs with half-Sommerfeld (HS), Reynolds, and Jakobsson-Floberg-Olsson (JFO) cavitation models when the supply pressure is larger or equal to the cavitation pressure. The loads at various eccentricity ratios are identical; however, the attitude angle is approximately 6% smaller when the eccentricity ratio is between 0.2 and 0.7 and the JFO model is used, compared to that when the Reynolds model is used. Dynamic coefficients obtained with the HS and Reynolds model show good agreement with each other, except for kxz, which is sensitive to changes in the force normal to the rotor weight, and is attributed to the difference in the attitude angle obtained with each cavitation model. Stiffness coefficients are determined using the pressure distribution in the film, and therefore, when the JFO model is used, the direct stiffness coefficients are affected and show opposite signs for most eccentricity ratios. The mass-conservative JFO model can predict at least a 30% smaller critical mass compared to that using the HS and Reynolds models. Thus, the instability analysis results can change based on the cavitation model used in a submerged PJB. The results of this research indicate that the JFO model should be used when designing a rotor system supported by submerged PJBs.","Dynamic coefficient(동특성 계수), JFO cavitation theory(JFO 공동 이론), Plain journal bearing(평면 저널베어링), Rotating stability(회전 안정성), Submerged(침수형)","최문호†\n한국수력원자력 중앙연구원 기계연구소 선임연구원","https://doi.org/10.9725/kts.2023.39.4.139"]
["39권4호\npp.148-153","레이저 표면 딤플 패턴된 PMMA 소재 표면의 식염수 윤활 하에서의 미끄럼 마찰특성\n(Sliding Friction Properties of Laser Surface Dimple Patternedon PMMA under Saline Lubricated)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","Laser surface dimple patterning is a method of laser surface texturing to reduce lubrication sliding friction. The dimple pattern improves friction properties by reserving lubricant and trapping worn particles. This surface texturing technology can reduce coefficients of friction and extend the service life by applying a uniform load to the surface of the material. This study investigates the friction properties using PMMA, a highly compatible polymer material, as a specimen. We observe the friction properties of untextured specimens by processing specimens with dimple pattern densities of 5 and 10 on the surface area using laser. Dimple pattern density affects the coefficient of friction. We present the following friction property results using a pin-on-disc sliding friction test under saline lubrication. The coefficients of friction for the dimple patterned specimens are lower than those for the untextured specimens. As the normal load and sliding speed increase, the coefficients of friction of the dimple pattern specimens decrease differently from those of the untextured specimens. The specimen with a dimple pattern density of 5 at a normal load of 24.5 N and a sliding speed of 0.22 m/s has the best friction properties. Notably, different friction properties are exhibited depending on the dimple pattern densities.","Dimple pattern(딤플 패턴), Laser surface texturing(레이저 표면 텍스쳐링), Polymethyl methacrylate(PMMA), Saline(식염수), Sliding friction(미끄럼 마찰)","현동호1ㆍ채영훈2ㆍ정다이3†\n1경북대학교 고분자공학과 학부생, 2경북대학교 기계연구소 교수, 3대구보건대학교 치기공과 교수","https://doi.org/10.9725/kts.2023.39.4.148"]
["39권4호\npp.154-166","복열테이퍼 롤러베어링 지지특성에 따른 오버헝 회전축시스템의 동적 거동 예측 및 접촉부 압력 해석\n(Prediction of the Dynamic behavior and Contact Pressure of Overhung Rotor Systems According to the Support Characteristics of Double-row Tapered Roller Bearings)","Contact Mechanics & Friction ,Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","This study establishes a numerical analysis model of the finite element overhung rotor supported by a DTRB and describes the stiffness properties of the DTRB. The vibration characteristics and contact pressure of the RBR system are predicted according to the DTRB support characteristics such as the initial axial compression and roller profile. The stiffness of the DTRB significantly varies depending on the initial axial compression and external load owing to the occurrence of rollers under the no-load condition and increase in the Hertz contact force. The increase in the initial axial compression increases the rigidity of the DTRB, thereby reducing the displacement of the RBR system and simultaneously increasing the natural frequency. However, above a certain initial axial compression, the effect becomes insignificant, and an excessive increase in the initial axial compression increases the contact pressure. The roller crowning radius, which gives a curvature in the longitudinal direction of the roller, decreases the displacement of the RBR system and increases the natural frequency as the value increases. However, an increase in the crowning radius increases the edge stress, causing a negative effect in terms of the contact pressure. These results show that the DTRB support characteristics required for reducing the vibration and contact pressure of the RBR system supported by the DTRB can be designed.","Contact pressure(접촉 압력), Double-row tapered roller bearing(복열테이퍼 롤러베어링), Edge effect(모서리 효과), Rolling bearing-Rotor(구름 베어링-로터), Roller profile(롤러 프로파일)","김태우1ㆍ서준호2ㆍ김민수3ㆍ유용훈4†\n1HD한국조선해양 혁신기계시스템연구실 연구원, 2부산대학교 기계공학과 부교수, 3한국철도기술연구원 도시철도연구실 책임연구원, 4한국철도기술연구원 국제철도연구실 선임연구원","https://doi.org/10.9725/kts.2023.39.4.154"]
["39권5호\npp.167-172","α-티타늄 평판표면에서 강체 구형팁의 스크래치로 인한 내부 결정구조 특성 변화에 대한 연구\n(A Study on Crystalline Structural Variations of the Rigid Spherical-Tip scratch on the Surface of α-Titanium substrates via Molecular Dynamics Simulations)","Micro/Nano-Tribology ,Modeling & Simulation in Tribology ","Titanium alloys are widely recognized among engineering materials owing to their impressive mechanical properties, including high strength-to-weight ratios, fracture toughness, resistance to fatigue, and corrosion resistance. Consequently, applications involving titanium alloys are more susceptible to damage from unforeseen events, such as scratches. Nevertheless, the impact of microscopic damage remains an area that requires further investigation. This study delves into the microscopic wear behavior of α-titanium crystal structures when subjected to linear scratch-induced damage conditions, utilizing molecular dynamics simulations as the primary methodology. The configuration of crystal lattice structures plays a crucial role in influencing material properties such as slip, which pertains to the movement of dislocations within the crystal structure. The molecular dynamics technique surpasses the constraints of observing microscopic phenomena over brief intervals, such as sub-nano- or pico-second intervals. First, we demonstrate the localized transformation of lattice structures at the end of initialization, indentation, and wear processes. In addition, we obtain the exerted force on a rigid sphere during scratching under linear movement. Furthermore, we investigate the effect of the relaxation period between indentation and scratch deformation. Finally, we conduct a comparison study of nanoindentation between crystal and amorphous Ti substrates. Thus, this study reveals the underlying physics of the microscopic transformation of the α-titanium crystal structure under wear-like accidental events.","Linear scratch wear(선형 스크래치 마모), Molecular dynamics(분자동역학), Nanoindentation(나노압입), Structural transformation(구조적 변환), Relaxation time effect(이완시간효과)","정예리1*ㆍ김진호1*ㆍ이태일2†\n1경남대학교 기계공학부 스마트기계융합공학전공 학부생, 2경남대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2023.39.5.167"]
["39권5호\npp.173-182","장갑차용 트랜스미션의 유성기어 설계 및 내구 강도 분석을 위한 유성기어 감속기 설계 소프트웨어의 개발\n(Developing Planetary Gear Reduction Design Software for the Planetary Gear Design and Durability Strength Analysis of Armored Vehicle's Transmission)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","The composite planetary gear reducer, a power transmission component of armored vehicles, operates at a high torque and is used in severe environments such as mountain, gravel or unpaved roads. Therefore, they must be designed and manufactured to have high durability. To design such a planetary gear reducer, there are numerous specifications to validate, such as selecting the module and the number of teeth of each gear satisfied the requirements, and calculating gear specifications and durability strength. Because planetary gears constitute a combination of several gears, there are many restrictions and interferences in selecting the number of teeth and addendum modification coefficients, and designing the tooth shape. Developing an auto design program is necessary to design various planetary gears more conveniently and quickly. In this study, a planetary gear reducer design software, widely used in various machines and armored vehicles, was developed. This design software can automatically select the number of teeth and modules of the gears, calculate specifications and quickly evaluate its fatigue durability strength and scoring failure according to the planetary gear reducer design theory.","Gear design(기어 설계), Gear bending strength(기어 굽힘 강도), Gear compressive strength(기어 면압 강도), Planetary gear reduction(유성기어 감속기), Scoring failure(스코어링 손상)","강신현1ㆍ박성호2ㆍ조연상3†\n1이엠코리아(주) 기술연구본부 전무, 2창원문성대학교 항공정비과 조교수, 3동아대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2023.39.5.173"]
["39권5호\npp.183-189","롤러의 형상 불확실성을 고려한 테이퍼 롤러 베어링의 구동마찰토크 평가\n(Evaluation of Running Friction Torque of Tapered Roller Bearings Considering Geometric Uncertainty of Roller)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","A bearing is a mechanical component that transmits rotation and supports loads. According to the type of rotating mechanism, bearings are categorized into ball bearings and tapered roller bearings. Tapered roller bearings have higher load-bearing capabilities than ball bearings. They are used in applications where high loads need to be supported, such as wheel bearings for commercial vehicles and trucks, aircraft and high-speed trains, and heavy-duty spindles for heavy machinery. In recent times, the demand for reducing the driving friction torque in automobiles has been increasing owing to the CO2 emission regulations and fuel efficiency requirements. Accordingly, the research on the driving friction torque of bearings has become more essential. Researchers have conducted various studies on the lubrication, friction, and contact in tapered roller bearings. Although researchers have conducted numerous studies on the friction in the lips and on roller misalignment and skew, studies considering the influence of roller shape, specifically roller shape errors including lips, are few. This study investigates the driving friction torque of tapered roller bearings considering roller geometric uncertainties. Initially, the study calculates the driving friction torque of tapered roller bearings when subjected to axial loads and compares it with experimental results. Additionally, it performs Monte Carlo simulations to evaluate the influence of roller geometric uncertainties (i.e., the effects of roller geometric deviations) on the driving friction torque of the bearings. It then analyzes the results of these simulations.","Bearing(베어링), Running friction torque(구동마찰토크), Tapered roller bearing(테이퍼 롤러 베어링), Roller(롤러), Geometric uncertainty(형상 불확실성)","박정수1ㆍ이승표2†\n1㈜일진글로벌 기술연구소 오토설계팀 책임연구원, 2㈜일진글로벌 기술연구소 이사","https://doi.org/10.9725/kts.2023.39.5.183"]
["39권5호\npp.190-196","점착필름 절단용 다이 칼날 소재에 적용된 점착 방지 코팅의 물 접촉각 및 박리강도에 관한 연구\n(A Study on Water Contact Angle and Peel Strength by Anti-Adhesion Coating on Die Blade Materials for Adhesive Film Cutting)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","Anti-adhesion coatings are very important in the processing of adhesive materials such as optical clear adhesive (OCA) films. Choosing the appropriate release coating material for dies and tools can be quite challenging. Hydrophobic surface treatment is usually performed, and its performance is often estimated by the static water contact angle (CA). However, the relationship between the release performance and the CA is not well understood. In this study, the water CAs of surfaces coated with anti-adhesion materials and the peel strengths of the acrylic-based adhesive films are evaluated. STC5 and SUS304 are selected as the base materials. Base materials with different surface roughnesses are produced by hairline finishing, mirror-polishing, and end milling. Four fluoropolymer compounds, including a self-assembled monolayer, are selected to make the base surface hydrophobic. Static, advancing, and receding CAs are mostly increased due to the coating, but the CA hysteresis is found to increase or decrease depending on the coating material. The peel strengths all decreased after coating and are largely dependent on the coating material, with significantly lower values observed for fluorosilane and perfluoropolyether silane coatings. The peel strength is observed to correlate better with the static CA and advancing CA than with the receding CA or hysteresis. However, it is not possible to accurately predict the anti-adhesion performance based on water CA alone, as the peel strengths are not fully proportional to the CAs.","Anti-adhesion coating(비점착 코팅), Contact angle(접촉각), Die blade(다이 블레이드), Interfacial energy(계면 에너지), Peel strength(박리 강도)","하유진1ㆍ김민욱2ㆍ김욱배3†\n1한국공학대학교 대학원 기계설계공학과 석사과정생, 2㈜파인테크글로벌 생산기술연구소 소장, 3한국공학대학교 기계설계공학부 교수","https://doi.org/10.9725/kts.2023.39.5.190"]
["39권5호\npp.197-202","비정형 기둥 형상을 가진 나노구조에서의 가스 투과성 실험 연구\n(Permeability of the Lateral Air Flow through Unstructured Pillar-like Nanostructures)","Micro/Nano-Tribology ","Recently, research on experimental and analytical techniques utilizing microfluidic devices has been pursued. For example, lab-on-a-chip devices that integrate micro-devices onto a single chip for processing small sample quantities have gained significant attention. However, during sample preparation, unnecessary gases can be introduced into the internal channels, thus, impeding device flow and compromising specific function efficiency, including that of analysis and separation. Several methods have been proposed to mitigate this issue, however, many involve cumbersome procedures or suffer from complexities owing to intricate structures. Recently, some approaches have been introduced that utilize hydrophobic device structures to remove gases within channels. In such cases, the permeability of gases passing through the structure becomes a crucial performance factor. In this study, a method involving the deposition and sintering of diluted Ag-ink onto a silicon wafer surface is presented. This is followed by unstructured nano-pattern creation using a Metal Assisted Chemical Etching (MACE) process, which yields a nanostructured surface with unstructured pillar shapes. Subsequently, gas permeability in the spaces formed by these surface structures is investigated. This is achieved by experiments conducted to incorporate a pressure chamber and measure gas permeability. Trends are subsequently analyzed by comparing the results with existing theories. Finally, it can be confirmed that the significance of this study primarily lies in its capability to effectively evaluate gas permeability through unstructured pillar-like nanostructures, thus, providing quantitative values for the appropriate driving pressure and expected gas removal time in practical device operation.","Degassing(기체 제거), Gas permeability(가스 투과성), Unstructure nanostructures(비정형 나노구조물), Metal assisted chemical etching(금속을 촉매로 한 화학적 식각 방법)","김혜원1ㆍ임혜원2ㆍ박정우3ㆍ이상민4ㆍ김형모5†\n1경상국립대학교 대학원 기계항공우주공학부 석사과정생, 2경상국립대학교 기계공학부 학부생, 3동의대학교 기계자동차로봇부품공학부 석사과정생, 4동의대학교 기계자동차로봇부품공학부 부교수, 5경상국립대학교 기계공학부 조교수","https://doi.org/10.9725/kts.2023.39.5.197"]
["39권5호\npp.203-211","회전각가속도가 가스 포일 스러스트 베어링의 마찰 및 마모 특성에 미치는 영향\n(Effects of Angular Acceleration on the Friction and Wear Characteristics of Gas Foil Thrust Bearings)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study experimentally investigates the effects of angular acceleration on the friction and wear performances of a gas foil thrust bearing (GFTB) using a typical GFTB with six pads. The outer radius of the bearing is 31.5 mm, the total bearing area is 2,041 mm2, and the bump foil and incline (ramp) height are both 500 μm. The newly developed GFTB test rig for measuring the friction torque and coefficient measures the axial load, drag torque, lift-off speed, and touch-down speed. The experiment is conducted for angular accelerations of 78.5, 314.2, and 328.3 rad/s2 at axial loads of 5, 10, and 15 N, respectively. The test shows that the start-up friction coefficient increases with increasing axial load at the same angular acceleration, and the friction coefficient decreases with increasing angular acceleration under the same axial load. As the angular acceleration increases, the lift-off speed at the motor start-up increases, and the touch-down speed at the motor stop decreases. The wear distance of the GFTB for a single on/off cycle increases with increasing axial load at the same angular acceleration and decreases nonlinearly with increasing angular acceleration under the same axial load. The test results suggest that adjusting the rotational angular acceleration helps reduce bearing friction and wear.","Gas foil thrust bearing(가스 포일 스러스트 베어링), Angular acceleration(각가속도), Friction coefficient(마찰 계수), lift-off and touch-down speed(부상 및 착지 속도)","황성호1ㆍ김대연2ㆍ김태호3†\n1국민대학교 기계공학부 박사후연구원, 2LG이노텍 Actuator 선행개발팀 사원, 3국민대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.5.203"]
["39권5호\npp.212-215","Evaluation of Scratch Characteristics of Diaphragm for Application of Hydrogen Compressor Parts","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","Diaphragm compressors play a crucial role in safely compressing large volumes of high-purity hydrogen gas without contamination or leakage, thereby ensuring quality and reliability. Diaphragm compressors use a thin, flat, triple-layered diaphragm plate that is subjected to repetitive piston pressure for compression. They are usually made of metallic materials such as stainless steel or Inconel owing to their high-pressure resistance. However, since they are consumable components, they fail due to fatigue from repetitive pressure and vibration stress. This study aims to evaluate the scratch characteristics of diaphragms in operational environments by conducting tests on three different samples: Inconel 718, AISI 301, and Teflon-coated AISI 301. The Inconel 718 sample underwent a polishing process, the AISI 301 sample used raw material, and the Teflon coating was applied to the AISI 301 substrate at a thickness of 50 μm. To assess the scratch resistance, reciprocating motion friction tests were performed using a tribometer, utilizing 220 and 2000 grit sandpapers as the counter materials. The results of the friction tests suggested that the Teflon-coated sample exhibited the lowest initial friction coefficient and consistently maintained the lowest average friction coefficient (0.13 and 0.11 with 220 and 2000 grit, respectively) throughout the test. Moreover, the Teflon-coated diaphragm showed minimal wear patterns, indicating superior scratch resistance than the Inconel 718 and AISI 301 samples. These findings suggest that Teflon coatings may offer an effective solution for enhancing scratch resistance in diaphragms, thereby improving compressor performance in high-pressure hydrogen applications.","Diaphragm compressor, Hydrogen gas, Friction, Surface polishing, Surface coating","Sung-Jun Lee1 and Chang-Lae Kim2†\n1Ph.D. Student, Graduate School, Dept. of Mechanical Engineering, Chosun University, 2Associate Professor, Dept. of Mechanical Engineering, Chosun University","https://doi.org/10.9725/kts.2023.39.5.212"]
["39권5호\npp.216-219","나노스케일 워터젯 가공에 대한 분자시뮬레이션 연구\n(Molecular Simulation of Nano-Scale Waterjet Machining)","Modeling & Simulation in Tribology ","This study employs molecular dynamics simulations to investigate the material behavior of workpieces in waterjet machining processes. To gain fundamental insights into waterjet machining, simulations were conducted using pure water, excluding abrasive particles. The simulation model comprised thousands of water molecules interacting with a single crystal metal workpiece. Water molecule clusters were imparted with various velocities to initiate collisions with the metal workpiece. The material behavior of the metal surface was analyzed with respect to the applied velocity conditions, considering the intricate interplay between water molecules and the workpiece at the atomic scale. The results demonstrated that the machining of the metal workpiece occurred only when water molecules were endowed with velocities above a certain threshold. In cases where energy was insufficient, the metal workpiece exhibited a slight increase in surface roughness due to mild plastic deformation, without undergoing substantial material removal. When machining occurred, the ejection of material revealed a 3-fold symmetric pattern, confirming that material removal in waterjet machining of the metal workpiece is primarily driven by plastic deformation-induced material ejection. This research provides crucial insights into the mechanisms underlying waterjet machining and enhances our understanding of material behavior during the process. The findings can be valuable in optimizing waterjet machining techniques.","Machining(가공), Molecular simulation(분자시뮬레이션), Plastic deformation(소성 변형), Waterjet(워터젯), Water molecule(물분자)","이상훈1ㆍ김현준2ㆍ김태욱3†\n1경북대학교 미래과학기술융합학과 석사과정, 2경북대학교 미래과학기술융합학과 부교수, 3경북대학교 미래과학기술융합학과 교수","https://doi.org/10.9725/kts.2023.39.5.216"]
["39권6호\npp.221-227","방향성 주파수 응답 함수를 이용한 회전체 동역학 해석\n(Rotordynamic Analysis Using a Direction Frequency Response Function)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","A rotordynamic system consists of components that undergo rotational motion. These components include shafts, impellers, thrust collars, and components that support rotation, such as bearings and seals. The motion of this type of rotating system can be modeled as two-dimensional motion and, accordingly, the equation of motion for the rotordynamic system can be represented using complex coordinates. The directional frequency response function (dFRF) can be derived from this complex coordinate system and used as an effective analytical tool for rotating machinery. However, the dFRF is not widely used in the field because most previous studies and commercial software are based on real coordinate systems. The objective of the current study is to introduce the dFRF and show that it can be an effective tool in rotordynamic analysis. In this study, the normal frequency response function (nFRF) and dFRF are compared under rotordynamic analysis for isotropic and unisotropic rotors. Results show that in the nFRF, the magnitude of the response is the same for both positive and negative frequencies, and the response is similar under all modes. Consequently, the severity of the mode cannot be identified. However, in the dFRF, the forward and backward modes are clearly distinguishable in the frequency domain of the isotropic rotor, and the severity of the mode can be identified for the unisotropic rotor.","Directional frequency response function(방향성주파수응답함수), Rotordynamics(회전체 동역학), Spindle(스핀들)","이동현1†ㆍ김병옥1ㆍ전병찬2ㆍ임형수3\n1한국기계연구원 시스템다이나믹스연구실 책임연구원, 2한국기계연구원 시스템다이나믹스연구실 선임기술원, 3한국기계연구원 에너지변환기계연구실 책임연구원","https://doi.org/10.9725/kts.2023.39.6.221"]
["39권6호\npp.228-234","Reciprocating Wear Test of AISI 52100 Bearing Steel in h-BN-based Aqueous Lubricants","Wear Phenomena & Mechanisms","In this study, reciprocating wear tests are performed on AISI 52100 bearing steel to investigate its tribological behavior in a hexagonal boron nitride (h-BN) water solution. The h-BN-based aqueous lubricant is prepared using an atoxic procedure called ultrasonic sonication in pure water. Ball-on-flat reciprocating sliding experiments are conducted, where the ball is slewed on a fixed flat at 50-μm displacement. The lubricating behavior of h-BN is compared with that of deionized (DI) water. Results show that the friction coefficient is higher in h-BN testing than that in DI tests, but the results are equalized as the friction coefficient reaches a stable level. Scanning electron microscopic images reveal significant material loss in the center and mild abrasion on the edge of the wear scar in h-BN tests. However, these effects are minor in DI water situations. The results of energy-dispersive X-ray spectroscopy show that considerable oxidation occurs in the central zone of the wear scar in h-BN cases with strong adhesion and material removal. These findings reveal the importance of determining ideal circumstances that can tolerate material friction and wear.","Lubricant, Hexagonal boron Nitride, Wear","Gowtham Balasubramaniam1 and Dae-Hyun Cho2,3†\n1Doctoral Research Scholar, Department of Computer Mechatronics Engineering,Gyeongsang National University, 2Associate Professor, Department of Mechatronics Enigneering, Gyeongsang National University, 3Associate Professor, Department of Energy System Engineering, Gyeongsang National University","https://doi.org/10.9725/kts.2023.39.6.228"]
["39권6호\npp.235-243","수-윤활용 플라스틱 베어링 개발에 관한 연구\n(Development of Water-lubricated Plastic Bearings)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","This paper presents the fabrication process of water-lubricated plastic bearings. Plastic bearings require good mechanical properties and tribological properties as well as elasticity and shock resistance, especially when lubricated in dirty water conditions. In this study, sleeve-type plastic bearings are produced by winding a prepreg sheet, which primary contains nitrile rubber (NBR)-modified epoxy, self-lubricating fillers, and various types of lattice-structured reinforcing fibers such as carbon, Aramid, and polyethylene terephthalate. A thermosetting epoxy is chemically modified with NBR to impart elasticity and low-friction characteristics in water conditions. Experimental investigations are conducted to examine the mechanical and tribological characteristics of the developed bearing materials, and the results are compared with the characteristics of a commercial plastic bearing (Thordon SXL), well known as a water-lubricated bearing. A Thordon bearing (mainly composed of polyurethane) exhibits an extremely low load-bearing capacity and is thus only suitable for medium loading (1~10MPa). The tribological characteristics of the test materials are evaluated through Falex block-on-ring (LFW-1) friction and wear tests. The results indicate that friction exhibited by the carbon-fiber-reinforced NBR-10wt.%-modified epoxy composite material, incorporated with the addition of 20wt.% UHMWPE and 6wt.% paraffin wax, is lower than that of the Thorden bearings, whereas its wear resistance surpass that of Thorden ones. Because of these features, the load carrying capacity of the fabricated composite (>10MPa) is higher than that of the Thorden bearings. These results confirm the applicability of water-lubricated plastic bearing materials developed in this study.","Plastic bearing(플라스틱 베어링), Water-lubricated(물-윤활), Sliding friction(미끄럼 마찰), Composite materials(복합재료), NBR-modified epoxy(NBR-변성 에폭시)","공호성1†ㆍ한흥구2\n1한국과학기술연구원 혁신기업협력센터 연구전문위원, 2한국과학기술연구원 혁신기업협력센터 연구원","https://doi.org/10.9725/kts.2023.39.6.235"]
["39권6호\npp.244-249","Influence of Surface Roughness on Friction and Wear Characteristics of SUS 321 for Hydraulic Cylinder Parts Application","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","This paper presents a comprehensive analysis of the impact of surface roughness on the friction and wear properties of SUS 321, an austenitic stainless steel variant produced using the laser powder bed fusion (LPBF) technique, which is a prevalent additive manufacturing method. After the LPBF fabrication, the specimens go a heat treatment process aimed at alleviating residual stress. Subsequently, they are polished extensively to achieve a refined and smooth surface. To deliberately introduce controlled variations in surface roughness, an etching process is employed. This multi-step method encompassed primary etching in a 3M hydrochloric acid solution, followed by secondary etching in a 35 wt% ferric chloride solution, with varying durations applied to different specimens. A comprehensive evaluation of the surface characteristics ensued, employing precise techniques such as surface roughness measurements and meticulous assessments of water droplet contact angles. Following the surface treatment procedures, a series of friction tests are performed to explore the tribological behavior of the etched specimens. This in-depth investigation reached its peak by revealing valuable insights. It clarified a strong correlation between intentionally altered surface roughness, achieved through etching processes, and the resulting tribological performance of LPBF-fabricated SUS 321 stainless steel. This significantly advances our grasp of material behavior in tribological applications.","Laser powder bed fusion, Friction/wear characteristics, Hydraulic cylinder, Surface roughness","Sung-Jun Lee1, Yonghun Jang2 and Chang-Lae Kim3†\n1Ph.D. Student, Graduate School, Dept. of Mechanical Engineering, Chosun University, 2Senior Research Engineer, Innovation Process Development Team, KEPCO KPS Global Institute of Technology, 3Associate Professor, Dept. of Mechanical Engineering, Chosun University","https://doi.org/10.9725/kts.2023.39.6.244"]
["39권6호\npp.250-255","모래 3체 마모시험 장비(3-body abrasion tester)를 이용한 PLA프린팅 표면의 형상별 트라이볼로지 성능 분석\n(Tribology Performance Analysis by Surface Patterns of PLA Printing Samples Using 3-body Abrasion Tester)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","This study applies various surface patterns to minimize material loss in construction equipment that is subject to severe wear due to sand, such as the wear-resistant steel plates of dump trucks or the teeth of excavators. The relationship between surface morphology and wear behavior is investigated using PLA+ polymer to observe the effect of the surface pattern. Five types of samples - smooth, concave, convex, wavy concave, and wavy convex designs - are created using a 3D printer. A wear experiment is conducted for a duration of 3 h using 6.5 kg of abrasive particles. The mass loss of the samples after the experiment is measured to assess the extent of wear. Additionally, the surface morphology of the samples before and after the experiment is analyzed using SEM and confocal microscopy. The study results reveal that the smooth design exhibits the highest wear loss, whereas the concave and wavy concave designs show relatively lower wear loss. The convex and wavy convex designs exhibit varying contact areas with the abrasive particles depending on the surface pattern, resulting in different levels of wear. Furthermore, a comparison between the experimental results and DEM simulations confirms the observed wear trends. This study reveals the relationship between wear damage according to surface pattern shape and is expected to be of substantial help in the analysis of wear and tear on agricultural and heavy equipment.","Wear behavior(마모 거동), Surface patterns(표면 패턴), 3D printing(3D 프린팅), 3-body abrasion (3 바디 마모), DEM simulation(DEM 해석)","최용석1*ㆍ박경렬1*ㆍ강성민1ㆍ김운성1ㆍ정경은2ㆍ박영진3†ㆍ이경준4‡\n1가천대학교 대학원 기계공학과 석사과정생, 2가천대학교 기계공학과 학부과정생, 3경상국립대학교 기계공학부 조교수, 4가천대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2023.39.6.250"]
["39권6호\npp.256-261","구름 마모시험 장비(Rolling wear tester)를 이용한 마모 후의 접촉각과 자가세정 효과와의 관계 규명을 통한 재료 내구성 평가\n(Evaluation of Material Durability by Identifying the Relationship between Contact Angle after Wear and Self-cleaning Effect Using Rolling Wear Tester)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification)","This study is conducted to evaluate the durability of superhydrophobic surfaces, with a focus on two aspects: contact angle measurement and self-cleaning-performance analysis. Superhydrophobic copper and aluminum surfaces are fabricated using the immersion method and subjected to a rolling wear test, in which a 2 kg weight is placed on a rolling tester, under loaded conditions. To evaluate their durability, the contact angles of the specimens are measured for each cycle. In addition, the surface deformation of the specimens before and after the test is analyzed through SEM imaging and EDS mapping. The degradation of the self-cleaning performance is evaluated before and after the wear test. The results show that superhydrophobic aluminum is approximately 4.5 times more durable than superhydrophobic copper; the copper and aluminum specimens could endure 21,000 and 4,300 cycles of wear, respectively. The results of the self-cleaning test demonstrate that superhydrophobic aluminum is superior to superhydrophobic copper. After the wear test, the self-cleaning rates of the copper and aluminum specimens decrease to 72.7% and 83.4%, respectively. The relatively minor decrease in the self-cleaning rate of the aluminum specimen, despite the large number of wear cycles, confirms that the superhydrophobic aluminum specimen is more durable than its copper counterpart. This study is expected to aid in evaluating the durability of superhydrophobic surfaces in the future owing to the advantage of performing wear tests on superhydrophobic surfaces without damaging the surface coating.","Superhydrophobic surface(초소수성 표면), Durability(내구성), Self-cleaning effect(자가세정 효과), Al and Cu(알루미늄과 구리), Rolling wear test(구름 마모 테스트)","박경렬1*ㆍ최용석1*ㆍ강성민1ㆍ김운성1ㆍ정경은2ㆍ박영진3†ㆍ이경준4‡\n1가천대학교 대학원 기계공학과 석사과정생, 2가천대학교 기계공학과 학부과정생, 3경상국립대학교 기계공학부 조교수, 4가천대학교 기계공학과 조교수","https://doi.org/10.9725/kts.2023.39.6.256"]
["39권6호\npp.262-267","온도 조건에 따른 폴리머 소재의 트라이볼로지 특성 연구\n(Effects of Temperature on Tribological Properties of Polymer Material)","Tribology of Materials (Characterization / Polymer Tribology / NewㆍSmart Materials)","Research to replace metal mechanical elements with polymer materials has recently accelerated. However, polymers exhibit less favorable mechanical properties than metal materials, and are often easily worn-out owing to frictional heat when their mechanical elements contact while in relative motion. Therefore, research on the polymer tribological properties is required to employ polymer materials in mechanical elements operating under harsh conditions. In this study, we examine the effect of mechanical part operating temperatures on the material friction and wear characteristics of polymer materials. We conduct ball-on-disk friction tests under dry conditions at various temperatures, using a metal ball with high hardness and a polymer as the counter surface. Each test is repeated at least three times to ensure the reliability of the test results. Before the friction test, we analyze the surface hardness and roughness of each polymer specimen; after the friction test, we use a three-dimensional confocal microscope to compare and analyze the polymer specimen wear characteristics. Based on this study, we systematically elucidate the polymer material tribological characteristics. This information should be useful for selecting and utilizing polymer materials at various temperatures.","Polymer(고분자 소재), Temperature(온도), Hardness(경도), Friction coefficient(마찰계수), Wear rate(마모율)","안치윤1ㆍ김대은2†\n1연세대학교 대학원 기계공학과 석사과정생, 2연세대학교 기계공학과 정교수","https://doi.org/10.9725/kts.2023.39.6.262"]
["39권6호\npp.268-272","Multiphysics Software를 활용한 원심 압축기용 틸팅 패드 저널 베어링 특성과 회전체 동역학 분석\n(Analysis of Tilting Pad Journal Bearing Characteristics and Rotordynamics for Centrifugal Compressors Using Multiphysics Software)","Lubrication (Lubricants & Additives)","This study explores the characteristics of tilting pad journal bearings used in the high-speed rotating shaft systems of centrifugal compressors. A centrifugal compressor is a high-speed rotating machine that is widely used to compress gases or vapors employed in various industrial applications. It transfers the centrifugal force of a fast-spinning impeller to the fluid and compresses it under high pressure. Many high-speed rotating shaft systems, which require high stability, use tilting pad journal bearings. The characteristics of these bearings can vary depending on several properties, and identifying the appropriate characteristics is essential to optimize the design on a case-to-case basis. In this study, the authors perform a time-dependent analysis of the properties of tilting pad journal bearings and the rotordynamics of the rotating shaft system using COMSOL Multiphysics software. Specifically, the authors analyze the characteristics of the tilting pad journal bearings by performing a parametric sweep using parameters such as pad clearance, maximum tilting angle, preload, number of pads, and pad pivot offset. The authors then use the results of the bearing-characteristics analysis to evaluate the vibration of the rotating shaft and verify its operation within a desirable range. The understanding gained from this study will allow us to determine the optimal properties of these bearings and the limiting operational speed using COMSOL Multiphysics software.","Rotordynamics(회전체 동역학), FEM(유한요소법), Tilting pad journal bearing(틸팅 패드 저널 베어링), Multiphysics(다중물리)","문소연1ㆍ윤종완1ㆍ박상신2†\n1영남대학교 대학원 기계공학과 석사과정생, 2영남대학교 기계공학부 교수","https://doi.org/10.9725/kts.2023.39.6.268"]
["39권6호\npp.273-277","표면 에너지가 물 윤활 현상에 미치는 영향에 대한 분자시뮬레이션 연구\n(Molecular Simulation of Influence of Surface Energy on Water Lubrication)","Modeling & Simulation in Tribology","This paper presents a molecular dynamics simulation-based numerical investigation of the influence of surface energy on water lubrication. Models composed of a crystalline substrate, half cylindrical tip, and cluster of water molecules are prepared for a tribological-characteristic evaluation. To determine the effect of surface energy on lubrication, the surface energy between the substrate and water molecules as well as that between the tip and water molecules are controlled by changing the interatomic potential parameters. Simulations are conducted to investigate the indentation and sliding processes. Three different normal forces are applied to the system by controlling the indentation depth to examine the influence of normal force on the lubrication of the system. The simulation results reveal that the solid surface's surface energy and normal force significantly affect the behavior of the water molecules and lubrication characteristics. The lubrication characteristics of the water molecules deteriorate with the increasing magnitude of the normal force. At a low surface energy, the water molecules are readily squeezed out of the interface under a load, thus increasing the frictional force. Contrarily, a moderate surface energy prevents expulsion of the water molecules due to squeezing, resulting in a low frictional force. At a high surface energy, although squeezing of the water molecules is restricted, similar to the case of moderate surface energy, dragging occurs at the soil surface–water molecule interface, and the frictional force increases.","Lubrication(윤활), Molecular simulation(분자 시뮬레이션), Sliding friction(미끄럼 마찰), Surface energy(표면에너지), Water molecule(물분자)","김현준1,2†\n1경북대학교 미래과학기술융합학과 부교수, 2경북대학교 정밀기계공학과 부교수","https://doi.org/10.9725/kts.2023.39.6.273"]

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["권호","제목","토픽","초록","키워드","저자","DOI"]
["40권1호\npp.1-7","전산유체역학을 이용한 케이지가 고려된 볼 베어링의 토크 예측\n(Torque Prediction of Ball Bearings Considering Cages using Computational Fluid Dynamics)","Contact Mechanics & Friction ","Ball bearings are a major component of mechanical parts for transmitting rotation. Compared to tapered roller bearings, ball bearings offer less rolling resistance, which leads to reduced heat generation during operation. Because of these characteristics, ball bearings are widely used in electric vehicles and machine tools. The design of ball bearing cages has recently emerged as a major issue in ball bearing design. Cage design requires pre-verification of performance using theoretical or experimental formula or computational fluid dynamics (CFD). However, CFD analysis is time-consuming, making it difficult to apply in case studies for design decisions and is mainly used in performance prediction following design confirmation. To use CFD in the early stages of design, maintaining analytical accuracy while reducing the time required for analysis are necessary. Accordingly, this study proposes a laminar steady-state segment CFD technique to solve the problem of long CFD analytical times and to enable the use of CFD analysis in the early stages of design. To verify the reliability of the CFD analysis, a bearing drag torque test is performed, and the results are compared with the analytical results. The proposed laminar steady-state segment CFD technique is expected to be useful for case studies in bearing design, including cage design.","Ball bearing(볼 베어링), Cage(케이지), Torque(토크), CFD(전산유체역학)","박정수1ㆍ김정식2ㆍ이승표3†\n1㈜일진글로벌 기술연구소 오토설계팀 책임연구원, 2㈜일진글로벌 기술연구소 구동시스템 분석팀 팀장, 3㈜일진글로벌 기술연구소 이사","https://doi.org/10.9725/kts.2024.40.1.1"]
["40권1호\npp.8-16","탄소성 변형을 고려한 타이로드 고정 회전체의 동역학 해석\n(Dynamic Analysis of Tie-rod-fastened Rotor Considering Elastoplastic Deformation)","Contact Mechanics & Friction ","This study conducts numerical modeling and eigen-analysis of a rod-fastened rotor, which is mainly used in aircraft gas turbine engines in which multiple disks are in contact through curvic coupling. Nayak's theory is adopted to calculate surface parameters measured from the tooth profile of the curvic coupling gear. Surface parameters are important design parameters for predicting the stiffness between contact surfaces. Based on the calculated surface parameters, elastoplastic contact analysis is performed according to the interference between two surfaces based on the Greenwood–Williamson model. The equivalent bending stiffness is predicted based on the shape and elastoplastic contact stiffness of the curvic coupling. An equation of motion of the rod-fastened rotor, including the bending stiffness of the curvic coupling, is developed. Methods for applying the bending stiffness of a curvic coupling to the equation of motion and for modeling the equation of motion of a rotor that includes both inner and outer rotors are introduced. Rotordynamic analysis is performed through one-dimensional finite element analysis, and each element is modeled based on Timoshenko beam theory. Changes in bending stiffness and the resultant critical speed change in accordance with the rod fastening force are predicted, and the corresponding mode shapes are analyzed.","Curvic coupling(곡률 커플링), Dual rotor(복 축), Rotordynamics(회전체 동역학), Contact mechanics(접촉 역학), Elastoplastic deformation(탄소성 변형)","서동찬1ㆍ김경희2ㆍ이도훈3ㆍ이보라4ㆍ서준호5†\n1부산대학교 대학원 기계시스템설계 석사과정생, 2한국산업기술시험원 기계재료기술센터 수석연구원, 3한화에어로스페이스 미래항공연구소 선임연구원, 4부산대학교 기계기술연구원 연구교수, 5부산대학교 기계공학부 부교수","https://doi.org/10.9725/kts.2024.40.1.8"]
["40권1호\npp.17-23","쉘 모델을 이용한 공기 포일 스러스트 베어링의 열-유체-구조 연동 해석\n(Thermo-Fluid-Structure Coupled Analysis of Air Foil Thrust Bearings using Shell Model)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements)","This study analyzes the thermal effects on the performance of an air foil thrust bearing (AFTB) using COMSOL Multiphysics to approximate actual bearing behavior under real conditions. An AFTB is a sliding-thrust bearing that uses air as a lubricant to support the axial load. The AFTB consists of top and bump foils and supports the rotating disk through the hydrodynamic pressure generated by the wedge effect from the inclined surface of the top foil and the elastic deformation of the bump foils, similar to a spring. The use of air as a lubricant has some advantages such as low friction loss and less heat generation, enabling air bearings to be widely used in high-speed rotating systems. However, even in AFTB, the effects of energy loss due to viscosity at high speeds, interface frictional heat, and thermal deformation of the foil caused by temperature increase cannot be ignored. Foil deformation derived from the thermal effect influences the minimum decay in film thickness and enhances the film pressure. For these reasons, performance analyses of isothermal AFTBs have shown few discrepancies with real bearing behavior. To account for this phenomenon, a thermal-fluid-structure analysis is conducted to describe the combined mechanics. Results show that the load capacity under the thermal effect is slightly higher than that obtained from isothermal analysis. In addition, the push and pull effects on the top foil and bump foil-free edges can be simulated. The differences between the isothermal and thermal behaviors are discussed.","Air foil thrust bearing(공기 포일 스러스트 베어링), Heat transfer(열전달), THD(열 유체 윤활), Multi physics(다중 물리 연동 해석), Thermal-Fluid-Structure coupled analysis(열 유체 구조 연동 해석)","윤종완1ㆍ문소연1ㆍ박상신2†\n1영남대학교 대학원 기계공학과 석사과정생, 2영남대학교 기계공학부 교수","https://doi.org/10.9725/kts.2024.40.1.17"]
["40권1호\npp.18-27","A Study on Vehicle-based Durability Evaluation for Weight-reduced Valve Parts of the Dual Clutch Transmission","Automotive Tribology","A monotype valve body for a dual clutch transmission has the potential to reduce costs, weight, and manufacturing time by modularizing various parts, including those of existing solenoid packs and valve bodies, into one through the application of super-precision die casting technology. However, this approach may lead to challenges such as reduced rigidity and increased interference due to modularization and compactness, impacting both product performance due to the reduced weight as well as durability and reliability. Unlike existing products, this approach requires a high-precision thin-wall block to avoid more complicated flow line formation, interference between flow lines, and leaks, as well as a strict quality requirement standard and precise inspections including detection of internal defects. To conduct precise inspections, we built an equivalent model corresponding to a driving distance of 300,000 km. Testing involved simulating actual road loads using a real vehicle and a chassis dynamometer in the FTP-75 mode (EPA Federal Test Procedure). The aim of the study was to establish a vehicle load-based part durability model for manufacturing a mono-type valve body and to develop fundamental technology for part weight reduction through preliminary design by introducing analytical weight reduction technology based on the derived results.","Dual clutch transmission, Valve-body, Mono type, Weight reduction, Fatigue analysis, Road load data acquisition","ChanEun Kim1† and TaeWook Kim2\n1Ph.D. Student, Graduate School, Development of Precision Mechanical Engineering, Kyungpook National University, 2Professor, Development of Precision Mechanical Engineering, Kyungpook National University","https://doi.org/10.9725/kts.2024.40.1.24"]
["40권1호\npp.28-37","열린 끝단과 중앙 홈을 갖는 스퀴즈 필름 댐퍼의 감쇠 특성에 대한 실험적 규명\n(Experimental Identification of the Damping Characteristics of a Squeeze Film Damper with Open Ends and Central Groove)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This paper presents the development of a squeeze film damper (SFD) test rig and experimental identification of the effects of clearance, damper length, journal eccentricity ratio, excitation amplitude, oil supply pressure, and oil flow rate on the damping coefficients of a test SFD with open ends and a central groove. Test data are compared with predictions from a simple model developed for short SFDs with open ends and a central groove. The test results show a significant decrease in the damping coefficient with increasing clearance and a dramatic increase with damper length, which are in good agreement with the simple model predictions. According to the simple model, the damping coefficient is inversely proportional to the cube of the clearance and directly proportional to the cube of the length. An increase in the journal eccentricity ratio results in a dramatic increase in the damping coefficient by as much as 15 times that of the concentric case, particularly at low excitation frequencies. By contrast, the measured damping coefficient remains almost constant with changes in the excitation amplitude and supply pressure, which are not major factors in the damper design. In general, the test data agree well with the simple model predictions, excluding cases that show increases in the SFD length and journal eccentricity, which indicate significant dependency on the excitation frequency.","Gas turbine(가스 터빈), Squeeze film damper(스퀴즈 필름 댐퍼), Vibration(진동), Damping coefficient(감쇠 계수)","김남규1ㆍ김태호2†ㆍ강경대3\n1국민대학교 대학원 기계시스템공학과 석사과정생, 2국민대학교 기계공학부 교수, 3한화에어로스페이스 수석연구원","https://doi.org/10.9725/kts.2024.40.1.28"]
["40권2호\npp.39-46","민감도 벡터를 이용한 스팀 터빈의 Morton Effect 발생 예측\n(Predicting the Morton Effect in a Steam Turbine withSensitivity Vector)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","The Morton effect (ME) is an instability phenomenon occurring in rotating machineries supported by fluid film bearings and is induced by the thermal deformation of the overhung mass, which is a part of the rotating shaft. Herein, we describe the ME during the high-speed balancing test of a 20 MW class steam turbine. Additionally, to predict the rotating speed at which the ME occurs, we apply the sensitivity vector theory for the steam turbine. During the operation of the steam turbine, we observe a continuous increase in vibration and hysteresis near the rated speed, which is typical of the ME. Increasing the temperature of the lubricating oil supplied to the bearings from 40 to 60oC suppresses the occurrence of the ME. The rotordynamic analysis for the steam turbine suggests the existence of a mode in which the overhung mass undergoes significant deformation near the rated speed, and we presume that such a mode will increase the occurrence of the ME. The predicted rotating speed of ME occurrence, obtained through the sensitivity vector method, correlates with the test results. Moreover, increasing the temperature of the supplied lubricating oil mitigates the occurrence of ME by reducing the sensitivity between the temperature deviation vector and unbalance mass vector.","Morton effect(모턴 효과), Rotorynamic(회전체 동역학), Steam turbine(스팀 터빈), Sensitivity vector(민감도 벡터)","이동현1†ㆍ김병옥1ㆍ전병찬2ㆍ서준호3ㆍ강신훈4ㆍ김세룡5\n1한국기계연구원 가상공학연구센터 책임연구원, 2한국기계연구원 가상공학연구센터 선임기술원, 3부산대학교 기계공학부 부교수, 4S-Oil(주) Defect Elimination팀 Specialist, 5S-Oil(주) Defect Elimination팀 책임매니저","https://doi.org/10.9725/kts.2024.40.2.39"]
["40권2호\npp.47-53","삼차원 표면 조도 측정기와 삼차원 레이저 공초점 현미경 적용에 따른 표면 거칠기에 대한 영향 연구\n(Study of the Effect of Surface Roughness through the Application of 3D Profiler and 3D Laser Confocal Microscope)","Surface/Interface Tribology (Treatment & Coatings / Texturing / Modification) ","Surface topography plays a decisive role in determining the performance of several precision components. In particular, the surface roughness of semiconductor devices affects the precision of the circuit. In this regard, the surface topography of a given surface needs to be appropriately assessed. Typically, the average roughness is used as one of the main indicators of surface finish quality because it is influenced by both dynamic and static parameters. Owing to the increasing demand for such accurate and reliable surface measurement systems, studies are continuously being conducted to understand the parameters of surface roughness and measure the average roughness with high reliability. However, the differences in the measurement methods of surface roughness are not clearly understood. Hence, in this study, the surface roughness of the back of a silicon wafer was measured using both contact and noncontact methods. Subsequently, a comparative analysis was conducted according to various surface roughness parameters to identify the differences in surface roughness depending on the measurement method. When using a 3D laser confocal microscope, even smaller surface asperities can be measured compared with the use of a 3D profiler. The results are expected to improve the understanding of the surface roughness characteristics of precision components and be used as a useful guideline for selecting the measurement method for surface topography assessment.","3D profiler(삼차원 표면 조도 측정기), 3D laser confocal microscope(삼차원 레이저 공초점 현미경), Surface roughness(표면 거칠기)","정희영1ㆍ김대은2†\n1연세대학교 대학원 기계공학과 석사과정생, 2연세대학교 기계공학과 교수","https://doi.org/10.9725/kts.2024.40.2.47"]
["40권2호\npp.54-60","피스톤 링 실 끝단을 갖는 스퀴즈 필름 댐퍼의 감쇠 계수 측정\n(Measurement of Damping Coefficients of a Squeeze Film Damper with Piston Ring Seal Ends)","Bearing / Seal / Gear Tribology (Tribology of Machine Elements) ","This study experimentally identifies the effects of end shape, clearance, total damper length, journal eccentricity ratio, oil supply pressure, and oil flow rate on the damping coefficient of a squeeze film damper (SFD) with piston ring seal ends and a central groove. The SFD is composed of a lubricating fluid flowing between the outer race of a rolling element bearing and cartridge, along with an anti-rotation pin to prevent the rotation of the outer race. The device provides additional viscous damping to a rotating system. Additionally, piston ring seals attached at both ends of the damper increase the damping coefficient of the rotating system by reducing oil leakage. Because these different design conditions affect the damping coefficient of an SFD, we perform experiments including different conditions. Tests show that the damping coefficient increases significantly in the SFD with piston ring seal ends compared with the SFD with open ends. The damping coefficient also increases with increasing total damper length and journal eccentricity ratio, and decreases with increasing clearance. Additionally, in contrast to the trend observed for the SFD with open ends, the damping coefficient for the SFD with piston ring seal ends increases with increasing supply pressure and flow rate as the frequency decreases but shows consistent results as the frequency increases.","Squeeze film damper(스퀴즈 필름 댐퍼), Damping coefficient(감쇠 계수), Piston ring seal(피스톤 링 실), Central groove(중앙 홈)","김남규1ㆍ송영채1ㆍ김태호2†ㆍ홍정기3ㆍ강경대4\n1국민대학교 대학원 기계시스템공학과 석사과정생, 2국민대학교 기계공학과 교수, 3한화에어로스페이스 주임연구원, 4한화에어로스페이스 수석연구원","https://doi.org/10.9725/kts.2024.40.2.54"]
["40권2호\npp.61-66","Cyclone separator의 형상에 따른 미세플라스틱 입자 거동 수치해석 연구\n(Numerical Analysis Study on Micro-plastic Particle behavior According to the Shape of Cyclone Separator)","Others","Micro-plastics are synthetic high-differentiation chemicals of less than 5mm in size, and are deposited not only on the sea surface but also on the coast. If these micro-plastics are not properly separated from the sand, they can threaten marine ecosystems. Thus, in the present study, we aimed to apply cyclone separator to the micro-plastic retrieval in order to predict the movement of particles according to the formation of the cyclone separator by applying the centrifugal force of the particle in accordance with the rotational movement of the air. The cyclone separator has three shapes, the first one is a typical interconnected cyclone separator. The second is the horn form, except for the cylinder in a regular cyclone separator, and the third is a form that increases the horn's height twice in the second. The numerical analysis simulation of the Cyclone separator used the Fluent software package. The output speed of the Cyclone separator was 5 to 13m/s at 1m/s intervals. The simulated particles include sand, Styrofoam, PET, PP, and PU. Sand particles are assigned a fixed diameter of 2mm, while other particles have a diameter of 3mm. As a result of the analysis, the first form was not separated from plastic. The Styrofoam separation efficiency in the second showed its highest efficiency at 72.7% at 7m/s, and the efficiency decreased after 12m/s as the sand particles were mixed into the plastic attachment location. In the third form, the separation efficiency of Styrofoam at 12m/s was highest at 67.9%.","CFD(전산유체역학), Cyclone separator(사이클론 분리기), Micro-plastics(미세플라스틱), Particle behavior(입자 거동)","강인선1ㆍ서원준2ㆍ유동호1ㆍ김영식3ㆍ김형철4ㆍ임석연5†\n1충남대학교 대학원 기계공학교육과 석사과정생, 2충남대학교 대학원 기계공학과 박사과정생, 3선박해양플랜트연구소 책임연구원, 4충북도립대학교 미래자동차과 교수, 5충남대학교 기계공학교육과 부교수","https://doi.org/10.9725/kts.2024.40.2.61"]
["40권2호\npp.1-7","CMP 패드 컨디셔닝에서 딥러닝을 활용한 컨디셔너 스윙에 따른 패드 마모 프로파일에 관한 연구\n(Study on the Pad Wear Profile Based on the Conditioner Swing Using Deep Learning for CMP Pad Conditioning)","Chemical Mechanical Polishing","Chemical mechanical planarization (CMP) is an essential process for ensuring high integration when manufacturing semiconductor devices. CMP mainly requires the use of polyurethane-based polishing pads as an ultraprecise process to achieve mechanical material removal and the required chemical reactions. A diamond disk performs pad conditioning to remove processing residues on the pad surface and maintain sufficient surface roughness during CMP. However, the diamond grits attached to the disk cause uneven wear of the pad, leading to the poor uniformity of material removal during CMP. This study investigates the pad wear rate profile according to the swing motion of the conditioner during swing-arm-type CMP conditioning using deep learning. During conditioning, the motion of the swing arm is independently controlled in eight zones of the same pad radius. The experiment includes six swing-motion conditions to obtain actual data on the pad wear rate profile, and deep learning learns the pad wear rate profile obtained in the experiment. The absolute average error rate between the experimental values and learning results is 0.01%. This finding confirms that the experimental results can be well represented by learning. Pad wear rate profile prediction using the learning results reveals good agreement between the predicted and experimental values.","Chemical mechanical planarization(화학기계적 평탄화), Pad conditioning(패드 컨디셔닝), Pad wear profile(패드 마모 프로파일), Deep learning(딥러닝)","박병훈1ㆍ황해성1ㆍ이현섭2†\n1동아대학교 대학원 기계공학과 박사과정생, 2동아대학교 기계공학과 부교수","https://doi.org/10.9725/kts.2024.40.2.67"]