• 대한기계학회논문집A
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• 제31권11호
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• pp.1083-1092
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• 2007

The objective of the present paper is to evaluate the effect of the evolution of contact surface profile caused by fretting wear on fatigue life of press-fitted shaft by means of an analytical method based on experimental data. A finite element analysis was performed to analyze the stress states of press-fitted shaft, considering the worn contact profiles of shaft. The fatigue lives of the press-fitted shaft reflecting the evolution of contact stress induced by fretting wear were evaluated by stress-life approach using fatigue notch factor. It is found that the stress concentration of contact edge in press-fitted shaft decreases rapidly at the initial stage of total fatigue life, and its location shifts from the contact edge to the inside with increasing number of fatigue cycles. Thus the change of crack nucleation position in press-fitted shaft is mainly caused by the stress change of contact edge due to the evolution of contact surface profile by fretting wear. Furthermore, the estimated fatigue lives by stress-life approach at the end of running-in period of the fretting wear process corresponded well to the experimental results. It is thus suggested that the effect of fretting wear on fatigue life in press fits is strongly related to the evolution of surface profile at the initial stage of total fatigue life.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.229-232
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• 2007

In hot strip rolling, the work roll profile is one of the main factors in predicting and correcting the strip profile. Various studies concerning the wear profile and the thermal crown of work roll have been performed, and the results of these studies have shown that the work roll profile must be predicted accurately so as to efficiently control the strip qualities such as thickness, crown, flatness, and camber. Therefore, a precise prediction model of roll profile is called for in a perfect shape control system. In this paper, a genetic algorithm was applied to improve on the roll profile prediction model in hot strip rolling. In this approach, the optimal design problem is formulated on the basis of a numerical model so as to cover the diverse design variables and objective functions. A genetic algorithm was adopted for conducting design iteration for optimization to determine the coefficient of the numerical model for minimization of errors in the result of the calculated value and the measured data. A comparative analysis showed a satisfactory conformity between them..

• 소성∙가공
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• 제16권4호
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• pp.250-253
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• 2007

In hot strip rolling, the work roll profile is one of the main factors in predicting and correcting the strip profile. Various studies concerning the wear profile and the thermal crown of work roll have been performed, and the results of these studies have shown that the work roll profile must be predicted accurately so as to efficiently control the strip qualities such as thickness, crown, flatness, and camber. Therefore, a precise prediction model of roll profile is called for in a perfect shape control system. In this paper, a genetic algorithm was applied to improve on the roll profile prediction model in hot strip rolling. In this approach, the optimal design problem is formulated on the basis of a numerical model so as to cover the diverse design variables and objective functions. A genetic algorithm was adopted for conducting design iteration for optimization to determine the coefficient of the numerical model for minimization of errors in the result of the calculated value and the measured data. A comparative analysis showed a satisfactory conformity between them.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2000년도 추계학술대회 논문집
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• pp.442-449
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• 2000

Before the complete construction of new high-speed line between Seoul and Pusan, KTX is going to operate on both new high-speed line between Seoul and Daegu and electrified conventional lines between Daegu and Pusan. Then, the wheels of KTX are going to operate on various rails such as KS50N and KS60 of conventional line as well as UIC60 of high-speed line. Also, conventional line will have a mixed traffic mode with various types of trains operating on it, such as Saemaul and Mugunghwa. Hence, this study reviews the wear phenomena of wheels and rails in geometrical point of view by comparing their profiles. The analyses of the results show that because UIC60 rail is designed for KTX, KS50N rail whose profile is similar to that of UIC60 will not have any impact on the shape of wheel wear. On the other hand, KS60 rail is expected to have partial wear on both the flange of KTX wheel and the gauge corner of the rail in the initial stages. However, the operation of the trains whose wheels have 1/20 conicity will cause partial sidewear on the inside of the rail and the movement of the contact point between KTX wheel and the rail toward the inside of the track. As a result, the flange wear of KTX wheel will be reduced and the formation of wear-equilibrium profile will be faster.

• 한국철도학회논문집
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• 제12권2호
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• pp.230-235
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• 2009

전동차 차륜에 대한 마모 특성과 차륜의 마모가 차량 진동특성에 미치는 영향을 분석하고자 도심 곡선구간에서 운용되는 전동차를 대상으로 실험적 연구를 수행하였다. 차륜답면의 마모는 차륜 원형삭정 후 주행 초기(30,000km 이하)에 차륜 치수 및 등가답면구배 변화가 심한 직립마모 특성을 보이고 있다. 시험차의 누적주행거리가 증가함에 따라 차륜의 마모가 진전되고 그에 따른 차체의 진동 수준은 증가하는 경향을 보이고 있음을 확인하였다. 차체 진동 평균은 좌우, 상하방향 모두 "양호" 수준으로 평가되고 있으나 누적주행거리 증가에 따라 증가하여 "양호" 구간의 한계치에 이르고 있다. 특히, 차체 진동 최대 값은 더욱 뚜렷한 증가 특성을 보이고 있으며, 이는 불균일한 진동발생 가능성이 커진다고 예측할 수 있다.

• KSTLE International Journal
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• 제6권1호
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• pp.1-7
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• 2005

Wear model for predicting the vehaviour of a depth is considered in this paper. It is deduced from the energy and volume based wear models such as the Archard equation and the workrate model. A new parameter of the equivalent depth ($D_e$= wear volume /worn area) is considered for the wear model of a depth prediction. A concenpt of a dissipated shear energy density is accommodated for in the suggested models. It is found that $D_e$ can distinguish the worn area shape. A cubic of $D_e$($D_e^3$) gives a better linear regression with the volume than that of the maximmum depth $D_{max}e$($D_{max}^3$) does. Both $D_{max}$ and $D_e$ are used for the presently suggested depth-based wear model. As a result, a wear depth profile can be simulated by a model using $D_{max}$. Wear resistance from the concern of an overall depth can be identified by the wear coefficient of the model using $D_e$.

• 한국정밀공학회지
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• 제17권3호
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• pp.149-157
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• 2000

Tool wear in the shearing process such as blanking, piercing and trimming is very important, because it has great effects on the dimensional accuracy, working efficiency and economy. Most of tools in the shearing process have the coated layer at surface fur good wear and corrosion resistance. When the surface of tool is teated, the wear Phenomena of coated surface layer and inner layer may be different. This paper describes a computer modelling technique by the finite element method in order to investigate the wear mechanism and to predict the wear profile of Ti-N coated tool in piercing process according to the volume of Production. Wear coefficients of the coated layer and inner layer are obtained through Pin-on-Disk wear test, respectively. To verify the effectiveness of the suggested technique, the technique is applied to wear analysis in piercing recess of piston pin and simulation results are compared with experimental ones.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1720-1729
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• 2001

Wear characteristics of Nylon and acetal pinions against steel gears for different pitch line velocities was studied with a power circulating gear test rig under unlubricated condition. Specific wear rate was measured as a function of tooth number, module, tooth width and total revolution. The worn tooth surfaces were examined with a profile projector. The Nylon pinion showed lower specific wear rate than the acetal pinion. However, the Nylon pinion was fractured at high tooth loads, whereas the acetal pinion exhibited a steady wear behavior. The wear characteristics of Nylon pinion varied significantly with the Pitch line velocity. Wear occurred most severely at the tooth tip and the region immediately below the pitch line of pinion. The dominant wear mechanisms were adhesion and abrasion.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.854-859
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• 2008

In a railway vehicle, contact between wheel and rail is a peculiar characteristic and variations of wheel and rail profile influence on the dynamic characteristics of railway vehicle. Thus the variations of the wheel and rail profile are very important in railway dynamics. Recently a research relating to active steering to improve the curving performance of vehicle is progressing actively at home and abroad. In this field, a pre-study for the wheel/rail contact geometry is needed and especially the variation of the wheel/rail contact geometry with wheel wear is the key design parameter to develop the controller of the active steering bogie. In this paper, we have experimentally studied to analyze the variation of the wheel/rail contact geometry with wheel wear as a pre-study to develop the active steering bogie for electric multiple unit (EMU). For this, we have made an experiment with EMU operating in curving area. We have measured the wear profiles of the wheel of the test vehicle and analyzed the wheel/rail contact geometry with a mileage of the test vehicle. In experiment with test vehicle, we have got the useful data to design the steering controller of the wheelset.

• Tribology and Lubricants
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• 제38권1호
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• pp.1-7
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• 2022

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.