• 한국정밀공학회지
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• 제28권5호
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• pp.537-542
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• 2011

The thermo-mechanical interaction between brake block and wheel tread during braking has been found to cause thermal crack on the wheel tread. Due to thermal expansion of the rim material, the thermal cracks will protrude from the wheel tread and be more exposed to wear during the wheel/block contact than the rest of the tread surface. The wheel rim is in residual compression stress when is new. After service running, the region in the tread has reversed to tension. This condition can lead to the formation and growth of thermal cracks in the rim which can ultimately lead to premature failure of wheel. In the present paper, the thermal cracks of railway wheel, one of severe damages on the wheel tread, were evaluated to understand the safety of railway wheel in running condition. The residual stresses for damaged wheel which are applied to tread brake are investigated. Mainly X-ray diffusion method is used. Under the condition of concurrent loading of continuous rolling contact with rails and cyclic frictional heat from brake blocks, the reduction of residual stress is found to correlate well with the thermal crack initiation.

• 대한토목학회논문집
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• 제37권4호
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• pp.693-703
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• 2017

달 탐사 로버 휠의 주행 성능은 지반 조건과 휠의 형상에 따라 크게 달라진다. 이에 본 연구에서는 한국형 인공월면토 및 주문진 표준사에서 휠 형상을 변화시켜 달 탐사 로버 휠의 주행성능 평가를 실시하였다. 단일 휠 성능평가 실험장비를 이용하여 지반조건에 따른 영향을 검토하였고, 이와 더불어 인공월면토에서 그라우저 높이에 따른 휠 주행성능 평가를 실시하였다. 휠 주행성능 평가는 슬립율에 따른 토크, 견인력 및 침하량을 측정하여 각 조건별로 상대적인 비교를 하였다. 실험 결과 주문진 표준사에 비해 한국형 인공월면토에서 로버 휠 주행성능이 우수하였으며, 휠 주행성능이 흙의 점착력과 마찰각 특성에 큰 영향을 받는 것으로 나타났다. 또한, 휠 그라우저 높이에 따라 견인성능이 증가하는 것으로 나타났다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2010년도 하계학술대회 논문집
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• pp.518-519
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• 2010

본 논문에서는 EV용 25kW급 In Wheel Type의 IPMSM을 제어 할 수 있는 구동장치를 제작하였다. 여기서 In Wheel Motor는 고성능의 전기모터를 Wheel에 직접 장착하여 파워트레인 요소를 모두 제거함으로써 차량 시스템의 효율을 높이고, 친환경 차량에 적용할 수 있는 신개념의 플랫폼을 제공할 수 있는 고효율, 고성능 차량 시스템이다. 따라서 본 논문에서는 EV용 In Wheel Motor와 이를 제어하기 위한 구동장치에 대한 제어시스템을 제안하고 이를 실험을 통해 검증하였다.

• 한국정밀공학회지
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• 제28권5호
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• pp.551-558
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• 2011

To analyze the effect of wear of wheel profile on the running stability of rolling-stock, theoretical and experimental studies were conducted on the profiles used in conventional lines. In experiment using 1/5 scale model to verify the results of the theoretical analysis, the test results of the critical speed for worn wheel profile samples show similar trend. In case of the conical type wheel profile(Profile 40), the equivalent conicity is increased with flange wear. But in case of the arc type wheel profile(Profile 20h), the equivalent conicity is decreased with flange wear. And the critical speed of the bogie was inverse proportion to the equivalent conicity. It is shown that the variation of the critical speed with the wheel wear could be changed according to the design concept and wear pattern of wheel profile. Results of the theoretical and experimental studies are discussed here.

• 한국정밀공학회지
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• 제8권2호
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• pp.106-113
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• 1991

A diamond grinding wheel is generally used to grind hard and brittle materials, such as advanced ceramics. It is, however, quite difficult to dress a diamond grinding wheel efficiently because of its high degree of hardness. In this study, some investigations are carried out to increase dressing efficiecy of resinoid bonded diamond grinding wheel. Dressing forces are measured over a wide range of dressing conditions, and SEM observation of a grinding wheel is carried out. Special attention is paid to comparison between stick method and rotary brake method. Results obtained in this study provide useful information determining reguired dressing time, and for choosing efficient dressing condition for diamond grinding wheel.

• International Journal of Automotive Technology
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• 제5권2호
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• pp.123-133
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• 2004

This paper describes a robust and fast wheel slip tracking control using a moving sliding surface technique. A traction control system (TCS) is the active safety system used to prevent the wheel slipping and thus improve acceleration performance, stability and steerability on slippery roads through the engine torque and/or brake torque control. This paper presents a wheel slip control for TCS through the engine torque control. The proposed controller can track a reference input wheel slip in a predetermined time. The design strategy investigated is based on a moving sliding surface that only contains the error between the reference input wheel slip and the actual wheel slip. The used moving sliding mode was originally designed to ensure that the states remain on a sliding surface, thereby achieving robustness and eliminating chattering. The improved robustness in driving is important due to changes, such as from dry road to wet road or vice versa which always happen in working conditions. Simulations are performed to demonstrate the effectiveness of the proposed moving sliding mode controller.

• Tribology and Lubricants
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• 제28권1호
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• pp.19-26
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• 2012

Rolling contact fatigue of an urban railway wheel was analysed during its rolling. A FEM analysis was performed using a 3D modelling of rail and wheel, considering the slope of the rail and nonlinear isotropic and kinematic hardening behavior of the rail and the wheel. The maximum von-Mises stress and contact pressure between the rail and wheel were 656.9 MPa and 1111.4 MPa, respectively, under axial load of 85 kN with friction coefficient of 0. The fatigue initiation life prediction relationships by strain-lifetime (${\varepsilon}$-N) and Smith-Watson-Topper method were drawn for the wheel steel as follows: $N_i=7.35{\times}10^6{\times}SWT^{-3.56}$ and $N_i=5.41{\times}10^{-9}{\times}(\frac{{\Delta}{\varepsilon}}{2})^{-5.77}$. The fatigue lifetimes of the wheel due to rolling contact were determined to be infinite by ${\varepsilon}$-N and SWT methods.

• 한국자동차공학회논문집
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• 제21권3호
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• pp.1-14
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• 2013

In this paper, a finite element analysis technique of rolling stock models for collision-induced derailments was suggested using rolling contacts for wheel-rail interaction. The collision-induced derailments of rolling stock can be categorized into two patterns of wheel-climb and wheel-lift according to the friction direction between wheel flange and rail. The wheel-climb derailment types are classified as Climb-up, Climb/roll-over and Roll-over-C types, and the wheel-lift derailment types as Slip-up, Slip/roll-over and Roll-over-L types. To verify the rolling contact simulations for wheel-rail interaction, dynamic simulations of a single wheelset using Recurdyn of Functionbay and Ls-Dyna of LSTC were performed and compared for the 6-typical derailments. The collision-induced derailment simulation of the finite element model of KHST (Korean High Speed Train) was conducted and verified using the theoretical predictions of a simplified wheel-set model proposed for each derailment type.

• 대한기계학회논문집A
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• 제37권11호
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• pp.1387-1395
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• 2013

차륜 불평형은 차륜의 무게중심이 윤축의 기하학적 중심축에서 벗어나 있을 때 발생한다. 차륜 불평형을 수정하지 않고 주행하면 불평형에 의한 원심력이 차체의 진동을 발생시키게 되며 차륜의 마모를 촉진시키거나 차축 베어링에 손상을 주게 된다. 본 연구에서는 철도차량 동적해석을 통하여 차륜 불평형이 차량 임계속도와 차체 진동에 미치는 영향을 검토하였다. 차륜 불평형은 임계속도를 감소시키고 차체 공진을 유발할 수 있음을 알 수 있었다. 또한 차륜의 정적, 동적 불평형에 따른 차체진동을 해석함으로써 불평형 수정은 양면 밸런싱이 필요함을 밝혔다.

• 한국자동차공학회논문집
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• 제24권4호
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• pp.439-446
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• 2016

An in-wheel motor vehicle is a type of car that is equipped with an electric motor for each wheel. It is possible to acquire vehicle stability through a seperate driving torque control per wheel, since it directly generates the driving torque via the wheel motors. However, the vehicle ride comfort and road holding performance worsen depending on the increase of the wheel weights. In order to compensate for the impaired performance, an integrated chassis control system of the rear in-wheel motor vehicle is proposed. The proposed integrated chassis control system is composed of a driving torque control system, a semi-active suspension system, and an ESC system. According to the vehicle dynamic simulation of an in-wheel motor vehicle equipped with the integrated chassis control system, it is found that the system can improve the driving stability, ride comfort, and driving efficiency of the in-wheel motor vehicle.