• Title/Summary/Keyword: Rolling contact

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Torsional Stiffness Analysis of a Cycloid Reducer using Hertz Contact Theory (Hertz 접촉이론을 이용한 사이클로이드 감속기의 비틀림 강성해석)

  • Lee S.Y.;Park J.S;Ahn H.J.;Han D.C.
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2005.06a
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    • pp.816-821
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    • 2005
  • The cycloid reducer has very high efficiency, high ratios, high stiffness and small size, in comparison with a conventional gear mechanism, which makes it an attractive candidate for limited space and precision application such as industrial robot. There are several publications on analysis and design of the cycloid reducer, however, it was assumed that the contact stiffness of pin rollers and cycloid disk is constant regardless of their contact geometry. Moreover, the torsional stiffness of the cycloid reducer couldn't be calculated due to the assumption. In this paper, we present a new procedure of calculating torsional stiffness of the cycloid reducer using Hertz contact theory. First, conventional force analysis of the cycloid reducer is briefly reviewed. Then, iterative numerical calculation procedure of the contact stiffness is proposed based on the Hertz contact theory where the contact stiffness depends on the contact force. In addition, total torsional stiffness of the cycloid reducer is estimated considering its rolling element bearing stiffness. The torsional stiffness of the cycloid reducer is dominated by the rolling element bearing stiffness since the contact stiffness of the cycloid disk is too large.

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Three-Dimensional Contact Dynamic Model of the Human Knee Joint During Walking

  • Mun, Joung-Hwan;Lee, Dae-Weon
    • Journal of Mechanical Science and Technology
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    • v.18 no.2
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    • pp.211-220
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    • 2004
  • It is well known that the geometry of the articular surface has a major role in determining the position of articular contact and the lines of action for the contact forces. The contact force calculation of the knee joint under the effect of sliding and rolling is one of the most challenging issues in this field. We present a 3-D human knee joint model including sliding and rolling motions and major ligaments to calculate the lateral and medial condyle contact forces from the recovered total internal reaction force using inverse dynamic contact modeling and the Least-Square method. As results, it is believed that the patella, muscles and tendon affect a lot for the internal reaction forces at the initial heel contact stage. With increasing flexion angles during gait, the decreasing contact area is progressively shifted to the posterior direction on the tibia plateau. In addition, the medial side contact force is larger than the lateral side contact force in the knee joint during normal human walking. The total internal forces of the knee joint are reasonable compared to previous studies.

Evaluation of Rolling Contact Fatigue Evaluation of Wheel for High Speed Train Using a Scan Type Magnetic Camera (자기카메라에 의한 고속철도 차륜의 구름접촉 피로평가)

  • Hwang, Ji-Seong;Kwon, Seok-Jin;Lee, Jin-Yi;Seo, Jung-Won
    • Proceedings of the KSR Conference
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    • 2011.10a
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    • pp.957-965
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    • 2011
  • Recently, railway industry has been developed not only functional parts such as acceleration and high performance of the railway but also emotional parts such as improved ride comfort and blocking noise. However, some important components of railway such as wheel and rail always had exposed too much operation time, cyclic load and rolling contact directly. The variations of load, vibration and chemical compositions were caused of wheel and rail having a lot of different types of contact fatigue damages. Therefore, It is necessary to improve inspection and maintenance technology in order to ensure safety and reliability of railway. Many researchers have already been reported the technology. Magnetic camera, one of the non-destructive testing technique can be used to inspect and evaluate the changes of magnetic field in ferromagnetic and paramagnetic materials with cracks. When an electromagnetic is applied to a specimen, a magnetic field will be distorted around a crack on the specimen. In present paper, the distribution of magnetic property in wheel with cracks using magnetic camera had investigated. The crack can be detected and evaluated by distribution analysis of magnetic field. The magnetic camera technique can be detected and evaluated the crack by rolling contact fatigue.

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Effect of Rail Surface Damage on Contact Fatigue Life (레일표면손상이 접촉피로수명에 미치는 영향)

  • Seo, Jung-Won;Lee, Dong-Hyong;Ham, Young-Sam;Kwon, Sung-Tae;Kwon, Seok-Jin;Cho, Ha-Yong
    • Journal of the Korean Society for Precision Engineering
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    • v.29 no.6
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    • pp.613-620
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    • 2012
  • Rails are subjected to damage from rolling contact fatigue, which leads to defects such as cracks. Rolling contact fatigue damages on the surface of rail such as head check, squats are one of growing problems. Another form of rail surface damage, known as "Ballast imprint" has become apparent. This form of damage is associated with ballast particles becoming trapped between the wheel and the surface of rail. These defects are still one of the key reasons for rail maintenance and replacement. In this study, we have investigated whether the ballast imprint is an initiator of head check type cracks and effect of defect size using Finite element analysis. The FE analysis were used to investigate stresses and strains in subsurface of defects according to variation of defect size. Based on loading cycles obtained from FE analysis, fatigue analysis for each point was carried out.

A Study on the contact force calculation by bending load of axle of rolling stocks (철도차량 차축의 굽힘하중에 의한 차륜/레일 접촉력 계산에 관한 연구)

  • Ham, Young-Sam
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.481-484
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    • 2008
  • The important factor to evaluate the running safety of a railway vehicle would be the interaction force between wheel and rail(derailment coefficient), for which is one of important factors to check the running safety of a railway vehicle that may cause a tragic accident. Element that analyze derailment coefficient is consisted of wheel load and lateral force. In this paper, studied about method that calculate vertical force(wheel load) by bending load of axle in rolling stocks.

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Development of Technique Predicting of the Wear of DCI Roll Using Carbon Steel in Hot Rod Rolling Process (탄소강 선재 압연공정의 DCI 롤 마멸 예측 기술의 개발)

  • Kim, Dong-Hwan;Kim, Byeong-Min;Lee, Yeong-Seok;Yu, Seon-Jun;Ju, Ung-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.9
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    • pp.1736-1745
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    • 2002
  • The objective of this study is to predict the roll wear in hot rod rolling process. In this study hot rod rolling process for round and oval passes has been investigated. In order to predict the roll wear, the wear model is reformulated as an incremental form and then wear depth of roll is calculated at each deformation step on contact area using the results of finite element analysis, such as relative sliding velocity and normal pressure at contact area. Archard's wear model was applied to predict the roll wear. To know the thermal softening of DCI (Ductile Cast Iron) roll according to operating conditions, high temperature micro hardness test is executed and a new wear model has been proposed by considering the thermal softening of DCI roll expressed in terms of the main tempering parameter curve. 3D wear program developed in this study might be used for adjusting the gap of rolls to set up a suitable rolling schedule for keeping dimensional tolerance of the product.

Development of intermediate roll which has a long life for cold rolling mills (냉간압연용 장수명 중간롤 개발)

  • Park Y. C.;Kim B. H.;Kim I. B.;Kim J. T.;KIM H. M.;Lee W. D.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2004.08a
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    • pp.207-215
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    • 2004
  • There are various characteristics called for in work roll and intermediate rolls for cold rolling mills. Among these characteristics, the two main requirements are to ensure the quality of the rolled products and to reduce roll cost. To achieve these needs, resistance to wear, to thermal shock and to contact fatigue are especially important. This paper describes that new material(named DSR1) for intermediate rolls which greatly increases rolling campaign and improves resistance to wear has been developed. DSR1 was successfully manufactured and has been used in the cold rolling mill. It showed that Trial product was homogenous in hardness distribution and sufficient usable diameter. Also in service test, trial product is much more excellent rolling performance than conventional $5\%Cr$.

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Development of a Cold Rolling Oil with Lubricity and Mill Cleanness Property (윤활성 및 압연기 청정성을 겸비한 냉간 압연유의 개발)

  • 한석영;송교봉;이준정
    • Tribology and Lubricants
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    • v.13 no.2
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    • pp.74-81
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    • 1997
  • The purpose of this study is to develop a cold rolling oil with lubricity and mill cleanness property under the rolling conditions of high reduction ratio and high rolling speed. Six kinds of oil samples were blended. Evaluation of lubricity and anti-seizuro property of the samples were carried out with a laboratory scale rolling mill, where the contact conditions between work roll and strip are very close to actual cold rolling mill. Laboratory evaluation for dispersion, contamination, anti-oil stain property and residual carbon, etc. were carried out with several testers such as longterm circulation tester, Coulter counter and Conradson tester. A new high speed cold rolling oil with good lubricity and mill cleanness property was developed compared with the previously developed rolling oil.