• 소음진동
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• 제7권6호
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• pp.953-958
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• 1997

Corrugation of railway track can be caused by the various dynamic behaviors of traveling wheels and track. In this paper, the coupled vibrations of traveling wheel and railway track are analyzed as the cause of corrugations. To analyze the coupled vibration, the track supported by the sleepers and the traveling wheels are identified to the elastically supported infinite beam and the spring-mass system which runs at constant speed. The Hertzian contact spring is considered between the infinite beam and spring-mass system are calculated. The cause and development of rail corrugation are discussed in the view point of contact force fluctuation affected by the elastic supports and the corrugated surface profile on the track. By the obtained results, the possibilities of resonance are checked between the excitation by the corrugated surface profile and the natural frequency of contact spring-mass system. It may be thought to a development of railway corrugation.

• Tribology and Lubricants
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• 제14권4호
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• pp.58-63
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• 1998

This paper presents a study of the elastohydrodynamic lubrication of elliptical contacts where lubricant entrainment coincides with the major axis of the Hertzian contact ellipse. A finite difference method and the Newton-Raphson method are applied to analyze the problem. Film contours and pressure distributions are compared with the results for lubricant entrainment coincides with the minor axis. Variations of the minimum and central film thicknesses with the radius ratio are also examined. The results showed that the present numerical scheme can be used generally in the analysis of the EHL of elliptical contacts where the lubricant entraining vector did not coincide with either of the principal axis of the conjunction.

• 한국감성과학회:학술대회논문집
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• 한국감성과학회 1998년도 추계학술발표 논문집
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• pp.261-266
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• 1998

손끝으로 물건을 문지르거나 잡아 질감을 느끼는 경우 나타나는 현상을 Hertzian 접촉이론을 응용하여 수학적인 모델링을 하였다. 물체표면에 손끝이 접촉하여 눌려지게되면 변형이 일어나게 되고 변형된 모양과 정도에 따라 촉감을 느끼게 .된다. 손끝은 점탄성체로서 누르는 변위에 따라 탄성계수와 점성계수 값이 비선형으로 변하게 되는 현상을 이론과 실험을 통하여 연구하였다. 특히 손끝이 직물을 누를 때 나타나는 현상을 측정하여 질감표현과의 관계를 분석하였다.

• 감성과학
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• 제2권1호
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• pp.27-33
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• 1999

손끝으로 물건을 문지르거나 잡아 질감을 느끼는 경우 나타나는 현상을 Hertzian 접촉이론을 응용하여 수학적인 모델링을 하였다. 물체표면에 손끝이 접촉하여 눌러지게되면 변형이 일어나게 되고 변형된 모양과 정도에 따라 촉감을 느끼게 된다. 손끝은 비선형으로 변형되므로 누르는 변위에 따라 탄성계수 값이 변하는 현상을 실험을 통하여 확인하였으며 모델링한 식과 비교한 결과 유사한 경향을 보였다. 특히 손끝이 직물을 누르며 문지를 때 힘이 크기변화를 측정하여 질감표현과의 관계를 분석하였다.

• 동력기계공학회지
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• 제12권2호
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• pp.41-47
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• 2008

This article deals with the stress analysis of the friction drive, which transmits the power via the rolling resistance on the contract area between the two rotating bodies. On the contact area, friction drives are normally involved with shear stress due to the transmitted force, as well as normal stress. Thus the stress analysis including the shear stress is necessary for the design of the friction drive. Hertzian results can be used to estimate the normal stress distribution and elastic deflection of the contact area, although the shear stress distribution is not well defined. In order to investigate the shear stress distribution and its effects in a friction drive, we have performed the stress analysis of the spherical continuously variable transmission(CVT) using finite element method. The spherical CVT is one of friction drives, which is used in small power applications. The numerical results show that the normal stress distribution is not affected by the transmitted shear force, and the maximal shear stress is increased in small amount along with the shear force.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 춘계학술대회논문집
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• pp.326-331
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• 2004

The linear motion (LM) guide using ball bearing has many advantages compared with conventional sliding guides. Therefore, LM guide using ball bearing has been used widely to increase the accuracy of the position of a system. This research investigates dynamic characteristics of LM guide through mainly linear analysis. Linear analysis is accomplished by Lagrange equation and finite element method. And another trial that is nonlinear analysis about one mode of LM guide(bouncing mode) from Hertzian contact theory is accomplished in the latter half of this research. Through nonlinear analysis we could observe the softening characteristic due to the Hertzian contact nonlinearity.

• 한국소음진동공학회논문집
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• 제14권9호
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• pp.868-876
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• 2004

The linear motion(LM) guide using ball bearing has many advantages compared with conventional sliding guides. Therefore, LM guide using ball bearing has been widely used to increase the accuracy of the position of a system. This research investigates dynamic characteristics of LM guide through mainly linear analyses. Linear analysis is accomplished by Lagrange equation and the finite element method. And another trial that performs nonlinear analysis about one mode(bouncing mode) of LM guide from Hertzian contact theory is accomplished in the latter half of this research. Through nonlinear analysis we could observe the softening characteristic due to the Hertzian contact nonlinearity.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 추계학술대회 논문집
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• pp.191-196
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• 2005

In this study, to describe vehicle-track-bridge dynamic interaction phenomena with 1/4 vehicle model, nonlinear Hertzian contact spring and nonlinear contact damper are introduced. In this approach external loads acting on 1/4 vehicle model are self weight of vehicle and geometry information of running surface. The constraint equation on contact surface is implemented by Penalty method. Also, to improve the numerical stability and to maintain accuracy of solution, the artificial damper and the reaction from constraint violation are introduced. A nonlinear time integration method, in this study, Newmark method is adopted for both equations of vehicles and structure. And to reduce the error caused by inadequate time step size, adaptive time-stepping technique is partially introduced. As the nonlinear Hertzian contact spring has no resistance to tensile force, the bouncing phenomena of wheelset can be described. Thus, it is expected that more versatile dynamic interaction phenomena can be described by this approach and it can be applied to various railway dynamic problems.

• 대한기계학회논문집A
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• 제38권7호
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• pp.751-756
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• 2014

우리 주변에는 수많은 알갱이들이 서로 상호작용하면서 운동하는 모습을 주로 볼 수 있다. 본 연구에서는 수많은 알갱이들의 접촉에 따른 동적 거동을 분석하였다. 접촉에 의한 각 요소의 거동을 해석하기 위해 이산 요소법(Discrete element method)을 사용하였다. 접촉 관계에 있어서 접촉 판별을 위해 Neighboring-Cell 알고리즘을 사용하였고, 접촉력 계산에 Hertzian contact model과 Tangential sliding friction contact 모델을 사용하였다. 수많은 알갱이의 접촉해석을 위해 GPU 기반의 병렬 프로그램을 구성하였다. 해석을 검증하기 위해서 댐 붕괴 실험을 수행하였다. 거동 종료시점에 입자들의 쌓인 형상을 시뮬레이션 결과와 비교하여 해석 프로그램의 신뢰성을 검증하였다.

• 한국항공우주학회지
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• 제30권7호
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• pp.44-50
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• 2002

본 논문에서는 저속충격을 받는 복합재 샌드위치 평판의 동적 거동에 관한 연구를 수행하였다. 접촉 하중의 산출을 위해서 Hertz의 접촉법칙을 새로이 수정하는 방법을 제시했는데, 지수를 줄이는 방법과 심재의 두께방향의 탄성계수의 값을 줄여 등가 탄성계수를 계산하는 방법을 사용했다. 접촉하중을 산출하는 비선형 방정식은 Newton-Raphson 방법을 사용하여 계산하였고, 시간적분에는 Newmark-beta 방법을 사용하였다. 이러한 기법과 18절점 가정변형률 솔리드 요소를 적용하여 저속충격 해석용 유한요소 프로그램을 개발했다. 이 프로그램을 이용하여 다양한 복합재 샌드위치 평판의 저속충격에 대한 동적 거동을 해석하였다. 제안된 접촉법칙을 적용한 해석결과를 분석하여 볼 때, 대부분의 경우에서 접촉하중과 접촉시간이 실험결과와 대체로 일치함을 확인하였다.