• 한국융합학회논문지
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• 제9권1호
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• pp.283-289
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• 2018

자동차 디스크 브레이크시스템에서는 열유속 및 열변형 등과 같은 이유로 마찰열이 균일하게 분산되지 않는다. 마찰열에 의한 열탄성 변형이 접촉압력 분포에 영향을 미치게 되고, 접촉하중이 디스크 브레이크 표면상의 작은 영역에 집중되어 열탄성 불안정성을 초래 할 수 있다. 본 연구에서는 실험적 계산식과 Kao 제안한 디스크와 패드의 접촉압력에 대한 해석방법을 참고로 하여 3차원 축대칭 모델을 통하여 실제로 제동 시 발생되는 디스크와 패드의 접촉을 고려한 온도해석 및 열변형 해석을 하였다. ANSYS를 사용하여 디스크와 패드의 접촉면에서 발생하는 열탄성 불안전성 문제를 열하중과 기계적 하중으로 동시에 고려하여 해석하였다. 디스크와 패드가 직접 접촉하는 3차원 축대칭 모델을 구성하여 디스크의 마찰면 온도, 열변형, 접촉 열응력을 관찰함으로써 디스크에서 일어나는 열적 거동을 보다 정확하게 관찰하였다.

• 대한토목학회논문집
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• 제33권4호
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• pp.1281-1293
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• 2013

현수교 주케이블용 평행강선 스트랜드(PPWS) 소켓의 엄밀한 수치해석을 위한 유한요소해석 모델을 제안하였고, 제안된 해석 모델을 이용하여 소켓의 거동을 분석하였다. 개별 강선과 소켓 내부 주입 합금재의 영향을 고려한 직교 이방성 재료 모델을 적용하였고, Coulomb 마찰 및 표면접촉 모델을 도입하여 소켓 내면과 주입 합금재 표면의 접촉 상태를 구현하였다. 인장 실험으로부터 측정된 소켓 외면의 변형율과 유한요소 해석 결과를 비교하여 제안된 유한요소 해석 모델의 타당성을 검증하였고, 마찰계수의 변화에 따른 소켓의 거동을 해석하였다. 해석 결과, 소켓 내면과 주입 합금재 표면의 마찰은 소켓과 주입 합금재에 발생하는 응력 집중을 크게 완화 시켰으며, 소켓 설계법에서 정의된 수직응력식은 소켓 내면과 주입 합금재 표면의 접촉응력 분포에서 상하부 사분위값의 평균을 대표하는 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제6권1호
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• pp.63-76
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• 1998

This paper presents dynamic responses of structures with sliding base which limits the translation of external loads from ground excitation. A discrete element model based on the discontinuous deformation analysis method is proposed to study this sliding boundary problem. The sliding base is simulated using sets of fictitious contact springs along the sliding interface. The set of contact spring is to translate friction force from ground to superstructure. Validity of the proposed model is examined by the closed-form solutions of an idealized mass-spring structural model subjected to harmonic ground excitation. This model is also applied to a problem of a three-story structural model subjected to the ground excitation of 1940 El Centro earthquake. Analyses of both sliding-base and fixed-base conditions are performed as comparisons. This study shows that using this model can simulate the dynamic response of a sliding structure with frictional cut-off quite accurately. Results reveal that lowering the frictional coefficient of the sliding joint will reduce the peak responses. The structure responses in little deformation, but it displaces at the end of excitation.

• 한국정밀공학회지
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• 제32권5호
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• pp.423-429
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• 2015

Linear motion (LM) ball guides have good accuracy and high efficiency. They are widely applied for precision machinery such as machine tools, semiconductor fabrication machines and robots. However, friction force incurs heat between the balls and grooves. Thermal expansion due to the heat deteriorates stiffness and accuracy of the LM ball guides. For accurate estimation of stiffness and accuracy during the linear motion, friction models of LM ball guides are required. To formulate accurate frictional models of LM ball guides according to load and preload conditions, rolling and viscous frictional analyses have been performed in this paper. Contact loads between balls and grooves are derived from Hertzian contact analysis. Contact angle variation is incorporated for the precision modeling. Viscous friction model is formulated from the shear stress of lubricant and the contact area between balls and grooves. Experiments confirm validity of the developed friction model for various external load and feedrate conditions.

• 대한기계학회논문집
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• 제18권3호
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• pp.540-547
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• 1994

Contact and frictional locking conditions and the effect of shielding due to contact at the facet, which could be represented by the difference in energy release rate, as a function of phase angle of loading are analyzed in this study for the case of interfacial cracks by assuming single crack-kink model. The analysis of contact effects on interfacial fracture resistance shows that relative shielding increases as the shear component was increased, which indicates a qualitative agreement with the previous experimental results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.620-623
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• 2000

The leaf spring is generally used effectively in load supporting because it has tension-diffused function in comparison with other springs. Nowadays the leaf spring is used widely in the suspensions of automobile and trains. The stiffness and the damping characteristics of the leaf spring being essential for the performance of vehicles, the exact evaluation is required. Various approximate formula are normally used for the leaf spring design. however, accuracy and trust are decreased because the contact and frictional characteristics between leaf plates are generally neglected. In this paper, nonlinear stiffness matrix of the leaf spring is solved by contact-element applying FEM for considering the contact and frictional characteristics between leaf plates. The results of proposed FE model are compared with test data.

• 제어로봇시스템학회논문지
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• 제10권10호
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• pp.887-898
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• 2004

In this paper a mathematical framework fur deriving acceleration bounds from given joint torque limits of multiple cooperating robots are described. Especially when the different frictional contacts for every contact are assumed and the torque limits are given in 2-norm sense, we show that the resultant geometrical configuration for the acceleration is composed of corresponding parts of ellipsoids. Since the frictional forces at the contacts are proportional to the normal squeezing forces, the key points of the work includes how to determine internal forces exerted by each robot in order not to cause slip at the contacts while the object is carried by external forces. A set of examples composed of two robot systems are shown with point-contact-with-friction model and insufficient or proper degree of freedom robots.

• 한국정밀공학회지
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• 제27권3호
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• pp.80-88
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• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

• Journal of applied mathematics & informatics
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• 제41권3호
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• pp.487-510
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• 2023

We propose a mathematical model which describes the frictional contact between a piezoelectric body and an electrically conductive foundation. The behavior of the material is described with a linearly electro-viscoelastic constitutive law with long term memory. The mechanical process is dynamic and the electrical conductivity coefficient depends on the total slip rate, the friction is modeled with Tresca's law which the friction bound depends on the total slip rate with taking into account the electrical conductivity of the foundation both. The main results of this paper concern the existence and uniqueness of the weak solution of the model; the proof is based on results for second order evolution variational inequalities with a time-dependent hemivariational inequality in Banach spaces.

• Journal of Electrical Engineering and Technology
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• 제8권6호
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• pp.1415-1423
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• 2013

The traveling wave ultra-sonic motor (TWUSM) is operated through the frictional force between the rotor and the stator. Hence, the contact mechanism should be analyzed to estimate the motor performance. However, the nonlinearity of the contact mechanism of the TWUSM makes it difficult to propose a proper contact model and a characteristic analysis method. To address these problems, a novel contact model is proposed and be termed the cylindrical dynamic contact model (CDCM) in this research. An estimation method of the motor performance is proposed using the CDCM, an analytical method, and a numerical method. The feasibility and usefulness of the proposed characteristic analysis are verified through experimental data.