• Structural Engineering and Mechanics
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• 제23권4호
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• pp.431-447
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• 2006

A new incremental finite element model is developed to simulate the frictional contact of elastic bodies. The incremental convex programming method is exploited, in the framework of finite element approach, to recast the variational inequality principle of contact problem in a discretized form. The non-classical friction model of Oden and Pires is adopted, however, the friction effect is represented by an equivalent non-linear stiffness rather than additional constraints. Different parametric studies are worked out to address the versatility of the proposed model.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제17권1호
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• pp.29-45
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• 2013

Central schemes offer a simple and versatile approach for computing approximate solutions of nonlinear systems of hyperbolic conservation laws. However, there are large numerical dissipation in case of contact discontinuity. We study semi-discrete central upwind scheme by changing flux functions to reduce the numerical dissipation and we perform numerical computations for various problems in case of contact discontinuity.

• Tribology and Lubricants
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• 제13권3호
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• pp.93-101
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• 1997

The numerical results on the stress distributions of rail-wheel contact problems are presented for three models in a high-speed rail system. These models which have straight and tapered (1:40 and 1:20) contact geometries between the wheelset and rail are analyzed using the finite element approach. From the simulation results we found that the tapered geometry (1:20) of railwheel contact base line showed very stable contact stress distributions for a whole contact position between the wheel and rail in a curved rail section. The FEM computed results may present an optimized slope geometry of rail-wheel contact in a high-speed railway system.

• Tribology and Lubricants
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• 제4권2호
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• pp.28-35
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• 1988

A general and efficient algorithm is proposed for the analysis of the frictionless elastic contact problems. It utilizes a simplex-type algorithm with a modified entry rule and incoporates finite element method to obtain flexibility matrices. The algorithmic solution is compared with the Hertzian solution for the contact problem between two cylinders to prove its accuracy and the contact problem between pin and piston rod is solved and compared with the numerical results of Frankavilla and Zienkiewicz to demonstrate the generality and effectiveness of the suggested algorithm. The contact problem between mating involute gear teeth at the worst load position is considered. The computed contact stress is smaller than the result of Hertz's theory applied to the contact between two kinematically equivalent discs and the contact area is larger than that of Hertz's theory.

• 한국정밀공학회지
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• 제33권7호
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• pp.541-549
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• 2016

Rolling contact fatigue and wear on rails are inevitable in railway operations due to excessive wheel-rail contact stress. The wear is influenced by vehicle speed, contact pressure, environmental conditions, and many other factors. Speeding on a curved track causes many problems such as wear on the gauge of the rail and rolling contact fatigue. Managing environmental conditions can reduce problems on the wheel and rail interface. In this study, the wear characteristics of wheel and rail materials were investigated by twin-disc testing using various parameters. The results of the wear test indicated that the wear rate under dry conditions was larger than that under wet conditions. We found that contact fatigue damage occurred on the rail in dry conditions, however, the surface of the specimen under water remained smooth. Also, the friction coefficient in dry conditions was larger than in wet conditions.

• 한국전산구조공학회논문집
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• 제24권2호
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• pp.121-131
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• 2011

본 논문에서는 경계요소법으로 평면 탄성 접촉문제를 해석하기 위하여 객체지향기법을 이용하여 프로그램을 구성하였다. 개발된 프로그램의 상세는 UML을 통하여 기술함으로써, C++로 구현된 프로그램이 일반적인 객체지향기법을 통해 구현될수 있도록 하였다. 개발된 프로그램은 접촉해석의 비선형성과 모퉁이 문제를 포괄할 수 있도록 추상화된 객체로 구현되었다. 접촉해석에 관련된 객체의 상세를 기술하였으며, 수치해석 예제를 통하여 개발된 프로그램의 정확성을 검증하였다.

• 한국가정과교육학회지
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• 제22권4호
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• pp.51-64
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• 2010

본 연구는 중학교에 재학 중인 남녀 청소년을 대상으로 성별에 따른 청소년 행동문제의 차이를 살펴보고 개인심리 요인과 가족환경 요인 및 사회환경 요인이 청소년의 행동문제와 어떠한 관련성을 가지고 있는지 파악하고자 하였다. 이러한 연구목적을 위해 기존의 연구와 관련 자료를 참고로 하여 자아존중감, 자기통제력, 부모의 양육행동, 부부갈등, 비행친구접촉, 학교생활적응 그리고 청소년의 행동문제에 관한 척도를 구성하고, 인천광역시에 있는 중학교 2학년 학생 500명을 대상으로 자료를 수집한 후 최종 483부의 설문 자료를 분석하였다. 본 연구에서 얻어진 연구결과를 요약하면 다음과 같다. 첫째, 청소년의 외현화 행동문제에서 성별에 따른 유의한 차이가 나타나지 않아, 남자 청소년과 여자 청소년은 비슷한 수준의 외현화 행동문제를 경험하는 것으로 나타났다. 내재화 행동 문제에서는 성별 차이가 나타나 여학생이 남학생보다 더 높은 수준의 내재화 행동문제를 경험하는 것으로 나타났다. 둘째, 개인심리와 가족환경 및 사회환경 요인이 청소년의 행동문제에 어떠한 영향력을 미치는지를 살펴보면, 남자 청소년과 여자 청소년 모두 자기통제력이 낮을수록 그리고 비행 친구 접촉이 많을수록 더 많은 외현화 행동문제를 경험하는 것으로 나타났다. 특히 여자 청소년은 부부갈등이 심할수록 더 많은 외현화 행동문제를 경험하였다. 또한 남자 청소년은 자기통제력이 낮을수록, 자아존중감이 낮을수록, 부부갈등이 심할수록 그리고 비행 친구 접촉이 많을수록 더 많은 내재화 행동문제를 경험하고, 여자 청소년은 자아존중감이 낮을수록, 비행 친구 접촉이 높을수록 그리고 부모의 양육행동이 적대적일수록 더 많은 내재화 행동문제를 경험하는 것으로 나타났다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 추계학술대회논문집
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• pp.84-87
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• 2009

Electrowetting is a versatile tool to handle tiny droplets and forms a backbone of digital microfluidics. Numerical analysis is necessary to fully understand the dynamics of electrowetting, especially in designing electrowetting-based devices, such as liquid lenses and reflective displays. We developed a numerical method to analyze the general contact-line problems, incorporating dynamic contact angle models. The method is based on the conservative level set method to capture the interface of two fluids without loss of mass. We applied the method to the analysis of spreading process of a sessile droplet for step input voltages and oscillation of the droplet for alternating input voltages in electrowetting. The result was compared with experimental data. It is shown that contact line friction significantly affects the contact line motion and the oscillation amplitude. The pinning process of contact line was well represented by including the hysteresis effect in the contact angle models.

• 대한기계학회논문집
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• 제7권1호
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• pp.52-63
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• 1983

The purpose of the study is to find development of contact area, contact pressure and friction forces occurring at joints or connection areas inbetween structural members or mechanical parts. The problem has a pair of difficulties intrinsically; a constraint of displacement due to contact, and presence of work term by nonconservative friction force in the variational principle of the problem. Because of these difficulties, the variational principle remains in the form of inequality. It is resolved by penalty method and perturbation method making the inequality to an equality which is proper for computational purposes. A contact problem without friction is solved to find contact area and contact pressure, which are to be used as data for the analysis of the friction problem using perturbed variational principle. For numerical experiments, a Hertz problem, a rigid punch problem, and the latter one with friction effects are solved using $Q_2$-finite elements.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1992년도 춘계학술대회 논문집 92
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• pp.11-26
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• 1992

In this research, a numerical algorithm has been developed, which can be applied to the large deformation and large displacement contact problems between angle change have been proposed considering the change in geometric shape and rate of contact force. A set of linear simultaneous equations is constructed by adding the geometric shape change and contact conditions to the original stiffness matrix. A new method to determine time increment has been proposed based on Euler method, in which the condition to prevent the contact bodies from penetrating and overrunning each other has been taken into consideration. Practical application to contact problem is extrusion in which bodies are sliding along the contact boundary.