• Title/Summary/Keyword: contact problem

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Finite Element Analysis of the Unconstrained Cylindrical Bending Process Considering Continuous Contact Treatment (연속 접촉 처리를 고려한 실린더 벤딩 성형 공정의 유한요소해석)

  • Kim T. J.;Yang D. Y.
    • Transactions of Materials Processing
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    • v.14 no.6 s.78
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    • pp.547-552
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    • 2005
  • In general, the sheet metal and die are described by finite elements for the simulation of the metal forming processes. Because the characteristics as continuum of the sheet metal are represented with triangles and rectangles, the errors occur inevitably in finite element analysis. Many contact schemes to describe the deformation modes exactly have been introduced in order to decrease these errors. In this study, a scheme for continuous contact treatment is proposed in order to consider the realistic behavior of contact phenomena during the forming process. The discrete mesh causes stepwise propagation of contact nodes of the sheet even though the contact region of the real forming process is altered very smoothly. It gives rise to convergence problem in case that the process, for example bending process, is sensitive to the contact between the sheet and the tools. The analysis of the unconstrained cylindrical bending process without blank holder is also presented in order to investigate the effect of the proposed algorithm.

Effects of Thermal Contact Resistance on Transient Thermoelastic Contacts for an Elastic Foundation (시간에 따른 탄성지지 열탄성 접촉에 대한 열접촉저항의 영향)

  • Jang, Yong-Hoon
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.330-333
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    • 2005
  • The paper presents a numerical solution to the problem of a hot rigid indenter siding over a thermoelastic Winkler foundation with a thermal contact resistance at constant speed. It is shown analytically that no steady-state solution can exist for sufficiently high temperature or sufficiently small normal load or speed regardless of the thermal contact resistance. However, the steady state solution may exist in the same situation if the thermal contact resistance is considered. This means that the effect of the large values of temperature difference and small value of force or velocity which occur at no steady state can be lessened due to the thermal contact resistance. When there is no steady-state the predicted transient behavior involves regions of transient stationary contact interspersed with regions of separation regardless of the thermal contact resistance. Initially, the system typically exhibits a small number of relatively large contact and separation regions, but after the initial transient the trailing edge of the contact area is only established and the leading edge loses contact, reducing the total extent of contact considerably. As time progresses, larger and larger number of small contact areas are established, until eventually the accuracy of the algorithm is limited by the discretization used.

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The Improvement of Incompatible Sliding Contact Problem Using Mesh Refinement And Its Application to Railway Skewed Culvert Problem (요소 세분화를 이용한 비적합 미끄러지는 접촉문제의 개선과 철도 사각암거 문제에의 적용)

  • Choi, Chan-Yong;Yeo, In-Ho;Chung, Keun-Young;Lee, Gye-Hee
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.30 no.5
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    • pp.435-444
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    • 2017
  • The vehicle-track structure dynamic interaction analysis problem can be treated as sliding contact problem, and it is assumed that vehicle run at a constant speed over a rail modeled as beam elements. Unfortunately, Salome-Meca can not satisfy the compatibility condition for the beam master elements, which are consist of the elements with higher order polynomial shape function, in sliding contact problem. In this study, it is suggested to use more finer beam master element mesh as the remedy for incompatibility in sliding contact problem, and the accuracy of the solution is secured. For this, the effect of beam element mesh refinement consisting runway is analysed through simple examples, and the applicability to the dynamic interaction analysis is evaluated. Finally, the dynamic interaction analysis of railway skewed culvert transition problem is carried out to evaluate the effect of supporting stiffness due to backfill pattern changes and track irregularity due to uneven subgrade settlement.

Reduction of Current Crowding in InGaN-based Blue Light-Emitting Diodes by Modifying Metal Contact Geometry

  • Kim, Garam;Kim, Jang Hyun;Park, Euyhwan;Park, Byung-Gook
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.14 no.5
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    • pp.588-593
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    • 2014
  • Current crowding problem can worsen the internal quantum efficiency and the negative-voltage ESD of InGaN-based LEDs. In this paper, by using photon emission microscope and thermal emission microscope measurement, we confirmed that the electric field and the current of the InGaN-based LED sample are crowded in specific regions where the distance between p-type metal contact and n-type metal contact is shorter than other regions. To improve this crowding problem of electric field and current, modified metal contact geometry having uniform distance between the two contacts is proposed and verified by a numerical simulation. It is confirmed that the proposed structure shows better current spreading, resulting in higher internal quantum efficiency and reduced reverse leakage current.

A Study on Evaluation and Improvement of Sealing Performance of Duct Cap Assembly for Ice Dispenser By Nonlinear Contact Problem Analysis (비선형 접촉문제 해석을 통한 얼음 디스펜서 덕트 캡 조립체의 밀봉성능 평가 및 개선방안 연구)

  • Lee, Boo-Youn
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.17 no.2
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    • pp.37-46
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    • 2018
  • Present research is to evaluate and improve the sealing performance of the duct cap assembly for the ice dispensers through structural analysis. The nonlinear contact problems to check the sealing performance were analyzed using ANSYS software. The results of the analyses related to the sealing performance: the displacement distribution, the contact condition between the cap-silicon and the case, and the pressure distribution on the contact surface, were examined and discussed. Based on the results of the existing design of the duct cap assembly, two cases of the design modifications to improve the sealing performance were introduced. By examining the results of the two cases, a final design improvement plan was proposed and analyzed. It is shown that the sealing performance of the proposed final design is much more favorable than the existing design. The method of structural analysis and design improvement of the duct cap assembly presented in this paper will help improve the sealing performance of the ice dispenser duct caps.

VARIATIONAL ANALYSIS OF AN ELECTRO-VISCOELASTIC CONTACT PROBLEM WITH FRICTION AND ADHESION

  • CHOUGUI, NADHIR;DRABLA, SALAH;HEMICI, NACERDINNE
    • Journal of the Korean Mathematical Society
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    • v.53 no.1
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    • pp.161-185
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    • 2016
  • We consider a mathematical model which describes the quasistatic frictional contact between a piezoelectric body and an electrically conductive obstacle, the so-called foundation. A nonlinear electro-viscoelastic constitutive law is used to model the piezoelectric material. Contact is described with Signorini's conditions and a version of Coulomb's law of dry friction in which the adhesion of contact surfaces is taken into account. The evolution of the bonding field is described by a first order differential equation. We derive a variational formulation for the model, in the form of a system for the displacements, the electric potential and the adhesion. Under a smallness assumption which involves only the electrical data of the problem, we prove the existence of a unique weak solution of the model. The proof is based on arguments of time-dependent quasi-variational inequalities, differential equations and Banach's fixed point theorem.

Sliding Contact Analysis of a Spherical Particle between Rubber Seal and Coated Steel Counterface (시일과 코팅된 스틸면 사이의 구형 입자에 의한 미끄럼 접촉 해석)

  • Park, Tae-Jo;Lee, Jun-Hyuk
    • Tribology and Lubricants
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    • v.28 no.6
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    • pp.283-288
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    • 2012
  • In this study, a new sliding contact problem involving an elastomeric seal, a spherical particle and a hard coated steel counterface was modeled to investigate the detailed wear mechanisms related to the sealing surface. The model was also used to design the optimum coating conditions. A three-dimensional finite element contact problem was modeled and analyzed using the nonlinear finite element code, MARC. The deformed steel surface and stress distributions are presented for different coating layers and thicknesses. When the coating thickness is relatively small, the entrapped particle produces surface plastic deformations such as groove and torus. In addition, the sealing surface can be damaged by abrasive wear as well as fatigue wear. For a relatively thick and multi-layered coating, on the other hand, surface plastic deformation does not occur, and the amount of abrasive and fatigue wear is reduced. Therefore, the proposed contact model and results can be used in the design of various sealing systems, further intensive studies are required.

Study on Analysis of Transfer Torque and Improvement of Transfer Torque in Non-Contact Permanent Magnet Gear (비접촉 영구자석 기어의 전달토크 분석 및 전달토크 향상에 대한 연구)

  • Park, Gyu-Sang;Kim, Chan-Ho;Kim, Yong-Jae
    • KEPCO Journal on Electric Power and Energy
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    • v.1 no.1
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    • pp.181-188
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    • 2015
  • The non-contact permanent magnet gear has advantages of high efficiency and improved reliability. It has other advantages of no mechanical friction loss, very little noise and vibration, and no need for lubricant. With these advantages, the non-contact permanent magnet gear that solves the physical contact problem of the mechanical gear has drawn attention. Due to this unique non-contact characteristic, the non-contact permanent magnet gear which is capable of non-contact torque transmission has replaced mechanical gear. The mechanical gears which is in many fields of the modern industry, is used mostly for power transmitting mechanical devices. However, it also has the problem of a low torque density, which requires improvement. In this paper, a novel pole piece shape is proposed in order to improve the problem of low torque density of the non-contact permanent magnet gear. The experiment data required for predicting the relationships among them are obtained using finiteelement Operating method based on two-dimensional (2-D) numerical analysis. Therefore, this paper derived an optimal model for thenon-contact permanent magnet gear with the novel pole piece using the Box-Behnken design, and the validity of the optimal design of the proposed pole piece shape through variance analysis and regression analysis demonstrated. In this paper, we performed the thransfer torque analysis in order to improve the torque density and power density, we have performed on optimal design of proposed pole piece shape using box-behnken.

Prediction of contact lengths between an elastic layer and two elastic circular punches with neural networks

  • Ozsahin, Talat Sukru;Birinci, Ahmet;Cakiroglu, A. Osman
    • Structural Engineering and Mechanics
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    • v.18 no.4
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    • pp.441-459
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    • 2004
  • This paper explores the potential use of neural networks (NNs) in the field of contact mechanics. A neural network model is developed for predicting, with sufficient approximation, the contact lengths between the elastic layer and two elastic circular punches. A backpropagation neural network of three layers is employed. First contact problem is solved according to the theory of elasticity with integral transformation technique, and then the results are used to train the neural network. The effectiveness of different neural network configurations is investigated. Effect of parameters such as load factor, elastic punch radii and flexibilities that influence the contact lengths is also explored. The results of the theoretical solution and the outputs generated from the neural network are compared. Results indicate that NN predicted the contact length with high accuracy. It is also demonstrated that NN is an excellent method that can reduce time consumed.

A Measurement of Adhesion Energy between Viscoelastic/Elastic, Viscoelastic/Viscoelastic Materials Using Contact Mechanics Approach (접촉 역학적 접근에 의한 점탄성/탄성, 점탄성/점탄성 재료간의 접합 에너지 측정)

  • Lee, C.;Earmme, Y.Y.
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.1030-1035
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    • 2003
  • The nanoimprint lithography technology makes higher density of semiconductor device and larger capacity of storage media. In this technology the induced damage while detaching polymer pattern from mold should be minimized. In order to analyze the problem, the basic knowledge of adhesion between the polymer and the mold is required. In this study a contact experiment of polyisobutylene specimen with spherical steel tip and polyisobutylene bead tip was conducted using nano indenter. During the contact experiment with various loading rate under load control the contact behavior of viscoelastic material was measured, i.e., the load and displacement between the tip and the specimen were measured. The data was analyzed by HBK model to obtain the stress intensity factor of contact edge and the contact radius as a function of time. Also the adhesion energies between steel/polyisobutylene and polyisobutylene/polyisobutylene were obtained employing the analysis of the crack of viscoelastic material by Schapery.

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