• Structural Engineering and Mechanics
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• 제52권1호
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• pp.75-87
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• 2014

To analyze the tension performance of laminated rubber bearings under tensile loading, a theoretical tension model for analyzing the rubber bearings is proposed based on the theory of elasticity. Applying the boundary restraint condition and the assumption of incompressibility of the rubber (Poisson's ratio of the rubber material is about 0.5 according the existing research results), the stress and deformation expressions for the tensile rubber layer are derived. Based on the derived expressions, the stress distribution and deformation pattern especially for the deformation shapers of the free edges of the rubber layer are analyzed and validated with the numerical results, and the theory of cracking energy is applied to analyze the distributions of prediction cracking energy density and gradient direction. The prediction of crack initiation and crack propagation direction of the rubber layers is investigated. The analysis results show that the stress and deformation expressions can be used to simulate the stress distribution and deformation pattern of the rubber layer for laminated rubber bearings in the elastic range, and the crack energy method of predicting failure mechanism are feasible according to the experimental phenomenon.

• 소성∙가공
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• 제23권5호
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• pp.317-322
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• 2014

Bursting during tube hydroforming is preceded by localized necking. The retardation of the initiation of necking is a means to enhance hydroformability. Since high strain gradients occur at the necking sites, a decrease in local strain gradients is an effective way to retard the initiation of necking. In the current study, the expansion at potential necking sites was intentionally restricted in order to reduce the strain gradient at potential necking sites. From the strain distribution obtained from FEM, it is possible to determine strain concentrated zones, which are the potential necking sites. Prior to the hydroforming of a trailing arm, an incompressible material(such as lead) is attached to the tube where the strain-concentrated zone would contact the die. Due to the incompressibility of lead, the tube expansion is locally restricted, and the resultant strain extends to adjacent regions of the tube during hydroforming. After the first stage of hydroforming, the lead is removed from the tube, and the hydroforming continues to the final targeted shape without any local restriction. This method was successfully used to fabricate a complex shaped automotive trailing arm that had previously failed during traditional hydroforming fabrication.

• 대한기계학회논문집A
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• 제26권10호
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• pp.2044-2051
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• 2002

In this paper, the deformed shape, the contact forces and the load-displacement curves of the real hollow gasket made of silicon rubber are analyzed using a commercial finite element program MARC. In the numerical analysis, the silicon rubber is assumed to have the properties of the geometric and material nonlinearity and the incompressibility, and the hyperelastic constitutive relations of that material are represented by the generalized Mooney-Rivlin and Ogden models. The outer frictional contact between the hollow gasket and the groove of rigid container and the inner self-contact of the hollow gasket are taken into account in the course of numerical computation. Experiments are also performed to obtain the material data for numerical computation and to show the validity of the mechanical deformation of the hollow gasket, resulting in good agreements between them.

• 한국정밀공학회지
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• 제15권9호
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• pp.117-126
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• 1998

For investigating rubber pad sheet metal forming process, the rubber pad deformation characteristics as well as the contact problem of rubber pad-sheet metal has been analyzed. In this paper, the behavior of the rubber deformation is represented by hyper-elastic constitutive relations based on a generalized Mooney-Rivlin model. Finite element procedures for the two-dimensional responses, employing total Lagrangian formulations are implemented in an implicit form. The volumetric incompressibility condition of the rubber deformation is included in the formulation by using penalty method. The sheet metal is characterized by elasto-plastic material with strain hardening effect and analyzed by a commercial code. The contact procedure and interface program between rubber pad and sheet metal are implemented. Inflation experiment of circular rubber pad identifies the behaviour of the rubber pad deformation during the process. The various form dies and scaled down apparatus of the rubber-pad forming process are fabricated for simulating realistic forming process. The obtaining experimental data and FEM solutions were compared. The numerical solutions illustrate fair agreement with experimental results. The forming pressure distribution according to the dimensions of sheet metal and rubber pads, various rubber models and rubber material are also compared and discussed.

• 한국해양공학회지
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• 제21권6호
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• pp.53-58
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• 2007

A particle method, recognized as one of gridless methods, has been developed to investigate non-linear free-surface motions interacting with structures. This method is more feasible and effective than conventional grid methods for solving flow fieldswith complicated boundary shapes. The method consists of particle interaction models representing pressure gradient, diffusion, incompressibility, and the free-surface boundary conditions without grids. In the present study, broken dam problems with various viscosity values are simulated to validate the developed method.

• 한국산학기술학회논문지
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• 제15권4호
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• pp.1859-1864
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• 2014

본 액화 실리콘 고무는 내열성 및 내화학적 우수성으로 전자 제품 및 다양한 제품에서 활용되고 있다. 하지만 초탄성 재료는 일반 금속재료와 다른 특성을 보인다. 초탄성 재료는 하중과 변형이 비선형 관계를 보이는 대변형 범위에서도 탄성거동을 나타내는 특성을 지니며, 비선형, 비압축성 및 대형의 특성을 지니고 있다. 이러한 특성 때문에 제품을 설계 및 생산 하기위해는 기능적 측면을 고려한 소재의 특성에 대한 물성 확보가 반드시 필요하기 때문에 현장에서 많은 어려움이 있다. 본 논문에서는 자동차용 방수커넥터 설계를 위해 소재의 인장, 압축 시험으로부터 구한 하중-변형관계를 이용하여 이를 유한 요소 해석에 적용한 결과를 비교하였으며, 해석결과와 제품의 성능 테스트 결과를 비교하여 방수커넥터용 씰의 경우 어떠한 소재특성을 적용할 경우 유용한 결과를 도출할 수 있는지를 확인하였으며, 이를 통해 제품 개발에 유용성을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집E
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• pp.404-409
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• 2001

An account of second-order fractional-step methods and boundary conditions for the incompressible Navier-Stokes equations is presented. The present work has aimed at (i) identification and analysis of all possible splitting methods of second-order splitting accuracy; and (ii) determination of consistent boundary conditions that yield second-order accurate solutions. It has been found that only three types (D, P and M) of splitting methods called the canonical methods are non-degenerate so that all other second-order splitting schemes are either degenerate or equivalent to them. Investigation of the properties of the canonical methods indicates that a method of type D is recommended for computations in which the zero divergence is preferred, while a method of type P is better suited to the cases when highly-accurate pressure is more desirable. The consistent boundary conditions on the tentative velocity and pressure have been determined by a procedure that consists of approximation of the split equations and the boundary limit of the result. The pressure boundary condition is independent of the type of fractional-step methods. The consistent boundary conditions on the tentative velocity were determined in terms of the natural boundary condition and derivatives of quantities available at the current timestep (to be evaluated by extrapolation). Second-order fractional-step methods that admit the zero pressure-gradient boundary condition have been derived. The boundary condition on the new tentative velocity becomes greatly simplified due to improved accuracy built in the transformation.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제14권4호
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• pp.1738-1756
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• 2020

To improve the accuracy and realism of the virtual surgical simulation system, this paper proposes an optimized mass-spring model with shape restoration ability based on volume conservation to simulate soft tissue deformation. The proposed method constructs a soft tissue surface model that adopts a new flexion spring for resisting bending and incorporates it into the mass-spring model (MSM) to restore the original shape. Then, we employ the particle swarm optimization algorithm to achieve the optimal solution of the model parameters. Besides, the volume conservation constraint is applied to the position-based dynamics (PBD) approach to maintain the volume of the deformable object for constructing the soft tissue volumetric model base on tetrahedrons. Finally, we built a simulation system on the PHANTOM OMNI force tactile interaction device to realize the deformation simulation of the virtual liver. Experimental results show that the proposed model has a good shape restoration ability and incompressibility, which can enhance the deformation accuracy and interactive realism.

• 한국항공우주학회지
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• 제45권11호
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• pp.939-950
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• 2017

본 연구에서는 세 가지 종류의 올레오식 2중 완충기 특성 비교를 위한 첫 단계 연구로서 수학적 모델링을 새롭게 수행하였다. 논문의 완결성을 위해 먼저 전형적인 올레오식 단일 완충기에 대한 모델을 제시한 후, 세 가지 종류의 올레오식 2중 완충기에 대한 수학적 모델을 유도하였다. 수학적 모델링을 위해 베르누이 방정식과 오리피스 방출계수를 이용하였으며, 완충기 내부의 기체와 유체는 각각 폴리트로픽 과정 그리고 비압축성으로 가정하였다. 올레오식 2중 완충기 특성 연구에 제안된 모델을 적극 활용할 수 있을 것으로 판단된다.

• Interaction and multiscale mechanics
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• 제2권1호
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• pp.45-68
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• 2009

An aim of the study is to develop an efficient numerical simulation technique that can handle the two-scale analysis of fluid permeation filters fabricated by the partial sintering technique of small spherical ceramics. A solid-fluid mixture homogenization method is introduced to predict the mechanical characters such as rigidity and permeability of the porous ceramic filters from the micro-scale geometry and configuration of partially-sintered particles. An extended finite element (X-FE) discretization technique based on the enriched interpolations of respective characteristic functions at fluid-solid interfaces is proposed for the non-interface-fitted mesh solution of the micro-scale analysis that needs non-slip condition at the interface between solid and fluid phases of the unit cell. The homogenization and localization performances of the proposed method are shown in a typical two-dimensional benchmark problem whose model has a hole in center. Three-dimensional applications to the body-centered cubic (BCC) and face-centered cubic (FCC) unit cell models are also shown in the paper. The 3D application is prepared toward the computer-aided optimal design of ceramic filters. The accuracy and stability of the X-FEM based method are comparable to those of the standard interface-fitted FEM, and are superior to those of the voxel type FEM that is often used in such complex micro geometry cases.