• Geomechanics and Engineering
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• 제7권4호
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• pp.335-353
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• 2014

The softening hyperelastic model based on the strain energy limitation is of clear concepts and simple forms to describe the failure of materials. In this study, a linear and a nonlinear softening hyperelastic model are proposed to characterize the deformation and the failure in granular materials by introducing a softening function into the shear part of the strain energy. A method to determine material parameters introduced in the models is suggested. Based on the proposed models the numerical examples focus on bearing capacity and strain localization of granular materials. Compared with Volokh softening hyperelasticity and classical Mohr-Coulomb plasticity, our proposed models are able to capture the typical characters of granular materials such as the strain softening and the critical state. In addition, the issue of mesh dependency of the proposed models is investigated.

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2001년도 제33회 춘계학술대회 개최
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• pp.392-400
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• 2001

The sealing performance of an elastomeric O-ring seal using bi-materials has been analyzed for the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring seal will occur when the pressure differential across the seal just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of restrained geometry(grooved), are investigated using the finite element method. The analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to a ratio of length between NBR and FFKM and temperature of vaccum chamber.

• Elastomers and Composites
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• 제56권2호
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• pp.79-84
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• 2021

A strain energy density function is used to characterize the hyperelasticity of rubber-like materials. Conventional models, such as the Neo-Hookean, Mooney-Rivlin, and Ogden models, are widely used in automotive industries, in which the strain potential is derived from strain invariants or principal stretch ratios. A fitting procedure for experimental data is required to determine material constants for each model. However, due to the complexities of the mathematical expression, these models can only produce an accurate curve fitting in a specified strain range of the material. In this study, a hyperelastic model for Neodymium Butadiene rubber is developed by using the Artificial Neural Network. Comparing the analytical results to those obtained by conventional models revealed that the proposed model shows better agreement for both uniaxial and equibiaxial test data of the rubber.

• 로봇학회논문지
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• 제17권1호
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• pp.68-75
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• 2022

In this paper, we considered the deformation shape of the soft rotation actuator as a double curvature shell and proceeded with the analytical development. Since the response of the hyperelastic material has a large nonlinear deformation, the analytical approach is very complicated and the solution cannot be easily obtained. it is assumed that the behavior of the flexible body, which is a superelastic material, takes the form of a double curvature shell, and the formulas for calculating the deformation are simplified. In this process, equilibrium equations in the related coordinate system representing a double curvature shell were derived. In addition, assuming a thin shell, the stress component in the thickness direction was ignored, and the equation was developed by adding the assumption of free rotation without load. In order to verify the analytically calculated value in this way, an experiment was conducted and the results were compared.

• 한국산학기술학회논문지
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• 제6권6호
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• pp.536-541
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• 2005

고무 성분에 대한 대변형 및 강성은 비선형 및 대변형의 해석 결과로 나타낼 수 있다. 또한 고무는 Mooney-Rivlin의 모델로서 적용되고 고무들 사이에서 자기 접촉이 성립되어지는데 강성체 및 고무 사이에서는 마찰력이 있게 된다. 본 연구에서 사용된 비선형 시뮬레이션 해석은 여러 가지의 고무 성분들의 설계, 분석 그리고 개발에 널리 사용될 수 있다. 이러한 방법을 이용하면 새로운 고무 제품을 개발하는데 있어서 시간과 비용을 절감할 수 있을 것으로 보인다. 고무 성분들의 분석은 특이한 재료의 모델링과 비선형 유한 요소 해석을 요하는데 금속 부품들에 대하여 해석하는 프로그램들과는 완전히 다르다. 본 연구의 목적은 대변형 및 비선형의 고무 부품을 해석하는데 있다.

• 대한기계학회논문집A
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• 제35권10호
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• pp.1237-1242
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• 2011

족저부의 압력 분포를 해석하기 위하여 인체에 근접한 족부 상세 해석용 모델을 개발하였다. 이 상세 해석용 모델은 족부의 단층촬영 영상(CT scan image)으로부터 밀도 차이에 따라서 골격부와 피부 및 피하조직을 각각 3D CAD 모델로 변환한 후에 결합하여 구성하였며, 근육과 뼈, 피부 모두를 반영한 3D 족부 유한요소해석 모델로 개발하였다. 개발된 3D 족부 유한요소모델에 대하여 NASTRAN의 접촉해석을 수행하여 족저압의 분포를 계산하였으며, 이러한 결과는 균일분포압력을 작용시키는 당뇨병 환자용 신발 설계의 기초 자료로 활용될 수 있다.

• 한국자동차공학회논문집
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• 제11권4호
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• pp.125-134
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• 2003

In this study, Mooney-Rivlin 1st model and Mooney-Rivlin 3rd model are adopted as strain energy density functions of the rubber compounds of a radial tire. It is shown that the FE analysis using Mooney-Rivlin models for rubber compounds may provide good approximations by employing the appropriate strain range of experimental stress-strain data in a way to describe the stress-strain relationship accurately. Especially, Mooney-Rivlin 3rd model gives an accurate stress-strain relationship regardless of the fitting strain range used within the strain of 100%. The static nonlinear FE analysis of a tire inflation is performed by employing an axisymmetric model, which shows that the outside shapes of the tire before and after inflating the tire agree well with those of the real tire. Additionally, the deformations at crown center and turning point on sidewall, distribution of belt cord force, interlaminar shear strain are predicted in terms of variation of belt cord angle which is known as the most influential factor in inflation behavior of a tire.

• 반도체디스플레이기술학회지
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• 제9권2호
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• pp.91-96
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• 2010

In recent years there have been considerable attentions on nanoimprint lithography (NIL) by the display device and semiconductor industry due to its potential abilities that enable cost-effective and high-throughput nanofabrication. Although one of the current major research trends of NIL is large-area patterning, the technical difficulties to keep the uniformity of the residual layer become severer as the imprinting area increases more and more. In this paper we consider the roll-to-plate type imprinting process. In the process a glass mold, which is placed upon the 2nd generation TFT-LCD glass sized substrate(370${\yen}$470 mm), is rolled by a rubber roller to achieve a uniform residual layer. The pressure distribution on the glass mold by rolling of the rubber roller is crucial information to analyze mold deformation, transferred pattern quality, uniformity of residual layer and so forth. In this paper the quantitative pressure distribution induced by rolling of the rubber roller was calculated with finite element analysis under the assumption of Neo-Hookean hyperelastic constitutive relation. Additionally the numerical results were verified by the experiments.

• Structural Engineering and Mechanics
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• 제76권5호
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• pp.653-661
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• 2020

The paper presents a study regarding rubber compressibility behavior. The objective is to analyze the effect of compression degree of rubber on its mechanical properties and propose a new methodology based on reverse engineering to predict compressibility degree based on uniaxial stretching test and Finite Element Analysis (FEA). In general, rubbers are considered to be almost incompressible and Poisson's ratio is close to 0.5. Since this property is intimately related to the rubber packing density, little changes in Poisson's ratio can lead to significant changes regarding mechanical behavior. The deviatory hyperelastic constants were obtained through experimental data fitting by least squares method for the most relevant constitutive models implemented in commercial software Abaqus, such as: Neo-Hooke, Mooney-Rivlin, Ogden, Yeoh and Arruda-Boyce, whereas the hydrostatic part was determined through an optimization algorithm implemented in the Abaqus environment by Python scripting. The simulation results presented great influence of the Poisson's ratio in the rubber specimen mechanical behavior mainly for high strain levels. A conventional pure volumetric compression test was also carried out in order to compare the results obtained by the proposed methodology.

• 대한건축학회논문집:구조계
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• 제35권9호
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• pp.159-169
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• 2019

This work presents the three-dimensional extended strain smoothing approach in the framework of finite element method, so-called smoothed finite element method (S-FEM) for quasi-incompressible hyperelastic materials undergoing the large deformations. The proposed method is known that the incompressible limits, such as over-estimation of stiffness and distorted mesh sensitivity, can be overcome in two dimensions. Therefore, in this paper, the idea of Cell-based, Edge-based and Node-based strain smoothing approaches is extended to three-dimensions. The construction of subcells and smoothing domains for each methods are explained. The smoothed strain-displacement matrix and the stiffness matrix are obtained on each smoothing domain in the same manner with two-dimensional S-FEM. Various numerical tests are studied to demonstrate the validity and accuracy of 3D-S-FEM. The obtained results are compared with analytical solutions to express the efficacy of the methods.