• The Korean Journal of Rheology
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• v.8 no.3_4
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• pp.215-225
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• 1996

평판형의 열가소성 수지를 유리전이온도 이상으로 가열한 다음 압력을 가함으로써 원하는 형상의 제품을 성형하는 열성형공정은 대상 수지가 큰 변형을 일으킬 뿐만 아니라 비선형적 거동을 보이게 된다. 따라서 수지의 변형거동 예측과 최적성형조건의 설정에 많은 어려움과 시행착오를 거치게 되는 바, 열성형 공정의 최적화를 위한 연구의 일환으로 원형 평판위 수지를 대상으로 수지의 부풀림 거동과 이에 따른 두께 분포를 예측할수 있는유한요 소법의 수치모사 알고리듬을 개발하고자 하였다. Piola-Kirchhoff 응력 텐서와 Green 변형 텐서 및 lagrangian 변형 텐서를 사용하여 평판상의 응력-변형에 대한 비선형의 에너지 수 지식을 수립하고 Newton-Raphson 반복수렴법을 이용하여 근사적으로 해석하였으며 수지의 유변학적 구성방정식으로는 neo-Hookean 모델, Mooney-Rivlin 모델 및 Ogden 모델등의 초탄성 모델을 사용하여 그결과를 비교하였다. 수치모사에는 두께가 매우 얇기 때문에 두께 방향의 응력변화를 무시할수 있는 membrane 가정을 도입한 2차원적 해석과 두께 방향의 응력 변화를 고려하는 3차원적 해석을 모두 수행하고 그 차이를 비교하였으며 3차원적 해석 의 경우에는 penalty법을 이용하여 비 압축성을 만족하였다. 일차적으로 내압을 받는 두꺼 운 원통계에 대한 수치모사 해석을 수행하고 완전해와 비교함으로써 개발된 수치모사 알고 리듬의 열성형 공정에의 적용 타당성을 검증하였으며 이를 이용하여 원형 평판의 자유부풀 림거동을 예측한 결과 Treloar 등의 실험결과와 잘 부합함을 확인하였다. 또 간단한 형상의 금형이 있는 경우와 반지름 방향으로의 온도변화에 따른 수지의 변형거동을 해석함으로써 실제 열성형 공정에서 요구되고 있는 성형품의 두께 분포를 균일하게 하기 위한 방안을 제 시하였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.10
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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.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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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.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.34 no.10
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• pp.24-31
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• 2006

In this paper, mechanical behavior of unidirectional composites with flexible matrix was predicted by geometrical non-linear finite element analysis. Two typical idealized unit cells of square and hexagonal fiber arrays were modeled and these were subjected to different loadings. The stress-strain behavior of composites was predicted from which the effective properties were calculated. The hyperelasticity of polyurethane matrix was considered using Mooney-Rivlin model. In result, the stress-strain behavior of flexible composites shows non-linearity, especially it is remarkable under transverse normal and shear loading conditions. In this cases, there are great difference between square and hexagonal fiber array models.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.875-882
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• 2011

In this paper, the finite element analysis model of the mult-axial wheel durability test configuration is created using SAMCEF. Mooney-Rivlin 2nd model is applied to the tire model, and the variation of the air pressure inside the tire is considered. Vertical load, lateral load and camber angle are applied to the simulation model. The tire rotates because of the friction contact with a drum, and reaches its maximum speed of 60 km/h. The dynamics stress results of the simulation and experiment are compared, and the reliability of the simulation model is verified.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.698-703
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• 2001

This paper is concerned with the nonlinear hyperelastic problem fur the incompressible characteristics of the rubber. Tension sensor is a strain gage type load cell element for a fence intrusion detection system and consists of the sensing part and the rubber housing. The analysis includes an elastic analysis and a hyperelastic analysis of a tension sensor for the deformed shape and variation of the maximum strain on the sensing part with respect to the vertical load. Numerical results show that the hyperelastic model is stiffer and less deformed than the elastic model. Comparing with the experimental test data, we know the hyperelastic model is the better approximation than the elastic model.

• Elastomers and Composites
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• v.56 no.2
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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.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.1 s.232
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• pp.81-87
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• 2005

A fracture of hand held device, such as radio, TV and CD-RW drive, mainly occurs due to drop situation. For CD-RW drive, the need of high reading/writing speed in conjunction with low price accelerates the fracture of the device. Computer simulation can reduce the period of development and enhance impact characteristic of device. In this study, the detailed finite element model of CD-RW drive was developed to predict the damage under drop conditions. Material property for shock absorbing damper was obtained from tensile test of raw material. A MOONEY-RIVLIN type rubber in LS-DYNA was used as the material model of damper. To assess the reliability of the developed model, drop test at 200G-2msec and 150G-10msec condition was conducted and acceleration at pick-up was compared.

• Elastomers and Composites
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• v.53 no.4
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• pp.226-233
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• 2018

Elastomers based on the thermoplastics are widely used in rubber industries. Thermoplastic elastomers have the advantages of an easy shaping process and elimination of recycling problems. Thermoplastic polyester elastomer (TPE) is used for making rubber bands in wearable devices and its applications are increasing. In this study, five wrist bands were designed and their mechanical behaviors were examined by computer simulation, using hyper elastic models, Mooney-Rivlin and Ogden models, and a linear elastic model. Simulation results were compared and discussed in terms of band design and material model.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.111-120
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• 1998

This paper is the first one of two-parted research efforts focusing on the modeling of rubber pad forming process. The rubber pad, driven by the pressurized fluid during the forming process, pushes the sheet metal to solid tool half and forms a part to final shape. In this part of the paper, a numerical procedure for the FE analysis of the rubber pad deformation is presented. The developed three-dimensional FE model is based on the total Lagrangian description of rubber maerial characterized by nearly incompressible hyper-elastic behavior under a large deformation assumption. Validity of the model as well as effects of different algorithms corresponding to incompresibility constraints and time integration methods on numerical solution responses are also demonstrated.