Chang Su Woo

Useful Lifetime Prediction of Rubber Components Using Accelerated Testing

Rubber material properties, and useful lifetime prediction and evaluation are very important in the design procedure to assure the safety and reliability of rubber components. We have been interested for many years in predicting the lifetimes of rubber materials in oxygen-containing environments using a combination of accelerated aging tests and extrapolation models. In this paper, we investigate the heat aging effects on the material properties, and useful lifetime prediction of ethylene-propylene diene M-class rubber (EPDM), and acrylonitrile-butadiene rubber (NBR) for refrigerator components. The experimental results sssay that the crosslink density changes are varied with compositions of rubber vulcanization, and characteristics of heat aging behaviors of rubber vulcanizates are described well using the activation energy change with aging time. The stress and strain curves were obtained from the results of the simple tension test for specimens. To predict the useful lifetime of EPDM, and NBR, the mechanical property changes were determined under accelerated aging conditions. Rubber was aged at temperatures ranging from 50°C to 100°C for times ranging from 1 to 180 days. We present a general approach for more confidently correlating accelerated aging results with aging under service conditions using the Arrhenius methodology. By using the compression set test, several useful lifetime prediction equations for rubber material are proposed.

Prediction for Weather Strip Using Nonlinear Finite Element Analysis

TPE is used as alternative for rubber, the best example is the weather strip for automobile. The nonlinear material properties of weather strip were important to predict the behaviors of weather strip. Uniaxial tension and equi-biaxial tension tests were performed to achieve the nonlinear material constant and stress-strain curves. The nonlinear material constant of weather strip is evaluated by using the nonlinear finite element analysis. In this paper, the prediction for weather strip is analyzed by using commercial finite element program, ANSYS. The nonlinear finite element analysis of weather strip is executed to predict the behavior of weather strip for automobile.

A Study on Finite Element Analysis and Aging Test for Automotive Grommet

Grommet is one of the Automotive rubber components and is made from EPDM(Ethylene Propylene Diene monomer M-class) rubber and the nonlinear hyperelastic material properties of rubber are important to predict the behavior of rubber product. In this study, the stable stress-strain relations were obtained from the uni-axial tension test and the equi-biaxial tension test. Finite element analysis for grommet was carried out and heat aging test for the lifetime prediction of grommet was introduced.

A Study on the Fatigue Life Prediction and Evaluation of the Natural Rubber Components for Automobile Vehicles

The fatigue analysis and lifetime evaluation are very important in design procedure to assure the safety and reliability of the rubber components. The interest of the fatigue life of rubber components such as the engine mount is increasing according to the extension of warranty period of the automotive components. In this study, the fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue tests. Finite element analysis of 3D dumbbell specimen of natural rubber was performed based on a hyper-elastic material model determined from the tension, compression and shear tests. The Green-Lagrange strain at the critical location determined from the finite element analysis was used for evaluating the fatigue damage parameter of the natural rubber. Fatigue tests were performed using the 3D dumbbell specimens with different levels of maximum strain and various load. The basic mechanical properties test and the fatigue test of rubber specimens under the normal and elevated temperature were conducted. Fatigue life curves can be effectively represented by a following single function using the maximum Green-Lagrange strain. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the engine mount agreed fairly with the experimental fatigue lives a factor of two.

Fatigue Life Prediction of the Vulcanized Natural Rubber

Fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue test. Finite element analysis of 3D dumbbell specimen of natural rubber was performed based on a hyper-elastic material model determined from the tension, compression and shear tests. Stroke controlled fatigue tests were conducted using fatigue specimens at different levels of mean strain. The Green-Lagrange strain at the critical location determined from the FEM was used for evaluating the fatigue damaged parameter of the natural rubber. It was shown that the maximum Green-Lagrange strain was proper damage parameter, taking the mean strain effects into account. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the natural rubber agreed fairly well the experimental fatigue lives a factor of two.

Fatigue Life Evaluation of Automotive Engine Mount Insulator

Fatigue life of automotive engine mount insulator made of natural rubber was evaluated. In order to develop an appropriate fatigue damage parameter of the rubber material, a series of displacement controlled fatigue tests was conducted using 3-dimensional dumbbell specimens with different levels of mean displacement. It was shown that the maximum Green-Lagrange strain was a proper damage parameter, taking the mean displacement effects into account. Nonlinear finite element analyses of the rubber engine mount insulator and 3D dumbbell specimen were performed based on a hyper-elastic material model determined from the simple and equi-biaxial tension tests. Fatigue life prediction of the engine mount insulator was made by incorporating the maximum Green-Lagrange strain values, which was evaluated from the finite element analysis and fatigue tests, respectively. Predicted fatigue lives of the engine mount insulator showed a fairly good agreement with the experimental fatigue lives.

Fatigue Life Evaluation of Rubber Components for Automobile Vehicles

The interest of the fatigue life for rubber components was increasing according to the extension of warranty period of the automotive components. In this study, the fatigue lifetime prediction methodology of the vulcanized natural rubber was proposed by incorporating the finite element analysis and fatigue damage parameter determined from fatigue tests. Finite element analysis of 3D dumbbell specimen and rubber component was performed based on a hyper-elastic material model determined from the mechanical tests. The Green-Lagrange strain at the critical location determined from the finite element analysis was used for evaluating the fatigue damage parameter of the natural rubber. Fatigue tests were performed using the 3D dumbbell specimens and rubber component with different levels of maximum strain and various load. Fatigue life curves can be effectively represented by a following single function using the maximum Green-Lagrange strain. Fatigue lives of the natural rubber are predicted by using the fatigue damage parameters at the critical location. Predicted fatigue lives of the rubber component for automobile vehicle agreed fairly with the experimental fatigue lives.

A Viscoelastic Model for an Automotive Transmission Rubber Mount

An automotive transmission (TM) rubber mount is a device that is used in automotive systems to cushion the loads transmitted from the vehicle body structure. A TM rubber mount is used to support the engine in the vertical direction. However, the dynamic behavior of loaded rubber mount is not yet known to a reasonable degree of accuracy. The relationship between the force applied to a TM rubber mount and the resulting deformation exhibits features of viscoelasticity. Therefore, in this study, viscoelastic properties were measured during ramp-toconstant displacement control tests. A force-displacement relationship for a TM rubber mount is important for multi-body dynamic numerical simulations. Hence, an explicit force-displacement relationship was developed and expressed in terms of a force relaxation function. A method that can be used to determine the force-displacement relationship from experimental data for a TM rubber mount was also developed. Solutions were obtained and the results were compared with experimentally measured force-displacement behavior. The predictions of the proposed forcedisplacement relationship were in very good agreement with the experimental results.

A Study of the Static and Dynamic Characteristics for Automotive Rubber Mount by FEA and Experiment

An automotive transmission rubber mount is a device used in automotive systems to cushion the loads transmitted from the vehicle body structure. TM (transmission) rubber mount has been used to support engine in the vertical direction. In this study, the rubber specimens of the transmission mount are tested to obtain the hyperelastic and viscoelastic properties by the static and dynamic test, respectively. Uni-axial tension test, biaxial tension test, and pure shear test are carried out and Mooney-Rivlin constants are obtained from those static tests. Also, the viscoelastic properties such as storage and loss modulus are obtained from dynamic test. Using the static and dynamic test data, the dynamic stiffness of TM rubber mount subjected to static and dynamic load are predicted with finite element analysis. Solutions allow for comparison between FEA and experimental results. It is shown that the predictions of FEA are close to the experimental results.