유한요소법을 이용한 중고속 변형률 속도에서의 박판 인장시편의 형상결정

Abstract

The strain-rate dependent mechanical properties of a sheet metal are indispensable for the reliability of the light- weight design and the crashworthiness of auto-body because the mechanical properties are remarkably changed by the level of the strain-rates. Since the level of the strain-rate in the crash analysis us between 10/sec and 500/sec, an appropriate experimental method has to be developed in order to acquire the material properties at the corresponding strain-rate. Design the specimen is important to perform the experiment because there is not standard tension specimen for the dynamic test. Numerical simulations are carried out in order to determine the dimensions and the shape of the specimen with an elasto-plastic explicit finite element method. In FE simulation and stress updata, the plastic predictor-elastic corrector (PPEC) method us applied in order to integrate the stress trackong the Johnson-Cook constitutive equation over a time step, The scheme adopts secant interation in the plastic perdictor-elastic corrector method un order to satisfy the plane stress condition. Finite element simulations are carried out to inverstigate the effect fo the variation of geometric parameters in specimen such as the gauge length, the width and the fillet radius. Optimum dimensions are determined for standard specimens at the various strain-rates considering