ANISOTROPY EFFECT ON THE FRACTURE MODEL OF DP980 SHEETS CONSIDERING THE LOADING PATH

Abstract

This paper is concerned with the anisotropy effect of DP980 sheets on the fracture model considering the variation of the loading path. For better application of a material, it is essential to understand its plastic behavior to predict the onset of the fracture in metals accurately. Especially in sheet metal forming, the anisotropy effect on the fracture strain should be taken into account to consider the fracture behavior more properly. In order to construct the fracture model, three different types of tests were carried out to obtain the facture strain from uniaxial tensile tests with classic dog-bone specimens, pure shear specimens and plane strain grooved specimens using Instron 5583. Each specimen was made along three different orientations: the angle of 0 degrees(RD); 45 degrees(DD); 90 degrees(TD) with respect to the rolling direction of sheet metals to evaluate the anisotropy effect on the fracture strain. Strains were measured using the two-dimensional digital image correlation (2D-DIC) method. In order to consider the influence of anisotropy on the fracture strain accurately, the Hill'48 yield function was applied to a Lou Huh fracture model instead of von Mises yield function. A modified Lou Huh fracture model was represented in the space of the strain path to use the experiment result directly. The effect of the change of the loading path was also applied to the modified Lou Huh fracture model to consider damage accumulation in the material.