A Method for Evaluating Stress Triaxiality and Fracture Strain of High Tensile Strength Steel Sheet Using Stereo Image Correlation

Abstract

This paper studies a method for evaluating the stress triaxiality and the fracture strains accurately considering the deformation of thin steel sheets which are used for an automobile body frame. Three-dimensional displacements and surface strains of thin steel sheets are measured using a stereovision. In particular, to measure the deformation of the board thickness of the steel sheets, the measurement is performed from the both sides of the steel sheet. Based on strain incremental theory, the stress triaxiality is evaluated from the measured strains considering the variation of the thickness of the steel sheets. The effectiveness of the proposed procedure is validated by applying it to the evaluation of the stress triaxiality of high strength steel sheets. Results show that the stress triaxiality and the fracture strains can be evaluated by the proposed method.