Comparison of Critical Shear Strain Evaluations for Simple Shear Test

The simple shear test for sheet metals has become a topic of growing interest in recent years, whose significance could be reflected in two aspects: obtaining the mechanical behaviors under large strain and investigating the ductile fracture under low-stress triaxiality. In the current stage, the community lacks a widely-accepted and standardized procedure to conduct simple shear tests, and it makes the interpretation and comparison of experimental results to be indirect and difficult. Shear strain is commonly used to characterize the degree of deformation, but the method to estimate it in experiments is often different from one to another, and uncertainties will appear due to the inconsistency. In this work, some representative methods to obtain shear strain will be evaluated analytically and experimentally. The influence of the perturbation phenomenon (that is, the emergence of axial deformation and the tilt of shear direction with respect to the coordinate axis of strain measurement during simple shear) will be investigated in detail, and it seemed that there were no universal methods to estimate shear strain in experiments (to the best of the authors’ knowledge). Some recommendations on this topic would be provided and the results were expected to enhance the understanding of the experimental mechanics of simple shear tests.