Biaxial tests on cruciform specimens for the validation of crystallographic yield loci

A biaxial tensile test has been designed for the experimental determination of yield locus points of thin steel sheets. Using texture-based anisotropic finite-element (FE) simulations, the geometry of the test sample has been optimised and the accuracy of the conversion procedure has been validated. It was found that the present technique has a high precision for principal stress ratios sigma(y)/sigma(x) between tan(20 degrees) and tan(70 degrees). Experimental tests have been carried out on five steel qualities (low and ultra-low carbon) with thickness between 0.8 and 1.5 mm. Both yield stresses and ratios of plastic strains have been compared to the theoretical predictions obtained with the Taylor-Bishop-Hill (TBH) model using the experimentally determined crystallographic textures. The {110}[111] and {112}[111] slip systems were considered using both full-constraints (FC) and relaxed-constraints (RC) assumptions for the TBH model. These comparisons are clearly in favour of the TBH-FC model. (C) 1998 Elsevier Science S.A. All rights reserved.