Use of abrupt strain path change for determining subsequent yield surface:Experimental study with metal sheets

A basic idea for a method for determining the subsequent yield surface in t he vicinity of a current loading point by using an abrupt strain path chang e has been proposed recently by Kuroda and Tvergaard (Acta mater., 1999, 47 , 3879). The proposed method is applied to real experimental studies. In a biaxial tensile testing apparatus, a cruciform specimen is used, with the s trains measured by a biaxial-strain gauge. Then, with the hydraulic pressur e of two sets of opposing hydraulic cylinders servo-controlled independentl y, the testing apparatus can be used to prescribe an abrupt change of the s train path. Both a cold-rolled steel sheet and an aluminum alloy sheet are investigated. The differences between the yield surface shapes found by the strain path change procedure and the shapes found by probing the yield poi nts from the elastic region are shown and discussed for different cases. (C ) 2000 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.