Determining Subsequent Yield Surface of Pure Titanium Sheet by Use of Abrupt Strain Path Change

A subsequent yield surface in the vicinity of a current loading point is determined for pure titanium sheet by using the abrupt strain path change method proposed by Kuroda and Tvergaard (Acta mater. 47 (1999) 3879-3890). An important feature of this method is that the yield surface in the vicinity of the path change point is determined without any influence of intermediate elastic unloading. When the unloading-reloading method is used, there is some concern on whether or not a vertex would be erased by the unloading needed to probe the yield surface. In a servo-controlled biaxial tensile testing apparatus, a cruciform specimen is used to prescribe an abrupt change of the strain path. A sharp yield vertex was successfully detected at the point of abrupt strain path change. The differences between the yield surface shapes found by the strain path change procedure and the shapes found by probing the yield points from elastic region are shown.