LAUSR

Abstract In this work, a group of four capable prediction tools—Classical Forming Limit Curve (FLC), Forming Limit Stress Curve (FLSC), Damage Curve (DC) associating stress-triaxiality with plastic strain and Nonlinear Strain Path Forming Limit Curve (nonlinear strain path FLC) based on an innovative punch originally designed by the Institute for Metal Forming Technology (IFU), University of Stuttgart—are employed to evaluate formability of DP590 advanced high-strength steel (AHSS). The results are subsequently compared. A classical FLC is created with restriction to the Nakajima stretching-test guideline, in which a 100-Tonne universal tensile testing machine is operated to press 1-mm thick DP590 sheets. A nonlinear strain path FLC is generated with an application of an IFU-designed punch to realise nonlinear strain paths under a particular standardised Nakajima testing environment. A stress-based FLC is computationally obtained by transforming the classical FLC, realised in a major-minor strain space, into an FLSC in a principal-stress space using the Hill’48 yield criterion equipped with the Swift strain-hardening law. A DC is arithmetically determined through a combination of the plastic flow rule and Hill’48 yield criterion. To verify and compare those gained curves, both hole-expansion and Fukui stretch-drawing tests are conducted both experimentally and numerically. Regarding the simulation model for numerical investigation, material flow behaviour and deformation anisotropy are modelled by the Swift hardening law and Hill’48 yield criterion, respectively. This research has once again proved that FLSC, DC and nonlinear strain path FLC can obviously identify the forming limit of DP590 AHSS more realistically than the classical FLC can.