Large strain flow curve identification for sheet metal

Abstract

The large strain flow curve is an essential input for the calibration of a myriad of plasticity models required for accurately simulating sheet metal forming processes and the mechanical performance of formed components. Studies on large strain flow curve identification can be divided in three main categories. The first class of experiments generate statically determinate stress states which unambiguously correlate analytically to the external load and measured strains, hence enable a direct measurement of the large strain flow curve. The second category relies on the intermittently measured flow stress using pre-strained samples to construct the large strain flow curve. The third category consists of methods that minimize the discrepancy between the experimentally acquired and the numerically computed measurand to inversely identify a chosen hardening law representing the large strain flow curve. The paper presents an overview of the state-of-the-art methods to acquire the large strain flow curve of sheet metal. A selected number of methods are reviewed and recent developments are discussed in detail. Finally, an objective assessment of the selected methods is pursued by applying them to a DP600 steel sheet.