Overview and comparison of various test methods to determine formability of a sheet metal cut‐edge and approaches to the test results application in forming analysis

This paper presents an overview of published test methods for determination of formability of a sheet metal cut‐edge. The presented test methods were developed to evaluate formability of a sheet metal edge that was produced by shear cutting. Due to high local strains, hardening, or even microcracks, the cut‐edge might have less formability than the base material. The presentation of the tests is structured according to the three steps each test can be divided into: cutting, forming and evaluation. Similarities and differences concerning these steps were worked out. Additionally, a classification of the tests is made regarding their strain gradients in the vicinity of the cut‐edge. For this, finite element models of exemplary tests were built up using LS‐DYNA explicit and analyzed accordingly. Evaluation approaches that go beyond the common hole expansion ratio (HER) from the hole expansion test (HET) standardized in the ISO 16630 are also described. The tests can be used not only for a quantitative comparison of materials and cutting processes with regard to the cut‐edge formability but to determine input data for the finite element analysis (FEA) of forming processes to allow a simulation based cut‐edge failure prediction. The paper also presents appropriate procedures on the transfer of the test results into the FEA of forming of a workpiece with a cut‐edge.