Assessment of yield and fracture criteria using shear and bending tests

This article deals with the calibration of a fracture criterion that has been implemented in a material model in LS-DYNA. The failure process in thin-walled metallic materials is complex and often due to interaction between plastic instability phenomena and ductile fracture. The material failure often occurs due to highly localized plastic deformation originating from plastic instability. The present work aims at establishing an in-plane shear test, which gives direct information about the phenomenon of ductile fracture, and a numerical scheme for identification of the fracture parameter. Shear tests of extruded plates in AA7108 temper T6 were carried out, and the fracture parameter was found through inverse modeling. AA7108 has previously been characterized and an anisotropic yield criterion has been calibrated with simple material tests including standard uniaxial tensile tests and through-thickness compression tests. It is discussed how the yield criterion calibration can be improved through in-plane shear tests and related numerical analyses. In order to evaluate the model and calibration, simple three-point bending tests of the same material were carried out. In these tests, the nose shape of the indenter was varied. Numerical analyses of the tests were then carried out with the implemented model and identified model parameters.