A dynamic ductile fracture model on the effects of pressure, Lode angle and strain rate

To improve the accuracy of impact failure prediction of ductile material under complex stress states, a novel multi-parameters dynamic ductile fracture model with constitutive relation and fracture criterion is proposed by involving the effects of hydrostatic pressure, Lode angle and strain rate. This novel dynamic fracture model is based on our proposed ductile fracture model under quasi-static loading. Furthermore, the corresponding material calibration strategy with some simple quasi-static and dynamic tests is also presented. In order to verify the present dynamic fracture model under complex stress states, both hydrostatic pressure and Lode angle, a plate specimen with notch made from Al 7075 was designed and the split Hopkinson bar (SHPB) tension tests with elevated loading forces were conducted. Meanwhile, parallel numerical simulations were performed with two fracture models, i.e., the Johnson-Cook model and the present novel model, implemented into the commercial finite element platform ABAQUS/explicit through user material subroutine VUMAT. By comparing with the numerical results and the SHPB experimental data, it is demonstrated that the novel dynamic ductile fracture model can predict favorably well with the SHPB experimental data. Furthermore, local strain rates and stress states of the specimen in the notch region during deformation were also studied.