A criterion for dynamic ductile fracture initiation of tensile mode

Dynamic behavior of a material is essential in applications such as collision, explosion, ballistic impact, high-speed machining, and metal forming. As impact loadings, as well as accidental or malicious explosions, may impose high loading rates to engineering structures, estimating the dynamic response of a material accurately is crucial. Therefore, an analytical strain rate-dependent criterion on ductile fracture initiation is developed at the continuum scale by further developing the energy balance concept. The criterion is based on continuum modeling of energy release rates, and the critical state is reached when the rate of energy change of fractured and unfractured states becomes equal. The formulation introduces a material length scale and a material property that is a function of strain rate and temperature. The developed ductile fracture criterion is implemented into two example applications, an aluminum alloy and a titanium alloy, whose experimental data are obtained from the open literature. Fracture loci of these alloys at various strain rates and the critical energy release rates as a function of strain rate are determined. The results of the example applications agree well with the experimental results reported in the literature.