Modeling of ductile fracture using the dynamic punch test

Abstract

Many models have been proposed for simulating events at quasi-static and dynamic rates. However, the Johnson–Cook constitutive model had been the workhorse for engineers and analysts when simulating such events, and it is readily available in the increasingly widespread numerical packages. Johnson and Cook also suggested a generalized failure model to be used with their constitutive model, but the challenge has always been in easily determining the correct parameters for these models. In this study, a procedure for determining the Johnson–Cook constitutive and, simplified, failure model parameters for three materials with specific importance in the aerospace industry, aluminum 6061-T6, titanium Ti-6Al-4 V and austenitic, nitrogen-strengthened, stainless steel (Nitronic 33) is proposed. Quasi-static and split Hopkinson pressure bar (SHPB) shear punch experiments were used to assess the materials’ ductility, while the quasi-static and SHPB compression experiments were used to determine the materials’ response. The laboratory results coupled with ABAQUS/Explicit simulations provided a tool for determination and validation of the models’ parameters for each material. While the use of the Johnson–Cook model with the proposed simplified failure model proved adequate for aluminum and titanium, the same could not be concluded for nitronic partly due to the intrinsic characteristics of this material and the multiplicative form of the Johnson–Cook model.