A Void Growth Failure Criterion Applied to Dynamically and Statically Loaded Thin Rings

摘要

The introduction of inertia terms in the theoretical model of thin ring expansion shows that classical plastic instability concepts, defined in terms of the local strain in the necking region, no longer apply. However, in this report it is shown that, when the plastically incompressible constitutive model is replaced with a model applicable to porous plastic materials, a criterion based on critical void volume fraction provides an alternative means to predict failure. The theory also provides a method in which both geometric and metallurgical imperfections in a given sample might be considered. The application of this theory to thin ring specimens was used to confirm that the critical void growth concept predicts the uniform strain at failure as observed in aluminum and copper rings, under both quasi-static and high strain-rate loading conditions. (Author)