Evaluation of Dynamic Compression Behaviour of Low-Density Porous Materials by Viscoplastic Constitutive Equation Incorporating Structure Transformation

Abstract

Low-density porous materials with a mesoscopic cellular structure exhibit complex mechanical behaviors macroscopically. The strain-rate dependency of plateau stress is one of the materials' characteristics, and it causes difficulties in the mechanical analysis of the behaviors. In this study, the level variation in the plateau stress is analyzed to formulate its strain-rate dependency. This dependency is investigated by performing various material tests under the conditions of quasi-static and dynamic compressions; results of these tests revealed that the dependency can be represented by the phenomenon of over stress. Then, Perzyna's equation is used to simulate the dependency with the concept of structure transformation of cellular materials. The compression tests with various strain-rates are simulated by using the formulated equations for analysing the over stress and structure transformation problems of the materials. Then, it is known that the strain-rate dependency of the plateau stress can be expressed by using Perzyna's equation, and it depends on the phenomenon of the cellular structure.