Multiaxial and dynamic compression behaviors of low-density porous materials and their constitutive equations

Abstract

In this paper, uniaxial compression tests are conducted for studying the nonlinear deformation behaviors of a porous material during compression. The results of uniaxial compression tests at some constant strain rates indicate that the plateau stress, which is the stress level in the plateau region, shows strain-rate dependency. In the compression tests by varying the strain rates, it is revealed that the strain-rate dependency relates to the behavior of well-known overstress phenomena. Therefore, the viscoplastic constitutive equation derived by Perzyna is adopted to simulate the uniaxial compression and to represent the strain-rate dependency. A comparison of experimental and simulation results shows that the overstress phenomenon during the compression of the material can be simulated by using the viscoplastic constitutive equation. The multiaxial behavior of the material is also observed for the designing. Equibiaxial pre-strained compression tests are adopted for the observation of the characteristics. The results of these tests show that the pre-strain causes the porous material to harden, and the extent of the hardening depends on the amount of change in the total volume of the material. The multiaxial behaviors of the porous material are simulated by using the constitutive equations incorporating the structure transformation of the porous material, and these results also indicate the effect of volume change on the compression behavior.