Numerical investigation of the dynamic behavior of a Ti/TiB functionally graded material using Split Hopkinson Pressure Bar test

Abstract

This work focuses on the mechanical behavior, at high strain rates, of metal-ceramic functionally graded materials (FGMs) using a Split Hopkinson Pressure Bar (SHPB) technique. The validity and the accuracy of the SHPB test results for these composite materials have not been meticulously studied due to their complex mechanical response under dynamic loadings. In this paper, numerical simulations of SHPB tests were performed to determine the dynamic response of specific FGMs at various strain rates. The effects of the compositional gradient exponent and the striker velocity, as well as increasing/decreasing stiffness through the thickness of the functionally graded specimen, were investigated. The considered material is composed of Titanium mono-boride ceramic (TiB) and Titanium metal (Ti) phases; the volume fraction (Vc) of the ceramic constituent varies through-thickness following a power-law distribution. The locally effective material properties were evaluated using a homogenization method based on the self-consistent method (SCM). The elastoplastic behavior of the FGMs under dynamic loading is described using dynamic Tamura-Tomota-Ozawa model (DTTO). The numerical simulations indicated that the compositional gradient exponent and striker velocity have significant effects on the dynamic response of the FGMs. On the other hand, the increasing/decreasing stiffness has a minor effect due to the low thickness of the experimental functionally graded specimen. Finally, the effect of the high strain rates the multiple interface reflection/transmission of the stress wave is very considerable for the design and the optimization of FGMs behavior under dynamic loading.