Comparison of Dynamic Hardening Equations for Metallic Materials with three types of Crystalline Structures

Abstract

This paper is concerned with dynamic hardening equations of metallic materials with various crystalline structures. The dynamic response of metallic materials is indispensable for analysis of high speed metal forming process. There is, however, no unique equation which can represent the dynamic hardening characteristics of all kinds of materials although various dynamic hardening equations have been suggested by many researchers. Dynamic hardening equations reported have been investigated using the dynamic hardening characteristics of three kinds of materials: 4340Steel (BCC); OFHC (FCC); and Ti6Al4V (HCP). Dynamic hardening characteristics of each material have been obtained by uniaxial tensile tests and SHPB tests. Uniaxial tensile tests have been performed with the variation of the strain rate from 0.001/sec to 100/sec and SHPB tests have been conducted at the strain rate ranged up to 4000/sec. Several existing models have been constructed and evaluated for Johnson-Cook model, Zerilli-Armstrong model, Preston-Tonks-Wallace model, modified Johnson-Cook model, and modified Khan-Huang model using test results of three materials. Strain rate hardening and thermal softening effect during the deformation process were investigated for accurate application of hardening equations. The most applicable equation for each material has been suggested by comparison of constructed results.