Elastic-plastic constitutive modeling of tantalum and AerMet 100 steel due to quasi-static and dynamic loadings

Four currently utilized constitutive models for metals (i.e. Johnson-Cook, Zerilli-Armstrong, Bodner-Partom and Khan-Huang) were investigated and used to predict the mechanical behaviors of the materials and compared with experimental results. Problems for each model in describing work-hardening behavior of metals were discussed. A modification to the Khan-Huang model based on these studies was proposed and used to give a better correlation with the experimental response.; The elastic-plastic mechanical behaviors of three body-centered cubic metals, tantalum, tantalum alloy with 2.5% tungsten, and AerMet 100 steel, were investigated over a wide range of strains (15%), strain rates (10 -6--104 s-1) and temperatures (77°--600°F).; Uniaxial tensile and compressive experiments were performed at different strain rates and temperatures. Quasi-static (low to medium strain-rate) experimental investigations were conducted on an MTS material test system. Dynamic tests were carried out using the Split Hopkinson Pressure Bar and the Direct Disc Impact techniques. Stress-strain relations get from these tests were used to determine material constants in constitutive models.; Biaxial compressive and torsion-tension non-proportional experiments were performed to compare with predictions using the constitutive model based on material constants from uniaxial experiments. Biaxial compressive test was performed using a die to produce a plane strain deformation. Non-proportional loading occurs if a specimen is loaded in uniaxial compression followed by biaxial compression. In case of torsion-tension loading, a thin-walled tubular specimen was used and non-proportional loading path is obtained when torsion is applied first, followed by tension.; The proposed constitutive model gave good correlations with the experimental results at uniaxial loading for the materials. It also gave very satisfactory predictions for complex path loading experiments.; The results of all these investigations will provide information pertaining to a better understanding the finite plastic deformation for the desired applications of the three metals.