Determination of Dynamic Constitutive Equations Based on an Information Criterion by the Elasto-Plastic Waves Propagation Analysis

Previously, we presented the determination method of a dynamic constitutive equation with strain- rate sensitivity from the results of an uniaxial longitudinal impact compression test. The proposed method could derive an appropriate strain-rate sensitive dynamic constitutive equation as a polynomial without consideration based on underlying material physics. However, the method needs a lot of test results over a wide strain-rate range. This paper presents the determination method of a dynamic constitutive equation from a few impact test results. The proposed method determines unknown coefficients involved in a polynomial that appears dynamic constitutive relations of a material by nonlinear least squares method. Furthermore, the proposed method determines the optimum degree of a polynomial constitutive equation by AIC (Akaike information criterion). This paper, further, presents the split Hopkinson pressure bar method using a stepped striker bar. The proposed method can obtain the relations between the dynamic stresses and strain-rates in a wide range from a single impact test.