Development and Application of Dynamic Integrated DIC Material Parameters Inversion Method for SHPB Tests

Dynamic mechanical parameters are significant to study the dynamic evolution, but multiple constitutive parameters are difficult to be measured or calculated directly in various dynamic tests. This paper develops a dynamic integrated digital image correlation (DIC) inversion method to characterize multiple parameters of 2A12-T4 aluminum alloy for the split Hopkinson pressure bar (SHPB) test.

Affine transformation is used to construct virtual deformed images based on time-varying images of dynamic impacts and deformation responses of finite element method (FEM). Through imitating the principle of DIC, the image correlation function embedded the Johnson–Cook constitutive parameters is constructed. The optimal constitutive parameters are obtained by the gradient optimization algorithm when the images are most correlated.

For dynamic tests of same strain rate, optimal parameters are obtained by substituting multiple experimental images to co-invert. By substituting inversion results into the FEM simulation, the simulated stress–strain curve is obtained. Meanwhile by extracting the stress–strain signals of multiple experiments, the real mean stress–strain curve is obtained. Through the coincidence of two stress–strain curves, the feasibility of dynamic integrated DIC inversion method and the accuracy of the inversion results are verified.

This dynamic inversion method is universal to obtain multiple parameters in various dynamic experiments, which considers the strain rate and time-varying. Besides this method simplifies the inversion process and obtains multiple dynamic parameters more easily.