Dynamic damage constitutive model of sandstone based on component combination theory

In this study, using a split Hopkinson pressure bar (SHPB) system, we conducted the impact tests of sandstone at different impact velocities to collect the characteristics of the strain rate effect and obtained the typical dynamic constitutive curve of sandstone. The curve can be divided into an approximately linear elastic stage, a plastic stage, a plastic enhancement stage and a forward unloading stage. We constructed the dynamic damage constitutive model of sandstone adopting the combination model, and utilized the user subroutine UMAT interface of LS-DYNA to achieve the secondary development of the constitutive model, which was then used to simulate the SHPB dynamic impact compression tests of sandstone at four impact rates of 7.5, 9.5, 11.5 and 13.5 m/s. The calculation results showed that the as-constructed model gave a good description of the effect of the strain rate and the elastic stage of the stress-strain curve of sandstone. Moreover, the dynamic peak strength and maximum strain were in good agreement with the test results, and the relative errors of the strain rate, peak strength, maximum strain were less than 10%, thus indicating that the as-constructed dynamic constitutive model can accurately describe the dynamic mechanical properties of sandstone under impact.