Numerical prediction of dynamic failure in concrete targets subjected to projectile impact by a modified Kong-Fang material model

•Modifications are conducted to the Kong-Fang concrete material model recently proposed.•A new crack softening model is introduced in the AUTODYN subroutine.•Improved performances of the modified model are demonstrated by single element tests.•The failures are well reproduced using the modified model combined with the SPH method. Typical failures such as cratering, cracking and spalling are frequently observed on the frontal and distal surfaces of concrete slabs when subjected to impact loadings. A high-fidelity physical-based numerical simulation should not only predict the ballistic parameters, but these failures, where an accurate material model and an appropriate algorithm are crucial. To this end, the Kong-Fang concrete material model recently proposed (Kong et al., 2018) is firstly modified. Modifications are made to the strength surfaces (including residual strength surface and yield strength surface) and definition of compression damage. The modified model is then implemented in the AUTODYN hydrocode through the user subroutine in which a new crack softening model is introduced to account for the triaxial tensile failure. Comprehensive single element tests are conducted to validate the improved performances due to these modifications focused on the tensile behavior and compressive behavior under high confinement. Then the modified Kong-Fang concrete material model is combined with the Smooth Particle Hydrodynamics (SPH) method to numerically predict ballistic parameters and dynamic failures in several sets of concrete penetration/perforation tests by steel projectiles. Compared with the RHT model and the original Kong-Fang model, the modified model can well capture the cratering, tunneling, cracking and the scabbing failure phenomena and numerical predicted ballistic parameters are found to be in excellent agreement with corresponding experimental data.