Modeling the Confinement and Prestress Effects on Dynamic Failure of Ceramic Deep Beam

Abstract

The present study performs numerical experiments to investigate the confinement and prestress effects on the dynamic failure of a ceramic deep beam. Johnson-Holmquist ceramic model (JH-2) is implemented into LS-DYNA through its user subroutines. The implementation and the effectiveness of the model are validated by a single element compression test and available plate impact test results. Failure of ceramics is isolated into two modes, i.e. tension induced cracking and compression generated crushing. Three different setups, i.e. bare ceramic beam, the beam with lateral constraints, and the beam with lateral constraints and a 100 MPa pre-applied pressure are considered in the numerical experiments. The results show that, in lower velocity impact, few tension induced cracks connecting the impactor head and the supports happened on the specimen, minor crush zone is found around the supports. Under higher velocity impact, however, a relative larger crush zone is also observed near the impact head, spreading tension cracks occurred in a triangular zone on the specimen.

The lateral confinement affects the tension induced failure under both lower velocity and higher velocity impacts. The pre-applied pressure has only minor effect on the failure of the deep beam in low velocity impact. In higher velocity impact, however, the pre-applied stress may change the distribution profile of the tensile cracks. Both pre-stress and the lateral constraints have negligible effect on the compression crush happened near the impactor head in the higher velocity impacts.

The dynamic failure patterns of the ceramic deep beam and the confinement and prestress effects are demonstrated clearly in the present study. Energy transformation mechanism during the impacts is briefly discussed.