Crack straining-based spall model

Mean void growth-based spall models that avoid the complications of nucleation have been successfully applied to the problem of ductile spallation. However, similar models based on mean crack growth, applicable to brittle spallation, are not promising. This is because it remains to be demonstrated how an appropriate mean crack size is chosen to identify the brittle spall strength as the threshold pressure for crack growth. In the authors' view, the solidity evolution is not merely a consequence of the nucleation and growth of cracks but also determined by the crack straining caused by the relaxed tensile pressure. This paper presents a crack straining-based spall model which assumes that the inelastic volumetric strain caused by the relaxed tensile pressure at a critical fragment volume is the main factor governing the solidity evolution during the process of coalescence and fragmentation. Such an approach makes the modelling of brittle spall compatible with that of ductile. The developed model requires only two additional parameters to those required by the chosen constitutive model and equation of state. We present the comparisons between experimental and computational simulation of the free surface velocity history of the target in a plane impact plate experiment. These show very good agreement. Copyright (C) 1996 Elsevier Science Ltd.