DYNAMIC DAMAGE AND FAILURE IN VISCOPLASTIC MATERIALS

In this paper, a dynamic damage model in ductile solids under the appl ication of a dynamic mean tensile stress is developed. The proposed mo del considers void nucleation and growth as parts of the damage proces s under intense dynamic loading (strain rates epsilon greater than or equal to 10(3) s(-1)). The evolution equation of the ductile void has the closed form, in which work-hardening behavior, rate-dependent cont ribution and inertial effects are taken into account. Meanwhile, a pla te impact test is performed for simulating the dynamic fracture proces s in LY12 aluminum alloy. The damage model is incorporated in a hydrod ynamic computer code, to simulate the first few stress reverberations in the target as it spalls and postimpact porosity in the specimen. Fa ir agreement between computed and experimental results is obtained. Nu merical analysis shows that the influence of inertial resistance on th e initial void growth in the case of high loading rate can not be negl ected. It is also indicated that the dynamic growth of voids is highly sensitive to the strain rates.