LAWS GOVERNING THE DYNAMIC FRAGMENTATION

摘要

Fragmentation processes of solids are of interest for specialists in different fields of fundamental and applied science. The reason for this interest, beside the importance of the applied problems, is related to the fact that the explosive fracture of solids is a unique tool for investigating many problems of the physics and mechanics of fracture.The known Mott relation is used for analyzing the fragmentation process. It was initially proposed for describing the fragmentation process of ductile metal rings. Moreover, many other relations, which are based, in particular, on the fractal approach assuming the slight effect of the mechanical properties of materials on the fragmentation characteristics, have been proposed. The application of numerous relations shows that the physical sense of the fragmentation phenomenon is poor studied, and its understanding calls for, in particular, answering the following questions:What kind of mechanisms of the crack initiation and propagation during the dynamic fragmentation process are, and how is the effect of the composition, structure and mechanical properties of material on themWhat criteria (or criterion) of fragmentation taking into consideration these mechanisms in different materials areIs it possible to describe the fragmentation process of brittle, ductile and quasibrittle materials by a common relationCan we use this relation for describing the natural fragmentation processes occurring at different scalesThis study aimed for answering these questions was carried out on cylindrical shells made from steels with different compositions and mechanical properties, which were tested under explosive loading conditions. The mechanisms of fragmentation were investigated by optical and scanning electron microscopy; a relation describing the cumulative number mass distributions of fragments was proposed; a criterion characterizing the influence of composition and mechanical properties of shell materials on the fragmentation was found. Based on the studied regularities, features of the natural fragmentation processes occurring at different scales were considered