On a model of structured medium fracture under compression conditions

Abstract

Extension is necessary in order to initiate brittle fracture in a structured medium. One possible version of the fracture scenario under compression conditions is the development of extension near local concentrators. The dimensions of such regions depend on the level of hydrostatic compression (pressure). As the hydrostatic compression increases, these dimensions decrease approaching the dimension of individual structure elements of the medium (e.g., grains or pores). Under these conditions, the mechanisms of brittle fracture of the medium differ from those in ordinary structural materials. We consider mechanisms of brittle fracture in compression. It is assumed that the sources of the local extension required for the development of discontinuities are the response of the heterogeneous structure elements of the medium (pores) at which the external compressive stresses can transform into local extensions sufficient for crack propagation. In this case, a characteristic cell representing the scale of the leading process of local fracture is a volume containing two pores. The coalescence of these pores is an elementary fracture process. An increase in the pressure level increases the role of such fracture processes and leads to the development of ordered fracture structures. Several examples of fracture scenarios under loads that are combinations of homogeneous compression and a concentrated action are used to illustrate the conditions for the development of discontinuities, in whose end regions an elementary act of pore coalescence takes place, and to demonstrate the appearance of linear structures such as curtains or echelons of microcracks.