When very brittle materials are subjected to a complex state of stress they fail by maximum intensified tensile stress criterion first introduced by Griffith [1]. Nominal applied stresses are intensified by defects present in all real materials. It appears that defects controlling the strength of brittle materials are of two types—open ones characterized by circular voids found in sintered materials such as tungsten carbide and thin, essentially closed ones found in brittle polyphase rock such as granite. This paper is concerned with the extension of a very simple two dimensional theory for circular voids [3] to the three dimensional case involving spherical voids. While the fracture locus for the two dimensional case represents a conservative approximation sufficient for most engineering applications, the three dimension solution is necessary to give detailed result for cases involving near hydrostatic tension or compression.

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