SPONTANEOUS FAILURE OF SOLIDS

Abstract

An important property of a deformable solid is that it can store energy, as, for example, in the form of the potential energy of bulk deformation; this energy can be applied from without by a mechanical or thermal agency, then expended on failure, i.e., for the creation of new surfaces. This is described as spontaneous if no external energy is applied to the body or volume in question during the generation of the new surface, i.e., if failure is generated only by the stored energy of elastic deformations. Considered also are brittle and plastic materials. Brittle failure of a material occurs when a single-valued relationship between stresses and strains is maintained until failure. Thus the critical stresses, strains and energies can be calculated from one another. A distinguishing characteristic of a plastic material is that the critical stress (or strain) may be insufficient to produce failure: a critical strain (or stress) and energy is needed in addition. Although in both cases spontaneous failure may be produced by the stored potential energy of elastic deformations alone, in a plastic material the work performed in relief of elastic strains may be hindered by residual strains.