ABSTRACT
Abstract By 'scaling' is meant the ability to predict the fracture behaviour of larger or smaller bodies, knowing the response of a reference body. Usually we are concerned with 'models' tested in the laboratory and the prediction of full-scale 'prototypes'. Relationships between the fracture stresses in model and prototype, and between energies absorbed, are typical items of interest both in static and dynamic cases. Cube/square energy scaling principles are inherent in all mechanics of fracture (i.e. at corresponding stresses, recoverable elastic energy, and irreversible remote plasticity, scale as the volume A,3 but fracture work scales as an area X2, where X is the scaling factor size ratio of bodies). The different dependencies translate into the well-known experience that components and structures, made of materials which are appreciably ductile in laboratory-size testpieces, behave in a progressively less ductile fashion the larger they get. Eventually above some critical size, their behaviour is globally elastic, and fractures are brittle. Conversely, when deformation zones are kept very small in normally-brittle materials, plastic deformation is possible (cf. limiting sizes in comminution of powders; micro-machining of glass).
