APPLICATIONS OF THE THEORY OF CRITICAL DISTANCES TO THE PREDICTION OF BRITTLE FRACTURE IN METALS AND NON-METALS

摘要

The theory of critical distances (TCD) proposes that the failure of a body containing a stress concentration (e.g. a crack or notch) can be predicted using elastic stress information in a critical region close to the notch tip. This paper investigates the use of TCD for predicting brittle fracture. The critical region is defined in terms of a characteristic material length constant, L, which is a function of the fracture toughness K{sub}c and a failure stress, σ{sub}o. For very brittle materials (ceramics), σ{sub}o is equal to the plain-specimen strength but for polymers and metals σ{sub}o has a larger value. Two complications arise: (i) there exist non-damaging notches whose strength is equal to the plain-specimen strength, and; (ii) strength varies with the degree of constraint. These effects can be incorporated into TCD allowing predictions of experimental data for many types of materials and stress concentration features.