FAILURE BY FRACTURE OR YIELDING IN STRAIN-HARDENING MATERIALS ACCORDING TO THE T-CRITERION

An attempt is described to develop an improved theoretical approach fo r the failure of materials, being initially either precracked or uncra cked. As a guide for this an idealized approach to the fundamental rea ction of solids during state transitions is employed. By setting an up per limit T(v,)0 of mechanical energy for volume change and another on e T(D,)0 for distortion, beyond which the material transits to either brittle fracture or general rupture by yielding, a closed limiting fai lure surface is obtained. The necessity of considering the constitutiv e relation between hydrostatic pressure, p, and unit volume change, th eta, in addition to the equivalent stress-strain relation (sigmaBAR - epsilonBAR) is emphasized. Finally conclusions are made concerning the experimental evaluation of T(v,)0 and T(D,)0 and the application of t he present failure criterion in the case of precracked materials. Pred ictions obtained from this criterion agree well those of McClintock's criterion based on void coalescence, and are clearly supported by the classical experiments performed by Bridgman.