Proposal of New Stability-instability Criterion for Crack Extension Based on Crack Energy Density and Physical Systematization of Other Criteria

Abstract

A new stability-instability criterion (named Tε(T*ε) criterion) for crack growth which is applicable to small scale yielding cracks and also to large scale yielding cracks is proposed based on crack energy density concept. Tε criterion is a criterion in which attention is paid to the rate of variation of crack energy density at a crack tip point of every moment, and T*ε criterion is another version of Tε criterion and is a criterion in which attention is paid to the rate of variation of crack energy density at a fixed point which will be a new crack tip point after extension. The relations between Tε(T*ε) criterion and other known criteria (criterion based on g-R-a curves; Tj, Tδ and TW criteria) are also discussed and it is shown that the physical meanings of other criteria can be made clear and all criteria can be systematized based on the new criterion.