Characterisation of constraint effect on cleavage fracture using T-stress

The second term in Williams' (1) expansion of Mode- l crack-tip stress fields in an elastic body, or T -stress, has shown great promise as a unified constraint parameter in characterising plane strain elastic-plastic crack-tip fields at large scale yielding. In this paper, plane strain elastic-plastic crack-tip fields of a blunted crack at a constant value of K l and various values of T -stress were analysed. The stress fields were incorporated into a local cleavage fracture model to determine the T -stress effect on macroscopic cleavage fracture toughness. The local cleavage fracture model is based on weakest link statistics using a microscale Weibull model. Significant variation of cleavage fracture toughness with respect to T was found at a constant value of K l . The model was able to qualitatively correlate experimentally observed constraint effects on cleavage fracture toughness.

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