Effect of Thermomechanical Loading on Near Tip Constraint

Two parameter approaches to elastic-plastic fracture mechanics were introduced to remove some of the conservatism inherent in the one parameter approach based on the J integral, ([l]) and to account for constraint effects on fracture toughness. It was shown in [2], [3] and [4] among others that much of the dependence of fracture toughness on specimen geometry could be explained by two parameter fracture theories based on Q or T. This paper examines the effect of residual or thermal stress fields on constraint in a mechanically loaded body. Finite element analyses of representative thermal loadings which give rise to high and low constraint stress fields (high and low T or Q) have been conducted. The structure is then subjected to mechanical loading, both tension and bending dominated to assess the effect on the near tip constraint. It is observed that the two parameter structure of the fields is maintained and values of Q stress have been obtained from the analyses. The thermal loading initially has a strong effect on the Q value but at higher loads when the mechanical loading dominates, this effect is much weaker. The ability of a two parameter approach using the T stress to account for constraint is assessed

Variations in fracture toughness test results A study across four laboratories

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Numerical Evaluation of T-stress under Mixed Mode Loading Through the Use of Coarse Meshes

The present paper investigates the employment of coarse meshes in evaluating the T-stress with the displacement method. Several finite element analyses have been carried out with different mesh refinements and accuracies. Mode I and mixed mode I/II loadings have been considered in finite element analyses. Under mode I loading, single and double edge notched geometries have been considered, while plate with central crack has been considerd for mixed mode loading condition. The analyses are compared with the results by the well-nown stress based approach, and showed that the displacement method permits the evaluation of the T-stress with the employment of coarse meshes. By the way, several precautions must be taken when dealing with coarse and very coarse meshes.Peer reviewe