Residual stress and constraint effects on cleavage fracture in the transition temperature regime

ABSTRACT Defects in structural components are often associated with welds that may contain significant levels of residual stress. Whilst the primary load acting on the component may induce low constraint conditions at the crack tip, the presence of residual stresses, e.g. due to welding, can modify this constraint level and consequently influence the observed fracture toughness behaviour. This paper presents the results of a combined experimental and numerical programme aimed at exploring this issue. Cleavage fracture toughness data for high and low constraint specimens are presented with and without residual stresses. The results indicate that under certain conditions, the constraint‐induced increase in cleavage fracture toughness may be eroded by the presence of a residual stress in the vicinity of the crack. The results are quantified with respect to two‐parameter fracture mechanics in which the T and Q parameters are appropriately defined. Preliminary guidance is provided for the assessment of defects when residual stresses may influence crack‐tip constraint.