Residual stresses influence the crack-tip driving force and constraint, and play a crucial role in the structural integrity assessment. The validity of the proposed parameter R for quantifying the effect of residual stresses on the crack-tip constraint has been investigated by means of a parameter study. A modified boundary layer (MBL) model has been applied into which the residual stresses have been introduced by means of the eigenstrain method.

Results:

• The R parameter accounts for the residual stress induced constraint in a simple manner to a sufficient degree of accuracy.

• R varies with geometry constraint levels; the higher geometry constraint, the weaker is the effect of residual stresses.

• The size of the weld-metal region affects the value of the R parameter.

• An increase in the external loading reduces the effect of the residual stresses.

• External loading affects the geometry constraint as well as the residual stress constraint.

• Residual stresses affect harder materials more strongly than softer materials.