This technical gap is particularly inconvenient for the development and optimization of new surface enhancement methods such as laser shock peening (LSP).  Numerous LSP process parameters can be adjusted to generate different residual stress states in specific component geometries and materials.  However, it has not been possible to predict analytically which residual stress states would provide the greatest improvements in fatigue life or damage tolerance capacity in service.  Instead, expensive trial-and-error sequences of fatigue experiments have been required.

This presentation describes recent advances in fatigue crack growth analysis methods directed at residual stress effects.  The advances include new stress intensity factor solutions that address complex bivariant stress gradients on the crack plane, and elastic-plastic analyses of local material response associated with the formation and modification of residual stress fields.  The methodology is implemented in a special version of the NASGRO fracture mechanics analysis software and evaluated by comparison with experimental crack growth data on laboratory coupons containing residual stresses induced by overload plasticity or by surface enhancement methods.