Computation of fracture mechanics parameters for structures with residual stresses

Most manufacturing processes induce residual stresses in metallic parts, which will influence the in-service behaviour of the part with respect to fatigue and damage tolerance resistance, corrosion resistance and strength. In the particular case of a compressive residual stress field, the fatigue and damage tolerance behaviour is actually improved. The objective of this work is to develop a numerical method, based on the boundary element method and the principle of superposition, to assess the influence of residual stresses on fracture mechanics parameters. The numerical procedures are detailed and applied on an actual toughness test specimen, for which failure loads with and without residual stresses where measured. In spite on the complexity of the failure process with internal stresses, the method captures well the magnitude of the toughness variation.