Fracture mechanics methods for residual stress evaluation in plane problems

The progressive cutting technique for residual stress evaluation based on a fracture mechanics approach is reviewed and extended to a more general plane problem. A crack-like cut is supposed to be produced in a plane body affected by residual stresses in order to measure relaxed strain. The crack is assumed to be straight but not necessarily perpendicular to the surface or lying in a plane of symmetry. In such a general condition, residual stress released on the crack-faces has both normal and shear components. The relationship between released residual stresses and measured relaxed strains is discussed for a general position of the strain-gage. The corresponding influence functions are obtained by taking into account Mode I and Mode II Loadings and their interaction by the application of the Weight Function Method.