Residual stress determination through the combined use of holographic interferometry and the boundary integral equations method

One of the widely used methods for determining residual stresses is hole-drilling, in which the radial strains produced when residual stresses are relieved by the hole and are measured by different experimental techniques including holographic interferometry. In this paper a superposed holographic interferometer is used to determine in-plane radial displacements due to releasing of residual stresses by hole-drilling. The term `superposed holographic interferometer' denotes the assembly of the object surface section and holographic plate in an immediate vicinity to the object. With the purpose of raising the interference patterns contrast the high-frequency grating is used. Residual stresses are obtained by the boundary integral equations method. In this method the distribution of interference fringe orders along the 2 - 3 concentric holes is used to determine the boundary conditions. The combined employment of holographic interferometry and boundary integral equations method allows us to calculate the residual stress distribution along the hole's round and inside this region too. Agreement between stress holographically determined with a computed value is satisfactory.