Optical Analysis of Weld-Induced Residual Stress by Electronic Speckle-Pattern Interferometry

摘要

Electronic Speckle-Pattern Interferometry (ESPI) is applied to analysis of residual stress induced by laser welding. A thin plate of stainless-steel is butt-welded to a carbon-steel plate of the same dimension to form a dissimilar-weld specimen. Similarly, a pair of stainless-steel plates and that of carbon-steel plates are respectively butt-welded to each other to form similar-weld specimens. The dimensions of the dissimilar and simlar-weld specimens are all the same. A tensile load is applied to the specimen perpendicular to the weld line and at a constant pulling rate until the stress on the sample is approximately a quarter of the yield stress. The resultant deformation is monitored with an ESPI setup sensitive to the in-plane displacement component parallel to the tensile axis. Interferometric images are formed at a fixed time interval, and fringe patterns representing contours of the in-plane displacement are created by subtracting the image taken at each time step from several time steps after. Resultant fringe patterns show behaviors that can be interpreted as revealing residual stress.