Residual Stress Measurement with Contour Method

Residual stresses are generated in a part during manufacturing which typically involves sequential thermo-mechanical processing including forming and heat-treatment steps. These stresses can then be influential during subsequent machining operations where the removal of material results in the redistribution of bulk stresses within the part leading to potentially significant distortions and problems with dimensional tolerances. Contour method is a residual stress measurement technique that can provide information about the magnitude and distribution of these stresses. It is a destructive technique whereby the part is sectioned to release the internal stresses, manifested as waviness of the cut face. The surface profile is then scanned, using either coordinate measuring systems or non-contact optical means, to measure out of plane distortions that will then be applied as boundary condition in an inverse simulation, to obtain a full cross-sectional map residual stresses. The technique offers evaluation of the bulk stresses with a good spatial resolution, reasonable accuracy, and is not limited by the shape or size of a part.