The contour method (CM) has emerged as a valuable technique for the measurement of residual stresses (RS). The method involves cutting the sample in which residual stresses are to be measured, using wire electric discharge machining (EDM), and measuring the deformation that occurs on the newly created surface, which can be related to the residual stresses that existed beforehand. The contour method provides a full 2-D map of the stresses acting in a direction normal to the plane of the cut. It is ideally suited to measurements in power plant welds since, unlike diffraction-based techniques, it is not affected by microstructure gradients, and it is well suited to thick section components. However, as with other mechanical strain relief techniques, it is prone to errors arising from plasticity when residual stresses close to the yield strength of material are encountered. This paper describes contour method measurements in an AISI Type 316L austenitic steel three-pass. A novel cutting and restraint strategy is applied in an attempt to reduce plasticity errors following optimisation studies simulating the cutting process using the finite element (FE) method.
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