Multi-Axial Contour Method for Mapping Residual Stresses in Continuously Processed Bodies

This paper describes a method for extending the capability of the contour method to allow for the measurement of spatially varying multi-axial residual stresses in prismatic, continuously processed bodies. Currently, the contour method is used to determine a 2D map of the residual stress normal to a plane. This work uses an approach similar to the contour method to quantify multiple components of eigenstrain in continuously processed bodies, which are used to calculate residual stress. The result of the measurement is an estimate of the full residual stress tensor at every point in the body. The approach is first outlined for a 2D body and the accuracy of the methodology is demonstrated for a representative case using a numerical experiment. Next, an extension to the 3D case is given and the accuracy is demonstrated for representative cases using numerical experiments. Finally, measurements are performed on a thin sheet of Ti-6Al-4V with a band of laser peening down the center (assumed to be 2D) and a thick laser peened plate of 316L stainless steel to show that the approach is valid under real experimental conditions.