H. Nasri, J. Lanteigne, and H. Champliaud
CONTOUR METHOD, WELDING, heat-affected zone
Residual stresses, which are inherent to many manufacturing processes, may considerably reduce the fatigue properties of mechanical systems. Welding is a process that induces residual stresses due to plastic deformation and phase changes, which take place within the heat-affected zone (HAZ). Mechanical surface treatments are often used to minimize or even reverse the tensile stresses due to welding. In this study the influence of peening on existing welding residual stresses, through all the plate thickness, is shown using the contour method. The contour method, the measurement protocol selected in this paper for estimating residual stresses, allows the assessment of these stresses over a whole cross-section, unlike other common methods which only provide limited local point measurements. This method is based on the relaxation of stresses resulting from EDM cutting. Displacements of the relaxed cross section are measured by a laser beam. The cut surface is treated and approximated through a polynomial surface, which is used to impose displacements on the nodes of a finite element model. The solution to this problem is the normal stress responsible for the released micro-displacements on the plane section cut. This method was applied on 516 carbon steel plates either in the as-welded condition or welded and peened.
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