Experimental evaluation of relaxed strains in a pipe-to-plate welded joint by means of incremental cutting process

Residual stresses play a major role in the fatigue life and static strength of welded components. The high thermal gradient to which the material is subjected to during welding often leads to tensile residual stresses in critical notched regions. Residual stresses evaluation is crucial as they can cause unexpected failures or premature degradation of components, thus shortening the service life. Since determining their magnitude a priori is challenging, the experimental evaluation is fundamental when tensile residual stresses could be degrading for a component. The assessment of residual stresses can be performed through different techniques, all involving indirect measurements based on the detection of elastic deformation or displacement. In this context, a method belonging to the sectioning method category is proposed to calculate relaxed strains in a pipe-to-plate welded joint. The relaxed strains are determined by means of strain gauges placed on the upper surface of the plate nearby the weld bead. The results thus obtained represent strains measurements generated after an incremental hole cutting process performed on the bottom surface of the plate, opposite respect to the surface where the strain gauges were attached. Through this method, the calculated strains are related to the diameter and depth of the performed hole, as well as the location where the strain gauges are placed on the plate surface.