Residual stress measurement in spot welds and the effect of fatigue loading on redistribution of stresses using high sensitivity moire interferometry

Residual stress distribution has been determined in spot welds, which are g enerally used to join mild steel sheets. Various spot weld configurations w ere investigated using the full-field, experimental, optical technique of h igh sensitivity moire interferometry. These stresses were found to be in th e range 250-300 MPa (tensile) in the center and decreased to 40-100 MPa (te nsile) at the edge of the weld nugget. Low cycle fatigue loading of the spo t weld caused the residual stress to drop in the weld center by about 30 pe rcent and increase at the edges by as much as 100 percent.