A residual stress evaluation in laser welded lap joint with hole drilling method

Residual stresses deteriorate strength of materials affecting the quality of industrial products. A removal or reduction of the residual stresses is an essential procedure in successful engineering component development. Effective and convenient methods are necessary for detection and evaluation of residual stresses. In this paper Hole Drilling Method is chosen for identification and a quantitative determination of the residual stresses in specimens of two groups under different laser welding speed conditions, 4.1m/min and 5.1m/min. The lap joints welded with STS 301L sheet of two different speeds were investigated along the welding line at two locations, the middle and the end location in the heat affected zone (HAZ). The identification of HAZ is carried out by taking hardness values from weld centerline to the raw material. Based on the experimental results and analysis, it is found that higher welding speed reduces the residual stresses. Also, the end location is found to be higher residual stress area compared with middle location due to the convective boundary condition. The residual stresses decrease as the depth increases from the top surface due to the lower heat input to depth increments.