Studies on the residual stress in circular patch weld

Abstract

Residual stress in 25mm thick plates of A5083-o, which to circular patches of 50-400mm in diameter had been welded with MIG-semiautomatic welding, was measured by the stress-relief method of cutting the gage section out of the plate. In all specimens, the circumferential stress, σθ, and the radial stress, σγ, were tensile within the patch. However, outside the patch, σθ became compressive, but σγ was still tensile. The maximums of σθ and σγ, σθmax and σγmax, were observed at the neighborhood of the welds. Only in the case of the patch with small diameter, σθmax and σγmax changed slightly along circumferential direction.σθmax and σγmax depended on the patch diameter. As the patch diameter increased to 100-200mm, σθmax and σγmax increased to 16.5 and 16.0kg/mm2, respectively. However, they approached to constant values in a decreasing way when the patch diameter was beyond 400mm, which was identified as the optimum size of the patch diameter. The dependence of the residual stress on the patch diameter was considered due to a heat cycle at the welding part. Although both-sides symmetrical block-welding was somewhat effective for reducing the residual stress, the effect was not so remarkable taat as in steel.