experimental determination of residual stresses in multi-pass girth welding of thermo-mechanical steel pipe

in this paper, two api x70 steel pipes (with spiral seam weld) of 56 inch outside diameter and 0.780 inch wall thickness were girth welded first. next, hole drilling tests were conducted for strain measurement on the surfaces of the pipes. the values of residual stresses on the internal and external surfaces of the pipe were determined, from strain data using astm 837 standard. the experimental data showed that the maximum tensile residual stress (318mpa) was located on the centre line of the weld gap on the pipe outer surface alongside with the pipe hoop direction. moreover, the maximum compressive (hoop and axial) residual stresses (137mpa) occurred on the pipe inner surface at 30mm from the centre line of the weld gap.