Measurement of the Residual Stresses Near a Short 20° Repair in a 19 mm Thick Stainless Steel Pipe Girth Weld

Abstract

The three-dimensional through-thickness residual stress field in the heat affected zone of a repair that was introduced in the girth weld of a 19 mm thick stainless steel pipe has been determined by neutron diffraction experiments. Results based on a preliminary estimate of the unstressed lattice spacing show a compressive radial stress (−160 MPa) that remains almost constant through the thickness, whereas the axial stresses decrease from a tensile magnitude of 100 MPa close to the inner surface to about −80 MPa compression towards the outer surface. The largest variation is observed in the hoop stress, which changes from 100 MPa in tension in the vicinity of the inner surface to −280 MPa in compression, approaching the outer surface. Very good qualitative agreement of the through-wall stress profiles is found between neutron diffraction and deep hole drilling (DHD) measurements, but both the axial and hoop stress magnitudes differ by over 150 MPa. This discrepancy could arise from either the uncertainty in the preliminary stress-free lattice parameter of neutron diffraction measurements or from the plane stress condition, assumed in DHD measurements.