Actual Stress Analysis of Small-Bore Butt-Welded Pipe by Complementary Use of Synchrotron X-Rays and Neutrons

Abstract

Residual stresses in astresses in small-bore butt-welded pipe of austenitic stainless steel have never been measured. It is difficult to obtain a detailed residual stress map of the root welded part, because the gauge volume in neutron diffraction is large. The stress evaluation of the welded part by synchrotron X-rays was also difficult due to the dendritic structure. In this study, a double exposure method (DEM) with high-energy synchrotron X-rays was applied to measuring the details of the residual stress of the welded part, and we succeeded in obtaining the detailed axial and radial stress maps of the root welded part of the plate cut from the welded pipe, though the stress map was under the plane stress condition. The hoop stress map of the butt-welded pipe was obtained using the strain scanning method with neutrons under the triaxial stress state. The axial and radialradius stress maps under a triaxial stress state were made up using the complementary use of the synchrotron X-rays and neutrons. As a result, the detailed stress maps of the root welded part of the butt-welded pipe were obtained. The result of the actual stress analysis sufficiently explained the initiation and propagation of SCC.