A study of residual stresses in a weld with one free surface

Abstract

The distribution of residual stresses in a multi-pass weld with one free surface was evaluated by X-ray diffraction techniques. It was determined that for specimens fabricated from the same materials in approximately the same manner, the resulting residual stress patterns bore a marked similarity. In the interface areas between successive passes abrupt increases in stress magnitudes were found and it is suggested these high stress values may be conducive to crack propagation. The literature survey failed to disclose any experimental study confirming the existence of these high values. Specimens used in this study consisted if four-inch diameter rounds of AISI-C1020 steel machined to receive a five-pass weldment. Airco No. 78E (AWS Type 010) 1/8-inch diameter electrodes served as filler metal. No preheating or control of interbead temperature was exercised and no stress-relief prior to welding was carried out. The only restriction placed on the welder was to continue welding until the specimen was completed. Momentary pauses between successive passes were allowed to permit wire-brushing for the removal of slag which also constituted the only post-weld treatment. It is believed these conditions simulate procedures normally followed by most steel fabricators and erection shops. Tensile stresses equivalent to about eighty percent of the yield strength of the base metal were found to exist in the circumferential and transverse directions at the surface. The magnitudes then decreased uniformly, the transverse values more rapidly than the circumferential, through the thickness of the outermost pass. At the first interaction region, approximately 0.100 inch from the surface, abrupt increases in stress values were noted which then decreased uniformly to the next interaction region at approximately 0.200 inch from the surface..