Evaluation of multiple residual stress components in a thick welded joint using extended contour method

Abstract

The conventional contour method (CM) needs multiple cuts at different locations to obtain the multiple components of residual stress in a specimen. To improve the convectional CM, an extended CM was proposed in the present study to determine the multiple stress components in a thick butt-welded joint without cutting at different locations. First, the longitudinal residual stress in the specimen was measured with the CM, then a thin slice was cut from the after-cut specimen, and the remaining transverse stress in the slice was measured with the X-ray diffraction method and the released transverse stress of the slice was constructed by the finite element analysis (FEA), and finally, the transverse stress on the same cross-section was obtained by the superposition of the remaining and the released transverse stresses on the slice. A two-cut CM was also carried out to get the transverse stress along the weld line center. The stress distribution characteristics of the specimen and the release extent of the transverse stress in the slice were discussed. The results show that the extended CM can evaluate the original biaxial residual stresses on a cross-section without multiple cuts at different locations. The transverse stress distribution trend obtained by the extended CM is close to that from the two-cut CM. Without considering the compressive stress induced by ultrasonic impact treatment, the longitudinal stress in the weld region is tensile with a maximum value of 550 MPa and the transverse stress at the weld line center is self-equilibrating with a maximum value reaching 552 MPa. Two peaks of tensile longitudinal and transverse stress appear at a certain distance beneath the top and bottom surfaces. When cutting a thin slice with a thickness of 5 mm along the transverse direction from the after-cut specimen, over 82% of the original tensile transverse stresses are retained in the slice.