Effects of local ultrasonic impact treatment on residual stress in an engineering-scale stainless steel pipe girth weld

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An engineering-scale stainless steel pipe girth weld was manufactured and the ultrasonic impact treatment (UIT) was applied to treat the local region of the girth weld. The as-welded and the after-UIT surface stresses were measured with the X-ray diffraction (XRD) method, and the internal stress distributions on the planes across the treated zone were measured with the contour method. The effects of local UIT on the stress distribution of the girth weld were investigated. Results show that UIT on the stainless steel pipe girth weld can introduce compressive stress on the impact surface despite the initial as-welded stress state (tensile or compressive); UIT can affect the stress distribution in the stainless steel pipe girth weld up to 8 mm depth and induce a compressive stress layer at the treated region with a depth of 4 mm, the peak value of the compressive stress occurs at the location of 1 mm depth beneath the surface, and it has little effect on the stresses near the inner surface and those outside the treated region.