Fatigue Resistance Enhancement and Residual Stress Modification of Welded Steel Structures by Various Post-Weld Treatments

1 Three post-weld treatemnt methods (UIT, Air Hammer Peening, Shot Peening) are discussed in this study. Fatigue tests carried out on AL-6XN stainless steel specimens treated by these techniques showed that fatigue resistance has been significantly enhanced compared with the as-welded conditions. The enhancement is comparably effective for these three treatment methods in circumstance of this study. 2 Residual stress measurements were carried out using X-ray and neutron diffraction techniques to characterize the magnitude and subsurface distribution of the compressive stresses induced by UIT and shot peening treatments. Both treatments induced very high compressive stresses near the treatment location and the material was plastically deformed. 3 The compressive strength region by UIT alone (base metal) was 1.5–1.7mm in depth and ∼±15mm in width. For the welded specimen, this compressive layer could be reduced to 1mm deep due to existence of tensile weld residual stress. 4 The magnitude of compressive stress induced by shot peening was comparable to UIT, but the compressive layer was about half the depth (0.8mm) of that for UIT.