Influence of stress ratio on residual stress redistribution at the weld toe of gusset joints welded with phase-transforming boxed welds

Low transformation temperature (LTT) welding materials can effectively mitigate detrimental tensile welding residual stresses (WRS) at fatigue-critical locations such as weld toes, while also inducing beneficial compressive stresses. However, the stability of these compressive stresses under cyclic loading remains insufficiently understood. This study numerically investigates the influence of a wide range of stress ratios ( R ) on residual stress (RS) redistribution at the weld toe of out-of-plane gusset welded joints made of S355 steel. The initial WRS distribution was first predicted for several welding cases, including joint with conventional boxed welds, joint with LTT boxed welds, and joints with LTT boxed welds of different sizes. Subsequently, elastic-plastic finite element analyses were conducted under cyclic uniaxial loading across a wide range of R values to assess RS redistribution while accounting for the WRS generated by each welding case. Additional analyses that neglected WRS effect were also performed to clarify the role of initial WRS in shaping the RS redistribution. The results showed that the predicted tensile WRS near the weld toe of the narrow joint with LTT boxed welds was reduced by 39.5% compared with that of the narrow joint using conventional boxed welds, and by 27.1% compared with that of the wide joint with LTT boxed welds. It is also noted that the applied R is the primary factor governing both the nature and magnitude of RS redistribution. In contrast, the phase transformation characteristics of the LTT welding material and the joint size primarily influence the extent of stress mitigation at the weld toe.