Residual stress stability of HFMI-treated transverse attachments under variable amplitude loading with the P(1/3) and the linear spectrum

Abstract

The potential of HFMI treatment to increase fatigue life under service loading remains in debate. However, some recent studies show that even under variable amplitude loading (VAL), fatigue strength is increased compared to untreated welds. Discussions generally focus on the stability of initial compressive residual stresses, which may be reduced during VAL due to high peak stresses. In this context, the potential of HFMI treatment is often only attributed to residual stress stability. This study presents further results on the effect of VAL with a P(1/3) and a linear load spectrum on the residual stress stability of HFMI-treated transverse stiffeners (TS) made of mild steel (S355) and high-strength steel (S700M). The impact of random, High-Low and Low-High loading sequences on the fatigue strength as well as on the residual stress behaviour of HFMI-treated joints will be discussed.

Local relaxation of residual stress in high-strength steel welded joints treated by HFMI

“…Welded steel structures in real situations can often experience a high-peak load, either a single overload or a part of variable amplitude loading. This type of loading may result in local material yielding and then the reduction in the compressive residual stress layer, i.e., relaxation of residual stress, which may suppress the effect of HFMI treatment [15][16][17][18]. To better understand the influence of residual stress relaxation on fatigue performance, studies by, e.g., Yonezawa et al [16] and Loschner et al [17] conducted extensive experimental measurements of residual stress change and stability under different cyclic loadings.…”

“…This type of loading may result in local material yielding and then the reduction in the compressive residual stress layer, i.e., relaxation of residual stress, which may suppress the effect of HFMI treatment [15][16][17][18]. To better understand the influence of residual stress relaxation on fatigue performance, studies by, e.g., Yonezawa et al [16] and Loschner et al [17] conducted extensive experimental measurements of residual stress change and stability under different cyclic loadings. In addition, numerical studies considering the dynamic elastic-plastic analysis of the HFMI process have been carried out by, e.g., Schubnell et al [18] and Ruiz et al [19].…”