Influence of stress ratio on fatigue behaviour of gas metal arc welded naval grade HSLA steel joints: Assessment of safe and unsafe region for ship hull fabrication

In this investigation, the influence of stress ratio on high cycle fatigue (HCF) behavior of GMAW butt joints made of micro alloyed HSLA steel is studied. The fatigue test was performed for 50–90 % yield strength with different stress ratios (R = 0.1, 0.5, 0.7, and −1). The evaluated fatigue strength of the GMAW joint is relative to 91 %, 89 %, 86 %, and 84 % of the parent metal fatigue strength, and 62.2 %, 57.4 %, 50.7 %, and 47.5 % are equal to the transverse tensile strength of the GMAW joints for the different stress ratio. From the experimentation, if the stress ratio increases from −1 to 0.7 the fatigue strength of the welded get decreased. Because the crack tip experienced deformation accelerated by higher stress ratio, which directly impacted on number of cycles to fracture. Although, the operating unsafe and safe regions are established through goodman – Soderberg diagrams with the effect of stress ratio, which clearly indicates that the R increases the area of safe region get decreased.