Strain Energy Density and hot-spot stress analysis of welded T-joints for marine applications

The objective of this work is to validate, through finite element analysis, the use of the hotspot stress and Strain Energy Density (SED) approaches for the fatigue life assessment of welded T-joints made of structural steel and Ti-6Al-4V alloy. While these methods are well established for steel, their application to titanium is less straightforward due to the absence of material-specific FAT curves and SED scatter bands for welded configurations. To enable the application of the hotspot stress method to titanium joints, a preliminary approach based on the normalization of steel FAT curves with respect to the Young’s modulus was implemented. The SED method was instead applied by adopting the control radius and design curve derived for the base material. Both methodologies proved to be reliable for steel joints, whereas in the case of titanium, the results emphasized the limitations of these approaches and the need for further experimental data to establish suitable design references.