Hot-Spot Stress of TI Welded Joints Used in Marine Structures

Experimental tests are crucial for evaluating the S-N curve to assess the fatigue life of welded joints. However, in the case of complex geometries, experimental tests often cannot provide the stress-strain data necessary for that specific material and welded joints. Therefore, finite element (FE) analyses are often required for assessing the fatigue behavior of complex geometries and discontinuities induced by welding processes. The fatigue properties of titanium welded joints, produced using an innovative laser source, were analyzed by means of numerical analyses. The structural hot-spot stress approach was applied to T -specimens fabricated from Ti6Al4V sheets and welded without the use of filler materials. The results, in terms of hot-spot stresses, exhibited a similar slope to the experimental load-number of cycles to failure curve. Furthermore, the International Institute of Welding provides specific FAT classes for the design of steel and aluminum welded joints, but they do not exist for titanium. This research activity highlights the need of performing suitable FE analyses on Ti6Al4V welded joints in order to achieve suitable FAT classes.