Fatigue of welded aluminium hollow section profiles

This paper presents a study of the fatigue properties of welded connections in extruded aluminium hollow section profiles based on the use of the hot spot stress method. The study includes experimental fatigue test data and analytical results, with a focus on the hot spot stress concentration factors (SCFhs). A welded aluminium rectangular hollow section T-joint forms the basis of the study covering numerical stress analysis (finite element analysis); 3-D laser profile scanning of the welds; experimental stress analysis (strain gauges); and fatigue testing. Finite element analysis was performed on both idealised and actual (scanned) weld geometries. Values of SCFhs were computed for three different load configurations and a comparison made of the effects of the idealised and scanned weld geometries. Differences ranging up to 17.5% were found from the variations in weld geometry alone. The dominant effect lay in the choice of standards-based guidance for calculating the hot spot stress – causing variations as high as 38%. An experimental programme of some 40 new fatigue tests was compared with tentative design guidance previously drawn from earlier test results. The published database for RHS joints in aluminium remains small and further expansion of the database would clearly be beneficial.