Local strain energy approach applied to fatigue analysis of welded rectangular hollow section joints

Abstract

This paper deals with fatigue life assessments of welded rectangular hollow sections made of steels and aluminium alloys, in a T-joint configuration, carried out by means of a local stress approach. The welded toe region is modelled like a sharp V-notch with an opening angle of 135 and the intensity of the asymptotic stress distributions is quantified by means of the Notch Stress Intensity Factors (NSIFs). In order to carefully evaluate the NSIFs of hollow sections welded in a T-joint configuration, some Three-Dimensional (3D) Finite Element (FE) analyses are firstly carried out. Afterwards, the NSIFs are used to evaluate the mean value of the strain energy density over a semicircular sector of radius RC at the welded toe. The radius RC is thought of as a material-dependent parameter. The experimental values of fatigue life are compared with those predicted by two previously scatter bands curves recently reported in the literature for welded joints made of structural steel and aluminium alloy. These curves were drawn by using mainly fatigue data obtained from cruciform and T-shaped welded joints. Although the analyses reported here represent only a first attempt to extend an energy-based approach to 3D hollow section joints, the comparison shows that a quite satisfactory assessment of the fatigue life can also be obtained for this type of welded joints. The agreement is good for welded joints made of structural steel, whereas the predictions are found to be in the safe direction for welded joints made of aluminium.