Fatigue strength of structural components under multi-axial loading in terms of local energy density averaged on a control volume

The approach based on the strain energy density (SED) averaged over a control volume is first used to summarise uniaxial and multi-axial fatigue strength data of welded joints made of structural steels and aluminium alloys. In all welded joints, the weld toe and weld root regions are modelled like sharp, zero radius. V-notches with different opening angles. The control volume radius is 0.28 mm for structural steels, 0.12 mm for aluminium alloys. Afterwards the SED approach is applied to multi-axial fatigue data from plain and V-notched specimens made of AISI 416 stainless steel (hardened and tempered state), subjected to tension, torsion and combined tension and torsion, both in-phase and out-of-phase. Notched specimens are characterized by a very small root radius, rho=0.1 mm, which results in high nonlinear effects ahead of the notch tips. All results are summarised in terms of Delta W-N (SED range versus cycles to failure) scatterbands. Together with the new results, a number of multi-axial fatigue data recently obtained from sharply notched specimens made of C40 steel (normalised state) and 39NiCrMo3 steel (hardened and tempered state) are represented with the aim to provide a global synthesis in terms of local SED.