Multiaxial fatigue assessment for automotive safety components of cast aluminium EN AC-42000 T6 (G-AlSi7Mg0.3 T6) under constant and variable amplitude loading

EN AC-42000 T6 (A 356 T6) is the most frequently used cast aluminium alloy for automotive safety components. Under non-proportional normal and shear stresses, fatigue life is increased in contrast to ductile steels where life is reduced. This behaviour is caused by the low ductility of this alloy (e < 10%) compared to structural steels suggesting the application of the Normal (Principal) Stress Hypothesis (NSH). Under multiaxial constant and variable amplitudes without and with mean stresses, the NSH was able to deliver, for most cases, conservative but non-exaggerated results. Fatigue lives under spectrum loadings were estimated by the application of the modified Palmgren-Miner Hypothesis using the allowable damage sum Dal = 0.3.