Cumulative damage of high-strength cast iron alloys for automotive applications

The cumulative damage calculation method generally applied in the automotive sector is the Palmgren-Miner-Hypothesis with its modification according to Haibach. In several design codes the theoretical Palmgren-Miner damage sum Dth = 1.0 is still recommended as the allowable damage sum Dal despite the fact that it renders unsafe calculated fatigue lives. Results obtained with modern high-strength cast iron alloys such as EN-GJS-500-7, SiboDur 700-10 and MADI (Machinable Austempered Ductile Iron) under a standard Gaussian spectrum for chassis applications and also under a fuller injection pump spectrum suggest the allowable damage sum Dal = 0.3 for fatigue life estimations.