The effect of superimposed high-cycle fatigue on thermo-mechanical fatigue in cast iron

Abstract

The effect of superimposing a high-cycle fatigue strain load on an out-of-phase thermo-mechanical fatigue test of a lamellar, compacted and spheroidal graphite iron has been investigated. In particular, different total mechanical strain ranges, maximum temperatures and high-cycle fatigue strain ranges have been studied. From this, a new property has been identified, measured and compared, namely the thermo-mechanical and high-cycle fatigue threshold, defined as the high-cycle fatigue strain range at which the life is reduced to half. Using a previously developed model, the lifetimes and the threshold have been successfully estimated for the lamellar and compacted graphite iron, however underestimated for the spheroidal graphite iron. Nevertheless, an expression of the threshold was deduced based on the model, which possibly can estimate the value in other cast irons and its high-cycle fatigue frequency dependence.