Experimental and stochastic investigations of the influence of the inclusions on the fatigue life (C04)

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The objectives of the subproject during the third funding period are – in continuation for the second funding period - the determination of the largest existing, i.e. fracture-initiating, non-metallic inclusion that has not been filtered, and the determination of the dependence of the fatigue life distribution in the case of fatigue loading in the range of long service lives on the inclusion distribution. In order to be able to investigate the failure of internal inclusions in the VHCF range more specifically, specimens with modified surface properties (residual compressive stresses) and under tensile mean stresses are tested. Microstructural characterizations of the inclusions in the cast as well as in the failed state serve to elucidate the formation and damage mechanisms of inclusion agglomerates. The development of a three-dimensional thermo-mechanical simulation model that can predict the heat generation during fatigue allows to conclude about the spatial distribution of the heat source(s) inside the samples, so that further conclusions about the crack initiation and growth behavior in the VHCF range can be expected from the dissipated energy.