Fast characterization of high-cycle fatigue properties of a cast copper–aluminum alloy by self-heating measurements under cyclic loadings

Abstract

Even if casting offers the possibility of producing complex shaped parts in a few operations, this process introduces inevitably casting defects such as shrinkage cavities which are harmful regarding fatigue resistance. In this work, this initial defects population is taken into account by indirect approach, i.e. without describing size and geometry of pores, to characterize rapidly High-Cycle Fatigue (HCF) properties of cast materials by the aid of self-heating measurements under cyclic loadings. A probabilistic multiaxial two-scale model is proposed to analyze the self-heating measurements in order to predict S/N curves. It is assumed that fatigue damage is due to microplasticity that induces a dissipative energy which is related to the temperature increase of the studied specimen under cyclic loadings for low stress amplitudes. To describe microplastic activity, a Poisson distribution of elasto-plastic sites within an elastic matrix is considered. In this paper, the identification procedure has been performed on the particular case of a sand cast copper-aluminum alloy used for casting marine propellers. The validation of the proposed approach concerns the prediction of classical fatigue results. The results of this study show a good matching between model predictions and experimental fatigue data, including scattering.