Fatigue Life of Cast Al Component

The reliable design of an industrial cast part requires the evaluation of high cycle fatigue strength as well as fatigue life. In this study A357-T6 aluminum alloy cast structures have been subject to constant amplitude loading fatigue tests with a load ratio R=0.1. An analysis of the microstructure of the material has been performed in order to estimate the Secondary Dendrite Arm Spacing (SDAS). The macroscopic crack initiation has been identified by a Dye Penetrant Liquid surface examination. The resulting fracture surfaces are analyzed through Scanning Electron Microscopy (SEM) analysis in order to identify the initiation site at a microscopic scale. A multiaxial fatigue criterion has been proposed in order to take into account the stress gradient effect at the scale of the structure. The proposed criterion has been implemented in finite element simulations of the component in order to estimate fatigue life. This approach has been compared with a traditional criterion based on the analysis of the local stress at the hotspot.