Fractographical quantitative analysis of EN-AW 2024 aluminum alloy after creep pre-strain and LCF loading

Abstract

This paper explores the applicability of a new damage parameter combining both fracture surface topography and loading features to estimate the fatigue lifetime under creep pre-strain and low-cycle fatigue loading. Fractures of EN-AW 2024 aluminum alloy caused by mixed creep and low-cycle fatigue loading are experimentally characterized and quantified via surface topography analysis. The specimens were preliminary damaged in a creep process at elevated temperature (100 °C, 200 °C, or 300 °C) considering two strain levels for each temperature. The specimens with preliminary damage were then subjected to fatigue tests at room temperature. The post-failure fracture surfaces were examined with an optical profilometer, and the focus was placed on the relationship between the creep-fatigue damage and the associated fracture surface topography parameters. In addition, an original fatigue life prediction model based on both the surface topography values and the applied strains was proposed and verified. The proposed model can be helpful for post-mortem analysis of engineering components subjected to fatigue loading accounting for creep pre-strain.