An engineering approach to estimate fatigue thresholds of wrought and additively manufactured defective metallic materials

Abstract

The threshold range of the stress intensity factor for long cracks, ΔKth,LC, is a material property of paramount importance in several fracture mechanics-based models to estimate the mechanical thresholds of materials and components affected by short cracks or defects. However, the experimental determination of ΔKth,LC is expensive in terms of time and costs, and the estimating model proposed in the literature often requires material parameters that are not readily available in the design phase or provides quite large approximations. Recently, the authors calibrated an empirical bi-parametric model for evaluating ΔKth,LC for load ratios equal to -1, 0 and 0.5 which is applicable to several wrought as well as additively manufactured alloys. where the only parameters involved are the Vickers hardness (HV) and a properly defined microstructural length l. The model was calibrated using data found in the literature and proved to be effective for estimations of the ΔKth,LC within an error band of ±20% of a quite wide range of wrought and additively manufactured metals.