Fracture and notch mechanics to estimate the uniaxial fatigue limit of plain and severely notched L-PBF AlSi10Mg specimens

Abstract

This work discusses the applicability of the notch mechanics and linear elastic fracture mechanics to estimate the uniaxial fatigue limit of sharply notched Additively Manufactured (AMed) specimens. It is well known that the fatigue behaviour of AMed materials is influenced by defects inherent to the manufacturing process and the fatigue strength of materials weakened by defects depends on material properties, load ratio R and size of defects. While defect sensitivity on fatigue thresholds has been studied extensively in the literature for different AM materials, investigations on the effect of notches, and especially sharp notches, including notch-defect interaction and competition are still limited, leaving considerable scope for theoretical and experimental investigations. In this study, fatigue tests were conducted on plain and sharply notched specimens AMed from AlSi10Mg powders to investigate the competition between AM process-related defects and sharp notches. The investigation highlighted that AM defects are detrimental for plain specimens, while they do not impact the fatigue strength of sharp notches. A previously published model proved satisfactory to predict the fatigue limit of the plain and sharply notched specimens; the model requires two material properties, namely the plain material fatigue limit and the threshold range of the mode I stress intensity factor for long cracks.