Strength Deterioration With Increasing Specimen Size of an Additively Manufactured Aluminum Alloy in High‐Cycle and Very‐High‐Cycle Fatigue

ABSTRACT We conducted a statistical fatigue analysis of an additively manufactured aluminum alloy (AlSi10Mg) with five different sizes of specimens to establish probabilistic S‐N curves and assess an anomalous behavior of strength deterioration in high‐cycle and very‐high‐cycle regimes. For the five specimen types, S‐N data were obtained by ultrasonic axial cycling at R = −1. Based on the fitted Basquin equations, the S‐N data were converted to equivalent stress amplitudes at the same life. In general, the stress amplitudes can be regarded as normal, log‐normal, and Weibull distributions, with the log‐normal slightly overestimating the fatigue performance, whereas the Weibull slightly underestimated it, and the normal being the most suitable. Finally, we compared the normal distribution of fatigue resistance with the control volume V 90 of specimen types and plotted the strength deterioration from 10 6 cycles to the extrapolated 10 10 cycles, indicating that the specimen size effect diminishes as fatigue life increases.