Comparison of Fatigue Life and Strength Models for Defective Materials: Application to Scalmalloy in Different Surface Conditions

Additive manufacturing (AM), particularly laser-powder bed fusion (L-PBF), has transformed the production of lightweight, high-performance metallic components, with Scalmalloy emerging as a promising material due to its excellent strength-to-weight ratio, making it ideal for aerospace and automotive applications. However, process-induced anomalies present challenges in achieving reliable fatigue performance, which requires robust methodologies for life prediction and defect-tolerant design. This study investigates the fatigue behavior of L-PBF Scalmalloy under various surface conditions (net-shape and sandblasted) and orientations (vertical and inclined at 55°) using an advanced fracture mechanics framework. An experimental campaign evaluates fatigue strength under these varying conditions, with results compared between conventional models incorporating different assumptions regarding the long-crack threshold (El-Haddad model and NASGRO-type equations) and R-curve-enhanced approaches. The analysis demonstrates the effectiveness of the R-curve in improving fatigue predictions in all conditions tested, particularly in mitigating nonconservative results. This work advances the understanding of fatigue mechanisms in AM Scalmalloy, offering a framework for life prediction and defect-tolerant design, ensuring more reliable applications of additively manufactured components in critical applications.