Defect sensitivity and fatigue design: Deterministic and probabilistic aspects in AM metallic materials

Fatigue performance in both traditional and additively manufactured materials is severely affected by the presence of defects, which deserve special attention to ensure the in-service reliability and the structural integrity of complex engineering components. The traditional empirical or semi-probabilistic approaches, provided in standards and codes, only account for defects statistically; such design methodologies cannot fully exploit the material mechanical properties. Design strategies aim to explicitly account for defects features constitute a promising solution to achieve both required safety performance and material mechanical property exploitation. With the development of non-destructive techniques, such design methodologies have become applicable. However, there is still a tardiness in adopting new design strategies especially when it comes to industrial applications, e.g. emerging additive manufacturing (AM). In this review, a systematic overview is provided on the recent developments regarding fatigue behavior and failure mechanisms affected by defects, together with the methodologies for defects features characterization and probabilistic assessment. Moreover, the defects criticality and design approaches of AM parts are introduced and compared with traditional counterparts. Finally, the status of AM standardization is presented.