Fatigue refers to the mechanical failure of materials subjected to repeated cyclic loads. It occurs in all materials including metals and alloys, and is a significant limitation that affects all engineering structures and devices (both structural and functional). It is a common cause of failure (and accidents) in devices including computers, cars, bridges and airplanes, and thus a significant economic, societal and national defense challenge.

Unfortunately many fundamental aspects of fatigue remain incompletely understood, even though decades of empirical knowledge have provided (conservative) material specific guidelines for the design of engineering components to avoid fatigue in specific materials. The advent of additive manufacturing and advanced alloys have pushed us beyond this empirical knowledge base. In particular, recent experimental observations suggest situations where additively manufactured metallic alloys have fatigue strength that greatly exceed their conventionally manufactured counterparts, and other situations where they greatly underperform.