Fatigue: Damage Tolerance Design

Design and verification of fatigue critical components typically involve several steps, including such obvious topics as stress analysis and fatigue testing of components and structures. Various methodologies may be used, depending on safety requirements and financial aspects, but irrespective of the choice made there are certain aspects that always have to be considered. The term damage tolerance is, however, frequently abused in the sense that as soon as crack growth is being studied it has become popular to refer to damage tolerance. This is erroneous and it must be emphasized that crack growth is but one of several ingredients within the total design philosophy that is damage tolerance. This article will discuss the various topics that constitute building blocks within the damage tolerant philosophy for aircraft structures. Application of damage tolerance to any other type of structure includes the same steps, i.e., design, verification, and operational management.