Abstract: The damage tolerance design is developed to ensure the safety of structures with cracks based on anti-fatigue and fracture design strategy. The key idea of this design principle is as follow:to avoid unstable crack propagation in engineering structure with inevitable initial defect, the fatigue crack growth life and residual strength of the structure with crack should be analyzed and verified in combination with regular maintenance. For the structures subjected to alternating loadings-such as aircrafts, ships, pressure vessels and so on-the conception of damage tolerance design has been widely recognized as the scientific principle to ensure safety and economic efficiency of large-scale equipments. In this paper we firstly summarize the scientific connotation of damage tolerance design based on reviewing the development of strength design concept for aircraft structures. Then we clarify the necessity for developing the theoretical basis of damage tolerance design from two-dimensional fracture theory to three-dimensional fracture theory. After that, the theory, method and application of three-dimensional damage tolerance design were described in detail. Finally, the future development trends of damage tolerance design are briefly prospected.

Key words: out-of-plane constraint, three-dimensional fracture mechanics, damage tolerance design, fracture criterion, crack propagation