Essential characteristic of foreign object damage tolerance design for airfoils in aeroengine and development of design criteria

Through the analysis of foreign object damage(FOD) and failure characteristic of fan and compressor airfoils,it was concluded that vibratory stress design and control of airfoils according to reduced material allowable due to FOD is the fundamental feature of FOD tolerance design.Then,by the analysis and review of specifications and standards for aeroengine,the development process of FOD tolerance design criteria was divided into three phases.In the first phase(1950s'-1960s'),FOD related failures were mainly regarded as prevention and maintenance problems.During the second phase(1970s'-1990s'),FOD tolerance design was equivalent to withstand to a notch with a stress concentration factor(K_t) not exceeding 3.0 at the most critical locations of flow path components.Since 2000,a probabilistic design criteria has being in its development phase and has obtained great progress.Finally,some advice was put forward on the research directions of FOD tolerance design technology in China.