Fatigue Propagation Life Evaluating for Materials or Components Suffered Load Spectrum by Quantitative Fractography

Abstract

Quantitative fractography is the important tool for evaluating the fatigue propagation life about material research and manufacturing process perfect, it is very useful in the circumstances that crack expands inside of the material or the crack cannot be observed because of the hidden part of the component. In-service components are usually suffered different load spectrums, and the fracture characteristics are combined created by random load spectrum and block spectrum, which are beach marks, small beach marks and fatigue striations. The most important thing for fractography quantitative analysis is to confirm the parameter used for evaluating the fatigue life and determine the relationship between the parameter and load spectrum. The relationships between different fracture characteristics and load spectrums are analyzed, and the selection means of characteristic parameter for different load spectrums are proposed. This paper also discussed a case of fatigue propagation life estimation of some aircraft lower wall panel suffered in-service aircraft flight load spectrum.