Load and Environment Interactions in Fatigue Crack Growth Under Spectrum Loading.
Final rept. 15 Jun 75-30 Sep 77,
LEHIGH UNIV BETHLEHEM PA INST OF FRACTURE AND SOLID MECHANICS
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The importance of delay or, retardation in the rate of fatigue crack growth produced by load interactions in variable-amplitude loading on the accurate prediction of fatigue lives of aircraft and other engineering structures has been recognized for some time and has begun to receive greater attention in recent years. Recent investigations showed that the effects of delay can be quite large, and that these effects need to be taken into account in developing improved fatigue analysis procedures for aircraft and other engineering structures. A number of models based on the concepts of crack closure, residual stress intensity factor, etc. have been proposed to account for the effects of delay. These models, while successfully predicting trends in the rate of fatigue crack growth for randomized load spectra, appear to break down for ordered spectra. Several basic problems contributed to the lack of complete success, and needs to be resolved in the development of improved models for predicting load interaction effects chiefly delay on fatigue crack growth.
- Metallurgy and Metallography