Fatigue Mechanisms and the Development of Fatigue-Resistant Materials.

Concentrated research on fatigue mechanisms during the past decade has removed much of the mystery of catastrophic fatigue failure. It is now known that failure is the certain result of the nucleation and growth of highly localized microcracks, and that the rate of accumulation of this type of damage depends on the microstructure of the material as well as certain mechanical properties. In this paper, the accumulated knowledge of fatigue mechanisms is applied to the problem of developing fatigue-resistant materials. Four questions are considered 1 How can high static yield stresses be maintained under cyclic loading. 2 How can crack initiation be suppressed. 3 How can crack growth rates be reduced. and 4 How do temperature and environment affect the fatigue response of materials. Out of the answers to these questions, guidelines are drown for the development of new materials, with illustrative examples given in which higher fatigue strength has been achieved. Finally, specifications for an ideal fatigue-resistant material are synthesized from the answers provided by fatigue mechanisms knowledge. Author