Considerations for fatigue crack growth relative to crack tip displacement

摘要

The underlying mechanisms are reviewed for insight into why fatigue crack growth per cycle is often so small compared to the macroscopic crack tip displacement. To help judge regimes, typical parameters and order-of-magnitude relations are given for various aspects of fatigue crack growth. A log-log plot of da/dN versus the tip displacement, from atomic to structural scales, is compared to a normalized Paris-rule correlation with the range of stress intensity factor. It is concluded that reliable and economical design and maintenance must still be based on tests that closely simulate the service needs, in the light of the history-dependent mechanisms of roughening and closure.