An approach to correlate fatigue crack growth rate with S-N curve for an aluminum alloy LY12CZ

摘要

By considering fatigue crack growth (FCG) as the consequence of fatigue fracture of crack front, the correlation between crack growth rate and S-N curve has been investigated. A method to calculate the fatigue life of crack front from the S-N curve has been developed by taking the initial damage at the crack front into account. It is found that the effect of initial damage on fatigue life can be approximately expressed by a parallel shift of S-N curve in bi-logarithmic graph. Thus, crack growth rate curve corresponding to an initial damage at crack front, can also be obtained by a parallel shift of the base curve, which can be calculated from the imaginary fatigue life of crack front without initial damage. The shift distance is dependent on the initial damage at crack front, and can be determined by just one or several experimental results of crack growth. Thereby, the test numbers to obtain crack growth curve can be reduced greatly by adopting this correlation.