A new approach to the correlation between the coefficient and the exponentin the power law equation of fatigue crack growth

The presented experimental results for 2xxx, 6xxx and 7xxx type aluminium a lloys show a variability of the fatigue crack growth rates in the Paris reg ime to an extent important for the materials selection according to the dam age tolerant design concept in the aircraft industry. This paper briefly re views the controversial views on the correlation between coefficient and ex ponent in the power law equation of fatigue crack growth. A new approach to the correlation based on a scaling factor of the stress intensity factor r ange is outlined. It is shown that the correlation is an algebraic one that can be suppressed by choosing a particular scaling factor characteristic o f the set of materials under investigation. The approach allows the variabi lity of the power law coefficient to be quantified more clearly and the res ponsible influence factors to be identified. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.