A study was made, of the amplitude of plastic strain and stress, from dislocation structures ahead of fatigue crack tips at various propagation rates. It was found that, for 5 x 10−5 and 5 x 10−6mm/cycle propagation rates, the maximum plastic strain amplitude was more than 1.2 x 10−3 and the maximum stress amplitude was more than 115MPa ahead of the crack tips. For a 4 x 10−7mm/cycle propagation rate, the maximum plastic strain amplitude was about 6 x 10−4 and the maximum stress amplitude was about 96MPa. For a 2 x 10−8mm/cycle propagation rate, the maximum plastic strain amplitude was about 7 x 10−5 and the maximum stress amplitude was about 70MPa ahead of the crack tips.

Estimating the Amplitude of Plastic Strain from the Distribution of the Dislocation Morphologies in Front of the Crack Tips. H.L.Huang, N.J.Ho, T.L.Hu: Materials Science and Engineering A, 2004, 386[1-2], 112-7