Estimating the amplitude of plastic strain from the distribution of the dislocation morphologies in front of the crack tips

The purpose of this study is to estimate the amplitude of plastic strain and stress from the dislocation structures in front of fatigue crack tips at various propagation rates in copper. The results are: (1) for both 5 × 10−5 and 5 × 10−6 mm per cycle propagation rates, the maximum plastic strain amplitude is more than 1.2 × 10−3 and the maximum stress amplitude is more than 115 MPa ahead of the crack tips; (2) for 4 × 10−7 mm per cycle propagation rate, the maximum plastic strain amplitude is about 6 × 10−4 and maximum stress amplitude is about 96 MPa; and (3) for a 2 × 10−8 mm per cycle propagation rate, the maximum plastic strain amplitude is about 7 × 10−5 and maximum stress amplitude is about 70 MPa in front of the crack tips.