Research on Fatigue Damage in High-Strength Steel (FV520B) Using Nonlinear Ultrasonic Testing

Table 3

Statistics of the cracks in the notched specimens (550 MPa stress concentration).

Samples number	Sample no. 1	Sample no. 2	Sample no. 3
Main crack length (mm)	1.03	3.10	6.56
Number of microcracks	25	10	29
Length of largest microcrack (μm)	10.993	7.993	14.883
Equivalent microcrack length (μm)	142.503	60.268	185.58