Fig. 1. Lamb wave dispersion curves. (a) Phase velocity curves; (b) group velocity curves

Fig. 2. Finite element model

Fig. 3. Comparison chart of received signals for non-destructive and damaged plates

Fig. 4. Signal frequency domain diagrams. (a) Non-destructive plate spectrogram; (b) spectrogram of damaged plate

Fig. 5. Received signal time-frequency domain diagrams. (a) Time-frequency domain diagram of non-destructive plate; (b) time-frequency domain diagram of damaged plate

Fig. 6. β fitting curve with crack length

Fig. 7. β fitting curve with crack width

Fig. 8. Crack simulation comparison. (a) Straight crack simulation cloud map; (b) 45° crack simulation cloud map

Fig. 9. Simulation diagram

Fig. 10. Harmonic signal comparison. (a) p2 probe extraction signal comparison at 0° and 15°; (b) p1 probe extraction signal comparison at 0° and 15°; (c) p3 probe extraction signal comparison at 0° and 15°; (d) comparison of signals extracted from three receiving points at 15°

Fig. 11. β fitting curves of p1, p2 and p3 probes extraction signals