Fig. 1. Time and space distribution function of pulsed laser. (a) Space distribution function; (b) time distribution function

Fig. 2. Gaussian pulse laser

Fig. 3. Finite element model for laser ultrasonic detection

Fig. 4. Mesh division

Fig. 5. Ultrasonic sound field distribution at different moments. (a) 210 ns; (b) 650 ns; (c) 4010 ns; (d) 5060 ns

Fig. 6. Time-domain signals at different probe locations without defect. (a) (0,0) location; (b) comparison of signals at (0,0) and (2.0,0)

Fig. 7. Time-domain signal of a 0.5 mm radius defect at (0,0) and compared with no defect. (a) 0.5 mm radius defect; (b) comparison of time-domain signals between defect-free and 0.5 mm radius defect

Fig. 8. Time-domain signal of a rectangular defect at (0,0) and compared with hole defect. (a) Rectangular defect; (b) comparison of time-domain signals between rectangular defect and hole defect

Fig. 9. Time-domain signals of defects at different locations at (0,0)

Fig. 10. Time-domain signals for defects of different radii at (0,0) and reflected surface wave amplitude change. (a) Time-domain signals at (0,0); (b) reflected surface wave amplitude change

Fig. 11. Time-domain signals for defects of different radii at (8.0,0) and transmitted surface wave amplitude change. (a) Time-domain signals at (8.0,0) and local amplification; (b) transmitted surface wave amplitude change

Fig. 12. Frequency-domain signal diagrams of transmitted waves for defects with different radii. (a) 0.1 mm; (b) 0.3 mm; (c) 0.5 mm

Fig. 13. Time-domain signals of reflected surface and diffracted transverse waves at (0,0) for different defect depths. (a) Reflected surface wave; (b) diffracted transverse wave

Fig. 14. Time-domain signals and amplitude variations of transmitted surface waves at (8.0,0) for different defect depths. (a) Time-domain signals at (8.0,0) and local amplification; (b) transmitted surface wave amplitude change