Converging ultrasonic shear-vertical waves generated by a double-line laser and its application for surface defect detection

A double-line laser source as an irradiation pattern for the generation of ultrasonic waves is proposed. Simulated results show that the shear-vertical (SV) waves generated by the double-line laser source superimpose and produce a convergence effect at the center axis with a fixed angle. The amplitude of the converging SV wave is significantly improved compared to the ultrasonic field generated by a single-line source under the same condition of the thermoelastic regime. Simulations show good agreement with experimental results, which demonstrate that the SV waves in a steel plate subjected to the double-line laser source converge efficiently at the center axis. Then, a method using the converging SV to detect surface defect on a steel plate is proposed. The characterization of the surface defect has been quantitatively measured with high accuracy by the well-designed double-line source.