Application of laser generated ultrasonic pulses in diagnostics of residual stresses in welds

The laser optoacoustic method is applied for nondestructive evaluation of residual stresses in metals. Theoretical background establishes the acoustoelasticity relationships between applied biaxial stresses and deviations of the longitudinal wave velocity in solids. The experimental technique bases on laser thermoptical excitation of nanosecond ultrasonic pulses on the surface of samples under study and their backward mode piezodetection with a high temporal resolution. The samples, produced from stainless steel, had thickness from 1.67 mm to 8.87 mm. Welds are made up by means of electronic beam overheating of the samples with different intensities of the beam. Plane distributions of relative longitudinal wave velocity deviations, produced by stresses, were obtained.