LASER ULTRASONIC RAYLEIGH WAVES TESTING OF RESIDUAL STRESS IN METALS

Laser ultrasonic technique for non-destructive subsurface biaxial residual stress testing in metals is developed in the current work. Th method is based on laser pulse excitation of surface acoustical Rayleigh waves (SAWs) with YLF:Nd laser and wideband piezoelectric detection of acoustical signals with especially designed high time-domain resolution wedge-shaped transducer . Developed technique implies measurement of relative variations of the SAWs velocities in two orthogonal directions. An accuracy of such measurements is substantially below 0.1%. Frequency bandwidth is 5-25 MHz, which corresponds to the depths approximately of 120-600 . Measurements were carried out in samples made of stainless steel. The samples were of