Stress detection of ultra-thin steel using laser ultrasonic spectral analysis

To meet the stress detection requirements of ultra-thin steel materials, a non-contact nondestructive stress detection platform was established based on laser ultrasonics and optical heterodyne interferometry. Using a self-developed small tensile platform, tensile tests were conducted on ultra-thin steel specimens with thicknesses of 0.20, 0.10, and 0.02 mm under 0-100 MPa stress. Lamb wave signals with a center frequency of 330 kHz were extracted using wavelet transform. Results showed that under stress-free conditions, group velocity errors remained within 4% of theoretical predictions, while under stress, group velocity exhibited a negative correlation with tensile stress. Wave packet peak arrival delay time and group velocity relative change rate characteristic quantities were calculated and linearly fitted with tensile stress, with fitting correlation coefficients exceeding 0.99, demonstrating that laser ultrasonic technology could effectively meet the stress detection needs of ultra-thin steel materials.