Non-destructive testing of cracks on metallic materials by laser double-impulse method

Techniques in the use of a single Q-switched laser, double Q-switched laser, or multiple Q-switched laser in holographic analysis of oscillations and deformations of loaded specimens are described. Specimen loadings can be static and aperiodic, periodic and dynamic, or transient. Irregularities in the natural mode of vibration are revealed by holographic vibration analysis or vibration of flaws at high amplitude. Surface flexural waves reveal irregularities in their propagation fronts in the neighborhood of flaws, and interference effects provide information on the size as well as the location of flaws. Cracks and thinning of material yield to analysis by multiple Q-switched laser pulses.