As part of an effort to apply laser ultrasonics to stress evaluation, sequential thermal and mechanical finitie element analyses were used to simulate heating a region of an aluminum surface by a laser pulse and the stress waves that result. As residual or applied stresses can be related to changes in wave velocities, time-of-flight measurements may be used to determine the stresses. The goal of the effort is to improve time-of-flight measurements, and therefore resolution of the calculated stresses, using calculated waveform shapes in model-based signal processing techniques [1]. Detailed finite element simulations of laser ultrasonics may also be used to aid development of techniques that can generate narrow band ultrasound. Because penetration of Rayleight waves is frequency dependent, they can be used to obtain information about gradients near a surface. If the frequency of the laser generated Rayleight waves can be controlled, laser ultrasound becomes a more useful tool for examining gradients in material properties or stresses at the surface of a part.
展开▼
