Effect of variable cross-section rod on laser-induced surface acoustic waves

The generation and propagation of surface acoustic waves (SAW) in an aluminum rod with variable cross-section subjected to laser beam illumination has been studied quantitatively by using the finite element method (FEM). The physical model of laser-induced SAW in the rod was built and the effects of the variable cross-section of the rod, the line source's width as well as the rising time of the exciting laser on the SAW were discussed. We have found that all of the three factors would evidently influence the SAW both in time and frequency domains. Based on our study conclusion, a broader frequency domain and higher amplitude of the SAW could be got to detect the defects in the rod. Our research findings would lay a foundation for the further application of laser ultrasound in nondestructive testing (NDT) field.