Determination of Elastic Constants of Aluminium Using Laser Based Ultrasonics

This paper deals with the determination of the elastic constants of aluminium from the analysis of laser generated ultrasonic bulk waves. A pulsed Nd:YAG laser (1064 nm) is used for ultrasonic generation in a thick stepped Al sample and a He-Ne laser is used for heterodyne detection of the generated signals. Ultrasonic signals obtained at epicenter and at off-epicenter position of the detection points are analyzed using wavelet transforms. Here the identification and of pressure as well as shear waves and the estimation of their velocities are done successfully. From the estimated velocities the elastic constants (Young's modulus, shear modulus, bulk modulus, Lames constant and Poisson's ratio) are calculated. The agreement of these constants with the standard values confirms the identification of shear waves at off-epicenter position. The work presented in this paper brings out the applicability of the study of laser generated bulk waves for the determination of elastic constants of any bulk material.