Studying the propagating properties of surface acoustic wave traveling in functional gradient materials by laser ultrasonic

A theoretical model which is used to describe the propagating properties of surface acoustic wave(SAW) excited by a pulse laser in functional gradient materials(FGMs) has been proposed by means of the finite element method(FEM).In the theoretical model,the pump laser is focused as the linear and grating source to excite SAWs in the surface of FGMs,the traveling properties of SAWs caused by gradual variation of physical parameters of FGMs have been analyzed.The numerical results of theoretical models indicate that the wide-band SAW induced by a line-source laser will obviously disperse when traveling in FGMs;while the frequency of the single-frequency SAW generated by a laser induced thermal grating method will shift accordingly due to the gradual change of different parameters of material. The numerical results provide a theoretical basis for non-contact characterization of FGMs.