FINITE-ELEMENT SIMULATION AND VISUALIZATION OF LEAKY RAYLEIGH-WAVES FOR ULTRASONIC NDE

The generation and propagation properties of transient leaky Rayleigh waves are characterized by a two-dimensional finite element model. The displacement vector is used as the primary variable for the solid med ium and a potential scalar, which is a replacement for the pressure, i s taken as the fundamental variable for the fluid medium. The coupled system of finite element equations are solved in the time domain by di rect integration through the central difference scheme. Three configur ations are considered: the conversion of a Rayleigh surface wave into a leaky Rayleigh wave, a focused beam probing a fluid/solid interface at the Rayleigh angle, and the interaction of a defocused wave with th e interface. The wave velocity in the fluid (water) is lower than the Rayleigh wave velocity in the solid (aluminum). The wave propagation p rofile in each case is predicted by the model. The finite element mode l proves to be an effective tool for surface acoustic device design an d ultrasonic NDE.