Surface acoustic wave measurements using an impulsive converging beam

A method for velocity and attenuation measurement of leaky surface acoustic wave on small areas of a solid surface was developed. This technique uses an impulsive converging beam generated with an acoustic lens. Reflected waves from a sample consisted of the axial wave and the leaky surface wave separated in time domain. From the time interval between these waves, the velocity of the leaky surface wave is determined using an expression derived along with ray optics. Because time interval measurements do not require any mechanical scanning, they can be done without special attention paid for mechanical precision of the scanning system, enabling rapid and simple measurement. Since the impulsive wave has a broad frequency spectrum, spectroscopic analysis of leaky surface wave is also possible. Frequency dependent attenuation measurement of leaky surface acoustic waves on heat treated steels and velocity dispersion measurement of leaky surface wave on titanium nitride film on tool steel are demonstrated.