Accurate non-contact measurements of Rayleigh wave speed and attenuation

For the measurement of wave speed and attenuation, where measurements are needed at two locations, the use of a probe with dual detection points is advisable. In the present work, a plane Rayleigh wave has been generated which does not require a diffraction correction. A measurement of signal reception at two points separated by a known distance in the detection of wave propagation has been achieved by modifying a heterodyne interferometer to a dual-probe modality. Surface wave pulses passing through the detection points have been recorded. Results are presented for metal sheets that have been subjected to cyclic loading, and the changes of surface wave speed and attenuation are reported.