Local phase velocimetry based on the spatio-temporal gradient analysis

Ultrasonic Lamb-wave techniques are potential candidates of non-destructive evaluation (NDE) methodology. The phase velocimetry in the material mostly is done by measuring the time-of-flight and distance between a pair of transmitter and receiver. This paper proposes a novel method of local phase velocimetry based on the spatio-temporal gradient analysis. The method has an ability to measure the local phase velocity of the zeroth order anti-symmetric Lamb wave field through the linearity among the four-dimensional vectors which is defined by following components: 1:a vertical displacement, 2:vertical particle velocity, and 3,4:a pair of shear strains of the surface. In this study, the computational process of the local phase velocimetry is discussed and their physical meanings are investigated through numerical experiments.