Mode and time delay estimation for non-destructive evaluation systems

This paper describes the development of a multi-path and multimode propagation model for NDE. The mode content of a multipath is estimated using Maximum Likelihood (ML) estimation based on a receiving array delay vector. The model analysis allows a defect to be located by employing both the mode estimates and a ML estimation of the shear and longitudinal propagation angles. Some aspects of the attendant processing hardware are also discussed.