Ultrasonic beam transmission through a water-immersed plate at oblique incidence using a piezoelectric source transducer. Finite element - angular spectrum modeling and measurements

A measurement system consisting of a piezoelectric transducer and a water-immersed steel plate is studied. A hybrid method, involving finite element modeling combined with an angular spectrum method, is used to simulate the three-dimensional signal propagation through this system. The description includes the transducer and its vibration, the radiated sound pressure field, excitation of viscoelastic leaky Rayleigh-Lamb modes (guided waves) in the plate, and the sound field transmitted through the plate. Calculations of the transducers input voltage-to-sound pressure transfer function, and sound pressure signal waveforms, are compared to measurements. Comparisons are made for a given distance between the transducer and the plate, for given angles of orientation of the transducer with respect to the plate, and for given receiver positions. The comparisons include signal frequencies dose to excited Rayleigh-Lamb modes in the plate, and in-between such modes.