Characterization of a sub-half-wavelength adhesive layer using ultrasonic spectroscopy

An ultrasonic spectroscopy technique in through-transmission is used to determine the acoustical properties of an adhesive layer in an adhesively-bonded joint. The joint is modeled as a thin adhesive layer 'immersed' in a solid medium. It is assumed that the adherend is sufficiently thick, so that h0/0> 5; h0is the adherend thickness and 0the wavelength. The problem of ultrasonic NDE is posed in one of the following ways: given thickness determine wavespeed; given wavespeed determine thickness, from the measured phase, amplitude or complex spectrum. An inversion scheme based upon the method of least squares is used to determine the unknown parameter, wavespeed or thickness, from the measured spectrum.

Characterization of a sub-half-wavelength adhesive layer using ultrasonic spectroscopy Conference Paper