Advanced signal analysis for the examination of multilayered structures using annular arrays

摘要

Multiple reflections in test objects with several layers complicate the analysis of ultrasound signals from interfaces covered with additional layers. The interpretation of the signals is hardly possible if the sound velocities of the layers are unknown. In this contribution a method for a simultaneous determination of sound velocity and thickness is presented. The signals of a 6 MHz annular array are analysed and the signal parts caused by normal and not normal propagation of the emitted wave are separated. The differences in time of flight between these signal parts are used in combination with a geometric model to evaluate the sound velocity and thickness simultaneously.