Determination of material properties of thin layers using angle beam ultrasonic spectroscopy

The objective of this paper is to describe a dual beam scanning approach for the characterization of free layers, coatings and embedded layers. We have developed and tested a prototype of the Angle Beam Ultrasonic Spectroscopy (ABUS) scanner. In addition to the capabilities of a conventional ultrasonic scanner, the system features dual beam scanning and it is optimized to display normal and oblique incidence frequency response of thin layers from which the above mentioned acoustical properties can be reconstructed. Software and hardware were developed to insure system operation and signal processing in real-time. The original feature of the system is the built-in layer property determination and display capability. The layer thickness, density, elastic moduli and attenuations can be determined at any location using the live signals or over the whole area in a postprocessing mode. The property determination algorithm is based on the optimized inversion of the normal and oblique reflection spectra. Experimental results and images of elastic properties obtained with the ABUS system will presented for immersed layers, coating and adhesive joint