Ultrasonic Spectroscopy to Characterize Flaws, Porosity and Adhesive Bonds
* Presenting author
Ultrasonic Spectroscopy is the study of ultrasonic waves resolved into their Fourier frequency components. Ultrasonic spectroscopy is used in many applications of Nondestructive Evaluation. In this presentation three methods developed by the author to apply ultrasonic spectroscopy in NDE will be discussed.1.Flaw characterization refers to the determination of size, orientation, and composition of discontinuities in solid materials. Multifrequency ultrasonic wave interaction with artificial and real defects measurements and subsequent theoretical analysis using diffraction of elastic waves provides these material discontinuities’ characteristics. 2.Gas porosity assessment. Measuring pore size and volume fraction from the spectrum of attenuation coefficient will be discussed. Theoretical analysis is based on the attenuation due to independent scatterer of spherical voids. The model prediction of the scattering of ultrasonic waves from porosities is in good agreement with measured values in aluminum casts.3.Evaluation of Adhesive Layers. A system was developed to determine both adhesive and cohesive properties of thin bonded layers using multi transducer spectroscopy. Scattered longitudinal and transverse waves spectra is used in this method. The method was further enhanced by combining with a low frequency dynamic load acting as a nonlinear enhancement. Ultrasonic measurements are in good agreement with actual layer properties.