DETECTION OF FLAWS IN STRUCTURAL MEMBERS USING SPECTRAL ANALYSIS OF ULTRASONIC SIGNALS

Abstract Ultrasonics is being increasingly used for inspection of structural members to identify defects and material properties. Time-or-flight and velocity measurements are primarily used in these testing. While these measurements lead to a fair estimate of stiffness and flaw detection, the sensitivity of the measurements is not always adequate to detect flaws in their early stages. This paper proposes the use of power spectral analysis in conjunction with velocity measurements to identify defects in structural members. The conditions necessary to make repeatable amplitude measurements are described and the data analysis techniques suitable for flaw detection are also discussed. The advantages of using power spectral analysis are illustrated using examples of defective aluminum, wooden, and composite wrapped concrete members. The proposed measurement and analysis technique can be easily generalized to structural members made from other materials such as steel or reinforced concrete. Keywords: Ultrasonics; Amplitude measurements; Spectral analysis; Power spectral density; PSD