Ultrasonic signal amplitude measurement and analysis techniques for nondestructive evaluation of structural members

摘要

Abstract: Ultrasonic technique has been increasingly used in recent years for nondestructive evaluation of defects and material properties (e.g., stiffness) in structural members made up of concrete, steel, wooden, and composite materials. Ultrasonic evaluation of structural members in the past has relied primarily on time-of-flight and velocity measurements. While these measurements lead to fair estimate of stiffness and detection of defects in structural members, the sensitivity of the measurements is not adequate to detect defects in their early stages. In order to enhance the sensitivity of the ultrasonic technique, this paper proposes to use ultrasonic signal amplitude measurements in conjunction with traditional velocity measurements. The conditions necessary to make repeatable amplitude measurements are described, and the data analysis techniques suitable for defect detection are discussed. Also, the advantages of signal amplitude measurement technique are presented using examples of defective steel, wooden, and composite members. The measurement and analysis techniques presented here can be easily generalized to structural members made from other materials such as concrete. !14