Ultrasonic approach for nondestructive testing of civil infrastructure

Inspection and rating of public infrastructure has become a focus of many recent studies because of well-documented deterioration and failure case studies. A new indirect inspection technique using ultrasonic spread-spectrum methods can significantly improve distress identification and monitoring of deteriorating infrastructure. This paper presents the general concept and application of using a continuous spread-spectrum signal to test structural objects. First of all, the basic theory for this technique will be outlined. Secondly, the basic hardware setup will be described. And finally, the results of two laboratory experiments will be presented. The laboratory results indicate that this new method may be feasible for monitoring and evaluating existing large or complicated structural members. The method does, however, have its limitations, as the signal is very sensitive to transducer orientations, couplant, and ambient conditions as is the case in all contact transducer-based nondestructive evaluation techniques.