Guided ultrasonic waves for detection of debonding in bars partially embedded in grout

摘要

This paper deals with theoretical, numerical and experimental investigations of guided wave propagation in multilayered cylindrical bars with pre-existing debonding. The research focuses on a complex description of the nature of the wave phenomena occurring in a debonded specimen with a special emphasis on the influence of the location of damage on the wave conversion and diffraction. Experimental nondestructive and destructive tests are conducted on the laboratory models of ground anchors with a variable debonding length and location. Debonding is simulated by wrapping the bar in the cellophane film with very small thickness, providing indirect contact between steel and grout but reducing grout adhesion to steel. Guided waves are excited and measured at the free end of the bar with the use of piezo actuators. Characteristic reflections are identified in signals registered for anchors with three locations of debonding and five debonding lengths. The obtained results show that despite of such small thickness of debonding (60 mu m), guided waves may be used as an effective method for detection of adhesive debonding at an early stage of its development. (C) 2018 Elsevier Ltd. All rights reserved.