A Piezoelectric Technique for Evaluation of Crack Closure

Abstract

The ability of the piezoelectric materials to work as sensors and actuators was employed in a technique for monitoring the degree of crack closure and to detect the crack opening load. The technique is demonstrated through experiments with a cracked beam. It consists in exciting the specimen with a piezoelectric actuator and recording the electromechanical response of piezoelectric sensors placed near the crack mouth, while applying a bending moment to open the crack. The sensors in the neighborhood of the crack present a reduction in the amplitude response signal due to the progressive decrease of the dynamic strains near the crack, as the bending load causes the crack to open, reducing the contact between the surfaces of the fatigue crack and the load transmission through the contact area. The results show that the method has a high sensitivity to the state of crack closure, allowing for the direct determination of the crack opening load.

A microcapsule-type fluorescent probe for the detection of microcracks in cementitious materials

“…Piezoelectric films were developed to monitor crack initiation and growth based on change in Page 2 of 23 A c c e p t e d M a n u s c r i p t output voltage signals from the sensors [2][3][4]. Change in electrical resistance of a carbon powder-glass fiber reinforced plastic sensor was measured for crack detection [5].…”