Applications of inter-digitized transducers (IDTs) for structural Health monitoring (SHM) of bridge structures

摘要

Ultrasonic surface wave generating inter-digitized transducers (IDTs) have been designed, fabricated and applied to a simulated critical component of a bridge structure. The goal of the current investigation using a simulated gusset plate was to find out the minimum number of IDT sensors required to achieve the maximum monitoring coverage over a given gusset plate, as well as the size and the optimum operating frequency for the sensors. These sensors can be customized depending on the design of gusset plate to include the number of bolt holes or welds, thickness, and overall dimensions. Various sizes of sensors ranging from several centimeters to several millimeters with resonance frequencies between 100 KHz and 3 MHz were tested. IDT sensors operating at 1 MHz with the overall physical dimensions of 15 mm × 17 mm were found to give the best coverage with a minimum number of sensors. A second test component investigated in this work was a dog-bone shaped fatigue test component to simulate fillet welds of bridge structures. The main goal for this fatigue testing was to find how early in the fatigue process a fillet weld failure can be detected using surface waves. Changes in the amplitude of surface waves were monitored in-situ for this study and it was found that the fillet welds tested on a fatigue loading frame showed an indication of weld failure at an early stage of the fatigue crack initiation.