High-resolution defect detection is a critical aspect of non-destructive testing (NDT). Ultrasonic array transducers have been developed to make ultrasonic images for high-resolution and high-sensitivity defect inspection. However coherent noise, due to grain scattering, makes the detection of small defects a challenging problem in the NDT field. This thesis presents an approach in which an NDT ultrasonic array is made with simplified structures to allow it to be adaptable for long-term installable application and continuous structural monitoring. First, a rapid ultrasonic array assessment framework is developed for the permanently installable ultrasonic array. Then, a design concept for the installable ultrasonic array is proposed involving a set of piezoelectric ceramic elements and a flexible printed circuit substrate. The array element geometry is designed by the consideration of its imaging performance for the desired application and the fabrication cost for permanent installation and large-volume manufacturing. The developed array transducer is then permanently installed on structures for long-term continuous monitoring evaluation. Different signal compensation strategies are designed and implemented on the long-term monitored ultrasonic data to reduce the variations due to changes in the ambient conditions. Small changes to the defect size are generated to evaluate the detection capability of the developed array. Results show that the developed ultrasonic array can detect changes as small as 0.1mm in the diameter of a side-drilled hole defect after three months of continuous monitoring experiments.
An ultrasonic array system for long-term localised structural health monitoring
Sun, X. (Author). 3 Oct 2023
Student thesis: Doctoral Thesis › Doctor of Philosophy (PhD)