Detection and monitoring of hidden fatigue crack growth using a built-in piezoelectric sensor/actuator network: I. Diagnostics

TLDR

A piezoelectric built‑in diagnostic technique was developed to monitor fatigue crack growth in metallic structures. The method employs piezoelectric actuators to generate ultrasonic Lamb waves, processes the signals to isolate a high‑SNR mode, and uses a physics‑based damage index to relate sensor readings to crack size, validated on notched coupons and studied for sensor‑location sensitivity. The damage index from the built‑in piezoceramics correlated well with visual measurements of crack growth.

Abstract

A piezoelectric based built-in diagnostic technique has been developed for monitoring fatigue crack growth in metallic structures. The technique uses diagnostic signals, generated from nearby piezoelectric actuators built into the structures, to detect crack growth. It consists of three major components: diagnostic signal generation, signal processing and damage interpretation. In diagnostic signal generation, appropriate ultrasonic guided Lamb waves were selected for actuators to maximize receiving sensor measurements. In signal processing, methods were developed to select an individual mode for damage detection and maximize signal to noise ratio in recorded sensor signals. Finally, in damage interpretation, a physics based damage index was developed relating sensor measurements to crack growth size. Fatigue tests were performed on laboratory coupons with a notch to verify the proposed technique. The damage index measured from built-in piezoceramics on the coupons showed a good correlation with the actual fatigue crack growth obtained from visual inspection. Furthermore, parametric studies were also performed to characterize the sensitivity of sensor/actuator location for the proposed technique.