Use Of Piezoelectric Wafer Active Sensors Research Articles

Exact Shear-Lag Solution for Guided Waves Tuning with Piezoelectric-Wafer Active Sensors

This paper addresses some unresolved predictive modeling issues related to the use of piezoelectric-wafer active sensors for ultrasonic structural health monitoring. An exact model for the shear-lag transfer between the piezoelectric-wafer active sensor transducer and the structure in the presence of N generic guided wave modes is derived from first principles using the normal-mode expansion formulation. The resulting integral–differential equation is solved using the variational iteration approach. The resulting solution is used to derive an improved modelforthetuningbetweenpiezoelectric-waferactivesensortransducersandthemultimodalguidedwavesusedin ultrasonic structural-health-monitoring applications. The numerical predictions generated by the improved tuning model are compared with experimental results obtained through pitch–catch experiments between two 7 mm piezoelectric-waferactivesensortransducersplacedona1-mm2024-T3aluminumplate.The10–700kHzfrequency range was explored. It was concluded that the improved model using the exact shear-lag solution matches much better the experimental results than previous models. Further theoretical and experimental work is warranted as a follow-up on the work reported in this paper to study the accuracy and convergence properties of the solution, to explore experimental comparison beyond the A1-mode cutoff frequency, and to extend the approach to layered structures and composite materials.

Space Application of Piezoelectric Wafer Active Sensors for Structural Health Monitoring

Piezoelectric wafer active sensors (PWAS) are lightweight and inexpensive enablers for a large class of structural health monitoring (SHM) applications. This paper presents and discusses the challenges and opportunities related to the use of PWAS in the structures specific to space applications. The challenges posed by space structures are often different from those encountered in conventional structures. After a review of PWAS principles, the paper discusses the multi-physics power and energy transduction between structurally guided waves and PWAS; predictive modeling results using a simplified analytical approach are presented. Experimental results on space-like specimen structures are presented. Survivability of PWAS transducers under cryogenic space-like conditions is experimentally verified. The paper ends with conclusions and suggestions for further work.

Piezoelectric wafer active sensors for in situ ultrasonic‐guided wave SHM

ABSTRACTIn situ structural health monitoring aims to perform on‐demand interrogation of the structure to determine the presence of service‐induced damage and defects using non‐destructive evaluation ultrasonic wave methods. Recently emerged piezoelectric wafer active sensors (PWAS) have the potential to significantly improve damage detection and health monitoring. PWAS are low‐profile transducers that can be permanently attached onto the structure or inserted in between composite laminates, and can perform structural damage detection in thin‐wall structures using guided wave methods (Lamb, Rayleigh, SH, etc.).This paper describes the analytical and experimental work of using PWAS‐guided waves for in situ structural damage detection on thin‐wall structures. We begin with reviewing the guided wave theory in plate structures and PWAS principles. The mechanisms of Lamb wave excitation and detection using PWAS is presented. Subsequently, we address in turn the use of PWAS to generate Lamb waves for damage (cracks and corrosion) detection in metallic structures. Pulse‐echo, pitch‐catch, phased array and time reversal methods are illustrated demonstrating that PWAS Lamb‐waves techniques are suitable for damage detection and structural health monitoring. The last part of the paper treats analytically and experimentally PWAS excitation and tuning in composite materials. The research results presented in this paper show that in situ SHM methodologies using PWAS transducers hold the promise for more efficient, effective and timely damage detection in thin‐wall structures.

Smart sensors for monitoring crack growth under fatigue loading conditions

Structural health monitoring results obtained with the electro-mechanical (E/M) impedance techniqueand Lamb wave transmission methods during fatigue crack propagation of an Arcan specimen instrumented with piezoelectric wafer active sensors (PWAS) are presented. The specimen was subjected in mixed-mode fatigue loading and a crack was propagated in stages. At each stage, an image of the crack and the location of the crack tip were recorded and the PWAS readings were taken. Hence, the crack-growth in the specimen could be correlated with the PWAS readings. The E/M impedance signature was recorded in the 100 - 500 kHz frequency range. The Lamb-wave transmission method used the pitch-catch approach with a 3-count sine tone burst of 474 kHz transmitted and received between various PWAS pairs. Fatigue loading was applied to initiate and propagate the crack damage of controlled magnitude. As damage progressed, the E/M impedance signatures and the waveforms received by receivers were recorded at predetermined intervals and compared. Data analysis indicated that both the E/M impedance signatures and the Lamb-wave transmission signatures are modified by the crack progression. Damage index values were observed to increase as the crack damage increases. These experiments demonstrated that the use of PWAS in conjunction with the E/M impedance and the Lamb-wave transmission is a potentially powerful tool for crack damage detection and monitoring in structural elements.