Structural Health Monitoring with Piezoelectric Wafer Active Sensors--Predictive Modeling and Simulation

This paper starts a review of the state of the art in structural health monitoring with piezoelectric wafer active sensors and follows with highlighting the limitations of the current approaches which are predominantly experimental. Subsequently, the paper examines the needs for developing a predictive modeling methodology that would allow to perform extensive parameter studies to determine the sensing method’s sensitivity to damage and insensitivity to confounding factors such as environmental changes, vibrations, and structural manufacturing variability. The thesis is made that such a predictive methodology should be multi-scale and multi-domain, thus encompassing the modeling of structure, sensors, electronics, and power management. A few examples of preliminary work on such a structural sensing predictive methodology are given. The paper ends with conclusions and suggestions for further wor

Structural Health Monitoring with Piezoelectric Wafer Active Sensors—Predictive Modeling and Simulation

This paper starts a review of the state of the art in structural health monitoring with piezoelectric wafer active sensors and follows with highlighting the limitations of the current approaches which are predominantly experimental. Subsequently, the paper examines the needs for developing a predictive modeling methodology that would allow to perform extensive parameter studies to determine the sensing method’s sensitivity to damage and insensitivity to confounding factors such as environmental changes, vibrations, and structural manufacturing variability. The thesis is made that such a predictive methodology should be multi-scale and multi-domain, thus encompassing the modeling of structure, sensors, electronics, and power management. A few examples of preliminary work on such a structural sensing predictive methodology are given. The paper ends with conclusions and suggestions for further work

Piezoelectric Wafer Active Sensors in Lamb Wave-Based Structural Health Monitoring

Recent advancements in sensors and information technologies have resulted in new methods for structural health monitoring (SHM) of the performance and deterioration of structures. The enabling element is the piezoelectric wafer active sensor (PWAS). This paper presents an introduction to PWAS transducers and their applications in Lamb wave-based SHM. We begin by reviewing the fundamentals of piezoelectric intelligent materials. Then, the mechanism of using PWAS transducers as Lamb wave transmitters and receivers is presented. PWAS interact with the host structure through the shear-lag model. Lamb wave mode tuning can be achieved by judicious combination of PWAS dimensions, frequency value, and Lamb mode characteristics. Finally, use of PWAS Lamb wave SHM for damage detection on plate-like aluminum structures is addressed. Examples of using PWAS phased array scanning, quantitative crack detection with array imaging, and quantitative corrosion detection are given

Piezoelectric Wafer Active Sensor Embedded Ultrasonics in Beams and Plates

ABSTRACT—In this paper we present the results of a sys-tematic theoretical and experimental investigation of the fun-damental aspects of using piezoelectric wafer active sensors (PWASs) to achieve embedded ultrasonics in thin-gage beam and plate structures. This investigation opens the path for sys-tematic application of PWASs for in situ health monitoring. After a comprehensive review of the literature, we present the principles of embedded PWASs and their interaction with the host structure. We give a brief review of the Lamb wave principles with emphasis on the understanding the particle motion wave speed/group velocity dispersion. Finite element modeling and experiments on thin-gage beam and plate spec-imens are presented and analyzed. The axial (S0) and flex-ural (A0) wave propagation patterns are simulated and ex-perimentally measured. The group-velocity dispersion curves are validated. The use of the pulse-echo ultrasonic technique with embedded PWASs is illustrated using both finite element simulation and experiments. The importance of using high-frequency waves optimally tuned to the sensor–structure in-teraction is demonstrated. In conclusion, we discuss the ex-tension of these results to in situ structural health monitoring using embedded ultrasonics. KEY WORDS—Piezoelectric wafers, piezoelectric sensors, active sensors, in situ diagnostics, structural health monitor-ing, piezoelectrics, ultrasonics, elastic waves, P-waves, S-waves, shear waves, axial waves, flexural waves, Rayleig

Development of Strength Theories for Random Fiber Composites

A ressessment of existing theories for calculating the strength of random and quasi-random fiber composites is presented. Fundamental aspects regarding the physical model, macromechanics analysis, fiber distribution functions, generalized failure criterion, and progressive versus sudden failure models are covered first. Progressive ductile failure, progressive brittle failure, and sudden brittle failure are treated in detail. In each case, the original theory is briefly reviewed, and then its extensions accompanied by numerical examples are presented. Several limitations originally imposed by Hahn, such as the monotonically nonincreasing requirement on the failure strain curve, are lifted and the mathematical formulations are generalized. Some common misconceptions are also highlighted and clarified. Comparison with experimental data is given for the SMC-R50 material system. Good reproduction of the experimental results and of the stress-strain response are illustrated. A review of the main points and opportunities for further work are presented in conclusion