Monitoring of acoustic emission activity using thin wafer piezoelectric sensors (original) (raw)
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Materials (Basel, Switzerland), 2017
Piezoelectric wafer active sensors (PWAS) are commonly used for detecting Lamb waves for structural health monitoring application. However, in most applications of active sensing, the signals are of high-amplitude and easy to detect. In this article, we have shown a new avenue of using the PWAS transducer for detecting the low-amplitude fatigue-crack related acoustic emission (AE) signals. Multiphysics finite element (FE) simulations were performed with two PWAS transducers bonded to the structure. Various configurations of the sensors were studied by using the simulations. One PWAS was placed near to the fatigue-crack and the other one was placed at a certain distance from the crack. The simulated AE event was generated at the crack tip. The simulation results showed that both PWAS transducers were capable of sensing the AE signals. To validate the multiphysics simulation results, an in-situ AE-fatigue experiment was performed. Two PWAS transducers were bonded to the thin aerospace...
Recent Advances in Piezoelectric Wafer Active Sensors for Structural Health Monitoring Applications
Sensors
In this paper, some recent piezoelectric wafer active sensors (PWAS) progress achieved in our laboratory for active materials and smart structures (LAMSS) at the University of South Carolina: http: //www.me.sc.edu/research/lamss/ group is presented. First, the characterization of the PWAS materials shows that no significant change in the microstructure after exposure to high temperature and nuclear radiation, and the PWAS transducer can be used in harsh environments for structural health monitoring (SHM) applications. Next, PWAS active sensing of various damage types in aluminum and composite structures are explored. PWAS transducers can successfully detect the simulated crack and corrosion damage in aluminum plates through the wavefield analysis, and the simulated delamination damage in composite plates through the damage imaging method. Finally, the novel use of PWAS transducers as acoustic emission (AE) sensors for in situ AE detection during fatigue crack growth is presented. Th...
Journal of Intelligent Material Systems and Structures
In this article, the effect of the acoustic emission sensor on the acoustic emission waveforms from fatigue crack growth in a thin aerospace specimen is presented. In situ acoustic emission fatigue experiments were performed on the test coupons made of aircraft grade aluminum plate. Commercial Mistras S9225 acoustic emission sensor and piezoelectric wafer active sensor were used to capture the acoustic emission waveforms from the fatigue crack. It has been shown that the piezoelectric wafer active sensor transducer successfully captured the fatigue crack–related acoustic emission waveforms in the thin plate. The piezoelectric wafer active sensor transducer seems to capture more frequency information of the acoustic emission waveform than the conventional acoustic emission sensor in this particular application. We have also shown the evolution of the acoustic emission waveforms as the fatigue crack grows. The signatures of the fatigue crack growth were captured by the evolution of th...
Advances in Civil Engineering, 2012
Monitoring of fatigue cracking in steel bridges is of high interest to many bridge owners and agencies. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In this paper, we presented a dual mode sensing methodology integrating acoustic emission and ultrasonic wave inspection based on the use of low-profile piezoelectric wafer active sensors (PWAS). After introducing the research background and piezoelectric sensing principles, PWAS crack detection in passive acoustic emission mode is first presented. Their acoustic emission detection capability has been validated through both static and compact tension fatigue tests. With the use of coaxial cable wiring, PWAS AE signal quality has been improved. The active ultrasonic inspection is conducted by the damage index and wave imaging approach. The results in the paper show that such an integration of passive acoustic emission detection with active ultrasonic sensing is a technological leap forward from the current practice of periodic and subjective visual inspection and bridge management based primarily on history of past performance.
Durability and Survivability of Piezoelectric Wafer Active Sensors on Metallic Structure
AIAA Journal, 2010
Piezoelectric wafer active sensors are small, inexpensive, noninvasive, elastic wave generators/receptors that can be easily affixed to a structure. Piezoelectric wafer active sensor installation on the health-monitored structure is an important step that may have significant bearing on the success of the health monitoring process. The purpose of this paper is to explore the durability and survivability issues associated with various environmental conditions on piezoelectric wafer active sensors for structural health monitoring. The durability and survivability of the piezoelectric wafer active sensor transducers under various exposures (cryogenic and high temperature, temperature cycling, outdoor environment, operational fluids, large strains, fatigue load cycling) were considered over a long period of time. Both free piezoelectric wafer active sensors and bonded piezoelectric wafer active sensors on metallic structural substrates were used. Different adhesives and protective coatings were compared to find the candidate for piezoelectric wafer active sensor application in structural health monitoring. In most cases, piezoelectric wafer active sensors survived the tests successfully. The cases when piezoelectric wafer active sensors did not survive the tests were closely examined and possible causes of failure were discussed. The test results indicate that lead zirconate titanate piezoelectric wafer active sensors can be successfully used in a cryogenic environment; however, it does not seem to be a good candidate for high temperature. Repeated differential thermal expansion and extended environmental attacks can lead to piezoelectric wafer active sensor failure. This emphasizes the importance of achieving the proper design of the adhesive bond between the piezoelectric wafer active sensor and the structure, and of using a protective coating to minimize the ingression of adverse agents. The high-strain tests indicated that the piezoelectric wafer active sensors remained operational up to at least 3000 microstrain and failed beyond 6000 microstrain. In the fatigue cyclic loading, conducted up to 12 millions of cycles, the piezoelectric wafer active sensor transducers sustained at least as many fatigue cycles as the structural coupon specimens on which they were installed.
Sensors
The main aim of the paper is damage detection at the microscale in the anisotropic piezoelectric sensors using surface acoustic waves (SAWs). A novel technique based on the single input and multiple output of Rayleigh waves is proposed to detect the microscale cracks/flaws in the sensor. A convex-shaped interdigital transducer is fabricated for excitation of divergent SAWs in the sensor. An angularly shaped interdigital transducer (IDT) is fabricated at 0 degrees and ±20 degrees for sensing the convex shape evolution of SAWs. A precalibrated damage was introduced in the piezoelectric sensor material using a micro-indenter in the direction perpendicular to the pointing direction of the SAW. Damage detection algorithms based on empirical mode decomposition (EMD) and principal component analysis (PCA) are implemented to quantify the evolution of damage in piezoelectric sensor material. The evolution of the damage was quantified using a proposed condition indicator (CI) based on normalized Euclidean norm of the change in principal angles, corresponding to pristine and damaged states. The CI indicator provides a robust and accurate metric for detection and quantification of damage.
2005
Piezoelectric wafer active sensors are small, inexpensive, noninvasive, elastic wave generators/receptors that can be easily affixed to a structure. Piezoelectric wafer active sensor installation on the health-monitored structure is an important step that may have significant bearing on the success of the health monitoring process. The purpose of this paper is to explore the durability and survivability issues associated with various environmental conditions on piezoelectric wafer active sensors for structural health monitoring. The durability and survivability of the piezoelectric wafer active sensor transducers under various exposures (cryogenic and high temperature, temperature cycling, outdoor environment, operational fluids, large strains, fatigue load cycling) were considered over a long period of time. Both free piezoelectric wafer active sensors and bonded piezoelectric wafer active sensors on metallic structural substrates were used. Different adhesives and protective coatings were compared to find the candidate for piezoelectric wafer active sensor application in structural health monitoring. In most cases, piezoelectric wafer active sensors survived the tests successfully. The cases when piezoelectric wafer active sensors did not survive the tests were closely examined and possible causes of failure were discussed. The test results indicate that lead zirconate titanate piezoelectric wafer active sensors can be successfully used in a cryogenic environment; however, it does not seem to be a good candidate for high temperature. Repeated differential thermal expansion and extended environmental attacks can lead to piezoelectric wafer active sensor failure. This emphasizes the importance of achieving the proper design of the adhesive bond between the piezoelectric wafer active sensor and the structure, and of using a protective coating to minimize the ingression of adverse agents. The high-strain tests indicated that the piezoelectric wafer active sensors remained operational up to at least 3000 microstrain and failed beyond 6000 microstrain. In the fatigue cyclic loading, conducted up to 12 millions of cycles, the piezoelectric wafer active sensor transducers sustained at least as many fatigue cycles as the structural coupon specimens on which they were installed.
Steel bridge fatigue crack detection with piezoelectric wafer active sensors
2010
Piezoelectric wafer active sensors (PWAS) are well known for its dual capabilities in structural health monitoring, acting as either actuators or sensors. Due to the variety of deterioration sources and locations of bridge defects, there is currently no single method that can detect and address the potential sources globally. In our research, our use of the PWAS based sensing has the novelty of implementing both passive (as acoustic emission) and active (as ultrasonic transducers) sensing with a single PWAS network. The combined schematic is using acoustic emission to detect the presence of fatigue cracks in steel bridges in their early stage since methods such as ultrasonics are unable to quantify the initial condition of crack growth since most of the fatigue life for these details is consumed while the fatigue crack is too small to be detected. Hence, combing acoustic emission with ultrasonic active sensing will strengthen the damage detection process. The integration of passive acoustic emission detection with active sensing will be a technological leap forward from the current practice of periodic and subjective visual inspection, and bridge management based primarily on history of past performance.
Piezoelectric Wafer Embedded Active Sensors for Aging Aircraft Structural Health Monitoring
Structural Health Monitoring, 2002
Piezoelectric wafer active sensors may be applied on aging aircraft structures to monitor the onset and progress of structural damage such as fatigue cracks and corrosion. The state of the art in piezoelectric-wafer active sensors structural health monitoring and damage detection is reviewed. Methods based on (a) elastic wave propagation and (b) the Electro-Mechanical (E/M) impedance technique are cited and briefly discussed. For health monitoring of aging aircraft structures, two main detection strategies are considered: the E/M impedance method for near field damage detection, and wave propagation methods for far-field damage detection. These methods are developed and verified on simple-geometry specimens and on realistic aging aircraft panels with seeded cracks and corrosion. The experimental methods, signal processing, and damage detection algorithms are tuned to the specific method used for structural interrogation. In the E/M impedance method approach, the high-frequency spectrum, representative of the structural resonances, is recorded. Then, overallstatistics damage metrics can be used to compare the impedance signatures and correlate the change in these signatures with the damage progression and intensity. In our experiments, the (1 À R 2 ) 3 damage metric was found to best fit the results in the 300-450 kHz band. In the wave propagation approach, the pulse-echo and acousto-ultrasonic methods can be utilized to identify the additional reflections generated from crack damage and the changes in transmission phase and velocity associated with corrosion damage. The paper ends with a conceptual design of a structural health monitoring system and suggestions for aging aircraft installation utilizing active-sensor arrays, data concentrators, wireless transmission, and a health monitoring and processing unit.
Structural Health Monitoring of Composite Structures with Piezoelectric-Wafer Active Sensors
AIAA Journal, 2011
Piezoelectric Q2 wafer active sensors are lightweight and inexpensive enablers for a large class of structural health monitoring applications such as 1) embedded guided-wave ultrasonics, i.e., pitch-catch, pulse-echo, and phased arrays; 2) high-frequency modal sensing, i.e., the electromechanical impedance method; and 3) passive detection (acoustic emission and impact detection). The focus of this paper will be on the challenges and opportunities posed by use of piezoelectric-wafer active sensors for structural health monitoring of composite structures as different from that of the metallic structures on which this methodology was initially developed. After a brief introduction, the paper discusses damage modes in composites. Then it reviews the structural health monitoring principles based on piezoelectric-wafer active sensors. This is followed by a discussion of guided-wave propagation in composites and how piezoelectric-wafer active sensor tuning can be achieved. Finally, the paper presents some damage detection results in composites: 1) hole damage in unidirectional and quasi-isotropic plates and 2) impact damage in quasiisotropic plates. The paper ends with conclusions and suggestions for further work.