The electro-mechanical impedance method for damage identification in circular plates (original) (raw)
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Electromechanical Impedance Method for Damage Detection in Mechanical Structures
2010
Non-destructive measurements of an electromechanical impedance allow for the effective assessment of the state of mechanical structures. Piezoelectric transducers, which are distributed in monitored construction, introduce coupling between mechanical properties and directly measured electric entities. Therefore incipient mechanical damage can be detected and its growth followed. The changes of mechanical properties are found with the comparison between plots of impedances measured for both original healthy system and the system which is operating in a current state. This paper presents the results of Finite Element analyses performed for a cantilever aluminium beam with bonded piezoelectric transducer. Modelled structure was excited to vibrate at high frequency range and electromechanical impedance plots were obtained from the harmonic analysis. Vertical notch was introduced in the beam and the damage metrics were used to asses qualitative changes in structural properties of the system. The numerical results were confirmed experimentally using laboratory equipment. With obtained numerical and experimental results there has been introduced the idea of a Structural Health Monitoring (SHM) system.
Damage Detection in Structures using Electromechanical Impedance and Finite Element Analysis
Impedance-based structural health monitoring (SHM) techniques have been developed as a promising tool for real-time structural damage assessment, and are considered as a new nondestructive evaluation method. It is gaining popularity due to its potential of reducing maintenance costs while increasing safety and reliability. This article present the results of Finite Element analysis performed for aluminum beam with bonded piezoelectric transducer (PZT). Modeled structure was excited to vibrate at high frequency range and electromechanical impedance (EMI) plots were obtained from the harmonic analysis. Notches were introduced in the beam and the damage metrics were used to asses qualitative changes in structural properties of the system. Furthermore, a parametric study of the effects of different variables was carried out. The numerical results show a good agreement was observed.
2000
1 This paper presents the electro-mechanical (E/M) impedance method for structural health monitoring and non-destructive evaluation. The precursors to this method have been developed over a period of several years by Professor Craig A. Rogers and a number of his Ph.D. students and research collaborators, but a unified approach has only recently been established. Section 1 of the paper gives a brief listing of the precursor work and the related research. Section 2 presents a description of the E/M technique, indicating the basic equipment, the conceptual system diagram and typical impedance response and damage index results. Section 3 deals with the main physical ingredients of the E/M technique, i.e., the direct and converse piezoelectric effects, and the elastic wave propagation through an elastic medium. Formulae for the electro-mechanical impedance and for the damage index are briefly presented. Section 4 presents the advantages and special characteristics of the E/M impedance method, and compares it with other NDE techniques such as vibrations, ultrasonics, eddy currents, E/C impedance, etc. Section 5 shows a number of experimental proof-of-concept demonstrations that illustrate the applicability of the E/M technique to a large number of engineering areas. The paper finishes with conclusions and a comprehensive list of references.
Experimental Analysis of Piezoelectric Transducers for Impedance-Based Structural Health Monitoring
Proceedings of International Electronic Conference on Sensors and Applications, 2014
In this paper, we experimentally analyze the sensitivity of piezoelectric transducers for damage detection in structural health monitoring (SHM) systems based on the electromechanical impedance (EMI) method, which has been reported as one of the most promising methods for non-destructive detection of damage. Three types of transducers were evaluated: conventional 5H PZT (lead zirconate titanate) piezoceramics; macro fiber composite (MFC) devices; and piezoelectric diaphragms, which are commonly known as "buzzers". Tests were carried out on aluminum beams and the experimental results conclusively demonstrate that the transducers have different sensitivities for detection of structural damage and an appropriate frequency range for damage detection, which provides high sensitivity.
Application of piezoceramic transducers for 3D Impedance modelling in damage assessment of plate
Scientific Journal of Pure and Applied Sciences, 2012
Cost-effective and reliable damage detection models are crucial for successful monitoring of any ancient or modern age engineering structure. Piezoceramic transducers (PZT) based electromechanical impedance (EMI) method is emerging as a promising alternate for conventional structural health monitoring (SHM) of various structures. The PZTs are usually surface bonded and then excited in the presence of electric field to a desired frequency range. The excitations result in prediction of unique frequency dependent electromechanical (EM) admittance signature. Any change in the signature during the monitoring period indicates dis-integrity in the structure. However, apart from locating damages, the increase in severity has to be predicted on time to avoid collapse of the entire structure. This paper presents such a model which had effectively predicted the severity of damages along two principle directions. This was achieved by experimental damage study on plates and subsequent verification by semi numerical 3D model. Statistical root mean square deviation (RMSD) index was used for evaluating the damages made on plates. A new frequency proximity index (FPI) was also introduced to measure the effectiveness of the model. RMSD measures the changes in height of peaks of signature and FPI scales the frequency spectrum of signature. Thus results of RMSD index and FPI are used as complementary to each other to study damage propagation in a structure.
2020
Monitoring of a structure after its construction is as crucial as it is during its designing or construction. Properly monitored structure could avoid a lot of catastrophic accidents. Structural Health Monitoring (SHM) plays a vital role. Earlier analysis of the systems by professional experts was performed visually. Various Non-Destructive Tests (NDT) like Rebound Hammer, Ultrasonic Pulse Velocity Test, etc. are utilized for the inspection. Along with these piezoelectric transducers have proven to be another way if evaluation of the structures. Electromechanical Impedance (EMI) technique by means of piezoelectric materials has been widely carried out for the structural response at various stages. EMI has the potential to detect damages, corrosion and even the strength of any structural member. This review paper includes the various studies that evolved from the past decade related to EMI dealing with new concepts and ideas.
Structural Health Monitoring, 2005
The use of the electro-mechanical (E/M) impedance method for health monitoring of thin plates and aerospace structures is described. As a nondestructive evaluation technology, the E/M impedance method allows us to identify the local dynamics of the structure directly through the E/M impedance signatures of piezoelectric wafer active sensors (PWAS) permanently mounted to the structure. An analytical model for 2-D thin-wall structures, which predicts the E/M impedance response at PWAS terminals, was developed and validated. The model accounts for axial and flexural vibrations of the structure and considers both the structural dynamics and the sensor dynamics. Calibration experiments performed on circular thin plates with centrally attached PWAS showed that the presence of damage modifies the high-frequency E/M impedance spectrum causing frequency shifts, peak splitting, and appearance of new harmonics. Overall-statistics damage metrics and probabilistic neural network (PNN) are used to classify the spectral data and identify damage severity. On thin-wall aircraft panels, the presence of damage influences the sensors E/M impedance spectrum. When crack damage is in the PWAS medium field, changes in the distribution of harmonics take place and when crack damage is in the PWAS near field, changes in both the harmonics and the dereverberated response are observed. These effects are successfully classified with PNN and overall-statistics metrics, respectively. This proves that permanently attached PWAS in conjunction with the E/M impedance method can be successfully used in structural health monitoring to detect the presence of incipient damage through the examination and classification of the high-frequency E/M impedance spectra.
MODELLING AND SIMULATION OF IMPEDANCE-BASED DAMAGE MONITORING OF STRUCTURES
Electromechanical impedance (EMI) based monitoring techniques are successfully in use in current engineering structures. With the help of piezoelectric sensors, the EMI technique is used for monitoring the health of such structures. Generally, potential damage to the host structure is detected by examining the EMI signature and identifying changes in that unique signature. Since this technique has the potential to offer greater safety and reliability while lowering maintenance costs, it is becoming increasingly popular. This paper investigates the use of finite element method (FEM) to simulate the electro-mechanical impedance technique. A numerical analysis of simple models, such as free piezoelectric patches of various shapes and thicknesses is used to comprehend the fundamentals of this technique. Then, studies on different parts of the structure are conducted to find the effect on the output of system when both damage and loading co-exist, and investigate the effect of temperature for structural health monitoring based on EMI. The simulation results are then compared to experimental data and a very good agreement is observed.