• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2434-2440
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• 2018

A new type of piezoelectric micromachined ultrasonic transducer (pMUT) with high resonant frequency was developed by using a thin lead zirconate titanate (PZT) as an insulation layer on a floating $10{\mu}m$ silicon membrane. The PZT insulation layer facilitated acoustic impedance matching at active pMUT, leading to a high performance in the acoustic conversion property compared with the transducer using $SiO_2$ insulation layer. The fabricated ultrasonic devices were wirelessly measured by connecting two identical acoustic transducers to two separate ports in a single network analyzer simultaneously. The acoustic wave emitted from a transducer induced a $3.16{\mu}W$ on the other side of the transducer at a distance of 2 cm. The transducer performances in terms of device diameters, PZT thickness, annealings, and different DC polings, etc. were investigated. COMSOL simulation was also performed to predict the device performances prior to fabrication. Based on the COMSOL simulation, the device was fabricated and the results were compared.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2007년도 춘계학술대회
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• pp.395-399
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• 2007

Renewable energy sources such as wind energy is copiously available without any limitation. Wind turbines are used to tap the potential of wind energy which is available in millions of megawatt. Reliability of wind turbine is critical to extract this maximum amount of energy from the wind. We reviewed different techniques, methodologies, and algorithms developed to monitor the performance of wind turbine as well as for an early fault detection to keep away the wind turbines from catastrophic conditions due to sudden breakdowns. To keep the wind turbine in operation, implementation of Condition Monitoring System (CMS) is paramount, and for this purpose ample knowledge of these types of system is mandatory. So, an attempt has been made in this direction to review maximum approaches related to CMS in this piece of writing.

• Smart Structures and Systems
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• 제25권4호
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• pp.423-432
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• 2020

In this paper, a novel but practical approach named series/parallel multi-sensing technique was proposed to evaluate the bolt looseness in a bolt group. The smart washers (SWs), which were fabricated by embedding a Lead Zirconate Titanate (PZT) transducer into two flat metal rings, were installed to the bolts group. By series connection of SWs, the impedance signals of different bolts can be obtained through only one sweep. Therefore, once the loosening occurred, the shift of different peak frequencies can be used to locate which bolt has loosened. The proposed multi input single output (MISO) damage detection scheme is very suitable for the structural health monitoring (SHM) of joint with a large number of bolts connection. Another notable contribution of this paper is the proposal of 3-dB bandwidth root mean square deviation (3 dB-RMSD) which can quantitatively evaluate the severity of bolt looseness. Compared with the traditional naked-eye observation method, the equivalent circuit based 3-dB bandwidth can accurately define the calculation range of RMSD. An experiment with three bolted connection specimens that installed the SWs was carried out to validate our proposed approach. Experimental result shows that the proposed 3 dB-RMSD based multi-sensing technique can not only identify the loosened bolt but also monitor the severity of bolt looseness.

• Smart Structures and Systems
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• 제6권4호
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• pp.349-362
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• 2010

Ultrasonic Guided Waves (UGWs) are a useful tool in structural health monitoring (SHM) applications that can benefit from built-in transduction, moderately large inspection ranges and high sensitivity to small flaws. This paper describes a SHM method based on UGWs, discrete wavelet transform (DWT), and principal component analysis (PCA) able to detect and quantify the onset and propagation of fatigue cracks in structural waveguides. The method combines the advantages of guided wave signals processed through the DWT with the outcomes of selecting defect-sensitive features to perform a multivariate diagnosis of damage. This diagnosis is based on the PCA. The framework presented in this paper is applied to the detection of fatigue cracks in a steel beam. The probing hardware consists of a PXI platform that controls the generation and measurement of the ultrasonic signals by means of piezoelectric transducers made of Lead Zirconate Titanate. Although the approach is demonstrated in a beam test, it is argued that the proposed method is general and applicable to any structure that can sustain the propagation of UGWs.

• Transactions on Electrical and Electronic Materials
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• 제6권4호
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• pp.177-185
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• 2005

Fatigue characteristics of lead zirconate titanate (PZT) films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD) were investigated. The fatigue characteristics were investigated with respect to PZT film thickness, domain structure, fatigue pulse height, temperature, electrode materials and electrode configurations. The used top and bottom electrode materials were Pt and $RuO_2$. In the fatigue characteristics with fatigue pulse height and PZT film thickness, the fatigue rates are independent of the applied fatigue pulse height at the electric field regions to saturate the P-E hysteresis and polarization $(P^*,\;P^A)$ characteristics. The unipolar and bipolar fatigue characteristics of PZT capacitors with four different electrode configurations $(Pt//Pt,\;Pt//RuO_2,\;RuO_2//Pt,\;and\;RuO_2//RuO_2)$ were also investigated. The polarization-shifts during the unipolar fatigue and the temperature dependence of fatigue rate suggest that the migration of charged defects should not be expected in our CVD-PZT films. It seems that the polarization degradations are attributed to the formation of charged defects only at the Pt/PZT interface during the domain switching. The charged defects pin the domain wall at the vicinity of Pt/PZT interface. When the top and bottom electrode configurations are of asymmetric $(Pt//RuO_2,\;RuO_2//Pt)$, the internal fields can be generated by the difference of charged defect densities between top and bottom interfaces.

• 통합자연과학논문집
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• 제8권4호
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• pp.244-249
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• 2015

The PZT thin films were deposited on Si(100) substrate using RF magnetron sputtering method. And the PZT thin films were post annealed at various temperatures to form perovskite phase. To analyze PZT thin films, surface profiler, XRD, XPS, CA, and SFE were used. The thickness increased from 536.5 to 833.2 nm as post annealing temperature increased. The perovskite PZT was observed from PZT-823 and pyrochlore PZT, $ZrO_2$, $TiO_2$, and perovskite $PbZrO_3$ were observed. From the XPS, the atomic percentages of Pb, Zr, Ti, and O were calculated and the portion of Pb increased to PZT-823 and decreased to PZT-923 and then increased to PZT-1023. Also, the CA and SFE was effected on post annealing temperature and as a function of atomic percentage of Pb, the CA and SFE was transformed.

• 한국해양공학회지
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• 제26권1호
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• pp.27-33
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• 2012

This paper presents the effect of temperature on the impedance-based damage monitoring of steel-bolt connections using wireless impedance sensor nodes. In order to achieve the objective, the following approaches are implemented. First, a temperature-compensated damage monitoring scheme that includes a temperature compensation model and damage detection method is described. The temperature compensation model is designed by analyzing the linear regressions between the temperatures and impedance signatures. The correlation coefficient of the impedance signatures is selected as the damage index to monitor the damage occurrence in the target structures. Second, a wireless impedance sensor node is described for the design of the hardware components and embedded software. Finally, the performance of the temperature-compensated impedance-based damage monitoring scheme is evaluated for detecting a loose bolt in the steel-bolt connections on a lab-scale steel girder under various temperatures.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권9호
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• pp.429-433
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• 2006

PZT(80/0) powder was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The coating and drying procedure was repeated 4 times. And then the PZT(20/80) precusor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5mol/L and the number of coating was varied from 0 to 6. The porosity decreased and the grain size increased with increasing the number of coatings. The thickness of the PZT-6(6: number of coatings) films was about $60{\mu}m$. The relative dielectric constant increased and the dielectric loss decreased with increasing the number of PZT(20/80) sol coatings. The relative dielectric constant and dielectric loss of the PZT-6 thick film were 275 and 3.5%, respectively. The remanent polarization, coercive field and breakdown strength of the PZT-6 film were $19.8{\mu}C/cm^2$, 13.7kV/cm and 130kV/cm, respectively.

• 한국전기전자재료학회논문지
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• 제15권10호
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• pp.865-869
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• 2002

The structural and electrical properties of PZT (lead zirconate titante) thin films grown on Pt (platinum) and Ru/Ru $O_2$(ruthenium/ruthenium oxide) electrodes were investigated. Thin films of PZT were deposited on a variety of electrodes using the rf-magnetron sputtering process. PZT films exhibited polycrystalline structure with strong PZT (100) plane and weak (211) plane for an optimizied Pt electrode and (100), (101), (111), (200), (210), (211) planes for Ru/Ru $O_2$. Switching polarization versus fatigue characteristic of Pt/Ti electrodes showed 20% degradation up to 1 $\times$ 10$_{9}$ cycles. No significant fatigue was observed in the films on Ru/Ru $O_2$ electrodes up to Ix109 test cycles. The results show that the new Ru/Ru $O_2$ bottom electrodes are expected to reduce the degradation of ferroelectric fatigue.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.734-739
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• 2003

Many types of smart materials and control laws are available to actively adjust the structure from various external disturbances. Usually, a certain type of control laws to activate a specific smart material is well established, but the effectiveness of the control scheme is limited by the choice of the smart materials and the responses of the structure. ER fluid is adequate to provide relatively large control force, on the other hand, the PZT patches are suitable to provide small but arbitrary control forces at any point along the structure. It was found that active vibration control mechanism using ER fluid failed to suppress the excitation off the resonant frequency with changed structural characteristics along the frequency response function of the closed loop of the control system. To compensate this additional peak of the closed loop system, PPF control using PZT as an actuator is added to construct a hybrid controller.