Browsing by Author "Yin, Ching-Chung"

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A modal sensor integrated circular cylindrical wedge wave ultrasonic motor
(2012-02-01)
Yu, Tai-Ho
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This study investigates a new circular cylindrical wedge wave ultrasonic motor (WW-USM) integrated with modal sensors. The presented motor is driven by continuous wedge waves of the fundamental modes with an integer circumferential number. In this design, the constructive interference of two equal-intensity standing waves actuated by two comb transducers generates a traveling wedge wave. Dual-phase electrodes were parallel to the axis placed on a piezoelectric (PZT) tube at a distance of 1/4 wavelength. Two orthogonal sinusoidal signals at the resonant frequency of designated flexural mode exerting on the electrodes have the WW-USM operate in bidirectional rotation. The base height of the stator was appropriately tuned to achieve an excellent modal separation from other vibration modes. A modal sensor on the border of the PZT tube was designed to detect the dynamic characteristics of the WW-USM and to improve the performance. The wedge wave motor has a flexible mechanical performance between the angular speed and output torque. Varying the contact position of the rotor on the inclined surface of the stator may exchange the angular speed for torque output. No further modification of the entire motor structure is needed. The prototype WW-USM driven by the flexural mode F(1, 4) under 1 N static preload was operated by an AC voltage of 400 V-pp at the frequency of 36.605 kHz. The maximum values of angular speed, output torque, and electromechanical transduction efficiency are 225 rpm, 15.736 mN m, and 16.22%, respectively. (C) 2011 Elsevier B.V. All rights reserved.
A Self-sensing Wedge-wave Ultrasonic Motor Using Modal Sensors
(2009)
Yu, Tai-Ho
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This paper experimentally and computationally examines the modal sensors integrated with a recently developed rotary ultrasonic motor (USM) driven by continuous wedge waves of the fundamental modes with the integer circumferential modal number. The traveling wave is formed from constructive interference of two equal-intensity standing waves induced by two comb transducers using dual sinusoidal excitations in 90 degree phase difference. The transducers and modal sensors are segmented in strips around the circumference of piezoelectric tube in the circular wedge-like motor stator. The latter are used to monitor the dynamic response of the stator during operation. The response of USM acquired by the proposed modal sensors has distinct vital characteristics in different frequency bands. The high-pass signals are used not only to note the variation in phase difference between excitations but to detect the resonant frequency, which is altered by payload, wear situation, etc. The low-pass signal reveals the revolution speed and dynamic reaction of the motor stator exerted by frictions and contact forces because of the rotor. The time-frequency response of stator is further characterized during the period in which the revolving direction of rotor is switched over.
Acoustic realigment of nematic liquid crystals by guided waves
(2007)
Lee, Yu-Ching
;
Shih, Wun-Bin
;
Su, Yu-Wei
;
Yin, Ching-Chung
;
機械工程學系
This paper presents an experimental evidence to correlate the acousto-optic effect of nematic liquid crystals to modal excitations of guided acoustic waves. The optic axes of liquid crystal molecules in a cell can be tilted by ultrasound at oblique incidence. The cell filled with homeotropically aligned liquid crystal material, 5CB, is fully immersed in a water tank situated between two crossed polarizers. Multi-modal guided acoustic waves have been excited in cell by changing the angle of incidence and driving frequency. The liquid crystal material sandwiched between two glass plates is regarded as a Newtonian fluid and modeled to be an isotropic hypothetical solid. The phase velocity dispersion curves and associated modal strains within the liquid crystal cell are determined numerically. Comparison between measured data and prediction reveals that guided acoustic waves have influence on the acousto-optic response of liquid crystals rather than bulk acoustic waves. Simulated results show that homeotropically and homogeneously aligned liquid crystals can be affected by symmetric and antisymmetric modes, respectively.
An Ultrasonic Motor Driven by Traveling Cylindrical Wedge Waves
(2006)
Yin, Ching-Chung
;
Yu, Tai-Ho
;
機械工程學系
;
Department of Mechanical Engineering
A novel ultrasonic motor driven by flexural waves traveling circumferentially along a circular cylindrical wedgelike acoustic waveguide is presented. A rotary motion can be induced via friction forces if a rotor normally contacts the internal inclined surface of the cylindrical wedge near the tips. The rotary motor stator has a simple structure constructed by a metal cylindrical wedge adhered on a piezoelectric tube whose polarization is in the radial direction. The wedge acoustic waves are excited by two sets of comb electrodes painted on the outer surface of the piezoelectric tube. Both comb transducers with an angular space apart are excited by AC signal in +/-90 degrees phase difference to achieve bidirectional operation for the motor. There exist a number of axial modes and circumferential modes in the stator in a broad frequency range below 100 kHz. Only the fundamental modes of the latter are considered to drive this rotary motor. Along with commercial codes of finite element method (FEM), a bi-dimensional FEM has been developed to determine the resonance frequencies of circumferential modes and their corresponding modal displacements. The angular speed and direction are controllable by altering the driving voltage and the phase difference between two comb transducers.
Bi-dimensional finite element analysis for modal separation of a circular cylindrical WW-USM
(2011-07-01)
Yu, Tai-Ho
;
Yang, Shin-Yueh
;
Lee, Chen-Liang
;
Yin, Ching-Chung
;
機械工程學系
This paper describes a modal separation model that improves the performance of wedge wave ultrasonic motors (WW-USMs) using the bi-dimensional finite element analysis (Bi-d FEA) method. Most USMs operate near the resonant frequency of a specific vibration mode, which must be well separated from the resonant frequencies of other modes. In the current prototype, unexpected disturbance induced at the instant of switching on/off or changing direction of the motor appeared in simulations and actual measurements. These fluctuations are due to vibration modes other than the driving mode occurring around the operating frequency. Bi-d FEA numerical simulation results indicate that selecting an appropriate height for the upper base under the piezoelectric tube achieves excellent modal separation. Measurements of the traveling wave taken by modal sensors show that the proposed motor performs better than traditional motors, offering a faster transient response in revolution speed and a more stable design. Suppressing the unexpected modes in excitation of the WW-USM increased the maximum output torque by 50% and the efficiency of mechanical/electrical transformation by 50%. (C) 2011 Elsevier B.V. All rights reserved.
Crack detection in photovoltaic cells by interferometric analysis of electronic speckle patterns
(2012-03-01)
Wen, Tzu-Kuei
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Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
Cracking is a common problem encountered during the fabrication of crystalline silicon photovoltaic (PV) cells. In this study, electronic speckle pattern interferometry (ESPI) is developed as a tool for rapid identification of cracks in PV cells. Thermally induced cell deformation of defect-free and defect-bearing PV cells was first modeled with numerical simulations and then experimentally studied by optical configuration for ESPI measurement of out-of-plane deformations. Both numerical and experimental results indicate that the speckle patterns imparted during thermal deformation of a cell allow for simultaneous quantification of crack size, location and type in both single- and poly-crystalline PV cells. Speckle patterns near defects were manifested as continuous, chevron-shaped, and broken fringes for scratch, surface cracks, and through cracks, respectively. For comparison to other existing techniques, full field electroluminescent images were also provided for every defective PV cell. Electroluminescent imaging is capable of detecting cracks, but unlike ESPI, is unable to distinguish between the different types of cracks. Because the amount of heating needed to induce out-of-plane deformation resolvable by ESPI is small (<0.5 degrees C) and because ESPI is sensitive to crack type, the ESPI-based imaging study presented here can potentially be developed into a rapid, non-destructive inspection tool for the structural integrity of solar cells at any point within the manufacturing process. (C) 2011 Elsevier B.V. All rights reserved.
Crack detection in photovoltaic cells using electronic speckle pattern interferometry
(2010)
Wen, Tzu-Kuei
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents a full field nondestructive testing method to inspect the micro-defects embedded in photovoltaic (PV) cells by using electronic speckle pattern interferometry. The edge-clamped solar cells were heated to induce thermal deflection. Interference fringe enhanced by speckle patterns correlated to thermal deformation were determined by subtraction of two pictures recorded at different temperatures and image processing technique based on Fourier optics. The interference fringes produced at the defect free specimen exhibit a number of polygons with regular patterns of bright and dark fringes which are concentric with the center of the specimen. The thermal deformation will be redistributed due to appearance of the defects. The heating-induced interference fringes become quite different from those of the undamaged one. Tangential discontinuities of interference fringes or locally concentric polygon patterns occur in the contiguous area around the micro-defects or damages. The application of large temperature gradient to silicon substrates will induce crack propagation and should be prevented in ESPI inspection.
Detection of edge delamination in surface adhered active fiber composites
(2009-11-01)
Wang, Dwo-Wen
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Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
A simple method has been developed to detect the bonding condition of active fiber composites (AFC) adhered to the surface of a host structure. Large deformation actuating capability is one of important features of AFC. Edge delamination in adhesive layer due to large interfacial shear stress at the free edge is typically resulted from axial strain mismatch between bonded materials. AFC patch possesses very good flexibility and toughness. When an AFC patch is partially delaminated from host structure, there remains sensing capability in the debonded part. The debonding size can be determined through axial resonance measured by the interdigitated electrodes symmetrically aligned on opposite surfaces of the patch. The electrical impedance and modal response of the AFC patch in part adhered to an aluminum plate were investigated in a broad frequency range. Debonding ratio of the AFC patch is in inverse proportion to the resonant frequency of the fundamental mode. Feasibility of in-situ detecting the progressive delamination between AFC patch and host plate is demonstrated.
ESPI Solution for Defect Detection in Crystalline Photovoltaic Cells
(2011)
Yin, Ching-Chung
;
Wen, Tzu-Kuei
;
機械工程學系
;
Department of Mechanical Engineering
The yield of photovoltaic (PV) cells is often reduced by micro-defects in crystalline silicon substrates during fabrication. Common optical inspection for a thin crack in such a large silicon photovoltaic cell is extremely time-consuming and fails in efficiency. This study developed a method of using electronic speckle pattern interferometry (ESPI) for rapidly testing for cracks in an entire field of PV cells. Thermally induced flexural cell deformation was measured by optical configuration for ESPI measurement of out-of-plane deformations. Experimental results indicate that the speckle patterns correlating with thermal deformation of cell enable simultaneous estimation of crack size and location in both single- and poly-crystalline PV cells. This nondestructive detection method has potential applications in PV cell sorting.
Flexible Ultrasonic Transducers for Transverse Horizontal Plate Waves
(2015-01-01)
Yin, Ching-Chung
;
Tsai, Wei-Che
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機械工程學系
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Department of Mechanical Engineering
Novel transverse horizontal (TH) guided wave transducers comprising of piezoelectric fiber composites (PFC) sandwiched between interdigital electrodes are presented and named as TH-PFC transducers. The driving electric field is applied in orientations perpendicular to the piezoelectric fibers, in which the poling direction parallels the fibers. Dispersive characteristics and frequency responses of the lowest several TH modes in PFC have been determined by a periodic finite-element method. The symmetric and anti-symmetric TH waves are induced by face shear and thickness shear mode vibrations, respectively. The TH guided waves in a PFC adhered on the surface of a host plate can be classified into two groups, PFC modes and plate modes, in accordance with the deformation that is dominated by the PFC or the host plate. Numerical and performance test results indicate that the TH-PFC transducers with anti-symmetrically aligned electrodes possess greater capacity to actuate and sense TH guided waves in structures.
Flexible Ultrasonic Transducers Using Piezoelectric Fiber Composites with Antisymmetric Interdigital Electrodes
(2013)
Yin, Ching-Chung
;
Wu, Yu-Chien
;
Liu, Yu-Shyan
;
Hsu, Shih-Ming
;
機械工程學系
A conformal ultrasonic transducer constructed by piezoelectric fiber composites (PFC) with new arrangement of electrodes is numerically and experimentally studied. This device is designed to transmit and receive guided waves of constant wavelength for structural health monitoring application. A periodic finite element approach has been used to demonstrate the electric field induced by symmetric or anti-symmetric electrodes as well as working principle of this device interacted with the host plate. The extensional mode of this device is used to actuate both A(0) and S-0 modes of Lamb waves in the host plate. The added mass effect of PFC has more notable influence on transmission of S-0 modes than A(0) mode in the area near both edges of PFC. The linear scan of transmitted acoustic waveforms along the axis in front of the transducer by a laser Doppler vibrometer reveals the near-field interference pattern, which is caused by the guided waves of constant wavelength.
Response of thermoacoustic waves in stressed thin plates
(2007)
Hsu, Shih-Ming
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Yin, Ching-Chung
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機械工程學系
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Department of Mechanical Engineering
The response of thermoacoustic waves propagating in a thin plate exerted by mechanical stress is characterized by the phase velocity dispersion curves and attenuation spectra in this paper. The stressed thin plate is assumed to be insonified. by an intensity modulated CW laser which is modeled as a Gaussian beam. The constitutive relations and governing equations are formulated within the framework of acoustoelasticity and thermo-elasticity. Attenuation spectra in the vicinity of folding frequency can be used as a significant Index correlative to residual stress in the specimen. The amplitude and phase of thermoacoustic response are sensitive to the mechanical stress applied to specimen if loading direction Is parallel to the direction of wave propagation.
Self-detection of Delamination in Active Fiber Composites
(2009)
Wang, Dwo-Wen
;
Tsai, Wen-Chih
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents a novel method to monitor the bonding condition of active fiber composites (AFCs). AFCs can be used as integrated acoustic sensors/actuators to compose functional structures because of their excellent properties. Debonds between AFC patch and host structure should be avoided and surveyed through its service life. A partially debonded patch bears an axial extensional vibration which is excited by a sinusoidal voltage and detected by the interdigital electrodes symmetrically aligned on opposite surfaces of the patch. The electric impedance and mechanical displacement of the AFC patch adhered on an aluminum plate were investigated in a broad frequency range. The modal characteristics depend on the size of debond and stiffness of adhesive in front of the edge of delamination. The debonding ratio of the AFC patch is in inverse proportion to the resonant frequency of the fundamental mode. Feasibility of self-detecting the progressive delamination between AFC patch and host plate is demonstrated through computational and experimental results.
Transient Response of Wedge-Wave Rotary Ultrasonic Motors
(2010)
Yu, Tai-Ho
;
Yin, Ching-Chung
;
機械工程學系
;
Department of Mechanical Engineering
This paper presents an effort to improve performance of the wedge-wave ultrasonic motors (WW-USM) driven by circumferentially traveling flexural waves. In general, USM is operated in the vicinity of the resonant frequency of a specific vibration mode, which needs to be well separated away from the resonant frequencies of other modes. In the current prototype, transient response to the designed flexural mode is accompanied by longitudinal modes because of poling of the PZT tube and electrode layout around the tube. Uncertain disturbance induced at the instant of switching on/off or changing direction of the motor were found through both simulation and measurement. The fluctuations are attributed to unexpected vibration modes occurring around the operating frequency. Simulated results indicate that the performance has been improved if the electrodes are placed over the entire wavelength around the hoop of PZT tube and/or the tube is periodically poled through the thickness in alternate directions. Transient response becomes smooth and has twice the amplitude of displacement when the longitudinal modes are suppressed from excitation of WW-USM.