Notification:
We are currently experiencing intermittent issues impacting performance. We apologize for the inconvenience.
By Topic

Piezoelectricity, Acoustic Waves, and Device Applications, 2008. SPAWDA 2008. Symposium on

Date 5-8 Dec. 2008

Filter Results

Displaying Results 1 - 25 of 126
  • Electro-elastic stress analysis of a screw dislocation interacting with interface in piezoelectric solid

    Publication Year: 2008 , Page(s): 1 - 5
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (267 KB) |  | HTML iconHTML  

    The electro-elastic interaction of a piezoelectric screw dislocation with interface is considered. The surface of layers is assumed to be mechanically free and electrically open. The electro-elastic fields have been given explicitly by using the perturbation concept and the method of Laurent series expansion. Based on the derived solutions, numerical examples are given to illustrate the influences of dislocation location, piezoelectric effect and material properties on the interfacial stresses and image force. The obtained results show that: the piezoelectric effect is able to change the interaction of a screw dislocation with an interface and a free boundary; the difference between elastic constants has obvious influence on the interfacial stress. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Free vibration of multiferroic simply supported circular cylindrical panels

    Publication Year: 2008 , Page(s): 6 - 10
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (326 KB) |  | HTML iconHTML  

    Two dimensional equations are derived for multiferroic circular cylindrical panels with small aspect ratio. The displacement, electrical potential and magnetic potential are assumed to be of zero-order of the radial thickness. The frequency equation is presented for a multiferroic cylindrical panel composed of CoFe2O3 and BaTiO3 with four edges simply supported. Numerical examples show clearly the effects of half-wave numbers in the axial and circumferential directions on the frequency parameters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Thermal shock problem of piezoelectric materials with temperature-dependent properties

    Publication Year: 2008 , Page(s): 11 - 16
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (312 KB)  

    Base on the generalized thermoelastic theories of Lord and Shulman (L-S) and Green and Lindsay (G-L), the thermal shock problem of an infinite piezoelectric plate with temperature-dependent properties are studied by using the finite element method (FEM). The governing equations are nonlinear of temperature due to temperature-dependent properties. It is difficult to solve the problem by using the integral transform method. The FEM equations are solved directly in time domain. The distributions of temperature, displacement, stress and electric field are obtained. In the results, it is easy to find that the properties have jumps at the heat wave under the L-S and G-L theories but change continuously under the classical theory. The temperature-dependent properties make the other parameters different from temperature-independent condition. From the results obtained in the paper, one can get that the time-domain solution method of FEM can describe the finite velocity of heat conduction accurately. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Finite element simulation of contact-impact dynamics for high-power ultrasonic processing system

    Publication Year: 2008 , Page(s): 17 - 21
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (525 KB) |  | HTML iconHTML  

    Nonlinear contact-impact dynamic behavior of high-power ultrasonic processing systems is studied in experiment and theory. Firstly, nonlinear contact-impact vibrations in a high-power ultrasonic processing system are studied experimentally. Then a finite element method is used to analyze the observed experimental phenomena, in which a 2D axisymmetric model is developed, and the nonlinear contact-impact dynamic behavior is analyzed. The finite element method simulation results of the contact-impact behavior between the transducer horn and the sample show that the contact force between the horn tip and the sample is very complicated and includes super- and sub-harmonic frequency components in addition to the ultrasonic excitation frequency. The subharmonic vibrations in the samples are simulated in detail, and the results show that the subharmonic vibrations will always occur as observed in the experiments. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Propagation features about the characteristic wave of acoustic full waveform in cased boreholes

    Publication Year: 2008 , Page(s): 22 - 27
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB)  

    Cementing quality directly influences exploitation of oil or gas layers in oil or water boreholes. Characteristic wave (or pseudo-Rayleigh wave) in acoustic full waveform can evaluate the cementing quality of the secondary interface in cased boreholes. Before evaluating the cementing quality of secondary interface, we must analyze bath propagation velocity and amplitude of the characteristic wave. To achieve this, we simulate the acoustic full waveform and 2-D spectrum (frequency-wavenumber spectrum) for various cementing quality of the secondary interface based on the real axis integration method, and analyze relation between bath velocity and amplitude of the characteristic wave and thickness of the water layer on the secondary interface. The simulating results for the waveform and 2-D spectrum of characteristic wave indicate that the velocity of characteristic wave is influenced by the velocity of bath the casing and cement annulus together and is small than that of cased wave. The velocity is increasing and up to the velocity of cased wave with the thickness of water layer. In efficient range of the thickness of water layer, the amplitude of characteristic wave is increasing with the thickness of water layer. Moreover, we validate the simulation results by comparing with experiment data in calibration pits. It is shown that the difference of amplitude or velocity for the characteristic wave can indicate the cementing quality of the secondary interface. These results are of great importance to build the standards of extracting the characteristic wave and criteria of evaluating the cementing quality of the secondary interface. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Study on polarization state in depolarized fiber optic gyroscope

    Publication Year: 2008 , Page(s): 28 - 32
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB) |  | HTML iconHTML  

    The instability of polarization state in interference fiber optic gyroscope (FOG) restricts the precision and stability of FOG. There are two methods to increase FOG's precision and stability, that is, to maintain or eliminate the state of polarization in fiber. Using Lyot fiber depolarizer not only reduces the effects of the states of polarization on the performance of FOG, but decreases the cost of FOG to a large extent, which is quite suit for the medium and low precision FOG. This article analyzes the principle of Lyot fiber depolarizer and the interchangeable character of input and output ports, deduces the structural parameters of Lyot fiber depolarizer and discusses the effects of parameters on the depolarizer's performance with Jones matrix. What's more, polarization transformation and polarization errors in depolarized fiber optic gyroscope (DFOG) are discussed in detail. Experimental result shows that the depolarizer we designed is very effective to reduce the drift of FOG, and depolarized fiber optic gyroscope is suit for fields using medium precision FOG. The analysis provides academic guidance to depolarizer used in depolarized fiber gyroscope or other fiber optic sensors. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Dispersion relations of SAW propagating under Al grating on 128°YX-LiNbO3

    Publication Year: 2008 , Page(s): 33 - 36
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    Based on discrete Green function and finite element method, properties about surface acoustic waves propagating under periodic Al grating on 128degYX-LiNbO3 substrate were studied. The dispersion relations of SAW and COM parameters for Al strips of different thickness are given, which can theoretically support the design of relevant SAW filters. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reverberation-ray analysis of orthotropic piezoelectric laminates with imperfect interfaces

    Publication Year: 2008 , Page(s): 37 - 41
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB) |  | HTML iconHTML  

    The static and dynamic problems of an imperfectly bonded, orthotropic, piezoelectric laminate in cylindrical bending are investigated based on the equations of piezoelasticity. A general spring layer is adopted to model the bonding imperfections at the interfaces of the laminate. The formulations of reverberation-ray analysis are developed. The approach is verified by comparing the results with those obtained from the state space method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Fast mixing of digital droplets under uni-direction acoustic field

    Publication Year: 2008 , Page(s): 42 - 46
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (300 KB) |  | HTML iconHTML  

    A micro-mixer for mixing digital droplets fabricated on 128degY cut X LiNbO3 is reported, which is composed of one interdigital transducers and one reflector for generating unidirectional acoustic field. After a RF signal amplified by a power amplifier was added on an interdigital transducer, surface acoustic wave was excided by the interdigital transducer, and was conversed into longitudinal acoustic wave and to drive a digital droplet to merge with the other droplet quickly by their rapid molecular diffusion when the surface acoustic wave passed through the droplets. Mixing experiments of 3ul NaCl solution-2ul red dye solution and 3ul glycerine-2ul red dye solution show that their mixing velocities can improve 35 folds and 50 folds respectively under unidirectional acoustic fields. The research is valuable for its simplicity in process and easy integration into lab-on-a-chip. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Wave propagation in a functionally graded piezoelectric coating on a cylinder

    Publication Year: 2008 , Page(s): 47 - 50
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB) |  | HTML iconHTML  

    In this paper, the wave propagation in a functionally graded piezoelectric coating on a cylinder is studied. Considering the piezoelectricity of the coating with an orthotropic symmetry, the wave equations and system matrices for state vector are obtained for SH and P-SV waves propagating along both the axial and circumferential directions. It is found that the wave propagation of the SH wave along the axial direction and the P-SV wave along the circumferential direction is not coupled to the electric field, i.e., their corresponding dispersion patterns are same as that for a functionally graded coating without piezoelectricity. However, the wave propagation of the P-SV wave along the axial direction and the SH wave along the circumferential direction is coupled to the electric field, i.e., their corresponding dispersion patterns depend on the applied electric field, their dispersion curves are different under the open or close electric boundary conditions. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Magnetoelectric response analysis of the piezoelectric/piezomagnetic thin-film heterostructure derived by low energy cluster beam deposition

    Publication Year: 2008 , Page(s): 51 - 54
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    The piezoelectric/piezomagnetic thin-film heterostructure has been prepared by using low energy cluster beam to deposit Tb-Fe clusters onto the Pb(Zr0.52Ti0.48)O3 (PZT) film substrate. The magnetoelectric voltage coefficient of the heterostructure is larger than that of the reported all-oxide ferroelectric-ferromagnetic composite film. A magnetic-mechanical-electronic transformation model is designed to deeply investigate the origin of the giant magnetoelectric effect. And the coupling coefficient k between the piezoelectric and piezomagnetic phase is introduced into this model to analysis the magnetoelectric response of the heterostructure. It is found that the coupling coefficient k plays a key pole in the production of the magnetoelectric effect for piezoelectric/piezomagnetic thin-film heterostructure. This work describes an ideal way to optimize the magnetoelectric effect of the piezoelectric/piezomagnetic thin-film heterostructure and facilitates their applications in MEMS devices. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A spatial impulse response based model for the acoustic field in detection of buried objects with low frequency WAVES

    Publication Year: 2008 , Page(s): 55 - 59
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (253 KB) |  | HTML iconHTML  

    A number of mathematical models have been developed and used for received signal processing in acoustic detection of buried objects with low frequency waves up to now. Most of them are linear combination of signals and impulses of the system. They are too simple to make in-depth analysis of the parameters of the system. Then, a spatial impulse response based model is proposed for the acoustic detection system, which is derived from the basic theory of sound propagation and geometrical relation of the system. And the physical meaning of the model is explicit. In this way, the model can be applied to predict and determine the parameters of the detection system, and it is the basic theory in signal processing of the system. The simulated results and the measured received signals are compared, and it is shown that the simulated and measured results are in good agreement. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The modifying generalized moving least squares approximation meshless method and application on plane piezoelectric problem

    Publication Year: 2008 , Page(s): 60 - 65
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Meshless method is a new numerical method on problem for determining solution of differential equation. The moving least squares approximation makes only require least squares approximation with regard to functional value at all nodes. It makes no require for the residual of derivative approximation. However, the generalized moving least squares approximation makes require least squares approximation with regard to functional and its derivative value at all nodes. For the sake of decrease the computing time, modifying generalized moving least squares approximation is constructed under adding the residual of high orders derivative only at the portion nodes. The modifying generalized moving least squares approximation has high accuracy not only for function value but also one or higher orders derivative. This method is well applied to plane piezoelectric problem. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • The high performance of finite element analysis and applications of surface acoustic waves in finite elastic solids

    Publication Year: 2008 , Page(s): 66 - 71
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    The characteristic of wave propagation in finite elastic solids is a major issue for surface acoustic wave (SAW) devices, which are designed based on accurate analysis. As a result, it is essential in engineering applications to analyze the SAW propagation in finite piezoelectric solids with the objective of revealing the influence of structural changes. As the finite element analysis of solids is already sophisticated, the problem of SAW analysis is reduced to the calculation of eigenvalues of extremely large linear equations that involves hundreds of thousands or even millions of degree of freedom because of the higher frequency. The operations of large scale matrices need high computing speed and large memory. In fact, these demands are beyond the capacity of widely available computing resources. For these reasons, we need to make use of computer clusters and parallel finite element method to improve the computing efficiency and expand applications. Based on our existing finite element program, the PARPACK package is used to compute eigenvalues in the specified range; the compressed sparse row (CSR) storage format is used to replace the Symmetric Skyline (SSK) storage method; the PETSc package is used to solve linear equations. The program is parallelized on a Linux cluster to utilize the computing power. The parallel FEM program with 3D elements is used to analyze the wave propagation in an actual SAW device model with interdigital transducers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Frequency analysis of thickness-shear vibratiions of thin film bulk acoustic wave resonators

    Publication Year: 2008 , Page(s): 72 - 77
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (542 KB)  

    The rapid development of wireless communication technology and the clear trend of higher frequency, miniaturization, and integration of RF components have provide opportunities through the research and production of thin film bulk acoustic resonators (TFBAR). In the design of TFBAR products, how to determine the frequency is always the starting point. The thickness-extension type of resonators can produce higher frequency, as it has been proven through products on the market. For the thickness-shear types of resonators, precise calculation of vibration frequency is important in the design. We established a vibration model of TFBAR and obtained the frequency equation based on the layered infinite plates. The frequency equation can be used to evaluate a design, or select structural parameters based on the given frequency. Our frequency equation has been validated with experimental data. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Structures and vibration analysis of film bulk acoustic wave resonators

    Publication Year: 2008 , Page(s): 78 - 86
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (474 KB)  

    The wireless communication technology demands for smaller size, high frequency, high performance, low energy consumption, and low cost RF components. Current products based on dielectric or SAW resonators are not enough either due to the size or the circuit loss. Film bulk acoustic resonators (FBAR) are the latest technology offering small size and high frequency RF components to the fast growing personal wireless communication technology. We reviewed the current state-of-art of the FBAR technology and explained the working mechanism of FBAR. With two major vibration models, thickness-extension and thickness-shear, we also described the FBAR structure and principle of material selection. Furthermore, we analyzed the effect of electrodes on the vibration frequency, and explained the choice of quarter wavelength reflectors in the SMR. We want to provide essential concepts and knowledge about FBAR technology to engineers who are interested in studying it further. With enough knowledge on the vibration models and materials, the design method of FBAR and SMAR can be established with accurate analysis. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Nonlinear Mindlin plate equations for the thickness-shear vibrations of crystal plates

    Publication Year: 2008 , Page(s): 87 - 92
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB) |  | HTML iconHTML  

    Mindlin plate equations have wide applications in engineering fields with piezoelectric crystal resonators in particular due to its accurate prediction of high frequency vibrations of plates in the vicinity of thickness-shear mode. As a linear theory based on the assumption of infinitesimal deformation, its applications have been limited mainly to vibration frequency analysis. Many important properties of quartz crystal resonators such as the electrical circuit parameters, and nonlinear phenomena such as the drive-level dependence (DLD), have to be studied with the consideration of higher-order material constants and subsequent inclusion of nonlinear strain components. This, in turn, implies that the consideration of large deformation related to the driving electrical field. The need of nonlinear theory for the analysis of high frequency vibrations of piezoelectric crystal plates have been noticed before, and research work concerning large electrical fields and deformation have been initiated for the calculation of electrical properties and DLD of quartz crystal resonators by many investigators recently. In this study, we start with higher-order constitutive relation which includes higher-order elastic constants. Then, nonlinear terms of strain components are considered in a compatible and systematic manner. By following Mindlin's procedure in deriving the two-dimensional equations, nonlinear Mindlin plate equations for large deformation are obtained. The equations take the familiar form of Mindlin plate theory except the inclusion of nonlinear terms in the strain tensor. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of power transmission through an elastic wall by piezoelectric transducers and acoustic waves

    Publication Year: 2008 , Page(s): 93 - 97
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (336 KB) |  | HTML iconHTML  

    We present our recent modeling results on power transmission through an elastic wall by piezoelectric transducers and acoustic waves. This includes the case of finite piezoelectric transducers on plates, power transmission through circular cylindrical shells, and mechanical nonlinearity due to large deformations near resonance. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Effects of preparation process on the properties of PMN based electrostrictive materials

    Publication Year: 2008 , Page(s): 98 - 100
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (744 KB)  

    In this study, the effects of preparation process on the properties of lead magnesium niobate (PMN) based electrostictive materials, such as phase structure, microstructure and electrical property, are investigated and discussed. The results of experiment show the powder samples, fabricated by a modified two-step synthesis method with alkaline-earth metal dopants introduced in the preparation of common electrical materials, has pure perovskite phase in XRD patterns without pyrochlore structure. From SEM figures, it can be seen the sinter temperature has certain influences on grain size and morphology. Especially, the sinter temperature is elevated over 124degC that the grain overgrows and grain boundaries become ambiguous. Moreover, the additive dopant can suppress the grain growth and reduce the grain size, which benefits to lowering sintering temperature and improves the density of materials. The induced strain curve measured by the optic fiber method shows the PMN based electrostrictive materials has a large strain, ~0.8times10-3 under a 2000 V/mm bias field. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Analysis of the existence of complete band gaps in periodic binary piezoelectric phononic crystals based on connectivity

    Publication Year: 2008 , Page(s): 101 - 104
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (176 KB) |  | HTML iconHTML  

    In this paper we analyze the existence of complete band gaps in periodic binary two-dimensional piezoelectric phononic crystals with {1-3} connectivity family from a point view of connectivity. For this structure and no wave-vector components parallel to the cylinders, there are two independent modes of vibration. One of them is the transverse polarization mode (Z mode) with the elastic displacement vector parallel to the cylinders. And the other one is the longitudinal-transverse polarization mode (XY mode) with the elastic displacement vector perpendicular to the cylinders. The plane-wave-expansion (PWE) method is applied to the theoretical derivation of secular equations of the two polarization modes. Band structures for the two modes are calculated to look for complete band gaps in piezoelectric phononic crystals with both 1-3 connectivity and 3-1 connectivity, which will be used to analyze the effect of connectivity on the existence of band gaps in piezoelectric phonic crystals. Numerical results reveal that the strong difference of physical properties between the constituents in piezoelectric phononic crystals can't dominate the existence of complete band gaps and the connectivity of the constituents plays an important role in the existence mechanism. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Modeling of multilayered acoustic wave devices with the method of reverberation-ray matrix

    Publication Year: 2008 , Page(s): 105 - 110
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (561 KB) |  | HTML iconHTML  

    The method of reverberation-ray matrix (MRRM) are modified and extended to the analysis of wave propagation in multilayered acoustic wave devices based on three-dimensional linear piezoelectricity. By the plane wave solution assumption, state equations are established whose solutions are expressed with unknown wave amplitudes. Within the framework of MRRM, the phase and scattering relations are properly set up to determine the unknowns without involving exponentially growing functions and matrix inversion operations in an easy and uniform way. Thus the present MRRM is unconditionally stable and free from limitations to the frequency, the thickness of individual layers and the total number of layers. The surface waves, the interface waves and the bulk waves are all included in the formulation. Therefore, the present formulation applies to SAW devices as well as BAW devices. Numerical examples are given to illustrate the well performance of the proposed formulation of MRRM for the analysis of free waves in multilayered acoustic wave devices. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • A mixed noise filtering algorithm based on the genetic algorithm and L-filter

    Publication Year: 2008 , Page(s): 111 - 114
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (457 KB)  

    A novel algorithm for mixed noise filtering in image processing is presented, combing the genetic algorithm and L-filter. The algorithm based on central limit theorem estimates mixed noise model through inter-selecting region of interest in the image, and adds this mixed noise model to a small test image for rebuilding degraded process. Aiming at this test image, the genetic algorithm is used to optimize the weight coefficients of L-filter. Then the optimized weight coefficients are used in combination with image edge information to execute L-filter to the image. Experiments demonstrate that this method is better than Laplacian filter and median filter. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of converse piezoelectric effects on the frequency properties of electron emission in PZT cathode

    Publication Year: 2008 , Page(s): 115 - 118
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB)  

    The influence of converse piezoelectric effect on the frequency of PZT cathode during the electron emission process was studied. The PZT cathodes were prepared by ordinary ceramic process and the diameter of PZT cathode is 25 mm as well as the thickness is 3 mm. The back electrode, whose diameter is 20 mm, and the grid electrodes, with intervals being 200 mum, were made of gold by using evaporation technology. The experimental setups include a high voltage pulse generator, vacuum chamber, oscilloscope and voltage divider. Several periodic peaks of emitted electron current were observed and the period is 180 ns. The prominent frequency of the waveforms is about 5.8 MHz, obtained from the frequency spectrum of the current waveforms. This value is close to the surface vibrating frequency of 6.6 MHz, calculated through the theories of surface acoustic waves in PZT ceramics. That the frequency of the emitted electron current was modulated by the surface vibration can be concluded from the above results based on the theories of surface acoustic waves, fast polarization switch and surface plasma induced ferroelectric emission. Thus the several periodic peeks observed from the emitted current can be well explained. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Slection of wavelet fuction on denoise qulities of ultrasonic inspection signal

    Publication Year: 2008 , Page(s): 119 - 124
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (466 KB)  

    It is suggested in this paper to denoise the ultrasonic inspection signals using wavelet transform. The theoretic base is that wavelet transform is a band-pass filter. Firstly, the frequencies of the inspection signal are evaluated according to the excited signal. Secondly, an appropriate scale for wavelet transform is computed following the laws between the scale and the frequency. Thirdly, wavelet transform with the scale would be operated. As results, the echoes by the flaws could be discerned in the wavelet coefficients. Finally, the propagation of the guided wave in a damaged pipe is simulated by code ANSYS and the signal processing are operated by code MATLAB. The different wavelet functions are also discussed aiming at the denoised qualities. The signal-to-noise ratio (SNR) is used to evaluate the quality for different wavelet. It could be concluded that the Morlet wavelet is suitable to operate the ultrasonic inspection signal excited by a sinusoidal signal modulation by Hanning windows. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Contact acoustic nonlinearity phenomenon caused by the acoustic wave propagating in the composite material

    Publication Year: 2008 , Page(s): 125 - 128
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB)  

    Due to the massive applications of multilayered composite materials (for example carbon fiber material, glass fiber material etc.) in material industry, aviation industry, medical enterprise and other consumer industries, it becomes an important work to carry on the non-destructive evaluation to the long-term characteristic and the security of the composite materials in use. The reliability of a composite material is mainly decided by the quality of its bonded interfaces. In the bonded interface, the weak bonding region is possibly the initial spot of the entire equipment's failure. Therefore the examination technology of the bonding state at the interface becomes the hot spot of the current research and application. Actually, in the bonded interface, micro-cracks or micro-flaws will be formed during the solidification of bonding material or after the composite material have been used for a period of time. When a longitudinal acoustic wave propagates through the interface with micro-cracks, it will drive the two surfaces of the micro-cracks to pop each other and the contact acoustic nonlinearity (CAN) phenomenon will happen. In this paper, we analysis the CAN phenomenon in the interface and propose a CAN parameter to describe the bonding state. Also an experiment is stated in the paper to scan the bonding state at the interface using the CAN parameter. The results show that the region with weak bonding strength can be easily distinguished from the scanning contour. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.