Showing papers on "Piezoelectric sensor published in 1998"

Piezoelectric Sensors and Sensor Materials

Abstract: This paper reviews the current trends and historical development of piezoelectric sensors and sensor materials technology. It begins with a discussion of the bases of piezo- and ferroelectric activity, followed by an overview of the most commonly used piezoelectric ceramic: lead zirconate titanate (PZT). A discussion of the properties and applications of piezoelectric crystals and additional piezoelectric ceramics is followed by a description of several sensor configurations prepared from bulk ceramics. An extensive review and comparison of piezoelectric ceramic—polymer composite sensors based on the connectivity of the constituent phases is also presented. We conclude our discussion of sensor configurations with recent examples of piezoelectric ceramic—metal composite sensors, and expected future developments in the area of piezoelectric sensors.

A Review on the Modelling of Piezoelectric Sensors and Actuators Incorporated in Intelligent Structures

Abstract: The main objective of this article is to present an overview of the modelling that has been proposed by various workers in the field of smart or intelligent structures. Before the main discussion o...

The Piezoelectric Quartz Crystal Mass and Dissipation Sensor: A Means of Studying Cell Adhesion

Abstract: We explore the potential of using a quartz crystal microbalance based technique for the characterization of living cells during the process of adhesion to a surface. The combined information from s...

Qualitative impedance-based health monitoring of civil infrastructures

Abstract: This paper presents a qualitative health monitoring technique to be used in real-time damage evaluation of civil infrastructures such as bridge joints. The basic principle of the technique is to monitor the structural mechanical impedance which will be changed by the presence of structural damage. The mechanical impedance variations are monitored by measuring the electrical impedance of a bonded piezoelectric actuator/sensor patch. This mechanical-electrical impedance relation is due to the electromechanical coupling property of piezoelectric materials. This health monitoring technique can be easily adapted to existing structures, since only a small PZT patch is needed, giving the structure the ability to constantly monitor its own structural integrity. This impedance-based method operates at high frequencies (above 50 kHz), which enables it to detect incipient-type damage and is not confused by normal operating conditions, vibrations, changes in the structure or changes in the host external body. This health monitoring technique has been applied successfully to a variety of light structures. However, the usefulness of the technique for massive structures needs to be verified experimentally. For this purpose, a 500 lb quarter-scale deck truss bridge joint was built and used in this experimental investigation. The localized sensing area is still observed, but the impedance variations due to incipient damage are slightly different. Nevertheless, by converting the impedance measurements into a scalar damage index, the real-time implementation of the impedance-based technique has been proven feasible.

Ink-jet recording head with piezoelectric device and method for manufacturing the same

Abstract: A piezoelectric device for an ink jet print head that has a greater displacement at a low drive voltage The ink-jet recording head includes a vibration plate, on which is mounted one or more piezoelectric devices that change the volumes of pressure chambers upon application of a voltage The device is mounted at least on one face of a pressure chamber substrate that is to be filled with ink Such piezoelectric device includes a second piezoelectric layer having a piezoelectric constant g of a constant value or higher; and a first piezoelectric layer having a dielectric constant of a specific value or higher Since the piezoelectric constant d of the piezoelectric device correlates with the product of the largest piezoelectric constant g and the largest dielectric device of the piezoelectric devices, a piezoelectric constant d larger than in the conventional case, ie, having a greater displacement, can be obtained

The Measurement of High-Power Characteristics for a Piezoelectric Transducer Based on the Electrical Transient Response

Abstract: In this paper, the theoretical and experimental considerations on the high-power characteristics of a piezoelectric transducer are presented. First, we propose a new measurement method for the large vibration amplitude region using an electrical transient response to eliminate the effect of temperature rise. Then, a new loss mechanism concerning the piezoelectric effect is explained by observing the relationship between the vibration velocity and the current and their harmonics. A `piezoelectric loss' is newly introduced in the equivalent circuit model to describe the real loss phenomena clearly.

Structural Health Monitoring

Abstract: can be found at: Structural Health Monitoring Additional services and information for http://shm.sagepub.com/cgi/alerts Email Alerts: http://shm.sagepub.com/subscriptions Subscriptions: http://www.sagepub.com/journalsReprints.nav Reprints: http://www.sagepub.com/journalsPermissions.nav Permissions: http://shm.sagepub.com/cgi/content/refs/2/3/257 SAGE Journals Online and HighWire Press platforms): (this article cites 14 articles hosted on the Citations

Monotonic and fatigue loading behavior of quasi-isotropic graphite/epoxy laminate embedded with piezoelectric sensor

Abstract: This study investigated the effects of embedding piezoelectric lead zirconate-titanate (PZT) sensors on the tensile strength and fatigue behavior of a quasi-isotropic graphite/epoxy laminate as well as the embedded sensor's voltage degradation under these loading conditions. For this, AS4/3501-6 laminates were fabricated with a lay-up where PZT was inserted into a cut-out area in the two middle plies. Monotonic tensile tests showed that both the average ultimate strength and Young's modulus of the tested laminate with or without PZT were within 4% of each other. The fatigue lives with and without PZT were very close to each other as well. Overall, the sequence of damage in this study agreed with previous investigations of the damage mechanisms for quasi-isotropic laminates. The ranges of modulus reduction in both cases, with and without PZT, were within 5 to 15% of each other during fatigue loading. Delamination growths in both cases during most of the fatigue life were also very comparable to each other. Further, this study showed that the embedded PZT would maintain a steady voltage output indefinitely when mechanically cycled within its operational strain limit. It thus appears that the embedment of PZTs in a cut-out area of plies of quasi-isotropic graphite/epoxy laminates would not affect their monotonic tensile and fatigue behavior.

Method for Multiple Mode Piezoelectric Shunting with Single PZT Transducer for Vibration Control

Abstract: We report a method for passive piezoelectric shunt-damping of multiple vibration modes using a single piezoelectric transducer (PZT). The method, which is different from other multiple-mode shuntin...

A New Calibration Method for Dynamically Loaded Transducers and Its Application to Cavitation Impact Measurement

Abstract: The erosion produced by cavitation is a serious problem in hydraulic machinery, During investigations of the dynamic loading generated by collapsing cavitation on a surface, a dynamic pressure transducer was developed. The piezoelectric polymer PVDF (Polyvinylidene fluoride) was used as the pressure sensitive material. A novel method of dynamic calibration has also been developed. The transducer is loaded through pencil lead by a beam supported at its other end on a knife edge and loaded at the center by weights. As the static load is increased, the pencil lead breaks and the load is released suddenly. The unloading time is faster than for any other conventional calibration method and is of the same order as cavitation loading. Descriptions of' the developments of both the calibration method and the transducer are given. The principal advantages of the new method are the short pulse duration and the simplicity of the test procedure, The paper is an extension of the previously reported work by Momma and Lichtarowicz (1994), giving further information on the operating characteristics of the transducer in comparison with the traditional ball-dropping method.

Identifying Impacts in Composite Plates with Piezoelectric Strain Sensors, Part I: Theory

Abstract: This paper summarizes the theory used in a system that identifies foreign body impact on a composite plate using built-in strain sensors. The identification system consists of a model of the composite plate and an identification algorithm. The algorithm compares the measured response of the plate to the model response and estimates the impact location and force time history. The solution, which uses a smoother/filter optimization, includes a new computational algorithm that saves considerable computation time for systems with many degrees of freedom.

Micromechanical prediction of the effective coefficients of thermo-piezoelectric multiphase composites

Abstract: The micromechanical generalized method of cells model is employed for the prediction of the effective elastic, piezoelectric, dielectric, pyroelectric and thermal-expansion constants of multiphase composites with embedded piezoelectric materials. The predicted effective constants are compared with other micromechanical methods available in the literature and good agreements are obtained.

Non-disturbing electric field sensor using piezoelectric and converse piezoelectric resonances

Abstract: This invention relates to an electric field sensor for near field measurement. The electric field sensor of the present invention uses both piezoelectric and converse piezoelectric resonances. Composed of no metallic parts, the probe of the sensor minimizes field disturbance. The most distinguished feature of this probe is that a signal is transmitted outside neither electrically nor optically, but mechanically.

Shaping of Piezoelectric Sensors/Actuators for Vibrations of Slender Beams: Coupled Theory and Inappropriate Shape Functions:

Abstract: Flexural vibrations of smart slender beams with integrated piezoelectric actuators and sensors are considered. A spatial variation of the sensor/actuator activity is achieved by shaping the surface electrodes and/or varying the polarization profile of the piezoelectric layers, and this variation is characterized by shape functions. Seeking shape functions for a desired purpose is termed a shaping problem. Utilizing the classical lamination theory of slender composite beams, equations for shaped sensors and actuators are derived. The interaction of mechanical, electrical and thermal fields is taken into account in the form of effective stiffness parameters and effective thermal bending moments. Self-sensing actuators are included. From these sensor/actuator equations, shaping problems with a practical relevance are formulated and are cast in the form of integral equations of the first kind for the shape functions. As a practical interesting aspect of these inverse problems, shape functions which fail to me...

Ultrasonic wire-bond quality monitoring using piezoelectric sensor

Abstract: This paper describes an ultrasonic wire-bond quality monitoring technique which involves the detection of changes in the mechanical impedance of the bond zone during bond formation by monitoring the changes in the ultrasonic vibrations of an ultrasonic wire-bonding transducer system. A lead zirconate titanate (PZT) piezoelectric ceramic having properties similar to the commercial PZT-5A has been selected as the sensor material. A PZT piezoelectric sensor is installed on an appropriate location on the transducer in order to measure the ultrasonic amplitude and bonding time during the bonding process. This sensor has dimensions 1 mm × 1 mm × 0.245 mm to avoid excessive loading on the transducer and to obtain a flat frequency response. A bond quality monitoring system has been developed to process and record the non-linear signal detected by the sensor. More significant changes are observed at the higher-frequency harmonics (second harmonic) of the ultrasonic signal. Good correlation is found between the change in the second harmonic and the bond quality. Bonding process drift towards unacceptable bond quality can be identified. This technique will be used to develop a multiparameter-based automatic process-control system for wire bonding.

Technical aspects of mechnomyography recording with piezoelectric contact sensor.

Abstract: The piezoelectric contact sensor has been widely utilised in mechanomyography (MMG). The authors aim to clarify the mechanical variables (i.e. acceleration, velocity or displacement) reflected by the MMG signal detected with a piezoelectric contact sensor (PEC), and compare the results with those obtained simultaneously by an accelerometer (ACC). To measure the acceleration-frequency response, a mechanical sinusoidal excitation of 5 to 300 Hz at a constant magnitude of 0.01 G was applied to the two transducers. The acceleration-frequency response of the ACC transducer was confirmed to be almost flat. The PEC without any restriction of the transducer housing (including the combined seismic mass) demonstrated a similar response to the ACC transducer. The PEC transducer output with restricted housing decreased with increasing sinusoidal frequency and an attenuation slope of −40 dB/decade and phase angle of −180 degrees. The voluntary MMG signal during isometric knee extension was recorded simultaneously with the two transducers. The amplitude spectral density distribution of the MMG from the PEC transducer was narrow and the mean frequency was approximately one-half that obtained from the ACC tranducer. The amplitude spectral density distribution with the PEC transducer resembled that of the double integral over time of the ACC transducer signal. The phase angle of the PEC transducer signal was different from that of the ACC transducer signal by approximately −180°. These results suggest that the PEC transducer acts as a displacement meter of muscle vibration. In addition, differences in the MMG frequency components relating to the transducer type must be taken into consideration when investigating the mechanical activity of muscle.

Experimental investigation of composite beams with piezoelectric actuation and debonding

Abstract: Piezoelectric transducers can be used as sensors and actuators for vibration reduction in composite structures. Debonding at the transducer-laminate interface results in significant changes to the dynamic response and control authority. This important issue is studied in the current work. Composite specimens with surface bonded piezoelectric transducers were constructed with varying stacking sequences and debonding lengths. Closed loop control was implemented using an analog circuit. Experimental results were obtained for both open and closed loop frequencies and damping ratios. The results correlate well with a newly developed higher order based theory for modeling composites with debonded piezoelectric transducers. Significant changes are observed in the open and closed loop frequencies and damping ratios as a result of debonding.

Piezoceramic actuated aperture antennae

Abstract: Recently, it has been demonstrated that aperture antennae can have their performance improved by employing shape control on the antenna surface. The antennae previously studied were actuated utilizing polyvinylidene fluoride (PVDF). Since PVDF is a polymer with limited control authority, these antennae can only be employed in space based applications. This study examines more robust antenna structures devised of a thick metalized substrate with surface bonded piezoceramic (PZT) actuators. In this work, piezoceramic-actuated adaptive antennae of cylindrical-cut shape are studied. When a PZT actuator is attached to the reflector surface, the converse effect develops a bending moment in the structure making the reflectors bend inward or outward. This bending can be employed in antenna beam steering and shaping. In order to effectively construct the antenna, the piezoceramic-actuated antenna surface was modeled using classical curved beam theory and Newton's method. The deflection versus voltage relationship was then experimentally verified, and the resulting far-field radiation pattern was simulated on computer. The results emphasize two major points: firstly, the far-field radiation pattern can be altered in a positive fashion, and secondly the first two radiation modes of the antenna correspond to the first vibration mode shapes of the structure.

Unidimensional modeling of multi-layered piezoelectric transducer structures

Abstract: Multi-layered transducer structures offer the potential of improved performance in terms of increased transmit sensitivity, greater bandwidth, and enhanced reception characteristics. Unfortunately, the successful design of such devices is often difficult, owing to the complex interaction between the active piezoelectric layers and passive intermediate interface layers. Furthermore, in many practical applications, the loading effects imposed by the electrical drive circuitry often limit the performance improvements that may be physically realized. This paper describes the development of a comprehensive, unidimensional modeling approach. This model may be employed to facilitate the analysis and subsequent optimization of laminated transducer assemblies. The devices currently under consideration include both piezoceramic and piezopolymer configurations, as well as alternative piezocomposite designs. The effects of varying bondline thickness and the introduction of passive interface layers are examined, as is the influence of the electrical load circuitry on overall system response. The ability to accurately predict the response of stacked piezoelectric structures is demonstrated through extensive comparison of experimental and theoretical responses. This paper concludes by highlighting the important role that modeling plays in the design, fabrication, and optimization of complex multi-layered transducer assemblies.

Diagnostics for vehicle deformation sensor system

Abstract: A sensor system for detecting impacts to a vehicle, including diagnostics for monitoring the sensor system. The sensor system includes one or more piezoelectric sensor assemblies (42), each including a coaxial piezoelectric cable (44) contained within a tube housing (54), which is mounted to a structural member of the vehicle. The sensor system may also include accelerometers (36, 38) that are also in communication with the restraints control module (40) and employed in combination with one or more piezoelectric sensor assemblies (42). Further, the sensor system includes diagnostics for monitoring one or more of the sensor assemblies (42) in order to detect a sensor failure, while not interfering with the impact signals from the sensor assemblies (42).

The Effect of Temperature Dependent Material Properties on the Response of Piezoelectric Composite Materials

Abstract: Analytical formulations for thermopiezoelectric composite materials are extended to account for thermal effects arising from temperature dependent material properties. The updated mechanics also has the inherent capability to capture thermal effects which arise due to coefficient of thermal expansion mismatch and pyroelectric phenomena, providing a comprehensive thermal analysis capability. The thermal effects are represented at the material level through the thermopiezoelectric constitutive equations. These equations are incorporated into a layerwise laminate theory to provide a unified representation of the coupled mechanical, electrical, and thermal response of piezoelectric composite materials. Corresponding finite element equations are derived and implemented for beams and plates to model the active and sensory response of piezoelectric composite laminates. Applications demonstrate the significance of incorporating temperature dependent material properties on the response of piezoelectric composite b...

Dynamics of an ultrasonic transducer used for wire bonding

Abstract: The vibration displacement distributions along a transducer used in ultrasonic wire bonding were measured using a heterodyne interferometer, and many nodes and anti-nodes were found. A mechanical finite element method (FEM) was used to compute the resonant frequencies and vibration mode shapes. The displacement distributions of the dominant 2nd axial mode agreed well with the measured values. Undesirable nonaxial modes, including the higher order flexural and torsional modes, also were excited at frequencies very close to the working frequency (2nd axial mode) of the transducer. Hence, the measured displacements were the resultant of all the allowable modes being excited. However, the excitation of these nonaxial modes were small enough not to affect the formation of consistent and high quality wire bonds. Results of the present study were used to determine a suitable location for installing a piezoelectric sensor to monitor the bond quality.

An approximated 3-D model of cylinder-shaped piezoceramic elements for transducer design

Abstract: In this paper an approximated 3-D model of cylinder shaped piezoceramics is described. In the hypothesis of axial symmetry, the element vibration in the extensional and radial directions is described by two coupled differential wave equations. The model is obtained choosing, as solution of these equations, two orthogonal wave functions, each depending only on one axis, corresponding to the propagation direction. The mechanical boundary conditions are applied imposing continuity between the stresses and the external forces on the surfaces of the element in an integral way, while, as far as the electrical boundary condition is concerned, two possibilities are explored: to neglect the piezoelectric constant in the transverse direction and to impose an integral condition also for the electric field. Comparisons with experimental results show this last approach to give better results. The model predicts with sufficient accuracy only the first radial and the first thickness modes of the cylinder-shaped piezoceramic element of arbitrary aspect ratio; but, for these modes, it is able to compute all the relations between the input applied voltage and the output forces and velocities on every external surface. Because only these two modes are of relevance in the practical applications of piezoceramic elements as ultrasonic transducers, the model can be used as a simple and useful tool in transducer design and optimization. Experimental validations of the model are also shown in the work.

Footwear incorporating piezoelectric spring system

Abstract: An article of performance enhancing footwear having a piezoelectric spring apparatus in the sole member. Walking or running applies a first force deforming a piezoelectric actuator, thereby generating electrical energy. An energy storage circuit stores electrical energy generated by the piezoelectric actuator. Sensing means is provided to sense the release of a second force greater than the first force, which triggers the release of stored electrical energy back into the piezoelectric actuator. The resulting deformation of the piezoelectric actuator imparts a force into the bottom contact surface of the sole member.

Relationships between acoustic emission signals and physical phenomena during indentation

Abstract: A commercial piezoelectric acoustic emission transducer has been used in conjunction with nanoindentation techniques to study the relationship between acoustic emission signals and discrete physical events to identify the type and strength of an event. Indentations into tungsten and iron single crystals have been used to study dislocation generation and passive film failure. In addition, indentations made into a thin nitride film on sapphire have been used to cause film delaminations. Parameters such as signal rise time and frequency for a piezoelectric sensor are related to sample geometry, and not to the type of event which caused the acoustic emission signal. As a possible calibration for acoustic emission sensors, the most meaningful parameter is the acoustic emission energy, which has been shown to scale with the elastic energy released during the event. The measured values of elastic energy released correspond very closely to those calculated using Hertzian contact mechanics.

Optimal Control of Laminated Plate with Piezoelectric Sensor and Actuator Layers

Abstract: A closed-form solution for the optimal control of vibrations of a simply supported symmetric thin laminated plate integrated with piezoelectric layers is obtained. The piezoelectric layers act as the distributed sensors and actuators. The method of designing the optimal steady-state regulator with output feedback is employed. Responses for various design parameters are illustrated. The results may be useful for the purpose of comparing the numerical models and experimental results.

Domestic appliance, such as cooking hob with touch controls

Abstract: The appliance has an operating plate (5) made of a thin metal plate with a piezo sensor stuck on the side opposite to the operating surface. The piezo sensor detects an operating pressure and outputs a signal to a control unit accordingly. The operating surface may have symbols in the form of depressions in the surface, especially by engraving.