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Explicit Determination of Piezoelectric Eshelby Tensors for a Spheroidal Inclusion

Description: In this paper, by systematically treating the integrals involved in the piezoelectric inclusion problem, explicit results were obtained for the piezoelectric Eshelby tensors for a spheroidal inclusion aligned along the axis of the anisotropy in a transversely isotropic piezoelectric material. This problem was first treated by Dunn and Wienecke (1996) using a Green's function approach, which closely follows Withers' approach (1989) for an ellipsoidal inclusion problem in a transversely isotropic elastic medium. The same problem was recently treated by Michelitsch and Levin (2000) also using a Green's function approach. In this paper, a different method was used to obtain the explicit results for the piezoelectric Eshelby tensors for a spheroidal inclusion. The method is a direct extension of a more unified approach, which has been recently developed by Mikata (2000), which is based on Deeg's results (1980) on a piezoelectric inclusion problem. The main advantage of this method is that it is more straightforward and simpler than Dunn and Wienecke (1996), or Michelitsch and Levin (2000), and the results are a little bit more explicit than their solutions. The key step of this paper is an analytical closed form evaluation of several integrals, which was made possible after a careful treatment of a certain bi-cubic equation.
Date: June 21, 2001
Creator: Mikata, Yozo
Partner: UNT Libraries Government Documents Department

Design of the First Ferromagnetic Piezoelectric (FINAL TECHNICAL REPORT)

Description: Abstract During the course of the grant we made the following scientific advances: • We developed a thorough understanding of piezoelectricity in antiferromagnetic wurtzite structure MnO. • We explained the absence of ferromagnetism in high quality samples of transition-metal-doped ZnO, and proposed a scheme for obtaining robust ferromagnetism in ZnO-based systems. • We demonstrated that the MgO-ZnO-CdO system is a promising candidate for the production of polarization field-effect transistors.
Date: April 3, 2007
Creator: Spaldin (Hill), Nicola
Partner: UNT Libraries Government Documents Department

Piezoelectric Effects on the Optical Properties of GaN/Al(x)Ga(1-x)N Multiple Quantum Wells

Description: Piezoelectric effects on the optical properties of GaN/AlGaN multiple quantum wells (MQWS) have been investigated by picosecond time-resolved photoluminescence (PL) measurements. For MQWS with well thickness 30 and 40 the excitonic transition peak positions at 10 K in continuous wave (CW) spectra are red-shifted with respect to the GaN epilayer by 17 meV and 57 meV, respectively. The time-resolved PL spectra of the 30 and 40 well MQWS reveal that the excitonic transition is in fact blue-shifted at early delay times due to quantum confinement of carriers. The spectral peak position shifts toward lower energies as the delay time increases and becomes red-shifted at longer delay times. We have demonstrated that the results described above is due to the presence of the piezoelectric field in the GaN wells of GaN/AlGaN MQWS subject to elastic strain together with screening of the photoexcited carriers. By comparing experimental and calculation results, we conclude that the piezoelectric field strength in GaN/Al.15G~.85N MQWS has a lower limit value of about 560 kV/cm: The electron and hole wave function distributions have also been obtained. The implication of our findings on the practical applications of GaN based optoelectronic devices is also discussed.
Date: November 10, 1998
Creator: Botchkarev, A.; Chow, W.W.; Jiang, H.X.; Kim, H.S.; Lin, J.Y. & Morkoc, H.
Partner: UNT Libraries Government Documents Department

Development and testing of an active platen for IC manufacturing

Description: The conflicting demands for finer features and increased production rates in integrated circuit manufacturing have emphasized the need for improved wafer positioning technology. In this paper we present operational test results from a magnetically levitated platen with structurally integrated piezoelectric acctuators. The strain based actuators provide active damping of the platen`s flexible body modes, enabling increased bandwidth on the mag-lev positioning system. Test results reveal a dramatic reduction in steady state positioning error and settling time through implementation of active vibration control.
Date: November 1, 1998
Creator: Redmond, J.; Barney, P.; Smith, T. & Darnold, J.
Partner: UNT Libraries Government Documents Department

Characteristics of self-sensing actuation for active control

Description: The benefits of a collocated sensor actuator pair are well known within the controls community. Generally speaking, collocation offers the use of simple control algorithms with reduced instabilities due to spillover. One method for achieving collocation is the implementation of a ``sentuator`` in which a piezoelectric element functions simultaneously as both a sensor and an actuator. Past work in utilizing a sentuator has primarily been limited to piezoelectric films and patches mounted to flexible structures. Additional papers have provided information and methodology for dealing with the non-linear aspects of a piezoceramic sentuator. The need arises for methods of self-sensing when performing active vibration control of very stiff structures. A method for understanding and using self-sensing lead zirconate titanate stacks for active vibration control is presented. This paper specifically provides a basic understanding of self-sensing methods as applied to stiff structures for the purposes of control. The discussion of the methodology is followed by a simple example in which active vibration control is applied to a model of a boring bar with embedded PZT stacks.
Date: December 31, 1996
Creator: Barney, P.; Redmond, J. & Smith, D.
Partner: UNT Libraries Government Documents Department

Effect of Substrate Composition on the Piezoelectric Response of Reactively Sputtered AlN Thin Films

Description: Deposition parameters were found to have a marked effect on piezoelectric response of reactive radio frequency (RF) sputtered AlN thin films. The authors observed peizoelectric response values ranging from {minus}3.5 to +4.2 pm/V for 1 {micro}m thick AlN films deposited onto Ti/Ru electrode stacks. An investigation of the effects of deposition parameters, in particular the nature of the Ru/AlN interface, was conducted. The lag time between deposition of adjacent thin film layers appeared to have the greatest affect on the value of the piezoelectric response. This suggests that chemical reaction occurring on the Ru thin film surface is responsible for changing an important thin film property such as dipole orientation within the overlying AlN thin film.
Date: April 21, 1999
Creator: Clem, P.G.; Dimos, D.B.; Gonzales, D.M.; Ruffner, J.A. & Tuttle, B.A.
Partner: UNT Libraries Government Documents Department

Comparison of bulk- and surface-micromachined pressure sensors

Description: Two piezoresistive micromachined pressure sensors were compared: a commercially available bulk-micromachined (BM) pressure sensor and an experimental surface-micromachined (SM) pressure sensor. While the SM parts had significantly smaller die sizes, they were outperformed in most areas by the BM parts. This was due primarily to the smaller piezoresistive gauge factor in the polysilicon piezoresistors in the SM parts compared to the single crystal strain gauge used in the BM parts.
Date: August 1, 1998
Creator: Eaton, W.P.; Smith, J.H.; Monk, D.J.; O`Brien, G. & Miller, T.F.
Partner: UNT Libraries Government Documents Department

Electron-gun-controlled thin film mirrors for remote sensing applications

Description: The ultimate limitation in obtainable resolution and sensitivity for space-based imaging systems is the size of the optical collecting aperture. Large collecting apertures are at odds with maintaining low launch costs and with current launch vehicle configurations. Development of a deployable mirror is one approach being considered to satisfy these conflicting requirements. The focus of this research is to develop fundamental technology toward the realization of deployable electron-gun-controlled piezoelectric thin films mirrors as shown below. A bimorph layer of film will bend in response to an applied electric field and can therefore be deformed into desirable shapes using a scanning electron gun. Surface curvature measurements govern the electron gun scanning strategy, yielding distributed shape corrections.
Date: February 15, 2000
Partner: UNT Libraries Government Documents Department

Distributed Sensing and Shape Control of Piezoelectric Bimorph Mirrors

Description: As part of a collaborative effort between Sandia National Laboratories and the University of Kentucky to develop a deployable mirror for remote sensing applications, research in shape sensing and control algorithms that leverage the distributed nature of electron gun excitation for piezoelectric bimorph mirrors is summarized. A coarse shape sensing technique is developed that uses reflected light rays from the sample surface to provide discrete slope measurements. Estimates of surface profiles are obtained with a cubic spline curve fitting algorithm. Experiments on a PZT bimorph illustrate appropriate deformation trends as a function of excitation voltage. A parallel effort to effect desired shape changes through electron gun excitation is also summarized. A one dimensional model-based algorithm is developed to correct profile errors in bimorph beams. A more useful two dimensional algorithm is also developed that relies on measured voltage-curvature sensitivities to provide corrective excitation profiles for the top and bottom surfaces of bimorph plates. The two algorithms are illustrated using finite element models of PZT bimorph structures subjected to arbitrary disturbances. Corrective excitation profiles that yield desired parabolic forms are computed, and are shown to provide the necessary corrective action.
Date: July 28, 1999
Creator: Redmond, James M.; Barney, Patrick S. & Henson, Tammy D.
Partner: UNT Libraries Government Documents Department

Energy changes in transforming solids. Final report, January 31, 1991--January 31, 1995

Description: The following topics are discussed: A new thermodynamical theory of continuum damage mechanics capable of incorporating non-isothermal processes and of providing explicit expressions for the thermal dissipation during damage evolution; the advancement of the methodology of heterogenization to analyze elastic bodies with defects; and investigations of bonded dissimilar piezoelectric half-spaces.
Date: April 3, 1995
Creator: Herrmann, G. & Barnett, D.M.
Partner: UNT Libraries Government Documents Department

Close-in Pressure and Shock Arrival Time Measurements. Final Report Project Scooter

Description: Project Scooter, a part of Operation Plowshare, was a 500-ton chemical explosive shot fired at the AEC Nevada Test Site. Personnel of Lawrence Radiation Laboratory undertook a program of measuring pressure-time histories and shock wave arrival times. Tourmaline piezoelectric transducers were used for both purposes. Only one instrument, located 49.4 feet from the center of the detonation, gave usable information. At this distance the shock wave arrived 11.2 plus or minus 0.4 msec after the X-unit signal, an the maximum pressure was 1.7 plus or minus 0.5 kilobars. (auth)
Date: September 1, 1961
Creator: Shearer, J. N.; Olson, R. G. & Krause, O. H.
Partner: UNT Libraries Government Documents Department

Measurement and calculation of PZT thin film longitudinal piezoelectric coefficients.

Description: The ferroelectric and piezoelectric properties of 2000 {angstrom} thick chemical solution deposited Pb(Zr{sub x}Ti{sub 1{minus}x})O{sub 3} (PZT) thin films were investigated. Several Zr/Ti ratios were studied: 30/70, 50/50 and 65/35, which correspond to tetragonal, near-morphotropic, and rhombohedral symmetries. In all samples, a {l_brace}111{r_brace}-texture is predominant. Longitudinal piezoelectric coefficients and their dc field dependence were measured using the contact AFM method. The expected trend of a maximum piezoelectric coefficient at or near to the MPB was not observed. The composition dependence was small, with the maximum d{sub 33} occurring in the tetragonal material. To explain the results, crystallographic texture and film thickness effects are suggested. Using a modified phenomenological approach, derived electrostrictive coefficients, and experimental data, d{sub 33} values were calculated. Qualitative agreement was observed between the measured and calculated coefficients. Justifications of modifications to the calculations are discussed.
Date: April 26, 1999
Creator: Christman, J. A.; Kim, S.-H.; Kingon, A. I.; Maiwa, H.; Maria, J.-P. & Streiffer, S. K.
Partner: UNT Libraries Government Documents Department

Characterizing the effects of friction liner materials on the performance of piezoelectric motors using finite element analysis

Description: A finite element model of a Panasonic USM-40D piezoelectric motor`s rotor was coupled with a finite element model of the motor`s friction liner/rotor so that the frictional interface could be further studied. Results from the model were used to study the affects of various friction liner material properties on motor stall torque. Statistical methods were used to determine the significant friction liner material properties and their interactions. An equation for predicting the stall torque as a function of the significant variables and their interactions was established.
Date: October 1, 1995
Creator: Gute, G.D. & Halter, S.L.
Partner: UNT Libraries Government Documents Department


Description: Military requirements for protective construction have in recent years included blast hardened designs. This often means putting the construction deep underground and sets up requirements for information on the behavior of blast waves in confined regions such as tunnels and chambers. The Shock Tube Facility at the Ballistic Research Laboratories (BRL) endeavored to obtain information on the behavior of blast waves in tunnels and chambers by instrumenting models of simple tunnel configurations with piezoelectric gages and subjecting the models to the blast wave from shock tubes. Data were obtained from models attached to the 24 in. circular tube, the 4 x 15 in. rectangular tube, and the high pressure tube. A compilation of the test results is presented. (auth)
Date: March 1, 1962
Partner: UNT Libraries Government Documents Department

Passive modal damping with piezoelectric shunts

Description: The use of piezoelectric materials in conjunction with passive inductance-resistance-capacitance (RLC) circuits to dampen specific vibration modes is explored. The piezoelectric materials convert mechanical energy to electrical energy, which is then dissipated in the RLC circuit through joule heating. An impulse is applied to a simple cantilevered beam and by varying the inductance and resistance values, the natural oscillation frequency fcir the RLC circuit is tuned to dampen the first mode of vibration.
Date: January 1, 2001
Creator: Granier, J. J. (John J.); Haundhausen, R. J. (R. Jason) & Gaytan, G. E. (Gabriel E.)
Partner: UNT Libraries Government Documents Department

Determination of equivalent circuit for PVDF shock-pressure gauges

Description: Broadband impedance measurements of a PVDF shock-pressure gauge are used to build an equivalent circuit for the gauge. The essential components are a gauge capacitance and a low-loss transmission line. Component features are consistent with the physical characteristics. With knowledge of this circuit, troublesome oscillations can be anticipated and prevented.
Date: July 1, 1993
Creator: Kotulski, J. D.; Anderson, M. U.; Brock, B. C.; Gomez, J.; Graham, R. A. & Vittitoe, C. N.
Partner: UNT Libraries Government Documents Department

The role of high pressure in the study and applications of the ferroelectric polymer polyvinylidene fluoride and its copolymers

Description: Effects of frequency, temperature and hydrostatic pressure on dielectric properties, molecular relaxations, and phase transitions of PVDF and a copolymer with 30 mol % trifluoroethylene are discussed. Pressure causes large slowing down of the {beta} molecular relaxations as well as large increases in the, ferroelectric transition temperatures and melting points, but the magnitudes of the effects are different for the different transitions. These effects can be understood in terms of pressure-induced hindrance of the molecular motions and/or reorientations. A unique application of these polymers as time-resolved dynamic stress gauges based on PVDF studies under very high pressure shock compression is discussed.
Date: August 1, 1994
Creator: Samara, G. A.; Graham, R. A. & Bauer, F.
Partner: UNT Libraries Government Documents Department

Stresses from flip-chip assembly and underfill; measurements with the ATC4.1 assembly test chip and analysis by finite element method

Description: The authors report the first measurements of in-situ flip-chip assembly mechanical stresses using a CMOS piezoresistive test chip repatterned with a fine pitch full area array. A special printed circuit board substrate was designed at Sandia and fabricated by the Hadco Corp. The flip-chip solder attach (FCA) and underfill was performed by a SEMATECH member company. The measured incremental stresses produced by the underfill are reported and discussed for several underfill materials used in this experiment. A FEM of a one-quarter section of the square assembly has been developed to compare with the measured as-assembled and underfill die surface stresses. The initial model utilized linear elastic constitutive models for the Si, solder, underfill, and PC board components. Detailed comparisons between theory and experiment are presented and discussed.
Date: December 31, 1996
Creator: Peterson, D.W.; Sweet, J.N.; Burchett, S.N. & Hsia, A.
Partner: UNT Libraries Government Documents Department