bluuebunny/crossref_metadata_2025 huggingface dataset:
Nuclear Power Plant Thermal Performance Improvement
Authors: Alder Greg C. , Todd Frank J.
Published: July 2009

With the combination of increased demand for electric power and advancing age of operating equipment in nuclear power plants, is more important than ever to monitor the condition of plant operation. There are many factors to monitor in nuclear power plant equipment condition. However, one that is frequently overlooked is thermal performance. Often this is an area where plant personnel can find “low hanging fruit” with great return on investment. Often thermal performance analysis can discover better methods to maintain critical plant equipment resulting in more efficient outage activities. Plants also benefit from increasing their operators’ awareness of the importance of thermal performance monitoring to find lost power generation. This paper will discuss proven methods to track, trend, and prioritize thermal performance issues in order to reduce the time from the occurrence of a loss to recovery.
Multi-Stage Centrifugal Compressors and Defining the Optimum Pressure Ratio According to Temperature Limitations
Authors: Hashemi Ehsan , Pezeshkpour Pegah
Published: July 2009

Multistaging is one of the conventional methods in centrifugal compressors to increase their efficiency and meet the process and material-related temperature limitations. Simple single-stage compressor pressure ratio is normally limited by constraints of both aerodynamic and structural types. Minimizing the total required gas head equation, resulting from summation of head for each stage, leads to the definition of pressure ratios of each stage which play an important role for required head determination. For minimum power with perfect inter-cooling between stages, there is a theoretical relation for the intake pressures of succeeding stages. As an assumption, both compression ratio and suction temperature is assumed constant in each stage. This assumption results in the mentioned identical magnitude for each stage pressure ratio. When the suction temperatures of gas leaving the intercoolers are different, assuming an identical pressure ratio for all stages, it increases the power required for compressing the gas up to the specified discharge pressure. A numerical method has been presented in this paper with the consideration of changes in suction temperature, compressibility factor, and poly-tropic efficiency. In conclusion it is shown that in order to optimize the power consumption for compressing the gas with specific properties, a numerical method can be used, so that the pressure ratio of the first stage compressor be higher than the successive stages as experimental results suggest.
Application of a Reliability Model to Gas Turbine Design
Authors: Engelbert Christian , Nilsson Mikael , Sutor Ariane , Montrone Francesco
Published: July 2009

The most important attribute of a product is quality. Quality influences the economics of an investment but also the economics of the manufacturer and can be a break point to the manufacturer’s prosperity. Consciously but often subconsciously quality is “just” expected and can therefore be seen as a straight measure of customer satisfaction — in the Kano-terminology quality is a “Must Have” parameter. In the power industry quality is generally being expressed and measured in RAMS (Reliability, Availability, Maintainability and Safety). For the development of new power generation equipment like gas turbines the targets are being laid out very early in the project. Since the development of gas turbine components can be a multi year undertaking it is paramount that the targets contain this element of future customer expectations. This ultimately drives the design team to challenge the technical boundaries — a gas turbine parameter that is satisfactory in today’s market environment might not be pleasing anymore in tomorrow’s changing environment. This is not only valid for the engines thermal performance but also for its reliability and availability. Siemens industrial gas turbines and components are therefore being developed with “Reliability Centered Design” in mind. This report describes the application of a predictive reliability engineering methodology to the development of new gas turbine components and how it influenced the design team’s decision making. The reliability analysis and prognosis is based on a predictive fault tree model with supporting Markov models to address consecutive failures or failure probabilities of stand by equipment. It has been validated with field data. While observation data retrieved from operational engines are being used for direct improvements of existing turbine designs the model based approach has its merits in supporting new designs by considering design or system alternatives. Further more it provides the sensitivities of the reliability of the gas turbine with respect to the components’ reliabilities. The model comprises the core engine but also the auxiliary systems within the package. This paper has been jointly prepared by the industrial gas turbine design team located in Lincoln (UK) and Finspa˚ng (Sweden) as well as Siemens reliability engineering team from Corporate Technology in Munich (Germany).
Performance Evaluation Using ASME Performance Test Codes
Authors: McHale Michael P. , Gerhart Philip , Korellis Sam J.
Published: July 2009

When faced with the question of “how well is this equipment performing and how can I improve its performance?” ASME Performance Test Codes (PTCs) can help guide us to an answer: ASME PTCs provide uniform rules and procedures for conducting and reporting tests of equipment and systems to evaluate plant and component performance.
Benefits of Conducting Periodic Critical Pump Hydraulic and Mechanical Performance Audits
Authors: Marchi John , Morgenstern Robert
Published: July 2009

The operability and efficiency of critical pumping equipment is essential. A cost-effective tool that has proven valuable in predictive and preventive maintenance and in the avoidance of unscheduled pumping equipment outages is a comprehensive program of periodic hydraulic and mechanical performance audits. This paper explains how hydraulic and mechanical field testing can be conducted without interrupting plant operations using non-intrusive measurement equipment including: ultrasonic flow measurements, vibration signature analysis, and for electric motor driven pumps, power and dielectric condition analysis. Methods and requirements to conduct the audits will be discussed and a case study with cost benefit analysis is presented. Pumps are basically energy transfer devices. The energy of the pump driver, e.g. electric motor, steam or gas turbine, reciprocating engine, is transferred into the pumpage to move it through the system at sufficient pressure to overcome system losses and meet process requirements. It is the efficient transference of the applied energy that is a critical consideration in pump design and operation. Efficiency of operation is of interest to everyone. The pump designer is motivated to maximize pump efficiency to remain competitive given the increasing cost of energy. However, the designer must not get overly zealous in the quest for pumping efficiency sacrificing reliability and durability. The end-user wants the most efficient pump with longest mean time between repair (MTBR) intervals to both reduce operating cost and minimizing production losses. With the reasons for maximizing pumping efficiencies and longer MTBR intervals established, the value of periodic in situ performance testing or auditing becomes an increasingly valuable and cost effective predictive and preventative maintenance tool.
Compact Diaphragm Turbine Technology and Its First Application in a Turbine Retrofit
Authors: Littlewood David M. , Hogg Simon I.
Published: July 2009

The merger between the Power Generation divisions of ABB and Alsthom in 1999, has resulted in the present day Alstom Steam Turbine Retrofit Business being the only supplier who can offer both impulse (disc and diaphragm) and reaction (drum rotor) turbine retrofit solutions across the entire product power range. The impulse and reaction turbine technologies both possess design features that are aimed at achieving the best evaluated performance for retrofit turbine solutions. Alstom has now combined service proven features from these two technologies to form the new Compact Diaphragm steam turbine technology. This will allow turbine retrofit design solutions to be optimised to levels beyond that possible with either of the contributing technologies. The Compact Diaphragm design features are described in this paper, together with the validation of the new technology. The first application entered service in June 2007 in the retrofitted HP cylinder of a G3 HP turbine in USA and is also described in this paper.
Measurement of Temperature Profile in Non-Premixed Turbulent Flame of Lean LPG/Air Mixture
Authors: Dhahad Hayder Abed
Published: July 2009

The current research was carried out on the topic of non-Premixed turbulent flames. The temperature profile of non-premixed turbulent flame of lean L P G- Air mixture (φ = 0.66) were obtained. A simple type of Bunsen burner with two different inside diameter and having two different perforated plates was designed in order to achieve turbulent flow. The temperature was obtained at the two diameters and different positions for perforated plates. The temperature profiles were obtained by using a fine thermocouple at height (3mm) above the burner mouth. The maximum temperature for all cases was found at flame adge, and start decreasing for both sides.
A Hydroelectric Plant Simulation Model to Test the Performance of Actual Governor Control Systems
Authors: Galindo-Garci´a Iva´n F. , Tavira-Mondrago´n Antonio , Rodri´guez-Lozano Sau´l
Published: July 2009

A simulation model of the hydraulic system of a hydroelectric power plant is developed and implemented in a real time simulator. The main purpose of the simulator is to test the performance of actual governor control systems using hardware-in-the-loop techniques, in which the actual governor control system is connected to a real time simulator instead of being connected to real equipment. This paper focuses on the modeling of the hydraulic system to be implemented in the simulator. The model consists of an unrestricted reservoir, conduits to transport water, and a turbine to convert the potential energy of the fluid into mechanical power. A nonlinear mathematical model for a non-elastic water column is implemented. Effects due to a surge tank and to various turbines connected to a common tunnel are included in the model by considering head and flow variations at the junction of the common tunnel and the individual penstocks. The model is evaluated by comparing results from simulations with field tests from a four-unit hydroelectric power plant (55 MW per unit). Comparisons show that the model reproduces the general behavior of the field tests. However some deviations are observed during the transient response, in particular the simulation results appear to respond faster than field data.
Design Considerations for High Speed Direct Drive Turbine Generators
Authors: Herbst John D. , Gattozzi Angelo L. , Wardell Douglas R. , Liu Hsing P. , Murphy Brian T.
Published: July 2009

The University of Texas at Austin Center for Electromechanics (UT-CEM) conducted development and testing of a 3 MW high speed generator and turbine drive system for a hybrid vehicle propulsion system as a part of the Advanced Locomotive Propulsion System (ALPS) Program [1]. Several critical design issues were identified that apply to high speed wound field synchronous generators and turbine drive systems. The focus of the paper is directed to the more aggressive designs that, like ALPS, are intended to maximize the power density of the turbine/generator package. Design issues addressed by the paper include: • Thermal management for the armature and field windings; • Structural support and insulation of the rotating field winding; • Design of the brushless exciter and rotating diode array; • Design of the rotor bearings, seals, and dampers; • System dynamic response to sudden load changes. The results of trade studies for selection of the generator technology (wound field, permanent magnet, high temperature superconducting) will also be presented to identify key size/weight and cost drivers in the design process. Lessons learned during the fabrication, assembly, and testing of the ALPS generator will be discussed in this paper, in particular, issues concerning the high pressure stator air cooling system, improvements to the field winding insulation, and field coil installation techniques will be addressed. A companion paper will present the results of testing the high-speed generator and turbine drive system to a 1.5 MW power level at NAVSEA (Philadelphia, PA) and UT-CEM with a fixed resistive load.
Wheel Spalling Literature Review
Authors: Cummings Scott M. , Lonsdale Cameron P.
Published: July 2009

As a means of determining the conditions under which a patch of martensite (and eventually a spall) is formed on a wheel tread, the Wheel Defect Prevention Research Consortium (WDPRC) has conducted a review of wheel slide test reports and analytical models for the prediction of contact patch temperature due to wheel slide. The relative merits of the analytical models are discussed and applied to the known/assumed conditions, i.e., speed, axle load, and wheel/rail coefficients of friction (COF) for each of the wheel slide tests. The accuracy of the analytical models is evaluated with respect to test data under a variety of conditions from multiple sources. After selecting the most appropriate analytical model, wheel slide temperature predictions are given for empty cars at a variety of speeds and wheel/rail COF levels. It is concluded that the potential exists to create martensite on sliding wheels with almost any realistic combination of axle load, wheel slide duration, train speed, and wheel/rail adhesion level. Additionally, sources of wheel spalling are discussed with a focus on misapplied hand brakes and malfunctioning air brake systems. Multiple authors noted the presence of tread damage on one wheel of a wheelset with no damage at the corresponding circumferential location of the mate wheel. The accompanying theories to explain this seemingly counterintuitive finding are restated in this literature review. At the end of the paper, the actions of the WDPRC to reduce wheel spalling are briefly outlined.
On the Crashworthiness Performance of the New GTW DMU Developed for Capital Metro (Austin, Texas)
Authors: Starlinger Alois , Castelli Benedetto , Gmu¨r Andreas
Published: July 2009

Stadler Rail has developed a new regional train, the Stadler GTW (‘Gelenk-Trieb-Wagen’, i.e., Articulated Powered Car) for Capital Metro, Austin, Texas. This DMU is compliant with the requests of EN15227, the new European standard for crashworthiness of railway vehicles. The following collision scenarios have been investigated: • train against identical train at a closing speed of 36 kmph (22 mph); • train against 80-ton-freight wagon at a closing speed of 36 kmph (22 mph), and • train against a large deformable obstacle (representing a truck) at a closing speed of 85 kmph (53 mph). Numerical analyses show that the new crashworthy train design guarantees sufficient and controlled energy absorption and maintains the survival space required. Dynamic testing of the crash absorber modules has validated the results of the nonlinear analyses. In the course of the certification process with the FRA additional requirements have been imposed for the dynamic qualification of cab car end structures: :These scenarios consist of a collision at a closing speed of 21 mph (34 kmph) with a rigid cylinder (diameter of 48 inches (1220 mm), length of 36 inches (914 mm) and a minimum weight of 10000 lbf (4535 kg). These requirements have been easily met. Additionally, new FRA proposals have been investigated: • collisions with a steel coil in different front positions; • collision with a rigid wall at a closing speed of 56 kmph (35 mph); • front end collision with a representative FRA compliant locomotive at a closing speed of 56 kmph (35 mph). The numerical analyses of these scenarios show that the crashworthy train design which has been developed to comply with the European requests is able to fulfill the FRA requirements.
A Dynamic Test of a Collision Post of a State-of-the-Art End Frame Design
Authors: Priante Michelle , Llana Patricia , Jacobsen Karina , Tyrell David , Perlman Benjamin
Published: July 2009

In support of the Federal Railroad Administration’s (FRA) Railroad Equipment Safety Program, a full-scale dynamic test of a collision post of a state-of-the-art (SOA) end frame was conducted on April 16, 2008. The purpose of the test was to evaluate the dynamic method for demonstrating energy absorption and graceful deformation of a collision post. The post aims to protect the operators and passengers in the event of a collision where only the superstructure, not the underframe, is loaded. Methods for improving the performance of collision and corner posts were prompted by accidents such as the fatal collision in Portage, Indiana in 1998, where a coil of steel sheet metal penetrated the cab car through the collision post. The improvements made for the SOA end frame structure include more substantial corner and collision posts, robust post connections to the buffer beam and anti-telescoping (AT) beam, and corner and collision posts integrated with a shelf and bulkhead sheet. Full length side sills improved support for the end frame. This test focused on one collision post because of its critical position in protecting the operator and passengers in an impact with an object at a grade-crossing. For the test, a 14,000-lb cart impacted a standing cab car at a speed of 18.7 mph. The cart had a rigid coil shape mounted on the leading end that concentrated the impact load on the collision post. The requirements for protecting the operator’s space state that there will be no more than 10 inches of longitudinal crush and none of the attachments of any of the structural members separate. During the test, the collision post deformed approximately 7.4 inches and absorbed approximately 138,000 ft-lb of energy. The attachment between the post and the AT beam remained intact. The connection between the post and the buffer beam did not completely separate, however the forward flange and both side webs fractured. The post itself did not completely fail. There was material failure in the back and the sides of the post at the impact location. Overall, the end frame was successful in absorbing energy and preserving space for the operators and the passengers.
An Interpretive Literature Review of Wheel Shelling
Authors: Stone Daniel
Published: July 2009

The loss of relatively large pieces of wheel tread material has been described as shelling or spalling. For the purposes of this paper shelling will be defined as loss of material from the action of rolling contact fatigue. The mechanism and characteristics of spalling has been presented in an earlier interpretive literature review. Shell cracks initiate at the near surface or surface of the wheel and grow inward. The cracks grow at an approximate 45° angle to the tread surface by shear as shown in figure 1. It appears that the shell forms due to shear failure along flow lines from to normal metal flow due to repeated rolling contact.
Evaluation of Emissions and Performance of Diesel Locomotives With B20 Biodiesel Blends: Static Test Results
Authors: McKenna David , Bhatia Krishan , Hesketh Robert , Rowen Christopher , Vaughn Timothy , Marchese Anthony J. , Chipko George , Guran Serpil
Published: July 2009

This paper describes the results to date of a study to quantify the exhaust emissions and performance characteristics of 20% soy methyl ester biodiesel blends (B20) in diesel locomotives representative of a typical commuter transit fleet. Testing is performed with #2 diesel summer blend, #2 diesel winter blend, ultra low sulfur diesel (ULSD) summer blend, ULSD winter blend and B20 blends with each of these fuels. Tests are performed on two different diesel locomotive types to determine the differences in performance and emissions between older and newer locomotive engines when operating on biodiesel blends. Specifically, tests are performed on a GP40FH-2 locomotive equipped with an EMD 16-645 engine manufactured from a 1960’s design and a recently manufactured ALSTOM PL42AC locomotive equipped with an EMD 16-710 engine. The tests are being performed in two phases. The first phase of the project is performed by operating the diesel engines statically (using a load bank) over the full test matrix of 8 fuels. During the static testing phase, brake specific exhaust emissions and fuel consumption are computed for each fuel blend using the line-haul and switcher duty cycles as outlined in the CFR Part 40 Title 92 Federal Test Procedure. Each fuel/locomotive test combination is performed 3 times to ensure repeatability. The second phase of the project consists of mobile in-use emissions testing using a simulated, mobile duty cycle based on actual commuter rail routes. To accurately quantify the exhaust emissions, measurements are made using a Sensors SEMTECH-D mobile emissions analyzer to measure CO, CO2, NO2, NO, O2, and total unburned hydrocarbons (HCs), along with a Wager 6500RR Railroad Opacity Meter. Instantaneous fuel consumption is monitored using two AW Company JV-KG positive displacement flow meters, which measure the supply and return fuel flow rate, respectively.
Orientation Dependence on Electro-Mechanical Coupling Behavior of 1-3 Piezoelectric Composites Under Compression
Authors: Zhao Ping , Li Jackie
Published: July 2009

The nonlinear electro-mechanical behavior of 1–3 piezoelectric composites with PZT5A1 fibers embedded in an epoxy matrix are studied under multi-axial mechanical loading. In order to evaluate the orientation effects of the polarization in PZT fibers to the overall performance of the ferroelectric composite system, the direction of the applied compressive loading is oriented by an angle of θ toward to the PZT fiber direction which is also the polarization direction. The non-linear responses in stress-strain and stress-electric displacement were measured at given loading angle θ. A two-level micromechanics theory based on irreversible thermodynamics and physics of domain switch is applied to compare with our experimental data. The theoretical results are found to be in good qualitative and quantitative agreement with our experimental data.
Structural Composite Capacitors, Supercapacitors, and Batteries for U.S. Army Applications
Authors: Snyder James F. , O’Brien Daniel J. , Baechle Daniel M. , Mattson Daniel E. , Wetzel Eric D.
Published: July 2009

Structural capacitors, supercapacitors, and batteries are fabricated and tested, using modified materials and processes based on conventional fiber-reinforced polymer matrix composites. Printed circuit board prepregs are used to create structural capacitors that demonstrate good dielectric energy density and mechanical stiffness and strength. Structural supercapacitors are created using carbon fabric electrodes and a liquid-plasticized, epoxy polymer electrolyte. A similar construction is used to create structural batteries, by substituting LiFePO4-coated carbon fiber fabric as cathodes opposed to unmodified carbon fiber anodes. Structural batteries and supercapacitors show basic electrochemical and mechanical functionality. However, significant additional work is required to improve their quantitative performance to values of practical engineering value.
Hysteretic Dynamics of Ferroelectric Materials Under Electro-Mechanical Loadings
Authors: Wang Linxiang
Published: July 2009

In the current paper, the hysteretic dynamics of ferroelectric materials under combined electro-mechanical loadings is investigated using a macroscopic differential model. The model is constructed on the basis of the Landau theory of the first order phase transformations. Hysteresis loops in the electric field and the butterfly-shaped behaviors in the electro-mechanical coupling are modeled as a consequence of polarizations and orientation switchings, together with nonlinear electro-mechanical coupling effects. The effects of bias stress on the orientation switchings are investigated numerically. Comparison of the model results with its experimental counterparts is presented, capability of the model is approved.
Multiscale Modeling of Light Activated Shape Memory Polymer
Authors: Beblo Richard , Weiland Lisa Mauck
Published: July 2009

Presented is the development of a multi-scale model predicting the material response of a light activated shape memory polymer. Rotational Isomeric State (RIS) theory is used to build a molecular scale model of the polymer chain backbone, tracking the distances between cross-links. Cross-link to cross-link distances are then used with Boltzmann statistical mechanics to predict material response, generating Young’s modulus and stress-strain relation predictions. Young’s modulus is predicted by the model to be 0.049 and 3.2 MPa for the soft and hard states of the polymer respectively. Experimentally determined properties are also presented with reported moduli of 2.0 and 11.4 MPa in the soft and hard states respectively.
Analysis of Microstructure Evolution During Tensile Stress Induced Martensitic Transformations
Authors: Peng C. , Yan Y. , Wang X. Y. , Huo Y. Z.
Published: July 2009

An image analysis technique was employed to document the layered parallel microstructures observed during tensile tests of CuAlNi single crystal shape memory alloys. The evolution of the microstructures during the stress induced martensitic transformation can be then well studied quantitatively by the evolution of the phase character function and its suitable averages. The results indicated clearly that the stress induced martensite transformation should consist three periods, initial formation, mixed formation and growth, merging due to growth. Euler-Lagrange equations for the minimizers of some one-dimensional energy functional were also studied for two types of two-well strain energy functions, the piecewise quadratic energy function and a smooth polynomial. The cell exclusive genetic algorithm was adapted to solve the nonlinear algebraic equations in the first case. The homotopy analysis method was used in the second case to find accurate series solutions. Multi-interface microstructures were obtained in both cases. The methods, especially the homotopy analysis seemed to be quite powerful to solve the nonlinear equations even with large number of interfaces.
A Variational Model of Ferroelectric Microstructure
Authors: Huber J. E. , Cocks A. C. F.
Published: July 2009

A simple model of the evolution of ferroelectric microstructure in single crystals is developed by using variational methods to minimize a functional based on free energy and dissipation. The thermodynamic variables in this formulation correspond to the positions of a set of domain walls within a single ferroelectric crystal. The total dissipation rate is taken to be a function of the velocities of the individual domain walls. With only two-degrees of freedom, a model of this type has sufficient richness to reproduce many of the observed features found in the single crystal response of a tetragonal ferroelectric. This includes the dielectric hysteresis, butterfly hysteresis, and the variation of the hysteresis loops under uniaxial compressive stress. Additional degrees of freedom can be used to capture multi-axiality. The model also highlights the marked differences in response that should occur when a single crystal is subjected to different boundary conditions.
Modeling of the Electromechanical Response of Ionic Polymer Transducers by Means of Streaming Potential Mechanism
Authors: Gao Fei , Weiland Lisa M.
Published: July 2009

A model for the electromechanical sensing response of ionic polymer transducers (IPTs) by means of a streaming potential mechanism is presented. It is argued that incomplete pairing of covalently attached pendant ionic groups with their electro-neutralizing counterions establishes the existence of a flowing electrolyte within the ionic polymer. This electrolyte exists in the hydrophilic phase of the otherwise hydrophobic material. The streaming potential is generated as the electrolyte flows past electroded regions interspersed within the hydrophobic phase. The model is developed for a recently argued parallel nanochannel morphology in Nafion® membrane, but is applicable to any two-phase ionic polymer morphology. Further, while this preliminary study considers only the bending mode, the proposed mechanism is readily adaptable to the other three modes of sensing (tension, compression, and shear).
Intrinsic Position Sensing of a Ni-Mn-Ga Microactuator
Authors: Auernhammer Daniel , Kohl Manfred , Krevet Berthold , Ohtsuka Makoto
Published: July 2009

This paper presents an investigation of the intrinsic magnetoresistance of a ferromagnetic shape memory alloy (FSMA) microactuator for position sensing. The microactuator is designed as a double-beam cantilever of a polycrystalline Ni-Mn-Ga thin film, which exhibits both, a martensitic transformation in the temperature range 333–359 K and a ferromagnetic transition at about 370 K. The microactuator is placed in the inhomogeneous magnetic field of a miniature Nd-Fe-B magnet causing a mixed thermo-magneto-resistance effect upon actuation. The maximum in-plane magnetic field is about 0.38 Tesla. In this case, the maximum magnetoresistance (MR) is 0.19%.
Polarization-Free Straining of Barium Titanate Single Crystals
Authors: Shieh Jay , Shu Yi-Chung , Lin Jhe-An
Published: July 2009

Large strain actuation in (001)-oriented barium titanate (BaTiO3) single crystals subjected to combined uniaxial stress and electric field is examined. The hysteresis evolution of the crystal under combined electromechanical loading reveals incomplete switching characteristics and a considerable disproportion of slope gradients at zero electric field for the measured polarization and strain hysteresis curves. A likely cause for the disproportion of slope gradients is the cooperative operation of multiple 90° switching systems by which “polarization-free” strain changes are induced. An in-situ domain observation study reveals the formation of bubble-like micro-domains prior to the macroscopic 90° switching of the crystal bulk. The presence of these bubble-like “switching weak points” indicates that regions within the crystal do not necessarily switch 90° at the same time, and hence, in a way, supports the existence of multiple 90° switching systems. The hysteresis evolution of the crystal is investigated again at 55 °C under identical electromechanical loading conditions. At a temperature higher than room temperature, the degree of discrepancy between the slope gradients at zero electric field for the measured polarization and strain hysteresis curves is significantly reduced. This is due to the increase in domain wall mobility, lowering the extent of incomplete switching at maximum electric field.
Control of Structural Flutter Using Piezoelectric Patches
Authors: Hariri M. , John S. , Trivailo P.
Published: July 2009

Aero-elasticity is a major concern in aerospace field. It resultes from the interaction between the air-stream and the structure. Wing flutter is a well known problem of the aero-elasticity. It which occurs when the two lowest system eigenvalues (plunge and pitch motion) coalesce at a certain air speed known as the flutter speed. The increasing use of active material induced-strain actuation such as piezoelectric materials in suppression of structural vibrations has seen its extension to wing flutter control. Higher flutter speed and hence, a wider operating envelope was achieved by delaying the coalescence of these two eigenvalues. This delaying is obtained by adding more strain energy to the system as a result of the activation of the piezoelectric actuators. This paper models a simple beam under nominal aerodynamic loading conditions for the determination of analytically-derived onset of flutter speeds. Also shown in this paper is the effect of orientation of actuated piezoelectric patches on the shift of the flutter speed.
Load-Induced Martensitic Transformations in Pseudo-Elastic Lennard-Jones Crystals
Authors: Kastner Oliver , Ackland Graeme J.
Published: July 2009

We present molecular dynamics (MD) simulations of a load-induced martensitic phase transformation in pseudo-elastic Lennard-Jones crystals. The model material exhibits martensitic transformations between cubic and hexagonal lattice structures in 2D which represent austenite and martensite. Under axial loading two martensite variants are favoured out of four generic variants possible with this model. In nucleation-and-growth processes the formation of martensite domains are observed in MD simulations and the reverse process upon unloading. Two possible re-transformation mechanisms are identified, a reversible and a reconstructive type. Reversible re-transformations conserve the reference unit cells, while the reconstructive mechanism involves the generation of dislocation motions which destroy the reference unit cells by slip. Both types re-establish the square lattice. While the reversible type represents the predominant reverse transformation mechanism, the reconstructive type is of special importance because it produces lattice defects, and plastic deformation which change both the evolution of subsequent transformation cycles and the magnitude of the phase transformation load.
Piezohydraulic Actuation for Next Generation Microjet Flow Control
Authors: Liu Fei , Oates William S.
Published: July 2009

This paper describes the development of a new piezohydraulic actuator for integration into a microjet flow control device. The actuator utilizes a lead zirconate titanate (PZT) stack actuator and a hydraulic amplification design to achieve relatively large displacements required to control flow through a microjet. Displacement amplification of 81 times the stack actuator displacement was achieved using a dual-diaphragm design that seals the fluid within the device. The nonlinear field-coupled structural dynamics and fluid behavior of the actuator is predicted using a system dynamic model and compared with experimental results. It is shown that minor loop hysteresis of the piezoelectric stack actuator and nonlinear deformation of the diaphragm play an important role in the piezohydraulic displacement amplification.
Energy Harvesting From Pneumatic Tires Using Piezoelectric Transducers
Authors: Khameneifar Farbod , Arzanpour Siamak
Published: July 2009

The concept of harvesting energy in our surrounding has recently drawn global attention. Harvesting the ambient energy of the deflected tire and convert it to electricity is discussed in this paper. An Elastic pneumatic tire deflects due to the load it carries. This deflection appears as a contact patch to the road surface. Initially, the concept of the tire deflection will be discussed. This deflection is then related to the wasted energy used for deflection. The dependency of this energy to some important parameters such as the tire air pressure, vehicle speed and tire geometry and forces are primarily discussed. To harvest the deflection energy different well established methods are exists. Due to the tire environment, piezoelectric transducers can serve as the best option. Those transducers are traditionally used to produce mechanical motion due to the applied electrical charges. This material is also capable of generating electrical charges by mechanical motion and deflections. For the tire energy harvesting application, the piezoelectric stacks can be mounted inside a tire structure such that electric charge is generated therein as the wheel assembly moves along a ground surface. For this application, lead-zirconate-titanate (PZT) is selected. The PZT inside the tire is modeled as a cantilever beam vibration in its first mode of vibration. The frequency of vibration is calculated based on the car speed, tire size, and PZT stack length. A mathematical model for this energy harvesting application is derived. Based on this model, the optimum load of the electrical circuit is also found. Finally the amount of energy harvested from tire using PZT is calculated. Although this energy is not significantly high, it will be enough to provide power for wireless sensors applications.
Multifunctional Airframe Structure for Energy Storage Using a Load Bearing Coaxial Capacitor
Authors: Baron William , Zeppettella David
Published: July 2009

Future directed energy systems may offer affordable, sustainable and scalable application of force to support emerging airborne missions with minimal collateral damage. These systems largely depend on the development of capacitors that can be used in pulse forming networks (PFNs) and/or Marx bank configurations for the conversion of available prime electrical energy into the necessary short and very fast pulses of energy needed to energize military device loads. Such loads may be lasers, electromagnetic guns/launchers, high power microwaves, etc. Compact, lightweight, low cost, pulse power capacitor devices are a necessity for airborne applications and space-borne systems. This paper will discuss research aspects of an innovative concept to integrate an energy storage function into load bearing airframe structure, in order to eliminate much of the parasitic weight associated with conventional pulse power systems. Current high energy capacitors can weigh in the thousands of pounds as shown in Figure 1. For an airborne application this can have a significant effect on the size and take off gross weight of the aircraft. If small aircraft will be used in future directed energy systems, significant improvements in weight efficiency are necessary. Structural capacitor implies that the aircraft/spacecraft structure carries load and also provides a means of maintaining capacitive charge for energy storage and power conditioning in a variety of applications, both pulsed and continuous. The specific objective of this effort is to demonstrate feasibility of a plausible design concept, by conducting a series of experimental trials to characterize the structural and electrical efficiency of the concept.
Investigation of the Behavior of Multilayer Piezoelectric Actuators: Modeling and Experiments
Authors: Gru¨nbichler Hannes , Kreith Josef , Bermejo Rau´l , Supancic Peter , Danzer Robert
Published: July 2009

Modern smart piezoelectrics such as low-voltage multilayer piezoelectric actuators consist of stacks of piezo-ceramic layers with interdigitated metallic electrodes in between. During their technical application mechanical stresses are an inherent loading scenario of such electro-mechanical converter components. Therefore, a detailed knowledge of the coupled phenomena among the field-type quantities such as mechanical stress, electrical field strength and temperature is absolutely necessary to guarantee demanded structural and functional integrity. A theoretical simulation is the only way to obtain these physical relevant field-quantities within piezo-electric devices. Hence, for FE-analysis of the highly nonlinear material behavior of piezoelectrics, basic modeling parameters have to be determined. Usually, such constitutive laws implemented into FEA-tools are parameterized by experiments as realized in this work.
Response of Optical Fiber Bragg Sensors With a Thin Film Shape Memory Alloy Coating
Authors: Mohanchadra K. P. , Emmons Michael C. , Karnani Sunny , Carman Gregory P. , Richards W. Lance
Published: July 2009

This paper describes the sputter deposition and characterization of nickel titanium (NiTi) shape memory alloy thin film onto the surface of an optical fiber Bragg sensor. The NiTi coating uniformity, crystallinity and transformation temperatures are measured using scanning electron microsocopy, x-ray diffraction and differential scanning calorimetry respectively. The strain in the optical fiber is measured using centroid calculation of wavelength shifts. Results show distinct and abrupt changes in the optical fiber signal with the four related transformation temperatures represented by the austenite-martensite forward and reverse phase transformations. These tests demonstrate a coupling present between optical energy and thermal energy, i.e. a modified multiferroic material.
Optimum Discrete Location of Shape Memory Alloy Wire for Enhanced Actuation of Slender Fixed-Free Beam
Authors: Banerjee A. , Badothiya J. , Bhattacharya B. , Mallik A. K.
Published: July 2009

Shape memory alloy (SMA) wires are capable of exerting large force and undergoing large recoverable strain. These capabilities render them suitable for being used as actuators. SMA wires are either embedded within the structure, as in a composite Choi et.al. [1], or can be placed discretely Chaudhry et.al. [2]. The advantage of discrete actuation is that, depending upon the offset provided between the structure and the wire, the actuating moment can be controlled. More the offset, higher is the actuating moment. But simultaneously the displacement requirement of the SMA wire increases with increasing offset. Depending on the nonlinear force-displacement characteristics of SMA and the flexural stiffness of the structure, there is an optimum value of the offset for which the maximum actuation of the structure can be achieved for a given input. In this paper large deflection of a cantilever beam actuated through SMA wire with varying offset has been analyzed. The results reveal the existence of an optimum offset yielding more than 100% increment in the end deflection in comparison to the minimum offset position. The value of the optimum offset depends on the flexural stiffness of the beam, SMA wire properties and the input actuation level. Experimental results obtained from beams of different stiffness actuated with a particular SMA wire validate the theoretical prediction.
Pumping Performance of a Valveless Micropump Using Three-Dimensional Electro-Fluid-Structural Interaction Simulation
Authors: Phan Van Phuoc , Goo Nam Seo , Han Cheol Heui
Published: July 2009

In this study, the pumping performance of a piezoelectric valveless micropump is simulated. The micropump, which was developed in the previous work, is composed of a four-layer lightweight piezocomposite actuator, a polydimethylsiloxane (PDMS) pump chamber, and two diffusers. The piezoelectric domain, the structural domain and the fluid domain are coupled in the three-dimensional simulation. For structural part, we used ANSYS. The fluid flow simulation is done with ANSYS CFX. The water flow rates are numerically predicted for geometric parameters of the micropump such as diffuser length and diffuser angle. The simulation is also verified with the experiment and the simulation results are acceptable for predicting the pumping performance.
Airfoil Morphing Architecture Based on Shape Memory Alloys
Authors: Barbarino Silvestro , Pecora Rosario , Lecce Leonardo , Concilio Antonio , Ameduri Salvatore
Published: July 2009

The adaptive structures concept is of great interest in the aeronautical field because of the several benefits which can be accomplished in the design of future aircraft. Improvements in terms of aerodynamic efficiency, aero-elastic behaviour and manoeuvrability were proved by many international studies. The development of new structural architectures implementing and integrating innovative materials is mandatory for succeeding in these critical tasks. The so-called Smart Structure idea is more and more taken into account in aerospace applications Among the family of Smart Materials, Shape Memory Alloys (SMAs) certainly represents a convenient solution for many static applications. In this work, an application for a morphing wing trailing edge is presented as alternative for conventional flap devices. A compliant rib structure has been designed, based on SMA components working both as actuators, controlling wing chamber, and as structural elements, sustaining external aerodynamic loads. Achievable performance has been estimated by a FE approach; SMA behaviour has been modelled through a dedicated routine implementing the Liang & Rogers’ model for evaluating the internal stress and the minimum temperature necessary for activation. The numerical results have been presented in terms of induced displacements and morphed shape.
Magnetostrictive Alloy Actuator for a Bone Transport Device
Authors: Hutapea Parsaoran
Published: July 2009

The ultimate goal of our research is to develop a bone transport device using a magnetostrictive alloy actuation system. The device is designed to be subcutaneously mounted on the periosteal surface of the tibia. The magnetomechanical behavior of Terfenol-D smart magnetostrictive material has been well investigated in the literature when a magnetic field is applied along the longitudinal direction of the Terfenol-D material (perpendicular to the material’s magnetic moment). However, the requirement of our device is to have the magnetic field transversely applied on the Terfenol-D material (along the material’s magnetic moment). Therefore, the objective of this work was to study the magnetomechanical behavior of Terfenol-D under a transversely applied magnetic field. Experimental work was performed and a Terfenol-D material constitutive behavior was investigated.
Surface Segregation of Sulfur and Its Effect on Surface-Energy-Induced Selective Grain Growth in Magnetostrictive Fe-Ga-B Alloy
Authors: Na Suok-Min , Flatau Alison B.
Published: July 2009

The surface-energy-induced selective grain growth with a specific plane can be governed in polycrystalline Fe-Ga-B alloys doped with sulfur. The segregated sulfur during texture annealing played an important role in controlling the surface energy to induce the selective growth of {100} or {110} grains, corresponding to maximum magnetostrictive performance, along <001> orientation with respect to rolling direction. The results show that sulfur diffuses (adsorbs) from bulk interior (sulfur atmosphere) then segregates on the surface. The amount of segregated sulfur increases with an increase of annealing time at the temperature of 1200°C. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) data on the surface as well as selective development of {100}<001> and {110}<001> preferred textures are presented in this work. The XPS fitted peaks of S 2p3/2 at binding energy of 161.2 and 163.2 eV for annealed Fe-Ga-B doped with sulfur represent the presence of stoichiometric FeS and FeSn (polysulfide), respectively. For all of the sulfur-free Fe-Ga-B sheets annealed in the ampoule with sulfur element, XPS indicated contributions centered at approximately 161.7 (S 2p) that has been assigned to iron sulfide as well. The presence of FeS was clearly confirmed by XRD patterns and XPS fitted peak positions at 161.5 eV (S 2p3/2) and 710.2 eV (Fe 2p3/2). The segregation of sulfur and boron during annealing were also confirmed by AES depth profile results, which exhibited peak concentrations of 10 at.%S and 20 at.%B at the surface, respectively. The peak magnetostriction of 201 ppm was obtained at annealed (Fe81.3Ga18.7)99B1 alloy with near {100}<001> orientation under sulfur atmosphere containing the amounts of 6.4 mg S. On the other hand, the texture of sulfur-free Fe-Ga-B alloy was close to {110}<001> after annealing at 1200°C for 6h under flowing argon, corresponding to the magnetostriction of 160 ppm.