bluuebunny/crossref_metadata_2025 huggingface dataset:
A Method to Characterize Cyclic Error in the Track Geometry Waveform
Authors: Chrismer Steven M. , Wnek Jonathan M.
Published: February 2012

A method [1] has been found to identify the presence of multiple cycles of harmonic error within track geometry measurement waveforms. This cyclic track geometry error can produce a buildup of resonant motion in vehicles, but may not be readily apparent from viewing the geometry error because it is often masked by the complexity of the waveform. However, due to the resulting large accelerations and poor ride quality, the dynamic rail vehicle response to the cyclic error will be unmistakable when the wavelength is at or close to a resonant frequency of the car body. Cyclic geometry error usually is unobserved and left uncorrected by maintenance because the associated mid-chord offset geometry error is typically far less than the safety limit per FRA. However, by using a band-pass filtering function on profile and alignment space curve data from the Amtrak geometry car, the presence and magnitude of any cyclic error becomes apparent. Further, it was found that shortcomings in the software used to calculate instructions for the tamper limit the effectiveness of tampers to remove the longer wavelengths commonly associated with this cyclic error. Therefore, improved methods to surface track with longer wavelength error are also being investigated.
Statistical Safe Braking Analysis
Authors: Thurston David F.
Published: February 2012

The main objective in optimizing train control is to eliminate the waist associated with classical design where train separation is determined through the use of “worst case” assumptions that are invariant to the system. In fact, the worst case approach has been in place since the beginning of train control systems. Worst case takes the most conservative approach to the determination of train stopping distance, which is the basis for design of virtually all train control. This leads to stopping distances that could be far more that actually required under the circumstances at the time the train is attempting to brake. Modern train control systems are designed to separate trains in order to provide safety of operation while increasing throughput. Calculations for the minimum distance that separates trains have traditionally been based on the sum of a series of worst case scenarios. The implication was that no train could ever exceed this distance in stopping. This distance is called Safe Braking Distance (SBD). SBD has always been calculated by static parameters that were assumed to be invariant. This is, however, not the case. Parameters such as adhesion, acceleration, weight, and reaction vary over time, location or velocity. Since the worst case is always used in the calculation, inefficiencies result in this methodology which causes degradation in capacity and throughput. This is also true when mixed traffic with different stopping characteristics are present at the same time. The classic theory in train control utilizes a SBD model to describe the characteristics of a stopping train. Since knowledge of these conditions is not known, poor conditions are assumed. A new concept in train control utilizes statistical analysis and estimation to provide knowledge of the conditions. Trains operating along the line utilize these techniques to understand inputs into their SBD calculation. This provides for a SBD calculation on board the train that is the shortest possible that maintains the required level of safety. The new SBD is a prime determinant in systems capacity. Therefore by optimizing SBD as describes, system capacity is also optimized. The system continuously adjusts to changing conditions.
Consistent and Repeatable Property and Residual Stress Control in Forged and Heat Treated Railway Wheels
Authors: Galbraith Jay , Ames George , Leister Scott
Published: February 2012

Consistent process control of wheel hardness and residual stresses developed during heat treatment are particularly important considerations for service life and safety of railway wheels. This paper details the process controls strategically located throughout an integrated, fully automated heat treatment system that can heat treat up to 65 railway wheels per hour. New, innovative technology such as in-line temperature measurements that control key process steps, uniform wheel heating and cooling, and quench water temperature and pressure control have resulted in wheel hardness and residual stress values with less statistical variation than older, traditional heat treat methods. Automatic serial number tracking and temperature measurement allow for statistical analysis of heat treat processes. Two years after the commissioning of this $18M facility, the quality and productivity benefits realized are discussed.
Case Studies Examining High Speed Rail Station Location Decisions From an International Perspective
Authors: Huang Jade , Morgan Curtis
Published: February 2012

As U.S. states are planning and designing for future nationwide and regional high-speed rail (HSR) services, an important issue to consider is where to locate stations. Station location determination is critical not only because it influences the perceived utility of the HSR services and can greatly influence ridership, but also due to its impact upon the local and regional transportation mobility, land use, and urban economic development. The main purpose of this paper is to provide information to HSR planners, engineers, and decision-makers in the U.S. on the practices of other countries in locating HSR stations. This paper examines HSR stations in several of the earliest countries which built HSR infrastructures: France, Spain, and Japan, to analyze how HSR station locations were selected, as well as the applicability of those methodologies in the planning process for the United States.
Full Scale Tank Car Rollover Test—Survivability of Top Fittings and Top Fittings Protective Structure
Authors: Trent Robert S. , Prabhakaran Anand , Gonza´lez Francisco , Sharma Vinaya , Chitti Srinivas
Published: February 2012

Full-scale rollover crash tests were performed on three non-pressure tank car bodies in order to determine the effectiveness of two different types of protective structures in protecting the top fittings and to validate previous analytical work. This included an unprotected base case car, a car with an added protective skid weldment, and a third car with an added protective bolt-on sleeve on the unloading nozzle with a reinforcing cone. Pivoting the carbodies in a fixture about a fixed axis controlled the test conditions. The fittings or protective structures impacted a concrete target pad. Dynamic Finite Element analysis work was done prior to each test to determine proper test conditions and parameters.
Vibration-Based Energy Harvesting Systems for On-Board Applications
Authors: Nagode C. , Ahmadian M. , Taheri S.
Published: February 2012

Currently, the onboard applications of many electronic devices that could benefit rail operation are hindered by the lack of availability of electrical power in freight cars. Although the locomotives, of course, have available sources of power, the freight cars usually don’t have any. The systems presented in this paper are meant to provide a solution for distributed power in freight trains. Although ideas like Timken’s generator roller bearing or solar panels exist, the railroads have been slow in adopting them for different reasons, including cost, difficulty of implementation, or limited capabilities. The solutions presented in this paper are vibration-based electromechanical energy harvesting systems. With size and shape similar to conventional shock absorbers, these devices are designed to be placed in parallel with the suspension elements, possibility inside the coil spring, maximizing underutilized space. As the train goes down the track, the suspension will accommodate the imperfections and its relative displacement will be used as the input for the harvesting systems. The first prototype generation used a linear generator, with the advantage of no need for a mechanical transformation of the input. They have proven that they could work but present some limitations in terms of power and efficiency. The second generation of prototypes is built around a rotating generator. The linear input motion is transformed into rotation by a ball screw. The possibility of including a gearbox to increase the speed is the key to greatly improve performances. The latest built prototype has shown during lab tests that it is capable of providing up to 75WRMS with displacements and velocities that resemble the relative motion across a vehicle suspension.
Sensitivity Analysis of Track Maintenance Strategies for the High Speed Rail (HSR) Services
Authors: Lautala Pasi , Pouryousef Hamed
Published: February 2012

Track Maintenance (TM) is one of the critical parts of rail operations and asset management. It has been estimated that about 25–35% of all operational costs are related to the track maintenance performance which can be typically classified as either corrective maintenance (CM) or preventive maintenance (PM). The first is a more reactive approach, where maintenance is conducted when inspections have revealed a need for action. The latter is a strategic approach that is mainly applied through maintenance planning. High Speed Rail (HSR) systems, especially on shared HSR corridors, can complicate track maintenance conditions due to the tight tolerances and precision, reliability and safety issues required by HSR. This paper evaluates strategic approaches for track maintenance planning along selected HSR corridors with either shared or dedicated operation pattern. The paper uses analytical and descriptive parameter tables to evaluate how sensitive a corridor is to changes in essential criteria for developing track maintenance strategies (TMS). These criteria may include: - HSR traffic conditions and operations regime; - TMS approach (or strategy) on current rail lines connected to the new HSR line; - Operation and Maintenance (O&M) structure of HSR management system. The descriptive parameter tables have been used by a specific PM modeling approach called preventive maintenance scheduling problem (PMSP). Before running PMSP model over a designated line, the respective parameters of the model should be calibrated and analyzed based on the line specifications. The descriptive parameter tables can be used during calibration procedure to assist in analyzing the sensitivity of model’s parameters and variables for the above mentioned criteria. This paper discusses and compares TMS approaches on three planned HSR corridors in Europe (Lisbon-Madrid HSR), Asia (Tehran-Isfahan HSR) and USA (California HSR). All three HSR rail corridors are under development, but each presents specific sensitivities to the given PM model’s parameters that can affect track maintenance strategic planning along these corridors. We concluded that TMS model calibration by these descriptive analytical tables can assist maintenance strategic planners in identifying different TMS approaches when dealing with maintenance contractors, HSR operators and public rail authorities.
The Influence of Track Stiffness Distribution on Dynamic Behavior of Track Transition
Authors: Lei Xiaoyan , Zhang Bin
Published: February 2012

A model for dynamic analysis of the track stiffness distribution on the impact of track transition is developed with vehicle element and track element. The vehicle element model has a total of 26 DOFs, in which 10 DOFs are used to describe the vertical movement of the car body, and 16 DOFs are associated with the rail displacements. The track element includes rail, rail fastening and pad, ballast and subgrade. By means of Lagrange equation, numerical method for coupling the moving wheel and the rail with explicit formula is presented and the associated finite element formulations are obtained. As an application, influences of four kinds of transition patterns, i.e., abrupt change, step by step change and linear change as well as cosine change for track stiffness distributions in track transition, on dynamic behavior of the vehicle and the track are investigated. The computational results show that the transition pattern of the track stiffness has great influence on the dynamic behavior of the vehicle and the track and smoothing of the track stiffness distribution can significantly reduce the wheel/rail interaction forces and the vertical rail accelerations. From abating wheel/rail impact and improving traffic operation’s point of view, the cosine change is the best, the linear change is the better and the abrupt change is the worst in the four kinds of the transition pattern of the track stiffness. However, the transition patterns of the track stiffness have nearly no influences on the vertical vehicle accelerations due to the excellent behaviour of vibration isolation resulting from the primary and the secondary suspension system of the vehicle.
Viscoelastic Homogenization Approach for Damping Properties of Polymer Composites Using Fractional Calculus
Authors: Shibuya Yotsugi
Published: February 2012

Polymer composites are attractive material system with damping ability to reduce vibration of mechanical structures and improve controllability of mechanical system. To understand effect of constituents and microstructure on damping properties of polymer composites, a detailed micromechanical study is needed to develop the method of analysis for microscopic viscoelastic deformation and macroscopic damping properties. Viscoelastic homogenization approach with fractional calculus is developed to evaluate effective damping properties of polymer composites. The microstructure of the composite is supposed to be periodic and polymer matrix is viscoelastic medium. Damping properties of the composite are evaluated from the stress strain diagram and associated energy dissipation during cyclic loading. Viscoelastic properties of the polymer matrix are identified using a generalized fractional Maxwell model with spring and fractional elements. Coefficients of elements in the generalized fractional Maxwell model are determined to be fitting into experimental data in frequency domain. The homogenized stress strain relation in time domain given by inverse Laplace transform is derived and numerical calculations are carried out.
Is the Stress Distribution Uniform in the Cross Section of SMA Bars Subjected to Uniaxial Loading? Is it Related to Rate Dependency?
Authors: Mirzaeifar Reza , DesRoches Reginald , Yavari Arash
Published: February 2012

In this paper, a coupled thermo-mechanical framework which takes into account the effect of phase transformation latent heat is presented for shape memory alloys. The governing equations are discretized for SMA bars and wires with circular cross sections by considering the non-uniform temperature distribution in the cross section. It is shown that a combination of three various effects (boundary condition, loading rate, and size) governs the intensity of temperature gradient in the cross section of SMA bars subjected to uniaxial loading. Also, it is shown that because of the strong coupling between the thermal and mechanical fields in SMAs, temperature difference in the cross section causes a non-uniform stress distribution in the cross section. The maximum non-uniformity in the stress and temperature distributions are calculated for a vast range of practical sizes, boundary conditions, and loading rates. The relation between the latent heat flux in the cross section and the rate dependency is studied. It is shown that the rate dependency in the response of SMAs cannot be studied independent of size and boundary condition effects. This phenomenon reveals that the definition of quasi-static loading is not absolute; it is affected by a number of parameters, e.g., the ambient condition and size of the structure.
Tracking Control of Piezoelectric Stack Actuator Using Modified Prandtl–Ishlinskii Model
Authors: Chen Yuansheng , Palacios Jose , Smith Edward C. , Qiu Jinhao
Published: February 2012

This paper presents the development of Prandtl–Ishlinskii hysteresis model and tracking control of piezoelectric stack actuator with severe hysteresis. Classic Prandtl–Ishlinskii model which is a linearly weighted superposition of many backlash operators with different threshold and weight values, inherits the symmetry property of the backlash operator at about the center point of the loop formed by the operator. To describe the asymmetric hysteresis of piezoelectric stack actuators, two sets of weighting parameters are proposed to modify the weight values of backlash operators in the ascending and descending branches. Hence, two weight values correspond to one operator. Each pair of the weight values slides smoothly from one to another when the output of their corresponding operator is at a desired threshold. A feedforward controller was designed based on the modified model, which can precisely describe the inverse of the hysteresis. Then the modified model and the hysteresis of the piezoelectric stack actuator cancelled each other. A feedback controller was design to compensate for actuator creep. Different types of signal are used to test the feedforward and feedback controllers. The results show that the proposed hysteresis control scheme which combines feedforward and feedback controllers greatly improves the tracking accuracy of the piezoelectric actuator and the error is less than 0.15 μm.
Technological Solutions for Realising an Active Gurney Flap for Green Rotorcraft Applications, Based on Piezoelectrics and Electromagnets
Authors: Diodati Gianluca , Ciminello Monica , Concilio Antonio
Published: February 2012

Gurney flaps are small devices whose dimensions are usually percentage units of the airfoil chord. Liebeck, first hypothesized that the Gurney flap effectively could change the flow field in the region of the trailing edge by introducing two contra-rotating vortices behind the flap, therein altering Kutta’s condition and circulation. In turn, this helps avoiding flow separation and thus allowing the achievement of higher angles of attack before the stall condition occurs. This paper presents preliminary investigations performed on different, original and feasible technological solutions, addressed at realizing Gurney flaps for rotorcraft smart blades.
Experimental Verification of Controllability of a Mixed Mode MR Fluid Mount
Authors: Wang Shuo , Elahinia Mohammad , Nguyen The
Published: February 2012

With the advent of alternative energy and hybrid vehicles come new vibration problems and challenges that require nontraditional solutions. Semi-active vibration isolation devices are preferred to address the problem due to their effectiveness and affordability. A magnetorheological (MR) fluid mount can provide effective vibration isolation for applications such as hybrid vehicles. The MR fluid can produce different levels of damping when exposed to different levels of magnetic field. The fluid can be working in three modes which are the flow mode, shear mode and squeeze mode. A mixed mode MR fluid mount was designed to operate in a combination of the flow mode and the squeeze mode. Each of the working modes and the combined working mode has been studied. The mount’s performance has been verified in simulation and experiments. Based on the simulation and experimental results, it can be seen that the mount can provide a large range of dynamic stiffness. Given this range of dynamic stiffness, a controller has been designed to achieve certain dynamic stiffness at certain frequencies. The experiments are set up to realize the hardware-in-the-loop tests. Results from the experiments show that the mixed mode MR fluid mount is able to achieve desired dynamic stiffness which is directly related to vibration transmissibility.
On the Design of Driver Electronics for Dielectric Elastomer Applications
Authors: Babicˇ Mitja , Lenarcˇicˇ Jadran
Published: February 2012

Actuators based on dielectric elastomers are a promising technology in robotic and mechatronic applications. Up to now, the practical electro-mechanical response and controllability of actuators based on dielectric elastomers are limited by the inadequacy of the employed driving circuits, which are based on voltage-regulated converters. In order to circumvent the aforementioned activation issues, the design procedure of a novel activation strategy for controlling dielectric elastomer actuators is presented in this article. The proposed electronic driver derives from the flyback converter topology and it is able of delivering to the dielectric elastomer actuator middle-frequency, current-pulse trains dependent on the duty-cycle value. The driver’s transformer, switching and protection circuit components design and optimization are based on an estimation of the dielectric elastomer actuator’s electrical parameters. The design of the transformer is crucial for the actuator’s performance and energy efficiency, meanwhile the driver’s switching and protection circuit components are important for the appropriate driver functioning and safety operation. The reported experimental results show that the proposed electronic driver performances are in accordance with the driver’s design.
Bioinspired Vasculatures for Self-Healing Fibre Reinforced Polymer Composites
Authors: Norris Chris , Bond Ian , Trask Richard
Published: February 2012

Self-healing in fibre reinforced polymer (FRP) composites is an active area of research, principally aimed at restoring the losses in mechanical strength associated with impact induced damage. This bioinspired function may be imparted upon a composite structure via the embedment of a vasculature that is capable of delivering functional agents from an external reservoir to regions of internal damage. A simple segregated vasculature design incorporated into a FRP via a ‘lost wax’ process was found to facilitate a self-healing function which resulted in an outstanding recovery (≥97%) in post-impact compression strength. The process involved infusion of a healing resin through the vascule channels. Resin egress from the backface damage, ultrasonic C-scan testing and microscopic evaluation all provide evidence that sufficient vascule-damage connectivity exists to confer a reliable and efficient self-healing function.
Characterization of VO2-Coated SiO2 Micromechanical Bridges Heated by Light Radiation
Authors: Merced Emmanuelle , Cabrera Rafmag , Da´vila Noraica , Sepu´lveda Nelson , Ferna´ndez Fe´lix E.
Published: February 2012

This letter reports the resistivity variations for a VO2 thin film on silicon dioxide (SiO2) micromechanical bridges when the coating’s insulator-to-metal transition (IMT) is thermally induced by optical radiation with a 635 nm laser diode or by conduction using a heater. The coating’s resistivity and temperature coefficient of resistance (TCR) were calculated as a function of temperature through heating-cooling cycles. A resistivity change of nearly three orders of magnitude through the IMT was observed, and the results obtained for the two different heating methods were compared. A peak TCR of −85%/°C during the heating process and −80.8%/°C during cooling were measured.
Optimization of Surface-Actuated Piezocomposite Variable-Camber Morphing Wings
Authors: Bilgen Onur , Saavedra Flores Erick I. , Friswell Michael I.
Published: February 2012

A theoretical, two-dimensional, static-aeroelastic design, modeling and optimization of a variable-camber morphing airfoil that employs surface-induced forces via smart material actuators is presented. The structural parameters of the airfoil, mainly the substrate features, are determined using a Genetic Algorithm optimization technique. A coupled treatment of the fluid-structure interaction is employed which allows the realization of a design that is not only feasible in a bench top experiment, but that can also sustain aerodynamic loads in the wind tunnel. The substrate is assumed to be a carbon nanotube reinforced composite whose constitutive response is obtained by means of a homogenization-based multi-scale finite element model. A separate parametric study on different geometric configurations of representative volume elements is carried out for the description of the substrate material. The analyzed representative volume elements consist of a single wall carbon nanotube embedded in a soft polymer matrix.
Characterization and Modeling of Opposing SMA-Wire System for Multifunctional, Resistance-Based Controls Applications
Authors: Furst Stephen J. , Crews John H. , Seelecke Stefan
Published: February 2012

Shape Memory Alloy (SMA) actuator wires are often discussed in the context of multi-functional materials. This is because the temperature-induced phase transformation causes a significant (∼4%) contraction and a corresponding change in resistance. When a restoring force such as a pre-stretched spring is placed in series with an SMA wire, the contraction creates a repeatable actuation force, and the resistance provides measurement of the strain the wire, or structural (spring) deflection. Work has already been presented to demonstrate the stress, strain, and resistance characteristics of a single SMA actuator wire in series with a spring flexure under different pre-stresses and heating power input frequencies. Also, a method has been presented to linearly approximate the resistance vs strain characteristic, thus providing a direct mapping from SMA wire resistance to flexure deflection. This mapping method has been tested in the context of a simple PID controller used to position a flexure in series with a single SMA. This paper expands previous work by characterizing a system consisting of a spring flexure in series with two opposing SMA wires. Such an opposing SMA configuration is relevant to embedded SMA applications and gives the potential to increase cycling frequency by providing an active restoring force. The characterization results show that coupling SMA wires introduces alters the resistance vs strain characteristics of both wires because the second SMA wire essentially becomes a non-linear, hysteretic spring in series with the first. However, knowledge of the physics behind the complicated behavior enables sensible calibration schemes to be developed to accurately map resistance to strain for simultaneous sensing and actuating applications.
Light-Weight, Fast-Cycling, Shape-Memory Actuation Structures
Authors: Stebner Aaron , Krueger Joseph , Neurohr Anselm J. , Dunand David C. , Brinson L. Catherine , Mabe James H. , Calkins Frederick T.
Published: February 2012

While bulk shape memory alloys (SMAs) have proven a successful means for creating adaptive aerospace structures in many demonstrations, including live flight tests, the time required to cool such actuators has been identified as a property that could inhibit their commercial implementation in some circumstances. To determine best practices for improving cooling times, several approaches to increase the surface area and reduce the mass of existing bulk actuator technologies have been examined. Specifically, geometries created using traditional milling and EDM techniques were compared with micro-channel geometries made possible by a new electrochemical milling process developed at Northwestern. The latter technique involves imbedding steel space-holders in a matrix of NiTi powders, hot isostatic pressing the preform into a dense composite, and then electro-chemically dissolving the steel. Thus, in a two-step process, it is possible to create an actuation structure with numerous micro-channels with excellent control of geometry, shape, size and placement, to reduce weight and increase surface area (and thus decrease response time) without compromising actuator performance. In this paper, the new, lighter-weight, faster cycling shape-memory alloy actuation structures resulting from each technique are reviewed. Their performances are compared and contrasted through the results of a numerical study conducted with a 3D SMA constitutive law developed specifically to handle the complex, non-proportional loadings that arise in porous structures. It is shown that using micro-channel technology, cooling times are significantly reduced relative to traditional machining techniques for the same amount of mass reduction.
Damage Detection in Flexible Propeller Beam Structures by Exploiting Impact-Induced Coupled Acceleration Signals
Authors: Georgiou Ioannis T.
Published: February 2012

A local damage at the tip of a composite propeller is diagnosed by properly comparing its impact-induced free coupled dynamics to that of a pristine wooden propeller of the same size and shape. This is accomplished by creating indirectly via collocated measurements distributed information for the coupled acceleration field of the propellers. The powerful data-driven modal expansion analysis delivered by the Proper Orthogonal Decomposition (POD) Transform reveals that ensembles of impact-induced collocated coupled experimental acceleration signals are underlined by a high level of spatio-temporal coherence. Thus they furnish a valuable spatio-temporal sample of coupled response induced by a point impulse. In view of this fact, a tri-axial sensor was placed on the propeller hub to collect collocated coupled acceleration signals induced via modal hammer nondestructive impacts and thus obtained a reduced order characterization of the coupled free dynamics. This experimental data-driven analysis reveals that the in-plane unit components of the POD modes for both propellers have similar shapes-nearly identical. For the damaged propeller this POD shape-difference is quite pronounced. The shapes of the POD modes are used to compute indices of difference reflecting directly damage. At the first POD energy level, the shape-difference indices of the damaged composite propeller are quite larger than those of the pristine wooden propeller.
Unimorph PZT Cymbal Design in Energy Harvesting
Authors: Mo Changki , Arnold Daniel , Kinsel William C. , Clark William W.
Published: February 2012

This paper presents power generation performance of unimorph PZT (lead zirconate titanate) cymbal harvesters optimally designed for the power requirements of a specific application. Proof-of-concept work has shown that the traditional cymbal design can be adapted to a new design that is capable of sustaining higher mechanical loads by replacing the piezoelectric plate with a unimorph circular piezoelectric diaphragm between the metal end caps. The unimorph circular diaphragm is constructed by bonding PZT to a steel substrate to provide increased strength. Additional work was performed to prepare the new cymbal design for large-scale implementation in a variety of applications. The parameters that affect energy harvesting performance for the cymbal structure are first optimized by parametric studies to produce optimum generated energy from a specific range of applied cyclic forces. Key parameters in the unimorph PZT cymbal design include the material properties and the dimensions of the end caps, the ratios of the diameters of the unimorph disc and the end cap cavity, and thickness ratio of the PZT layer and the substrate. Based on the optimized unimorph PZT cymbal structure, a specimen was then fabricated and tested on the load-frame to validate analytically predicted energy generating performance. The specimen was tested under a 1 Hz cyclic load of up to 2,100 N. The measured open circuit output voltages for two different load inputs were in accordance with the analytical prediction.
Smart Insulation for Thermal Control in Buildings
Authors: Knotts Wesley , Miller Danielle , Mo Changki , Schaefer Laura A. , Clark William W.
Published: February 2012

Buildings are a significant source of energy consumption in the US and worldwide, and conditioning building interiors occupies a major portion of that expenditure. At the building level, a particular scenario can occur where it becomes more advantageous for a structure’s walls to be “open” to the outside, as opposed to remaining “closed”, in an insulating state. For instance, a cool night may follow a hot summer day after the sun sets, but traditional insulation captures heat built up inside a home. A clear, sunny day may also heat a building’s exterior during a cold winter day, and heat transfer to the interior would be more desirable than insulation. This paper presents a study of a concept, termed “smart insulation”, that could be used in such scenarios to take advantage of beneficial thermal gradients in order to save heating and cooling costs. Enabling heat transfer without moving air can also help control humidity within interior spaces, as well as limit noise either from moving air or through open windows. Unlike traditional insulation that maintains a specific insulating value during its useful life, smart insulation changes between an insulating and a conducting state depending on the thermal gradient. Some design concepts have been fabricated and were tested in an insulated chamber that provides a “hot side” and a “cool side”. In the test chamber, temperature measurements were taken and the insulating capacity of each design specimen was calculated. Results indicate that the designs have potential to operate between two states (with the best case ranging from 11% to 61% of a benchmark insulation case) and effectively provide sustainable heating or cooling by capitalizing on ambient outdoor conditions.
Bias-Dependent Impedance Model for Ionic Polymer-Metal Composite Actuators
Authors: Fotsing Yannick Kengne , Tan Xiaobo
Published: February 2012

Ionic polymer-metal composites (IPMCs) are a novel class of soft sensing and actuation materials with promising applications in robotic and biomedical systems. In this paper we present a model for nonlinear electrical dynamics of IPMC actuators, by applying perturbation analysis on the dynamics-governing partial differential equation (PDE) around a given bias voltage. By approximating the steady-state electric field under the bias with a piecewise linear function, we derive a linear PDE for the perturbed charge dynamics, which has piecewise constant coefficients and coefficients linear in the spatial variable. Through power series expansion, we solve the PDE to get the charge distribution up to any prescribed order. The perturbed electric field and current are subsequently obtained, which results in a bias-dependent impedance model. This model captures the nonlinear nature of the IPMC electrical dynamics, and degenerates to the linear model when the bias is zero. Simulation results are presented to illustrate the modeling approach.
Fine-Tuned Polymer Nano-Composite Coatings for Use in Geothermal Plants
Authors: Cheng Kuok , Yang Eunsoo , Lee Chi Young , Ricks Zane , Palmre Viljar , Kim Kwang
Published: February 2012

Often times erosion, corrosion, and fouling by scale deposition are primary issues for geothermal-fluid-wetted process equipment. In particular, wet heat exchangers used in geothermal power plants must deal with scale deposition. Previously, a surface-coating of polytetrafluoroethylene (PTFE) was considered to provide a non-stick surface. However, intrinsically poor thermal conductivity of PTFE, along with its poor abrasion resistance and weak adhesion to metal substrate, turns out to be a serious concern for engineering use. In this paper, we report a fine-tuned nano-composite by incorporating PTFE/Carbon-nanotube (CNT) into the polyphenylene surfide (PPS) host matrix. PPS is a thermoplastic polymer exhibiting outstanding high-temperature stability, excellent flame resistance, and good chemical resistance. By adding PTFE/CNTs into a PPS matrix, a superhydrophobic surface can also be created by contemplating the chemical composition of the surface material and the cooperative effect of nano-micro structures at the surface. Furthermore, carefully engineered superhydrophobic surfaces can create so-called “dropwise condensation [1]” which can dramatically enhance steam condensation heat transfer. We report the performance results of such nanocomposites regarding steam condensation, along with other surface characteristics. It is our anticipation that, with proper treatment, PTFE/CNT blended PPS can be widely adopted for use in high performance heat exchangers in geothermal industries.
Superelastic Shape Memory Elements Using Intrinsic Sensor Effects
Authors: Czechowicz Alexander , Langbein Sven
Published: February 2012

The superelastic effect of shape memory alloys (SMA) allows reversible material deformations of up to 8% of an element’s length. Although such SMA elements are commonly used for medical applications, only a few utilizations are used in the field of industrial automation. An often disregarded advantage of superelastic elements is the option to replace a conventional elastic element with a smart element including elastic characteristics as well as a deformation sensor. The resistance change of pseudoplastic and superelastic alloys in dependency of varying ambient temperatures, their characteristics during deformation and concepts for different elastic elements with intrinsic sensor functions are the topics of the paper at hand. Additionally, this paper offers an overview over possible combinations of both alloy types utilized as sensing elements. A demonstrator device, capable of elastic-deformation and sensor-feedback signals is presented at the end of this publication.
Modeling Ionic Polymer Transducer Transient Sensing Response
Authors: Zangrilli Ursula T. , Weiland Lisa M.
Published: February 2012

Ionic Polymer Transducers (IPTs) exhibit extraordinary charge sensing capabilities in comparison to other electro active polymers (EAPs), such as piezoelectric materials. It has been proposed that the physical mechanism responsible for this behavior is streaming potential, which can explain this sensing response in all forms of deformation. The existence of an electric signal in shear deformation can currently be only explained by the streaming potential hypothesis. Recently, experimental reports have observed a sustained electrical signal from IPT sensing arrangements over long periods of time, suggesting a more active microstructure than is currently considered. This work presents a simplified model to begin exploring this transient and experimentally observed phenomenon within the framework of the streaming potential hypothesis by looking specifically at shear deformation. There will be an emphasis on the the active microstructure and how the motion of the microstructure affects the development of the streaming potential.
Bond Graph Modeling and Simulation of a Constant-Force Dielectric Elastomer Actuator
Authors: Berselli Giovanni , Vassura Gabriele
Published: February 2012

Constant-Force actuators based on Dielectric Elastomers (DE) can be obtained by coupling a DE film with particular compliant frames whose structural properties must be carefully designed. In any case, the practical achievement of a desired force profile can be quite a challenging task owing to the time-dependent phenomena which affect the DE electromechanical response. Within this scenario, a hyper-viscoelastic model of a rectangular Constant-Force actuator is reported. The model, based on the Bond Graph formalism, can be used as an engineering tool when designing and/or controlling actuators which are expected to work under given nominal conditions. Numerical simulations are provided which predicts the system response to fast changes in activation voltage and actuator position as imposed by an external user.
Tower Deflection Monitoring of a Wind Turbine Using an Array of Fiber Bragg Grating Sensors
Authors: Bang Hyung-Joon , Kim Hong-Il , Jang Moonseok , Han Jae-Hung
Published: February 2012

This paper introduces a fiber Bragg grating (FBG)-based sensing system for the multi-MW scale wind turbine health monitoring, and describes the results of field tests of dynamic strain monitoring and the deformed shape estimation of the wind turbine tower structure. An FBG interrogator was developed with a spectrometer-type demodulator based on a linear photo detector. Real-time shape estimation of the wind turbine tower was accomplished using strain data gathered by surface mounted fiber Bragg grating sensors. The finite element model of the wind turbine tower was created and the displacement-strain transformation (DST) on the basis of the modal approach was obtained. The time histories of the strain were gathered for the cases of blade stop and start using the FBG sensors located at the upwind side of the tower. Finally, the full deflection shapes of the tower were successfully estimated using arrayed FBG sensors.
Density Function Optimization for the Homogenized Energy Model of Shape Memory Alloys
Authors: Crews John H. , Smith Ralph C.
Published: February 2012

In this paper, we present two methods for optimizing the density functions in the homogenized energy model (HEM) of shape memory alloys (SMA). The density functions incorporate the polycrystalline behavior of SMA by accounting for material inhomogeneities and localized interaction effects. One method represents the underlying densities for the relative stress and interaction stress as log-normal and normal probability density functions, respectively. The optimal parameters in the underlying densities are found using a genetic algorithm. A second method represents the densities as a linear parameterization of log-normal and normal probability density functions. The optimization algorithm determines the optimal weights of the underlying densities. For both cases, the macroscopic model is integrated over the localized constitutive behavior using these densities. In addition, the estimation of model parameters using experimental data is described. Both optimized models accurately and efficiently quantify the SMA’s hysteretic dependence on stress and temperature, making the model suitable for use in real-time control algorithms.
Analog Velocity Feedback Controller for Vibration Suppression and Sound Attenuation
Authors: Boz Utku , Ku¨lah Serkan , Arıdog˘an Ug˘ur , Bas¸dog˘an I˙pek
Published: February 2012

In this paper, an analog velocity feedback controller is considered for active vibration suppression of a thin plate for attenuation of sound levels in the frequency range of 0–100 Hz. The active control methods can be applied to interior cavity noise reduction, as encountered for instance in automotive applications. For that purpose, a simplified experimental vibro-acoustic cabin model was built in our laboratory and developed methodologies are demonstrated on the set-up. The set-up includes a rectangular box (1 × 1 × 2 m) which is separated with a flexible thin plate (1 × 1 × 0.001 m) to obtain two enclosed cavities: the passenger compartment (PC) and the engine compartment (EC). The vibration control is applied only on the flexible plate since the walls enclosing the cavities are made of more rigid material (wood filled concrete). By employing piezoelectric patch as actuator and laser doppler vibrometer as vibration sensor, an analog proportional velocity feedback controller is designed and built experimentally for suppressing the low-frequency modes of the flexible plate. In order to attenuate only lower-frequency structural modes of the thin panel, pre-filters are also included in analog circuit. The vibration of thin plate and sound in the passenger compartment is measured for controller-inactive and active cases while disturbing the thin plate via shaker. By measuring vibration and sound response, closed and open loop experimental frequency responses are obtained and presented. The aim of this experimental study is to investigate performance of active vibration control applications on acoustic attenuation as the first step towards robust structural acoustic control.
Water Purification Through Selective Transport
Authors: Freeman Eric , Weiland Lisa Mauck , Soncini Ryan
Published: February 2012

Accumulation of inorganic nitrates and phosphates in regions such as the Mississippi river basin has resulted in catastrophic growth of algal blooms. These algal blooms deplete the surrounding oxygen and asphyxiate nearby aquatic life, resulting in large regions incapable of sustaining life. Using biomimicry principles to design a tailored active material to selectively transport these pollutants may offer a strategy to restore these dead zones to health. Theoretically a combination of selected protein transporters may be employed to create a selective sponge to reclaim these nitrates and phosphates. Presented is a feasibility study of various configurations of transporters, and a unique solution for restoring the aquatic ecosystem back to health.
Damage Localization in Complex Composite Panels Using Guided Wave Based Structural Health Monitoring System
Authors: Liu Yingtao , Kim Seung Bum , Chattopadhyay Aditi , Doyle Derek
Published: February 2012

Knowledge of the damage location in composite structures is a necessary output for both Non-Destructive Evaluation (NDE) and Structural Health Monitoring (SHM). Although several damage localization approaches using a triangulation method and Time-of-Flight (ToF) of guided waves have been reported in literature, the damage localization technique is still not mature for composite structures with complex material properties, varying thickness and complex geometries. This paper investigates the development of a new approach for SHM and damage localization using a guided wave based active sensing system. In contrast to the traditional ellipse method, the proposed method does not require the information of structural thickness, ToF, or the estimation of group velocities of each guided wave mode at different propagation angles, which is one of the main limitations of most current ToF methodologies involving composites. This approach uses time-frequency analysis to calculate the difference of the ToF of the converted modes for each sensor signal. The damage location and the group velocity are obtained by solving a set of nonlinear equations. The proposed method can be used for composite structures with unknown lay-up and thickness. To validate the proposed method, experiments were conducted on both composite plates and stiffened composite panels. Eight piezoelectric (PZT) transducers were surface-bonded on each composite specimen and used in four pairs. The PZT transducers in each pair were bonded close to each other. In the PZT array, one PZT transducer from one PZT pair was used as the actuator and the other three pairs were used as sensors. A windowed cosine signal was used as the excitation signal. The locations of the delaminations in the composite specimens were validated using a flash thermography system. The accuracy of the proposed method in localizing delaminations was examined through comparison with the experimental measurements.
An Exact Levy Solution for Free Vibration Analysis of FGM Plates With Integrated Piezoelectric Layers
Authors: Askari-Farsangi M. A. , Saidi A. R.
Published: February 2012

In the present research, an exact Levy solution for the free vibration analysis of FGM plates with integrated piezoelectric layers is established. The electrical boundary conditions and the Maxwell’s equation are satisfied by assuming the transverse distribution of electric potential to be a combination of a parabolic and a linear function. On the basis of classical plate theory, the coupled governing equations for both closed and open circuit piezoelectric coupled structures are reformulated into two new decoupled equations. The numerical results for the Levy type of boundary conditions, two opposite edges simply supported and arbitrary boundary conditions at the other edges, and both closed and open circuit piezoelectric coupled plates have been presented. The effects of piezoelectric layer thickness on the natural frequency for different power law indices, thickness-length ratios, modes, boundary conditions, and material properties are investigated.