bluuebunny/crossref_metadata_2025 huggingface dataset:
Semi-Analytical Approach to Estimate Railroad Tank Car Shell Puncture
Authors: Jeong David Y. , Tang Yim H. , Perlman A. Benjamin
Published: February 2012

This paper describes the development of engineering-based equations to estimate the puncture resistance of railroad tank cars under a generalized shell or side impact scenario. Resistance to puncture is considered in terms of puncture velocity, which is defined as the impact velocity at which puncture is expected to occur. In this context, puncture velocity represents a theoretical threshold limit. A given object striking the side of a tank car at an impact speed below the threshold velocity is not expected to penetrate the commodity-carrying tank. This definition for puncture velocity is similar to that for ballistic limit velocity, which is used to measure a target’s ability to withstand projectile impact in military applications [1]. The term “semi-analytical” is used to characterize the current approach in developing equations for shell puncture in order to distinguish the present work from the semi-empirical approach used previously to develop equations corresponding to head puncture. While several tests have been conducted to study tank car head puncture, only a limited number of tests have been performed to study tank car shell puncture. The semi-analytical approach employs a combination of three tactics to deal with the paucity of test data. The first tactic applies collision dynamics to derive an idealized relationship between impact speed and maximum force for a generalized tank car shell impact scenario. Specifically, the principle of conservation of energy is applied. The second tactic applies computational methods to simulate tank car shell impacts in greater detail. Specifically, finite element analysis is used to examine the force-deformation behavior of different tank car configurations under different loading conditions. Regression analyses are performed on the results of the detailed finite element results to develop best-fit curves to account for the effects of various factors such as shell thickness, tank diameter, internal pressure and indenter size. The third tactic is empirical, in which various factors are related to puncture force using empirical formulas that have been developed in research to examine impact resistance in pipeline applications. Results from applying the semi-analytical method to estimate shell puncture velocity are presented. Similarities and differences between the current method for shell puncture and the semi-empirical method for head puncture are discussed. In addition, results from sensitivity studies are presented to show the relative effect of different factors on estimated puncture velocity. These studies indicate that indenter size and internal pressure have the most significant effect on shell puncture velocity. Conversely, these studies indicate that tank diameter and ram car weight have a relatively weak effect on shell puncture velocity.
Prediction of Track Geometry Status Based on Gray Forecast-Kalman Filter Analysis
Authors: Jia Chaolong , Xu Weixiang , Wang Hanning
Published: February 2012

Excellent condition of track geometry status is the foundation to ensure train travel security. The detection data of track inspection car contains many valuable features of the track status. The technique of gray forecast and Kalman filtering can be used to investigate the problem and predict the status change of the track geometry. In this paper, gray forecast is used in qualitative analysis of track geometry status changes, and we predict the development of track geometry status change using the Kalman filter prediction model and specific recursive algorithm, established prediction model of the track geometry to make an emulation experiment to analyze the data that track inspection car has detected, and predict changing trends of track geometry the state. Experiment results show that the application model of improved Kalman filter to predict the track geometry status changes gets a higher accuracy, and it can reflect the real change tendency of the track status.
Numerical Analysis of the Dynamic Interaction Between Pantograph and Overhead Contact Line Using FEM
Authors: Jung Sung Pil , Park Tae Won , Lee Jin Hee
Published: February 2012

This study aims to create a numerical analysis model which can investigate the interaction between pantograph and overhead contact line used for railway vehicles, and validate the simulation results according to EN 50318 standards. Finite element analysis models of pantograph and overhead contact line are created using SAMCEF, a commercial FE analysis program, and mean, standard deviation, maximum and minimum values of contact forces are obtained. The simulation results are validated according to EN 50318, and the reliability of SAMCEF as an analysis solver of railway vehicle’s catenary system is discussed.
Review of Intermodal Train Loading Metrics for North American Railroads
Authors: Rickett Tristan G. , Edwards J. Riley , Barkan Christopher P. L.
Published: February 2012

Intermodal freight transportation is one of the highest sources of revenue for North American freight railroads. However, intermodal trains are the least energy efficient in comparison to other types of trains and typically operate at higher speeds, thus creating significant aerodynamic resistance. The high resistance associated with intermodal trains results in significant fuel expenditures, and opportunities exist to reduce the aerodynamic drag through improved loading practices. An important step in the improvement of loading practices is gaining a greater understanding of how railroads load their intermodal trains and what metrics are used to evaluate loading configurations. Current North American railroad loading metrics consider equipment utilization, number of units, and/or total train length. However, these loading metrics do not account for the size of the well or platform and the size of the load placed in it. One proposed metric, slot efficiency, compares the difference between the ideal container/trailer size for the slot and the actual length of the load that is placed into the slot. Adopting this metric would enable railroads to better understand how their intermodal loading practices affect train energy efficiency. This paper reviews loading metrics used by North American railroads, identifies their strengths and weaknesses, and compares them to the slot efficiency metric using the AAR Aerodynamic Subroutine. The paper will also investigate potential challenges to improving slot efficiency of intermodal trains.
Railroad Industry Workforce Assessment—Next Steps: Working Together to Shape the Rail Workforce of the 21st Century
Authors: Kesler John K. , Stewart Monique F. , Chappell Debra M. , Parker Lloyd
Published: February 2012

Since 2009, the Obama Administration’s focus on rebuilding the nation’s infrastructure and creating jobs has generated a tremendous amount of investment in transportation related initiatives. Championed by U.S. Department of Transportation (USDOT) Secretary, Ray LaHood, these initiatives have spanned the transportation industry including a portion being allocated to rail. At the 2010 ASME Joint Rail Conference (JRC), Kevin Kesler, Federal Railroad Administration (FRA) Chief of Equipment and Operating Practices Division shared insight into FRA’s tentative workforce development activity (FRA-WDT). This effort is being conducted as part of the larger USDOT National Transportation Workforce Strategy Initiative, which endeavors to identify and report workforce challenges and commonalities across all modes of transportation and discuss strategies to address those issues. Since that presentation, the FRA Workforce Development Team (FRA-WDT) has identified six railroad industry specific challenges and submitted them for incorporation in the USDOT Framework for a National Transportation Workforce Strategy: 1. Aging railroad workforce – highlighting need for knowledge transfer. 2. Workforce diversity – shortages of women and minorities in the rail workforce. 3. Overall image of the rail industry – declining and stagnant technologically. 4. Need for national training standards for freight rail craft and trade positions. 5. Work-life balance issues – attrition among employees with less than five years of service. 6. Availability of suitable metrics to constantly monitor the collective railroad workforce. These issues were derived from independent research as well as interviews conducted with representatives from across the railroad industry (i.e. Class I railroads, short line and regional railroads, labor unions, associations, academia, and FRA staff). Thus, FRA is interested in continuing the dialog and information exchange with railroad industry stakeholders as a means to strategize about these workforce concerns that impact each facet of the industry. An initial set of approaches to each challenge has been identified, which includes partnering with industry stakeholders. Full details and additional insight into the analysis will be shared in the paper.
Use of Communications Based Train Control Systems in the Presence of Radio Frequency Noise and Interference
Authors: Fitzmaurice Michael
Published: February 2012

A common concern with Communications Based Train Control (CBTC) systems is that the wireless subsystem (usually referred to as the data communications subsystem or DCS) is susceptible to radio frequency (RF) interference from the plethora of wireless devices (especially wireless local area networks or WLANs) that generally share the same 2.4 GHz spectrum as that used by the DCS. This concern is investigated in greater detail given the operational histories of two CBTC-equipped public transit lines: NYCT’s “L” or Canarsie Line in New York City and the Las Vegas monorail. Measurements of the RF environment in both locations showed a substantial level of activity in the 2.4 GHz band from WLANs and other devices but with no obvious adverse impact on the operational performance of either line. This paper presents RF measurements at 4 locations in New York City and 1 location in Las Vegas, discusses the relative severity of the RF noise and interference environment and explores why both CBTC systems are able to perform in the presence of in-band RF noise and interference without any obvious adverse impact.
Importance of Railway Intelligent Transportation Systems and Architectural Design Issues of Indian Railway Network Scenario
Authors: Kumar Navin , Ashwani Deepak , Kumari Nidhu
Published: February 2012

The railway system, one of the backbones of transportation systems in many countries is becoming more and more complex. It plays increasingly significant role in economic development of the country. Therefore, it becomes necessary to ensure that it operates effectively, efficiently and safely. To achieve that railway industries have to move from old traditional manual work, mechanization and electronic usage to intelligent transportation system (ITS). The transformation of railway transportation to railway intelligent transportation system (RITS) can be a core stratagem to keep and improve the competivity from other modes of transportation. Rapid development of emerging technologies such as communication and computing, intelligent system, technological development of railway industries along with 36,000 kilometers (kms) of laid optical fiber cable make it feasible for Indian Railway (IR) to develop and design RITS. This new generation of railway transportation with higher speed, higher performance and zero tolerance for safety may be able to meet the challenges beyond IR vision 2020. The use of RITS architecture encourages structured development and integration of ITS systems that leads to maximization of benefits by minimizing redundancies and maximizing capabilities. This paper presents a distributed framework for a multi-layered RITS architecture that can be designed for integrating generated information. It also addresses the design issues and challenges in the IR scenario.
Preliminary Development of Locomotive Crashworthy Components
Authors: Llana Patricia , Stringfellow Richard
Published: February 2012

The Federal Railroad Administration (FRA) and the Volpe Center are continuing to evaluate new technologies for increasing the safety of passengers and operators in rail equipment. In recognition of the importance of override prevention in train-to-train collisions in which one of the vehicles is a locomotive, and in light of the success of crash energy management technologies in cab car-led passenger trains, the Volpe Center seeks to evaluate the effectiveness of components that could be integrated into the end structure of a locomotive that are specifically designed to mitigate the effects of a collision and, in particular, to prevent override of one of the lead vehicles onto the other. This paper provides preliminary results of a research program that aims to develop, fabricate and test two crashworthy components for the forward end of a locomotive: (1) a deformable anti-climber, and (2) a push-back coupler.
Experimental Studies on Aerodynamic Characteristics of Pantograph System According to the Pantograph Cover Configurations for High Speed Train
Authors: Lee Yeongbin , Kwak Minho , Kim Kyu Hong , Lee Dong-Ho
Published: February 2012

In this study, the aerodynamic characteristics of pantograph system according to the pantograph cover configurations for high speed train were investigated by wind tunnel test. Wind tunnel tests were conducted in the velocity range of 20∼70m/s with scaled experimental pantograph models. The experimental models were 1/4 scaled simplified pantograph system which consists of a double upper arm and a single lower arm with a square cylinder shaped panhead. The experimental model of the pantograph cover is also 1/4 scaled and were made as 4 different configurations. It is laid on the ground plate which modeled on the real roof shape of the Korean high speed train. Using a load cell, the aerodynamic force such as a lift and a drag which were acting on pantograph system were measured and the aerodynamic effects according to the various configurations of pantograph covers were investigated. In addition, the total pressure distributions of the wake regions behind the panhead of the pantograph system were measured to investigate the variations of flow pattern. From the experimental test results, we checked that the flow patterns and the aerodynamic characteristics around the pantograph systems are varied as the pantograph cover configurations. In addition, it is also found that pantograph cover induced to decrease the aerodynamic drag and lift forces. Finally, we proposed the aerodynamic improvement of pantograph cover and pantograph system for high speed train.
Emerging Condition Monitoring Technologies for Railway Track Components and Special Trackwork
Authors: Molina Camargo Luis Fernando , Edwards J. Riley , Barkan Christopher P. L.
Published: February 2012

North American Railroads and the United States Department of Transportation (US DOT) Federal Railroad Administration (FRA) require periodic inspection of railway infrastructure to ensure the safety of railway operation. Tracks that are subjected to heavy haul or high-speed traffic necessitate frequent inspection and more stringent maintenance requirements, but present railroads with less time to accomplish it. The international railroad community has undertaken significant research to develop innovative applications for advanced technologies with the objective of improving the process of visual track inspection. Some of these technologies are currently in use or under development for a variety of railroad inspection tasks, both wayside and mobile. This paper presents an overview of different systems for condition monitoring applications for inspection of railway components. These technologies, in conjunction with defect analysis and comparison with historical data, will enhance the ability for longer-term predictive assessment of the health of the track system and its components, more informed and proactive maintenance strategies, and improved understanding of track structure degradation and failure modes.
Bending of Superelastic Shape Memory Alloy Tubes
Authors: Reedlunn Benjamin , Churchill Christopher , Nelson Emily , Daly Samantha , Shaw John
Published: February 2012

Many shape memory alloy (SMA) applications exploit superelasticity in a bending mode, yet the large displacements and rotations associated with bending of slender structures make controlled experiments difficult. A custom pure bending fixture was built to perform experiments on superelastic NiTi tubes. To understand the bending results, the tubes were also characterized in uniaxial tension and compression, where a custom fixture was utilized to avoid buckling. In addition to measuring the global mechanical response, stereo digital image correlation (DIC) was used in all the experiments to capture the local surface displacement and strain fields. Consistent with the tension/compression data, our bending experiments showed a significant shift of the neutral axis towards the compression side. Also, the tube had strain localization on the tension side, but no such localization on the compression side. Detailed analysis of the strain distribution across the tube diameter revealed that the usual assumption of beam theory, that plane sections remain plane, did not hold along the tension side. Averaged over a few diameters of gage length, plane sections remain plane is a reasonable assumption and can be used to predict the global moment–curvature response. However, this assumption should be used with caution since it can under/over predict local strains by as much as 2× due to the localized deformation morphology.
Experimental Modal Analysis of Fractal-Inspired Multi-Frequency Piezoelectric Energy Converters
Authors: Castagnetti D.
Published: February 2012

An important issue in the field of energy harvesting through piezoelectric materials is the design of simple and efficient structures which are multi-frequency in the ambient vibration range. This paper deals with the experimental assessment of four fractal-inspired multi-frequency structures for piezoelectric energy harvesting. These structures, thin plates of square shape, were proposed and numerically analyzed, with regard to their modal response, in a previous work by the author. The aim of this work is twofold. First, to assess the modal response of these structures through an experimental investigation. Second, to evaluate, through computational simulation, the performance of a piezoelectric converter prototype relying on one of these fractal-inspired structures. The four fractal-inspired structures are examined experimentally in the range between 0 and 100 Hz, both with regard to eigenfrequencies and eigenmodes. In the same frequency range are investigated the modal response and power output of a converter prototype.
A Constant Stroking Load Regulator for Shock Absorption
Authors: Wang Gang , Hiemenz Gregory , Hu Wei , Wereley Norman M.
Published: February 2012

The goal of this study is to provide shock mitigation in an active (or semi-active) shock absorption system, typically comprising of a spring, and an adjustable stroking load element, such as an adaptive energy absorber (EA) or semiactive damper element, in which the stroking load can be electronically adjusted in real-time. Typically, there is a maximum limiting stroking load that can be accommodated by a payload. Thus, a Constant Stroking Load Regulator (CSLR) is developed that accepts sensor feedback, and then selects control gains that result in the energy absorber (EA) providing the required controllable stroking load. A key benefit of this regulator is that it is capable of adapting to a varying range of payload mass, impulse types, and impulse excitation levels. The payload mass is measured and used as a control input parameter. The measured impact velocity is used to determine the impulse acceleration level by assuming an impulse profile, which tends to be application-specific. Finally, the required constant stroking load is determined using a physics-based model. The CSLR is designed to achieve a “soft landing” such the payload comes to rest when the available stroke is used completely, in order to minimize the stroking load and thereby minimize the potential for payload damage. The CSLR methodology was then experimentally validated for a representative occupant protection system consisting of a seat suspension with an adaptive stroking element, which in this case was a magnetorheological energy absorber (MREA). A MREA was used as the stroking element because its stroking load can be adjusted electronically. To validate the CSLR strategy, experimental drop tests were conducted for two different payloads. The impact velocity was 10.3 ft/s (3.15 m/s) and the acceleration profile was a 50 ms duration half-sine pulse. The constant stroking load was pre-calculated as a function of payload mass and initial velocity. During each drop test, the required stroking load was supplied to the MREA in order to achieve a “soft landing.” The CSLR was successfully demonstrated under laboratory conditions. These tests demonstrated feasibility of using the CSLR, in conjunction with a MREA as the stroking element.
A New Robustness Theorem for the Adaptive Control of Nonlinear Systems
Authors: Balas Mark J. , Nelson James P.
Published: February 2012

Many systems must operate in the presence of bounded perturbations. In this paper we present a new robustness result for nonlinear systems. We use this result to show that for bounded perturbations, a simple adaptive controller with leakage can produce output regulation to a neighborhood with radius dependent upon the size of the perturbation. This regulation occurs in the presence of persistent disturbances and the convergence is exponential.
Fully Coupled Three-Scale Finite Element Model for the Mechanical Response of a New Bio-Inspired Composite
Authors: Saavedra Flores Erick I. , Murugan Senthil , Friswell Michael I. , de Souza Neto Eduardo A.
Published: February 2012

This paper proposes a fully coupled three-scale finite element model for the mechanical description of an alumina/magnesium alloy/epoxy composite inspired in the mechanics and architecture of wood cellulose fibres. The constitutive response of the composite (the large scale continuum) is described by means of a representative volume element (RVE, corresponding to the intermediate scale) in which the fibre is represented as a periodic alternation of alumina and magnesium alloy fractions. Furthermore, at a lower scale the overall constitutive behavior of the alumina/magnesium alloy fibre is modelled as a single material defined by a large number of RVEs (the smallest material scale) at the Gauss point (intermediate) level. Numerical material tests show that the choice of the volume fraction of alumina based on those volume fractions of crystalline cellulose found in wood cells results in a maximisation of toughness in the present bio-inspired composite.
Multi-Mode Self-Healing in Composite Materials Using Novel Chemistry
Authors: Bond Ian , Coope Tim , Trask Richard , McCombe Greg , Wass Duncan , Mayer Ulrich
Published: February 2012

A novel Lewis acid-catalysed self-healing system is investigated for implementation in epoxy-based fibre reinforced polymer (FRP) composite materials. The catalyst, scandium(III) triflate, is selected using a qualitative approach and subsequently embedded with pre-synthesised epoxy-solvent loaded microcapsules, into an epoxy resin. Healing is initiated when microcapsules are ruptured at the onset of crack propagation. The epoxy monomer healing agent contained within, actively undergoes ring-opening polymerisation (ROP) on contact with the locally placed catalyst, forming a new polymer to bridge the two fractured crack surfaces. Self-healing performance is quantified using tapered double cantilever beam (TDCB) epoxy resin test specimens and the effects of microcapsule loading, microcapsule content and healing temperature are all independently considered. As an initial proof of concept study, results show that a material recovery value of greater than 80% fracture strength is achieved for this novel Lewis acid-catalysed self-healing epoxy resin. The same self-healing agent system was subsequently demonstrated in a larger scale FRP component by incorporating both a microcapsule and hollow glass fibre (HGF) delivery system within an FRP laminate using a End-Notched Flexure (ENF) test configuration.
Photocatalytic Behaviors of TiO2-SrTiO3 Composite Thin Film and Nanostructure
Authors: Chen Chun-Hsien , Shieh Jay , Lin Chao-Sung , Shyue Jing-Jong
Published: February 2012

To improve the efficiency of water splitting by photocatalysis, a semiconductor heterojunction made of titanium dioxide (TiO2) and strontium titanate (SrTiO3) is constructed to promote the separation of photo-induced electron and hole (e− /h+) pairs. The photocatalytic behaviors of the TiO2-SrTiO3 composite film and nanostructure fabricated by the sol-gel and hydrothermal methods are studied. UV-visible and ultraviolet photoelectron spectroscopies (UV-Vis & UPS) are adopted to identify the band structure of the TiO2-SrTiO3 heterojunction. For the composite film system, an approximately 0.5 eV band shift at the heterojunction improves the separation of photoinduced e−/h+ pairs. The photocurrent density of the composite film is about 2–3 times larger than that of the TiO2 or SrTiO3 film alone. For the composite nanostructure system, it is composed of an array of TiO2 nanotubes coated with SrTiO3 nanoparticles. An approximately 0.2 eV band shift at the heterojunction is determined for the composite nanostructure. It is found that the size of the SrTiO3 nanoparticles, which can be controlled by the hydrothermal temperature and time, is a key factor in influencing the photocurrent density of the TiO2-SrTiO3 composite nanostructure.
Repetitive Control Design for Piezoelectric Actuators
Authors: Shan Yingfeng , Leang Kam K.
Published: February 2012

Piezoactuators exhibit hysteresis and dynamic effects which often cause significant positioning error in a wide variety of motion control applications, especially in applications where the reference trajectory is periodic in time, such as the raster motion in scanning probe microscopy. A feedback-based approach known as repetitive control (RC) is well-suited to track periodic reference trajectories and/or to reject periodic disturbances. However, when an RC is designed with a linear dynamics model and subsequently applied to a system with hysteresis, stability and good tracking performance may not be guaranteed. In this work, the effect of hysteresis on the closed-loop stability of RC is analyzed. In the analysis, the hysteresis effect is represented by the Prandtl-Ishlinskii hysteresis model. Using this model, stability conditions are provided for an RC designed for piezoelectric actuators which commonly exhibit hysteresis. The approach is applied to a custom-designed piezo-driven nanopositioner for tracking periodic trajectories.
Multilayered Structures for Electro Bonded Laminates
Authors: Di Lillo Luigi , Carnelli Dario Albino , Bergamini Andrea , Ermanni Paolo
Published: February 2012

This paper reports on the investigation and optimization of the electric properties of a geometry based variable stiffness concept. The concept relies on the combination of electrostatic normal forces and friction between the layers of a multi-layer beam to develop structures, electro bonded laminates (EBL), with an actively tuneable bending stiffness. Previous studies have detailed the connection between the mechanical response of these system and the electrical properties of its polymer constitutive films. Particularly, they pointed out the need to improve both the dielectric and the insulating properties of these films in order to have an enhancement of the bending tunability range of the system. In this paper a multilayer polymer configuration is considered as a possible answer to this need and it is put forward together with the electric model and the relatively high frequency experimental evidence of the proposed solution.
Effects of Electric Field on the Fracture Toughness (KIC) of PZT Ceramics
Authors: Goljahi Sam , Pisani David , Gallagher John , Lynch Christopher S.
Published: February 2012

Ceramic PZT with a controlled crack was subjected to combined four point bending and longitudinal electric field loading to determine the fracture toughness (KIC) as a function of electric field. Application of a positive DC electric field (in the polarization direction) during mechanical loading was observed to reduce the critical stress intensity factor and application of a negative electric field increased the critical stress intensity factor.
On the Path-Dependency of the J-Integral in a Pseudoelastic Shape Memory Alloy
Authors: Baxevanis Theocharis , Chemisky Yves , Lagoudas Dimitris
Published: February 2012

Detailed finite-element calculations are carried out to examine the path-dependence of the J-integral in a pseudoelastic Shape Memory Alloy (SMA) for mode I loading under the approximation of linear kinematics. The evolution equation for the transformation strain is consistent with the classical rate-independent J2 flow theory. The small-scale nonlinearity assumption is employed using a boundary layer approach, wherein the actual boundary conditions have been replaced by the requirement of an asymptotic approach to the linear elastic inverse-square-root stress/strain distribution at large distances from the crack tip. The J-integral is found to be path-dependent inside the transformation zone, close to the crack tip.
Nonlinear Stochastic Feedback Controllers for Vibratory Energy Harvesters With Power Flow Constraints
Authors: Cassidy Ian L. , Scruggs Jeffrey T. , Behrens Sam
Published: February 2012

This study addresses the formulation of feedback controllers for stochastically-excited vibratory energy harvesters. Maximizing power generation from stochastic disturbances can be accomplished using LQG control theory, with the transducer current treated as the control input. For the case where the power flow direction is unconstrained, an electronic drive capable of extracting as well as delivering power to the transducer is required to implement the optimal controller. It is demonstrated that for stochastic disturbances characterized by second-order, bandpass-filtered white noise, energy harvesters can be passively tuned such that optimal stationary power generation only requires half of the system states for feedback in the active circuit. However, there are many applications where the implementation of a bi-directional power electronic drive is infeasible, due to the higher parasitic losses they must sustain. If the electronics are designed to be capable of only single-directional power flow (i.e., where the electronics are incapable of power injection), then these parasitics can be reduced significantly, which makes single-directional converters more appropriate at smaller power scales. The constraint on the directionality of power flow imposes a constraint on the feedback laws that can be implemented with such converters. In this paper, we present a sub-optimal nonlinear control design technique for this class of problems, which exhibits an analytically computable upper bound on average power generation.
Optimal Design of Elastomer Composites for Morphing Skins
Authors: Murugan Senthil , Saavedra Flores Eric I. , Friswell Michael I. , Adhikari Sondipon
Published: February 2012

Morphing aircraft concepts aim to enhance the aircraft performance over multiple missions by designing time variant wing configurations. The morphing concepts require wing skins that are flexible enough to allow large in-plane stretching and high bending stiffness to resist the aerodynamic loads. In this study, an optimization problem is formed to enhance the in-plane flexibility and bending stiffness of wing skins modeled as composite plates. Initially, the optimal fiber and elastomer materials for highly flexible fiber reinforced elastomer laminates are studied using materials available in the literature. The minor Poisson’s ratio of the laminate is almost zero for all the fiber and elastomer combinations. In the next stage, the effects of boundary conditions and aspect ratio on the out-of-plane deflection of the laminate are studied. Finally, an optimization is performed to minimize the in-plane stiffness and maximize the bending stiffness by spatially varying the volume fraction of fibers of a laminate. The optimization results show that the in-plane flexibility and bending stiffness of the laminate with a variable fiber distribution is 30–40% higher than for the uniform fiber distribution.
Parametric Amplification in the Context of Vibratory Energy Harvesting
Authors: Bode R. Donovan , Daqaq Mohammed F.
Published: February 2012

In this manuscript, we propose a technique to harvest energy from excitation sources that possess two frequency components: a fundamental component with large energy content, and a super-harmonic component with smaller energy content at twice the fundamental component. Excitations of this nature are common in the environment due to inherent nonlinearities in the dynamics of the excitation source. Normally, two separate energy harvesters are needed to extract the energy at each frequency; however, this paper discusses a single cantilevered piezoelectric vibratory energy harvester (VEH) that exploits the parametric amplification phenomenon to scavenge energy from both frequencies by varying the tilt angle between the axis of the harvester and the direction of the excitation. To investigate the efficacy of the proposed concept, the equations governing the electromechanical dynamics of the harvester are derived. The resulting partial differential equations and associated boundary conditions are then reduced to a single-mode Galerkin based reduced-order model. Analytical expressions for the steady-state output power across a purely resistive load are obtained using the method of multiple scales. Results indicate that percentage improvement in the output power depends on the excitation’s parameters, the tilt angle, and the mechanical damping ratio. It is observed that there is an optimal tilt angle at which the flow of energy from the environment to the electric load is maximized. Furthermore, when the mechanical damping ratio is small, significant enhancement in the output power is attainable even when the magnitude of the super-harmonic is very small when compared to the fundamental component. Such findings reveal that, under certain conditions, parametric amplification can be utilized to enhance the output power of a VEH especially for micro-scale applications where the damping ratio can be easily controlled. Experimental results are presented to validate the theoretical concepts.
Electrochemical Analysis of Alamethicin Reconstituted Planar Bilayer Lipid Membranes Supported on Polypyrrole Membranes
Authors: Zhang Hao , Sundaresan Vishnu Baba , Salinas Sergio , Northcutt Robert
Published: February 2012

Conducting polymers possess similarity in ion transport function to cell membranes and perform electro-chemo-mechanical energy conversion. In an in vitro setup, protein-reconstituted bilayer lipid membranes (bioderived membranes)perform similar energy conversion and behave like cell membranes. Inspired by the similarity in ionic function between a conducting polymer membrane and cell membrane, this article presents a thin-film laminated membrane in which alamethicin-reconstituted lipid bilayer membrane is supported on a polypyrrole membrane. Owing to the synthetic and bioderived nature of the components of the membrane, we refer to the laminated membrane as a hybrid bioderived membrane. In this article, we describe the fabrication steps and electrochemical characterization of the hybrid membrane. The fabrication steps include electropolymerization of pyrrole and vesicle fusion to result in a hybrid membrane; and the characterization involves electrical impedance spectroscopy, chronoamperometry and cyclic voltammetry. The resistance and capacitance of BLM have the magnitude of 4.6×109Ω-cm2 and 1.6×10−8 F/cm2.The conductance of alamethicin has the magnitude of 6.4×10−8 S/cm2. The change in ionic conductance of the bioderived membrane is due to the electrical field applied across alamethicin, a voltage-gated protein and produces a measurable change in the ionic concentration of the conducting polymer substrate.
Novel Bismaleimide-Based Shape Memory Polymers: Comparison to Commercial Shape Memory Polymers
Authors: McClung Amber J. W. , Shumaker Joseph A. , Baur Jeffery W.
Published: February 2012

A series of novel shape memory polymers, synthesized from 4-4-bismaleimidodiphenyl-methane, an extended chain aliphatic diamine, and a bis-isocyanate, have been created and characterized with the aim of providing a family of robust high temperature shape memory polymers with tailorable transition temperatures for use in reconfigurable aerospace structures. In the present study, three of the polymers are chosen for more detailed study of their thermomechanical properties. These materials are compared to commercial resins Veriflex® and Veriflex-E® which are styrene- and epoxy-based proprietary formulations, respectively. The thermal and mechanical properties are determined utilizing thermogravimetric analysis and dynamic mechanical analysis. The temperatures at which 2% weight loss is observed in dry air ranges from 272 to 305 °C for the synthesized polymers, and occurs at 242 and 317 °C for the commercial Veriflex® and Veriflex-E® respectively. The glass transition temperatures, as measured by the peak in the tan(δ) curve, for the synthesized polymers range from 110 to 144 °C which is a higher than the Veriflex® and Veriflex-E® achieve at 84.3 and 100 °C respectively. With operation temperatures of subsonic structural aircraft components often reaching 121 °C (250 °F), the transition temperatures of the bismaleimide-based shape memory polymers are clearly desirable to ensure that shape memory polymers used in aircraft structures will not be prematurely triggered by the existing heat loads. In addition, the shape memory performance of the bismaleimide-based shape memory polymers compares well with the Veriflex® and Veriflex-E® resins.
FEM Simulation of a Magnetic Shape Memory Foil Actuator Under Different Loading Conditions
Authors: Krevet B. , Kohl M. , Pinneker V.
Published: February 2012

This paper presents a finite element model and simulation results on the performance of a novel linear actuator using the magnetic shape memory (MSM) effect in a Ni-Mn-Ga foil loaded by a mechanical spring. We present finite element simulations with a material model based on the thermodynamic Gibbs free energy in a finite element program (FEM) using beam elements, which is combined with an integral magnetic solver. The simulations qualitatively describe the observed tensile stress-dependence of magneto strain of a first demonstrator of a MSM foil actuator. We demonstrate that complete reversible cycles of the magnetic field induced strain are possible if the spring is preloaded to induce a prestress in the foil. The effect of inhomogeneous material on variant reorientation and corresponding magneto strain are discussed.
Energy Harvesting Circuit for Pulse Generator
Authors: Tiwari Rashi , Schlichting Alex , Zhang Yuan , Feldman Danielle Juliana , Garcia Ephrahim
Published: February 2012

Due to the recent advancement in wireless technology, the demand on power sources has increased dramatically. Personal electronics like cell phones, mp3 or electronics devices like wireless keyboard, both are dependent on batteries as the source of energy. However, with the ever-shrinking electronics, existing battery technology imposes a limitation on size, weight and often times maintenance. Technology like energy harvesting from ambient sources like solar or vibration is believed to play a critical role in these devices and can act as power source for uninterrupted operation. In this paper we discuss, energy harvesting from personal devices like cell phones or keyboards. Since, most of the signal generated is in the form of pulse, an energy harvesting circuit for energy extraction from pulse is discussed. Conventional energy harvesting circuits for this kind of signal are also evaluated in terms of efficiency.
Improving Vehicle Performance and Operator Ergonomics: Commercial Application of Smart Materials and Systems
Authors: Ivers Douglas , LeRoy Douglas
Published: February 2012

This paper will discuss how controllable material technology, such as the use of active magneto-rheological (MR) dampers, improves vehicle primary and secondary suspensions. Although relatively new to the marketplace, semi-active suspensions in commercial automobiles and off-highway vehicles have been proven through the use of active MR dampers since 1998. In fact, MR suspension dampers are found today on the commercial vehicles of an increasing number of automotive OEMs and leading off-highway OEMs. MR fluid dampers are simple in design and have the advantage of no moving parts. The resistive force from an MR damper is generated as iron particles, suspended in the magneto-rheological fluid (MR fluid); pass through a magnetic field controlled by the electrical current passing through an electric coil contained within a moving piston surrounded by fluid. By adjusting the current to the damper coil in response to feedback from vehicle sensors and a controller, the damping response of the suspension can be optimized and controlled in real time to provide optimal operator comfort. The MR Damper System has a full-scale step response of less than 10 milliseconds. Sophisticated control algorithms adapt to large changes in payload, enabling the vehicle to meet ride metrics without pneumatic load leveling. Other benefits of the MR damping system include higher speed in NATO double-lane change tests, reduced risk of roll-over, improved accuracy of mounted weapons, and improved vehicle durability and readiness.
A Discrete Phase Model for Ferroelectric Domain Evolution
Authors: Dong Wen , Pisani David , Lynch Christopher S.
Published: February 2012

Discrete phase modeling utilizes a finite element framework with a Landau-Devonshire type multi-well potential as a material subroutine to model domain evolution in ferroelectrics. The time-dependent Ginzburg-Landau equation with polarization as an order parameter governs evolution of polarization. In the discrete phase method, the domain wall width is not controlled by an adjustable parameter, the gradient energy term used in phase field models; rather, it is controlled by a balance between mechanical, structural, and electrostatic contributions to the free energy. The effect of this energy balance on the resulting domain wall width of 90° and 180° tetragonal domain walls is discussed and examples are presented.
Fluid Structural Interactions of Flapping Photomechanical Liquid Crystal Polymer Networks
Authors: Bin Jonghoon , Hussaini M. Yousuff , Oates William S.
Published: February 2012

A class of active polymers that respond mechanically to ultraviolet and visible light is studied using an advanced fluid-structural interaction model that photomechanically couples three dimensional, unsteady Navier-Stokes equations with a plate model of liquid crystal networks. These materials have been shown to exhibit fast response times that scale with the resonant frequency of the polymer film structure. Moreover, these films are classified as glassy (modulus ∼ 1GPa) and thus have demonstrated flapping behavior on the order of 100Hz or greater in millimeter length films. A variety of applications include micro-propulsion systems for insect size aircraft and biomedical actuators for micro-manipulation of biological materials. A critical challenge in utilizing these materials is explored here by quantifying photomechanical performance and efficiency under unsteady, aerodynamic loads. To quantify the active material performance, we utilize detailed fluid-structural computational methods that couple light input energy, strain energy of the photomechanical film, and interactions with ambient air. The effect of ambient air pressure is found to have a significant impact on photomechanical performance.
Numerical Analysis of Composites Embedded With Magnetostrictive Material for Sensing Capability
Authors: Rudd Jonathan , Myers Oliver
Published: February 2012

In this paper, numerical models are constructed to analyze the magneto-mechanical interaction in a laminate embedded with terfenol-D (TD) for sensing purposes. The first model is a linear 3D model constructed in multi-physics finite element software and examines mechanical and magnetic sensing parameters of a sensing layer embedded in a composite laminate with a delamination along the sensing layer. The structural plies in the model are defined with the anisotropic properties of T300/ carbon fiber reinforced polymer (CFRP) plies. The results of the first model show that there is a local change in stress and strain in the region of the delamination. However, by assuming the magnetic permeability is constant in the constitutive sensing equation, the sensing parameter (magnetic flux density) does not change as a function of stress but only magnetic field intensity. The second model is a 2D boundary element model constructed in FADD2D that analyzes the stress intensity factors generated by a crack in a beam of similar geometry and loading configuration. It is loaded mechanically through two endpoints on a beam and the crack is offset from the center of the beam. The results of the second model show no significant stress increase in the crack region due to the Poisson’s effect creating crack closure on the crack. These models are used to analyze the mechanical and magnetic mechanisms that allow Terfenol-D to be used as an embedded sensor in composites.
Concept for a Bistable Composite Twisting Structure
Authors: Lachenal Xavier , Daynes Stephen , Weaver Paul
Published: February 2012

A novel type of morphing twisting structure capable of large deformations is investigated. The structure consists of two flanges subject to a uniform distributed bending moment along their length and joined to introduce two stable twisted configurations. These equilibria are positioned symmetrically with regards to the vertical axis of the device and the structure can be twisted between these configurations by a snap-through action. By tailoring the design parameters of the structure, different twist angles and snap-through moments can be achieved. An analytical model and finite element model (FEM) are presented. A prototype made of carbon-fibre reinforced plastic (CFRP) was manufactured and tested. Agreement in terms of angle of twist, axial force and stiffness is found. Moreover, comparison between the two models confirms their validity in terms of snap-through moment, torsional stiffness and strain energy levels. The influence of the lay-up employed and design parameter is also investigated. Potential applications include deployable and morphing structures.
A Strain Model for Piezoelectric Materials Operating in Highly Hysteretic Regimes
Authors: Hu Zhengzheng , Smith Ralph C.
Published: February 2012

Piezoelectric materials exhibit hysteresis in the field-strain relation at essentially all drive levels. Furthermore, this non-linear relation is dependent upon both prestresses and dynamic stresses generated during employment of the materials. The accurate characterization of this nonlinear and hysteretic material behavior is critical for material characterization, device design, and model-based control design. In this paper, we will discuss the characterization of hysteresis using the homogenized energy model (HEM) framework. At the mesoscale, energy relations characterizing field and stress-dependent 90 and 180 degree switching are used to develop fundamental kernels or hysterons. Material and field nonhomogeneities are subsequently incorporated by assuming that certain parameters are manifestations of underlying densities. This yields a macroscopic model that accurately characterizes the fundamental material behavior yet is sufficiently efficient for optimization and control implementation. Attributes of the model will be illustrated through comparison to experimental data.