bluuebunny/crossref_metadata_2025 huggingface dataset:
Improving the Quality and Reliability of Large Truck Castings
Authors: Gonzales Kari , Koch Kevin , Carter Daniel
Published: February 2012

Recent failures of large freight car castings have resulted in a comprehensive review of the specifications governing the manufacture, inspection, and repair of these steel castings. As part of an overall industry effort to improve the quality and reliability of large freight car castings, the Transportation Technology Center, Inc. (TTCI) conducted finite element and fatigue analyses of the S-2-HD bolster and side frame. The objective of this project is to improve the capacity and safety of train operations by reducing the number of in-service failures of bolsters and side frames. To meet the objective, a total of six S-2-HD bolster and side frame castings from different manufacturers were modeled to estimate the fatigue life of each of the components with and without defects. The results from the finite element analysis were combined with load/stress environment data and mechanical test data to predict the fatigue life of each of the components. The fatigue life analysis covered a variety of defect and no defect conditions and used a strain-life based approach. All of the fatigue estimates are based on life until crack initiation and compared to a target life of 1.5-million loaded miles. Results from the analysis show that few combinations of casting design and defect type/size offer sufficient fatigue strength to reach a target life of the desired 1.5-million loaded miles. The analyses also indicate that a reduction in component stress is necessary to improve the overall fatigue performance of the S-2-HD bolster and side frame castings when defects are present in critical stress areas. To reduce the number of derailments associated with truck castings, improvements in component design, manufacturing processes, and materials are necessary. Implementation of changes in design and materials has the potential to reduce stress in critical areas and increase fatigue life performance when defects are present. In addition, it is critical to develop inspection methods capable of reliably detecting defects to prevent in-service failures. If the aforementioned changes are implemented successfully, there is a potential of reducing in-service failures of truck castings by approximately 30 percent. This paper presents the approach and results of the bolster analysis and gives a brief summary of the results of the side frame analysis.
A Physically Motivated Internal State Variable Plasticity/Damage Model Embedded With a Length Scale for Hazmat Tank Cars’ Structural Integrity Applications
Authors: Ahad Fazle R. , Enakoutsa Koffi , Solanki Kiran N. , Tjipowidjojo Yustianto , Bammann Douglas J.
Published: February 2012

In this study, we use a physically-motivated internal state variable plasticity/damage model containing a mathematical length scale to represent the material behavior in finite element (FE) simulations of a large scale boundary value problem. This problem consists of a moving striker colliding against a stationary hazmat tank car. The motivations are (1) to reproduce with high fidelity finite deformation and temperature histories, damage, and high rate phenomena which arise during the impact and (2) to address the pathological mesh size dependence of the FE solution in the post-bifurcation regime. We introduce the mathematical length scale in the model by adopting a nonlocal evolution equation for the damage, as suggested by Pijaudier-Cabot and Bazant (1987) in the context of concrete. We implement this evolution equation into existing implicit and explicit versions of the FE subroutines of the plasticity/failure model. The results of the FE simulations, carried out with the aid of Abaqus/Explicit FE code, show that the material model, accounting for temperature histories and nonlocal damage effects, satisfactorily predicts the damage progression during the tank car impact accident and significantly reduces the pathological mesh size effects.
San Pedro Bay Ports Rail Enhancement Program: 2010 Update
Authors: Leue Michael , Luzzi Carlo
Published: February 2012

The San Pedro Bay Ports of Long Beach and Los Angeles continue to provide vital rail connections to the rest of the country. The Rail Enhancement Program sets forth the rail improvements necessary to maintain performance as cargo volumes grow through the year 2035. Implementation of the Rail Enhancement Program has faced hurdles including environmental permitting, funding and competing stakeholder concerns. Cargo growth eased in the years approaching 2010, but the timing of proposed improvements to the rail infrastructure remains critical and challenging. The Rail Enhancement Program is the result of work over the past ten years. Conditions affecting the program have continued to change since the original Rail Master Planning Study of 2000. Updates to the Master Plan have been performed in 2005 and 2010. These documents provide analyses and recommendations for rail improvements to maintain adequate rail service on the Alameda Corridor and through the Port to its rail yards. In developing the Rail Enhancement Program, simulation is used to understand the impacts of increasing cargo volumes on the rail system and to investigate infrastructure and operating improvements required to address deficiencies and to determine improvements to efficiently handle projected traffic. This paper describes the development process with a summary of the analysis methods, resulting proposed rail projects, implementation process and current status of implementation. The steps of the rail system development process include the following: • Evaluation of existing and proposed rail operations; • Conceptual design of over forty potential rail improvement projects; • Analysis of the capacity of existing and proposed facilities; • Scheduling of project development to meet demand; • Estimation of environmental, community and regional impacts and benefits; • Determination of schedule including environmental permit requirements; • Development of project funding plans; and • Preparation of engineering designs and construction documents. The paper will conclude with a summary of the status of key projects from the Rail Enhancement Program. Implementation of the Rail Enhancement Program has included permitting, funding and design efforts on individual projects. The projects currently under development total $1B out of the overall $2B program. The Rail Enhancement Program provides significant benefits to operating efficiencies, environmental impacts and economic impacts. Implementation has been a challenging effort and illustrates the myriad obstacles facing public infrastructure development.
Shared Corridors, Shared Interests
Authors: Zarembski Allan M. , Blaze James , Patel Pradeep
Published: February 2012

What are some of the practical obstacles to a “shared interests” between a freight railway business and the proposed new higher speed passenger entity? This paper discusses the real “tension” between the two business interests that fund freight trains versus those that support and fund higher speed passenger trains as they attempt to share the same tracks in a safe manner. There are fundamental laws of physics that have to be addressed as the two different sets of equipment are “accommodated” on a shared corridor. This may not always be an easy accommodation between the two commercial parties. One real tension between the two commercial interests involves the physical problem of accommodating two radically different train sets on areas of curved track. For one example, what will be the passenger train required future higher speeds and how will these speeds be accommodated in existing main line tracks with curves varying from 1% to 6% in degrees? How much super elevation will need to be put back into the heretofore freight train tracks? How will the resulting super elevation affect the operation of so called drag or high tonnage slow speed bulk cargo trains? Accommodating such differences in train set types, axle loadings, freight versus passenger train set speeds, requires making detailed choices at the engineering level. These may be shared interests, but they are also variables with far different outcomes by design for the two different business types. The freight railways have spent the last few decades “taking the super elevation out” because it is not needed for the modern and highly efficient freight trains. Now the requirements of the passenger trains may need for it to be replaced. What are the dynamics and fundamental engineering principles at work here? Grade crossings have a safety issue set of interests that likely require such things as “quad” gates and for the highest passenger train speeds even complete grade separation. Track accommodating very high speed passenger trains requires under federal regulations much closer physical property tolerances in gauge width, track alignment, and surface profile. This in turn increases the level of track inspection and track maintenance expenses versus the standard freight operations in a corridor. Fundamentally, how is this all going to be allocated to the two different commercial train users? What will be the equally shared cost and what are examples of the solely allocated costs when a corridor has such different train users? In summary, this paper provides a description of these shared issues and the fundamental trade-offs that the parties must agree upon related to overall track design, track geometry, track curvature, super elevation options, allowed speeds in curves, more robust protection at grade crossings, and the manner in which these changes from the freight only corridors are to be allocated given the resulting much higher track maintenance costs of these to be shared assets.
Preliminary Reconstruction of the November 30, 2007, Chicago, IL Rail Collision
Authors: Llana Patricia , Tyrell David
Published: February 2012

The Volpe Center is supporting the Federal Railroad Administration in performing rail passenger equipment crashworthiness research. The overall objective of this research is to develop strategies for improving structural crashworthiness and occupant protection. A field study of passenger train accidents is being conducted to investigate the causal mechanisms of the injuries incurred by train occupants. The investigation of the November 30, 2007 collision in Chicago, IL has provided preliminary data on the structural damage as well as occupant injuries resulting from the impact. This data will be used in simulations to guide the development of crashworthiness strategies.
Railway Education Today and Steps Toward Global Education
Authors: Ma Chao , Lautala Pasi T.
Published: February 2012

Both passenger and freight railway transportation has changed dramatically during the past decades in most parts of the world. Many new technologies have emerged or have been increasingly applied in rail industry to improve the competitiveness of the mode. At the same time, globalization and changes in the political landscape have contributed to the growing pressure to expand the use of rail transportation across national boundaries. All the development is accelerating the need for international cooperation in railway design, construction and operation and the educational framework should shift accordingly to consider rail transportation beyond national boundaries. In addition to discussing the changes with global dimensions that are taking place in the railway industry, this paper reviews the history and current status of university level railway education in the world, including examples from the USA, Russia, China and selected countries in the European Union (EU). The paper also reviews some of the current methods and approaches used by the other industries and engineering fields to improve the global reach and cooperation in education. Based on these proven concepts, the paper provides some recommendations and suggestions for the railway industry how it can start taking its first steps toward a more global railway education.
Crack Initiation in Railway Wheels Resulting From Rolling Contacts
Authors: Dedmon Steven L. , Guzel Huseyin
Published: February 2012

Classic shelling of a railway wheel begins with crack initiation resulting from wheel rail interactions. This investigation shows the complex relationships that occur between contact stress, cold work, residual stresses, and temperatures from brake heating and non-metallic inclusion types which can lead to the formation of shelling cracks. Our investigation also includes an explanation of how these interactions affect mechanical properties such as yield strength, elastic modulus, and ductility. In turn, mechanical property changes also affect how cold work and its associated residual stresses develop under cyclic loading. Destructive testing and Finite Element Analyses were used in support of this work.
Fabrication of a Novel Monolithic NiTi Based Shape Memory Microgripper via Multiple Memory Material Processing
Authors: Daly M. , Pequegnat A. , Zhou Y. , Khan M. I.
Published: February 2012

The exciting thermomechanical behavior of nickel-titanium shape memory alloys have sparked significant research efforts seeking to exploit their exotic shape memory properties. The performance capabilities of conventional nickel-titanium alloys are currently limited, however, by the retention of only one shape memory geometry. In this paper we demonstrate the application of an unprecedented manufacturing process known as Multiple Memory Material technology to create a novel monolithic nickel-titanium shape memory microgripper. In our design, actuation and gripping maneuvers are achieved by thermally activating processed material regions which possess unique shape memory transformation temperatures and shape set geometries. The existence of multiple shape memory regimes is confirmed through differential scanning calorimetry analysis and in situ resistivity measurements.
Study of Piezoelectric Actuation for Cross-Ply Laminates
Authors: Murray Darryl V. , Myers Oliver J.
Published: February 2012

Experimental and numerical methods are presented for piezoelectric actuation of thin deformed post-cure cross-ply carbon fiber composite laminates. During the fabrication process, the composite laminates are held under a press until the curing temperature is reached. After which, the press is released and the laminates are allowed to cool. During this cooling period the once flat composite laminates deform to one of the two cylindrical shapes. The curvature of the cross-ply post-cure cylindrical shape is symmetric and therefore the transverse displacement is measured using a FARO gage coordinate measuring machine (CMM). The snap through force studied here is generated by a macro-fiber composite patch (MFC), which is bonded to the deformed composite plate. Applying a voltage to the MFC patch induces a mechanical strain in the patch which is then transferred from the patch to the composite laminate causing it to snap through to an orthogonal cylindrical shape. After snap through, the second cylindrical shape is measured using the FARO gage CMM. The numerical post fabrication curvatures and piezoelectrically morphed curvatures compare well to the experimental data.
Effect of Internal Pressure on Flow Properties of Magnetorheological Fluids
Authors: Spaggiari Andrea , Dragoni Eugenio
Published: February 2012

Magnetorheological (MR) fluids have a lot of applications in the industrial world, but sometimes their properties are not performing enough to meet system requirements. It has been found that in shear mode MR fluids exhibits a pressure dependency called squeeze strengthen effect. Since a lot of MR fluid based devices work in flow mode (i.e. dampers) this paper investigates the behaviour in flow mode under pressure. The system design is articulated in three steps: hydraulic system design, magnetic circuit design and design of experiment. The experimental apparatus is a cylinder in which a translating piston displaces the fluid without the use of standard gear pumps, incompatible with MR fluids. The experimental apparatus measures the MR fluid yield stress as a function of pressure and magnetic field allowing the yield shear stress to be calculated. A statistical analysis of the results shows that the squeeze strengthen effect is present in flow mode as well and the presence of internal pressure is able to enhance the performance of MR fluid by nearly ten times.
Modeling, Manufacturing and Experimental Characterization of NiTi Based Belleville Springs
Authors: Maletta Carmine , Filice Luigino , Furgiuele Franco
Published: February 2012

The properties of NiTi based Belleville springs have been analyzed by numerical simulations and experimental tests. In particular, the unique features of these components, mainly due to stress and/or thermally-induced phase transformation mechanisms, have been preliminary analyzed by finite element simulations, by means of a special constitutive model for NiTi alloys. Subsequently, Belleville washers have been manufactured from a commercial pseudoelastic NiTi alloy, by disk cutting and a successive shape setting by a thermo-mechanical treatment. Furthermore, the thermo-mechanical response of the washers, in terms of isothermal force-deflection curve and thermal cycles between phase transition temperatures, has been experimentally analyzed. The experimental observations confirm the numerical results, i.e. the springs show a significant effect of the temperature on the characteristic curve as well as a marked hysteretic behavior. Due to these properties NiTi Belleville washers can be used as smart elastic elements, i.e. with tunable stiffness and damping, as well as solid state actuators. Furthermore, the marked hysteretic behavior of the washers, in terms of force-deflection response, is particularly useful for the realization of vibration and/or seismic absorbers.
Investigation on the Dynamic Shearing Characteristics of Magnetic Responsive Gel
Authors: Sunakoda Katsuaki , Yamamoto Naoki , Nasuno Hiroshi , Sakurai Hirohisa
Published: February 2012

Material which would be largely changed its physical properties such as storage modulus and loss modulus under magnetic field has a potential of application on industrial fields. Magneto-rheological (MR) fluid has been widely studied since its viscosity is changed under magnetic field, but it is restricted for application of the industrial fields as it has liquid nature. Authors are proceeding with the development of magnetic responsive gels which contain the magnetic responsive particles in consideration of their prior studies. Three kinds of magnetic gels are selected and dynamic shearing characteristics are examined. Storage modulus and loss modulus are obtained under different dynamic frequencies and different magnetic fluxes. Some physical properties such as storage modulus and loss modulus are largely changed by applying magnetic field. The developed gels have an effect of energy dissipation, judging from hysteresis loops of stress-strain. And these smart materials have a potential of semi active vibration control materials.
Digital Resistance-Map Generation for a Magnetorheological Damper Based Platform for Rehabilitation Applications
Authors: Asadi Ehsan , Arzanpour Siamak
Published: February 2012

This paper introduces a methodology for generating digital resistance-map that can be utilized in an MR-Damper based robotic rehabilitation. Typically, in rehabilitation procedures, patients are getting involved in the recovery process of gradually training weak and damaged muscles by constraining motion in repetitive exercises. The whole purpose of robotic rehabilitation is to restrict body organ motion to the one prescribed by the therapist at the initial steps of treatment to avoid further damages to other weak muscles while focusing on recovering a particular muscle. MR-Dampers are semi-active actuators that can potentially be employed for this application. These dampers can be activated to produce high resistance to motion, and a platform that contains sufficient number of them can be manipulated to create regions of different resistance against motion. To apply this to the robotic rehabilitation, the motion recommended by the therapist should be converted to the resistance-maps that can be used by MR-Damper for implementation. To accomplish that, procedure of generating the digital resistance map is introduced and several digital resistance-maps are created. An MR-damper control methodology is also developed to activate the dampers. This controller relies on the accurate modeling of the MR-Damper. Bouc-Wen model is used for MR-Damper modeling. A 3-D platform containing three linear MR-Dampers is modeled using SimMechanics. 1-D and 2-D models are used to develop the idea and build up 3-D model. Several simulations are carried out to investigate the performance of the systems in generating the prescribed digital resistance-maps. The promising results of the simulations indicate that the method can be adopted for robotic rehabilitation purposes.
A Model of Compatible Twin Patterns in Shape Memory Alloys
Authors: Tsou N. T. , Huber J. E. , Shu Y. C.
Published: February 2012

A sharp interface model is developed to allow rapid discovery of exactly compatible or averagely compatible laminate twin patterns in a cubic-orthorhombic shape memory alloy system. Given an imposed strain state, the method finds a corresponding exactly compatible twin structure if one exists; otherwise, the method produces an averagely compatible solution. Two cases are considered: The first case allows austenite and martensite phases to be arbitrarily mixed. The second is an essentially flat austenite-martensite phase boundary, with an exactly compatible martensite laminate on one side. The results show several well-known configurations and also many new structures. A full search reveals the routes in strain space along which the two-phase structure can continuously evolve. The influence of the middle eigenvalue of the martensite transformation strain on twin patterns is explored.
A Phase-Field Fracture Model of Ferroelectric Materials Under Electro-Mechanical Loading
Authors: Abdollahi Amir , Arias Irene
Published: February 2012

A phase-field model is proposed for the coupled simulation of microstructure and fracture evolution in ferroelectric materials. The model is based on energetic phase-field approaches for brittle fracture and ferroelectric domain formation and evolution. The variational nature of these approaches makes their coupling very natural. However the main challenge is to encode the electro-mechanical conditions of the sharp crack faces into the phase-field framework since the crack in this model is smeared and represented by an internal layer. We develope the model for different crack face boundary conditions. Simulations show the microstructure induced by the presence of the crack. Interactions between the microstructure and the crack are investigated under different electro-mechanical loadings.
Drastic and Fast Changes in Stress/Strain of Photothermally Actuated VO2-Coated Microcantilevers
Authors: Cabrera Rafmag , Merced Emmanuelle , Da´vila Noraica , Sepu´lveda Nelson , Ferna´ndez Fe´lix E.
Published: February 2012

The time-dependent response of a 300 μm-long VO2-coated silicon micro-cantilevers photothermally driven over the film’s insulator-to-metal transition (IMT) by laser light pulses was studied and tip displacements of ∼ 80 μm were found for driving frequencies over 100 Hz, while displacements of ∼ 10 μm were found for frequencies close to 1.2 kHz, with no performance degradation after millions of pulses. Additionally, the deflection of a 250 μm-long VO2-coated silicon micro-cantilever as a function of temperature heated through a Peltier heater was studied. The main mechanism limiting amplitude was found to be the time required for heat transport during heating and cooling. Hence, wireless actuation in this manner is expected to be even faster for smaller cantilevers.
Thermal Properties of Magnetite Nanoparticle and Carbon Fiber Doped Epoxy Shape Memory Polymer
Authors: Beblo Richard , Joo James , Smyers Brian , Reich Gregory
Published: February 2012

Presented are the results of an experimental investigation into the effects of particle and carbon fiber (CF) doping in epoxy shape memory polymer (SMP). Motivation for the work originates from the need to increase the thermal performance, and thus decrease the time required to transition the polymer given a finite amount of thermal energy, of a SMP link in a bi-stable linkage. Such a multi-functional link is responsible for structural support, mechanism reconfigurability, as well as system damping. Thus any improvement in thermal properties must be weighed against increases in brittleness and weight as well as altered mechanical properties as a result of the chosen method. Two part epoxy SMP by CRG Industries is doped with Fe3O4 (magnetite) nanoparticles (20–30nm spheres) at a weight fraction of 10% as well as 3mm and 10mm carbon fibers at a weight fraction of 5.4%; resulting in all dopants having a volume fraction of approximately 2.5%. The thermal conductivity, specific heat, and diffusivity are experimentally measured by a Hot Disk Thermal Constants Analyser from ambient through transition and the results compared with several thermal composite models. Changes in the thermal properties of the composites and neat polymers with respect to temperature are presented and the effects these changes have on the predictions of thermal models discussed, specifically the effect of changes in thermal properties near the transition temperature and the resulting change in predicted energy required for transition. The effects of adhesion between the particles and the matrix and particle dispersion on conductive paths and material thermal properties are also discussed.
Mitigating IPMC Back-Relaxation Effect Through Controlled Activation of Patterned Electrodes
Authors: Fleming Maxwell , Hubbard Joel , Kim Kwang J. , Leang Kam K.
Published: February 2012

With low driving voltage (<5V) and the ability to be operated in aqueous environments, ionic polymer-metal composite (IPMC) materials are quickly gaining attention for use in underwater applications. There are, however, drawbacks to IPMCs, including the “back relaxation” effect. Specifically, when subjected to a DC input (or an excessively slow dynamic input), the IPMC actuator will slowly relax back toward its original position. There is debate over the physical mechanism of back relaxation, although one prevalent theory describes an initial current, caused by the electrostatic forces of the charging electrodes, which drives water molecules across the ion-exchange membrane and deforms the IPMC. Once the electrodes are fully charged, however, the dominant element of the motion is the osmotic pressure, driving the water molecules back to equilibrium, thus causing back relaxation. A new method to mitigate back relaxation is proposed, taking advantage of controlled activation of patterned (sectored) electrodes on the IPMC. Whereas previous approaches to correct back relaxation rested on an increase of input voltage which can lead to electrolysis, subsequently damaging the material, this method involves only proper control of isolated electrodes to compensate for the back relaxation and does not require sensor feedback. An electromechanical model of the actuator is used to guide the design of these input signals, and the feasibility of using electrode patterning to mitigate back relaxation is demonstrated. Without reaching electrolysis, an IPMC is able to maintain its position for approximately 30 seconds. Compared to a simple step response, the rate of relaxation is reduced by 94% and the maximum error is reduced by 64%.
Potential Well Shaping Through the Use of Impact Barriers for Broadband Electroelastic Energy Harvesting
Authors: McGehee Clark C. , Ballard Zach C. , Mann Brian P.
Published: February 2012

Many recent advances in electroelastic energy harvesting have benefitted from the use of nonlinear effects that reshape the potential well of the device and lead to bandwidth improvement. In this letter, the merits of using impact barriers for potential well shaping and bandwidth improvement in nonlinear electroelastic energy harvesters are considered. A bistable piezoelectric cantilever beam with symmetrically placed impact barriers is developed and tested through numerical simulation and experiment. Preliminary results indicate that impact barriers prolong the stability of large-amplitude attractors across a wider frequency range than an equivalent nonimpacting device, albeit at the expense of a greater peak amplitude. A mathematical model and simulation parameters are provided, and the system is investigated through both numerical simulation and experiment. A nontrivial relationship between barrier placement and the linewidth of the frequency response was observed in experiments. Future work will seek to improve the mathematical model to more accurately capture the behavior seen in the experiment.
Dynamic Finite Element Analysis of a Highly Parallel Robotic Surface
Authors: Salisbury Chris
Published: February 2012

A novel three-dimensional robotic surface is devised using triangular modules connected by revolute joints that mimic the constraints of a spherical joint at each triangle intersection. The finite element method (FEM) is applied to the dynamic loading of this device using three dimensional (6 degrees of freedom) beam elements to not only calculate the cartesian displacement and force, but also the angular displacement and torque at each joint. In this way, the traditional methods of finding joint forces and torques are completely bypassed. An effiecient algorithm is developed to linearly combine local mass and stiffness matrices into a full structural stiffness matrix for the easy application of loads. An analysis of optimal dynamic joint forces is carried out in Simulink® with the use of an algebraic Ricatti equation.
Computational Setup of Structural Health Monitoring for Real-Time Thermal Verification
Authors: Doyle Derek , Reynolds Whitney , Arritt Brandon , Taft Brenton
Published: February 2012

Research at the AFRL Space Vehicles Directorate is being conducted to reduce schedule times for assembly, integration, and test, to make satellite-based capabilities more responsive to user needs. Structural Health Monitoring has been pursued as a means for validating workmanship and has been proven on PnPSat-1. Embedded ultrasonic piezoelectric wafer active sensors (PWAS) have been utilized with local and global inspection techniques, developed both in house and by collaborating universities, to detect structural changes that may occur during assembly, integration, and test. Specific attention has focused on interface qualification. It is now reasonable to believe that evaluation of interfaces through the use of such sensors can also be used to indirectly qualify the structure thermally and that tedious thermal-vacuum testing may be truncated or eliminated altogether. This paper focuses on the computational development of extracting thermal properties from ultrasonic transmission records. Methods are validated on simple bolted lap-joint cantilever beams.
Modelling and Experimental Validation of Buckling Dielectric Elastomer Actuators
Authors: Vertechy Rocco , Frisoli Antonio , Bergamasco Massimo , Carpi Federico , Frediani Gabriele , De Rossi Danilo
Published: February 2012

Buckling dielectric elastomer actuators are special type of electro-mechanical transducers that exploit electro-elastic instability phenomena to generate large out-of-plane axial-symmetric deformations of circular membranes made of non-conductive rubbery material. In this paper a simplified explicit analytical model and a monolithic finite element model are described for the coupled electro-mechanical analysis and simulation of buckling dielectric elastomer membranes which undergo large electrically induced displacements. Experimental data are also reported which validate the developed models.
Use of Intrinsic Electrical Resistance Changes in Shape Memory Alloys as Robust Actuator State and Fault Detection Sensors
Authors: Herrera Guillermo A. , McKnight Geoffrey P. , Gao Xiujie , Johnson Nancy , Browne Alan L.
Published: February 2012

Shape memory alloy (SMA) used as electrically controlled on-demand actuators provide engineers new opportunities to create lighter automated components and devices in vehicles due to their compact size, silent operation, and inherently low mass. Outstanding and critical issues are cost-effective and robust control and protection of the SMA actuator element within the device to achieve long lasting service. SMA responds autonomously to external conditions such as temperature and stress and exhibit many property changes during excitation, but many current devices only use SMA as compact actuators; not making use of their intrinsic sensing capabilities. Inherent SMA property changes during use can provide significant utility for improved optimal control strategies. The motivation for this work is to create a robust control method for electrically controlled SMA actuation to simplify device implementation and improve reliability by using intrinsic material property changes. The current work demonstrates the use of electrical resistance feedback in an integrated controller to allow reduction of parasitic mass, cost, and complexity in 2-position devices. Using signal processing and algorithm logic states, we create virtual sensors that successfully identify start of the actuation, end of actuation, reset, and stress overload events. Using electrical resistance to sense the start of actuation allows successful/repeatable performance over a wide range of environmental conditions. Sensing the end of actuation and reset readiness prevents overheating and allows for shorter actuation cycle times, respectively without additional position and state sensors. While many previous efforts have examined the use of resistance in control schemes, one critical need not addressed in previous controllers is the ability to detect stress overload of the SMA during excitation. To protect against unintentional blocked deployment, many current devices include bulky mechanical overload protection systems that prevent stress spikes and SMA damage accumulation. Using resistance feedback, we demonstrate the detection of stress overloads thus extending device lifetime without the need for external mechanisms. The time derivative of the electrical resistance, logic state of the controller, and detection and use of peak/valley widths and thresholds define control events. These events become software based sensors that can augment or replace dedicated external sensors. Software based sensors were successfully employed to control an SMA wire actuator under various environmental temperatures and stress conditions. The control algorithm is not affected to changes in electrical contact resistance, material degradation and other noise sources yielding a powerful method for simple control of two position SMA devices without the need of external sensors.
Experimental Characterization of Direct Assembly Process Based Ionic Polymer Transducers in Sensing
Authors: Kocer Bilge , Weiland Lisa Mauck
Published: February 2012

Ionic Polymer Transducers (IPTs) are electroactive ion exchange membranes that are plated with metals which provide a capacitive property appropriate for sensor/actuator applications. IPTs bend when a voltage difference is applied across the surfaces of the transducer performing actuation behavior and produce current when they are deformed exhibiting sensing behavior. However, the response of the IPT as an actuator or as a sensor differs from each other since the mechanism responsible from actuation and sensing are different. Existing research in this field is mostly focused on actuation behavior. Therefore, in this study emphasis is on sensing where the IPTs have been prepared via the Direct Assembly Process (DAP). The DAP is selected because it enables experimental control over the electrode architecture, which may ultimately be exercised to explore the underlying physics responsible for sensing. Five lithium exchanged transducers are prepared with 1-ethyl-3 methylimidazolium trifluoromethanesulfonate (EmI-Tf) ionic liquid as the diluent, and high surface area RuO2 as the metallic powder. The IPTs are then cantilevered and subject to step displacements.
Adaptive Output Feedback Control of the IPMC Propelled Vehicle With Unknown High Frequency Gain Matrix
Authors: Gutta Shivakanth , Yim Woosoon , Singh Sahjendra N.
Published: February 2012

This paper presents model reference adaptive control (MRAC) of underwater vehicle propelled by the Ionic polymer metal composite (IPMC) actuator. Trajectories of the vehicle are controlled by simultaneously controlling the bias and amplitude of the sinusoidal voltage applied to the IPMC actuator attached at the real end of the vehicle. It is assumed that the system parameters as well as high frequency gain matrix are unknown. Using Lyapunov stability theory and factorization of the high frequency gain matrix, an adaptive output feedback control is designed for trajectory control of a heading angle and a speed of the vehicle. In the proposed approach, SDU (Square Diagonal and Upper triangular matrix) decomposition of the high frequency gain (HFG) matrix is used. Only signs of the leading principle minors of the HFG matrix are assumed to be known. Simulations results are presented to show that precise trajectory control of the heading and speed is achieved in spite of the coupling between controlled variables.
Polypyrrole Bridge as a Support for Alamethicin-Reconstituted Planar Bilayer Lipid Membranes
Authors: Northcutt Robert , Sundaresan Vishnu-Baba , Salinas Sergio , Zhang Hao
Published: February 2012

Conducting polymer actuators and sensors utilize electrochemical reactions and associated ion transport at the polymer-electrolyte interface for their engineering function. Similarly, a bioderived active material utilizes ion transport through a protein and across a bilayer lipid membrane for sensing and actuation functions. Inspired by the similarity in ion transport process in a bilayer lipid membrane (BLM) and conducting polymers, we propose to build an integrated ionic device in which the ion transport through the protein in the bilayer lipid membrane regulates the electrolytic and mechanical properties of the conducting polymer. This article demonstrates the fabrication and characterization of a DPhPC planar BLM reconstituted with alamethicin and supported on a polypyrrole bridge measuring 100 μm × 500 μm and formed across micro-fabricated gold pads. The assembly is supported on silicon dioxide coated wafers and packaged into an electronic-ionic package for electrochemical characterization. The various ionic components in the integrated ionic device are characterized using electrical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry (CA) measurements. The results from our experimental studies demonstrate the procedure to fabricate a rugged electro active polymer supported BLM that will serve as a platform for chemical, bioelectrical sensing and VOC detection.
Geometric Optimisation of Hinge-Less Deployment System for an Active Rotorblade
Authors: Paternoster Alexandre , Loendersloot Richard , de Boer Andre , Akkerman Remko
Published: February 2012

The Green Rotorcraft project (part of Clean Sky JTI) is studying the Gurney flap as a demonstrator of a smart adaptive rotorblade. Deployment systems for the Gurney flap need to sustain large centrifugal loads and vibrations while maintaining precisely the displacement under aerodynamic loading. Designing such a mechanism relies on both the actuation technology and the link which transmits motion to the control surface. Flexible beams and piezoelectric patch actuators have been chosen as components to design this mechanism. Flexible beams are providing an hinge-less robust structure onto which the piezoelectric actuators are bonded. A candidate topology is determined by investigating the compliance of a simple wire structure with beam elements. A parametrized finite element model is then built and optimized for displacement and force through surrogate optimization. The whole process does not requires many finite element analyses and quickly converge to an optimized mechanism.
Limit-Cycle Oscillation Suppression of Bioinspired Ornithopter: Wind Tunnel Testing
Authors: Lee Jun-Seong , Lee Dong-Kyu , Lee Juho , Han Jae-Hung
Published: February 2012

This study experimentally shows that an oscillatory behavior observed in a trim flight of an ornithopter has a stable limit-cycle oscillation (LCO) characteristics and that the magnitude of the LCO in body pitch dynamics can be suppressed by active tail motion. A free flight of the tested ornithopter is emulated in the wind tunnel using a specially devised tether that provides the minimal mechanical interference to the flight of ornithopter. Due to the symmetric wing motion in forward trim flight, the longitudinal flight dynamics is more focused than the lateral one. The non-contact type sensors are used to measure the time histories of the flight state variables such as wing and tail motions, body pitch angle, and altitude. The tail motion for the pitch LCO reduction is achieved by two actuators: 1) Servo motor for the rigid-body motion of the tail elevation angle, and 2) Macro-Fiber Composite strain actuator for the elastic deformation of the tail camber. The performances of the LCO suppressions are compared in the root-mean-square-error sense and the harmonically activated in-phase tail motion linked to wing motion is observed to effectively reduce the pitch LCO.
Multi-Objective Design Optimization of a Shape Memory Alloy Actuated Robotic Catheter
Authors: Crews John H. , Buckner Gregory D.
Published: February 2012

In this paper, we present a method for optimizing the design of a shape memory alloy (SMA) actuated robotic catheter. The robotic catheter is designed for use in endocardial ablation procedures, where “trackability” (bending flexibility) and “pushability” are desirable but conflicting catheter traits, leading to a multi-objective optimization problem. The catheter uses SMA tendons for internal actuation, which create a bending moment about a central structure. The design of SMA actuators is often non-intuitive and complicated due to the material’s hysteretic dependence on stress and temperature. The modeling and design difficulties increase when considering antagonistic SMA actuation, which is the case for the robotic catheter. The catheter is optimized using a genetic algorithm coupled with COMSOL Multiphysics Modeling and Simulation software. The objective functions are formulated in order to improve bending flexibility and pushability. Bending flexibility is quantified by radius of curvature. Pushability is a more subjective characteristic that depends on axial stiffness and friction, but for optimization purposes, it is quantified using axial stiffness and the surface area of the catheter. Several design variables that affect the catheter behavior are considered; these include the SMA tendon diameter and its pre-strain, the offset of the SMA tendon from the neutral axis of the central structure, and the central structure’s diameter and elastic modulus.
Multidirectional Circular Microstrip Patch Antenna Strain Sensor
Authors: Daliri Ali , Wang Chun H. , John Sabu , Galehdar Amir , Rowe Wayne S. T. , Ghorbani Kamran
Published: February 2012

In this paper, a new design for microstrip patch antenna strain sensors is proposed. The new antenna sensor works based on the meandered microstrip patch antennas. It is threefold more sensitive than previously proposed circular microstrip patch antenna strain sensors. Also, the overall physical dimension of the new antenna sensor is reduced by the factor of five. The current sensor is able to detect strain in all directions. In order to design the antenna sensor, two available commercial FEM software packages ANSYS™ and HFSS™ are used. Both experimental and FEM results corroborate the multidirectional feature of the new antenna sensor. Also, the effect of the hole size in the structure (for coaxial connection to the antenna) on the antenna performance has been studied. Based on the results obtained, the antenna sensor can be recommended for use in structural health monitoring for strain-based damage detection in aerospace structures.
Field Driven Stiffness Control of Legged Robotic Structures Using Dielectric Elastomers
Authors: Morton Jeffrey , Haldane Duncan , Hays Michael , Clark Jonathan , Oates William S.
Published: February 2012

Dielectric elastomers are known for their electro-mechanically coupled constitutive behavior which has demonstrated the potential for developing a number of novel adaptive structures. Despite the advances in understanding these materials using nonlinear field theory and experimental characterization, several questions remain regarding how to effectively integrate these materials in adaptive robotic structures. Here, a new design is proposed to integrate these materials into legged robotic structures that can achieve relatively large and rapid stiffness changes for enhanced mobility and agility of a field demonstrated hexapod robot. A set of resonance test are performed to quantify changes in effective stiffness as a function of the applied electric field. The results are incorporated into a bi-layer beam model to estimate changes in the effective stiffness of a robotic C-shaped leg. The results show promise for developing adaptive robotics legs for multi-terrain mobility.
Ultra-Low Energy Army Installations
Authors: Bawden Kim , Prado Valentina , Seager Thomas P. , Mechtenberg Abigail R. , Bennett Erin
Published: February 2012

The concept of energy conservation is now deeply entrenched in building design and operation. Typical approaches take a first law perspective that seeks to reduce energy quantity losses at individual system components. While this conventional approach often results in energy savings, it is not sufficient to realize ultra-low energy communities. However, the concept of energy quality, which derives from the second law of thermodynamics, is capable of more holistic, systems analyses, revealing opportunities for efficiency improvement, energy quality matching, or energy cascading that may otherwise go unnoticed. This paper makes two cross-comparisons of analytic perspectives for understanding energy consumption in different types of Army communities. The first is a comparison of first and second law perspectives of energy improvement technologies at a permanent Army base in the United States. The second is a comparison of electricity generation efficiencies at forward operating bases under conditions that do not consider supply chain fuel consumption and those that do. Considerable differences exist in the conclusions and recommendations that are generated by the different perspectives in each case. In the permanent community, second law analysis is useful for demonstrating the value of combined heat and power at an existing heating district. In the second case, the consumption of fuel in long convoys suggests that delivery of energy equipment (such as solar panels) is in itself an important source of fuel consumption that should be considered in optimization of solar energy technologies.