bluuebunny/crossref_metadata_2025 huggingface dataset:
Durability Assessment of Fabric-Reinforced Shape-Memory Polymer Composites
Authors: Tandon G. P. , Goecke K. , Cable K. , Baur J.
Published: February 2010

The present study is a baseline assessment of the environmental durability of current state-of-the-art, fabric-reinforced shape memory materials being considered for morphing applications. Tensile dog-bone-shaped specimens are cut along three different directions, namely, along 0°, perpendicular (90°), and at 45° to the orientation of the fabric. The shape memory properties and elastomeric response before and after relevant environmental exposure to water at 49°C for 4 days, in lube oil at room temperature and at 49°C for 24 hours, and after exposure to Xenon Arc (63°C, 18 minutes water and light/102 minutes light only) and spectral intensity of 0.3 to 0.4 watts/m2 for 125 cycles (250 hours exposure time) are measured. Weight loss of the as-received and conditioned specimens is monitored while the dog-bone-shaped specimens are subjected to recovery following fixation. Parameters being investigated include stored strain, recovery stress, shape fixity, shape recovery, and modulus in the glassy and rubbery state.
Real-Time Optimization of a Research Morphing Laminar Wing in a Wind Tunnel
Authors: Coutu Daniel , Brailovski Vladimir , Terriault Patrick , Mamou Mahmoud , Laurendeau Eric
Published: February 2010

This paper presents a new approach of real-time control of a morphing wing based on a coupled fluid-structure numerical model. The 2D extrados profile of an experimental laminar wing is morphed with the purpose to reduce drag, through extension of the laminar flow over the upper wing surface. As a first step, the active structure has been modeled, manufactured and experimentally tested under variable flow conditions in a subsonic wind tunnel (the Mach number ranges from 0.2 to 0.3 and the angle of attack from −1° to 2°). In this work, a real-time closed-loop control strategy is designed to find the optimum actuator strokes using an experimentally measured lift-to-drag ratio (feedback parameter). An extensive wind-tunnel characterization of the laminar wing prototype has been performed to design the algorithm and to set up the parameters. To calculate the initial strokes of the actuators and thus to accelerate the optimization procedure, a validated ANSYS-XFoil coupled fluid-structure numerical model is used. The robustness and efficiency of the developed real-time control system is tested under two flow conditions. The morphing wing performance obtained is slightly superior or similar to the open loop control approach proving the high performance of the numerical model. The proposed control strategy appears to be well suited to benefit from the complete morphing potential (according to the lift-to-drag ratio) of the wind tunnel prototype although higher feedback resolution is recommended from the numerical simulation algorithms.
Multivariant Formulation of the Thermomechanically Coupled Mu¨ller-Achenbach-Seelecke-Model for Shape Memory Alloys
Authors: Kastner Oliver , Richter Frank , Eggeler Gunther
Published: February 2010

Temperature changes caused by latent transformation heats are an integral part of the behavior of shape memory alloys and inevitably couple the thermal and the mechanical fields. This general behavior is covered by the Mu¨ller-Achenbach-Seelecke (MAS) model. Its versatility has been documented extensively in the literature. In the original formulation the MAS model is restricted to uniaxial states of stress in a SMA, which limits its application to cases where such stress states prevail, such as axial loading in wires and trusses, as well as pure beam bending, pure torsion and shrink-fit problems. Unreliable results, however are expected under arbitrary multiaxial loading conditions. To overcome this limitation we present an extension of the model capable of arbitrary stress/strain/temperature states in 3D. Our model adopts ideas presented by Xie but employs a different non-convex free energy function. Rate equations are employed to model temperature or stress/strain induced transformations between austenite and eight variants of martensite present in the model. As the MAS model, the multi-variant model is capable of fully-coupled thermo-mechanical processes which is shown by simulations of temperature-induced processes, quasiplasticity and pseudoelasticity under variable load directions. At the present level of sophistication, the model is restricted to single crystalline SMA. All examples are explained by the use of a standalone model implementation. The model is intended for future implementation into the finite-element-method environment ABAQUS™ to provide a powerful tool useful in the framework of engineering design studies, especially in situations which require non-isothermal conditions and phase transitions.
Real-Time Structure Shape Estimation Using Distributed Fiber Bragg Grating Sensors
Authors: Kim Hong-Il , Kang Lae-Hyong , Han Jae-Hung
Published: February 2010

One of the emerging issues in lightweight aerospace structures is the real-time estimation of the structural shape changes. In order to reconstruct the structure shape based on the measured strain data at multiple points, the displacement-strain transformation (DST) method has been used. In this study, simulation for a 1-D beam model was performed to verify the DST method. Bending displacements for various excitation conditions were successfully estimated using the simulated strain signals. Strain sensor positions were optimized by the minimization of the condition number of the DST matrix for the 1-D beam. We further expanded the shape estimation method to rotating beams. A rotating flexible beam experimental model was constructed and a numerical simulation model was also prepared. Multiplexed four FBG sensors were fabricated and attached to the rotating beam structures to measure strains at four different locations. The experimental device has an optical rotary coupler, and the sensor signals are transmitted through the optical rotary coupler. Bending displacements were estimated based on the FBG signals and compared with directly measured displacement data using photographs taken by a high-speed camera. This shows the validity of the proposed shape estimation technique based on DST matrix for rotating beam structures.
Magnetostrictive Blocked-Force Clamping Mechanism for Secure and Heavy-Load Inchworm Motion
Authors: Yang B. T. , Meng G. , Xu P. Y. , Tan X. T. , Feng Z. Q. , Yang D. H.
Published: February 2010

The capability of inchworm motor for long-displacement, heavy-load and precise positioning is greatly conditioned by the effectiveness of the clamping mechanism. A need exists in the art for clamping mechanism capable of delivering precise and heavy load motion. This paper presents a novel giant magnetostriction material (GMM) application to the development of such mechanism. GMM is advantageous over other smart materials in this particular aspect by its remarkable magnetostriction and especially the huge blocked stress. It can, e.g., display around 4000N at moderate magnetization with a φ25×100mm GMM rod. Most desirably, such large force could be used as clamping force in inchworm movement. However, the force can only be generated under blocked state, which is generally hard to reach, especially in a moving regime. Addressing this problem, the research utilizes GMM rod’s capacity to both positively stretch and negatively contract under permanent-magnet-biased condition and presents a specially designed clamping mechanism, a permanent-magnet-biased actuator fastened in a rigid guideway. Being applied reverse magnetic field, the formerly stretched actuator may contract to a suitable size to be put into the rigid guideway. Then, removal of the field will theoretically result in the restoration of the actuator. Practically, stretching of the actuator is blocked by the rigid guideway. This forms the so-called Pre-blocked-clamping-on state, where no-power fastening behavior exists. Moreover, the blocked force is adjustable. When being applied the same-direction field as the permanent one, the blocked force becomes greater (Blocked-clamping-on state). When being applied adequate reverse field, the blocked force is diminished with the shrinking of the actuator, till the actuator released from the rails (Blocked-clamping-off state). This process realizes the utilization of blocked force in clamping action, thus provides resolution for secure and heavy load inchworm motion. A clamping mechanism prototype (Size:φ32×130mm, with a φ10×100mm GMM rod) has been realized. The design and working process of the setup is presented. Through experiments, the prototype can be facilely manipulated by square-instant and sinusoid-continuing current and it can agilely perform to meet the proposed blocked force the proposed clamping principle.
Experimental Analysis of the Effect of the Structure Area on the PZT-Based SHM Systems
Authors: Baptista Fabricio Guimaraes , Vieira Filho Jozue , Turra Antonio Eduardo , Lopes Junior Vicente
Published: February 2010

The structural health monitoring (SHM) systems based on electromechanical (E/M) impedance technique have been widely investigated. Although many studies indicate the reliability of this technique, some practical considerations still have to be considered in real applications. This paper presents an experimental analysis of the effect of the structure area on the system’s performance. The results indicate that the sensitivity of the system to detect damage decreases significantly when the host structure has large cross-section area.
Sensitivity of NL-RDM to Errors in the Non-Linear Test Process
Authors: Sarmast Mehdi , Bostan Manesh M. Saeed , Mehran Mahmood R.
Published: February 2010

NL-RDM is a non-linear system identification method that combines a number of linear and non-linear system identification methods and offers a practical approach to the identification of lumped parameter and continuous systems using a classical linear modal model with additional non-linear terms. The method was started by identifying the modal parameters of the underlying linear system via the FRF, MMIF and appropriated force vector. The criteria for an ideal method are detailed in the some earlier papers, but the reality creates a limitation. This paper is divided into several sections relating to the “Nonlinear Test Process”. Error which arise from test, environmental and equipment effects, are quantization errors, input (or process) noise and measurement noise. So, the effects of these inaccuracies and possible solutions for decreasing any negative effects are considered. Then, The sensitivities to noise and quantization which could be encountered in practical applications of the NL-RDM, are discussed in concept, generated, applied and analyzed through simulation programme for two degree of freedom uncoupled and coupled examples.
Sensor Networks for In-Situ Failure Identification in Woven Composites
Authors: Park Chun , Propst Adam , Peters Kara , Zikry Mohammed A.
Published: February 2010

This paper presents experimental measurements of the response of woven composite laminates to multiple low-velocity impacts. Damage initiation and progression occur at multiple physical and temporal scales in heterogeneous materials, including fiber breakage, matrix cracking, delamination and matrix relaxation. The sensor networks/interrogators were therefore chosen specifically to provide insight into the order and progression of different failure modes. Measurements of the contact force between the impactor and composite are measured throughout impact. Additionally, the dissipated energy per impact event is also calculated from the impactor velocity. Surface mounted and embedded fiber Bragg grating sensors are used for the measurement of the laminate response. Peak wavelength measurements are performed during impact at 1 kHz, while full-spectral scanning is performed at 5 Hz during relaxation period of the laminate immediately after impact and quasi-statically to measure post-impact residual strain states within the laminate. The results highlight the depth of information embedded within the FBG full-spectral data sensors, as well as the added insight to be gained from combined global-local measurements.
Effect of Segmented Electrodes on Piezo-Elastic and Piezo-Aero-Elastic Responses of Generator Plates
Authors: De Marqui Carlos , Erturk Alper , Inman Daniel J.
Published: February 2010

In this paper, the use of segmented electrodes is investigated to avoid cancellation of the electrical outputs of the torsional modes in energy harvesting from piezo-elastic and piezo-aero-elastic systems. The piezo-elastic behavior of a cantilevered plate with an asymmetric tip mass under base excitation is investigated using an electromechanically coupled finite element (FE) model. Electromechanical frequency response functions (FRFs) are obtained using the coupled FE model both for the continuous and segmented electrodes configurations. When segmented electrodes are considered torsional modes also become significant in the resulting electrical FRFs, improving broadband (or varying-frequency excitation) performance of the generator plate. The FE model is also combined with an unsteady aerodynamic model to obtain the piezo-aero-elastic model. The use of segmented electrodes to improve the electrical power generation from aeroelastic vibrations of plate-like wings is investigated. Although the main goal here is to obtain the maximum electrical power output for each airflow speed (both for the continuous and segmented electrode cases), piezoelectric shunt damping effect on the aeroelastic response of the generator wing is also investigated.
Design, Modeling and Control of a New Robotic Module Actuated by Shape Memory Alloy Springs
Authors: Hadi Alireza , Elahinia Mohammad , Ghazavi Asadollah , Moghadam Majid M.
Published: February 2010

Modular robotic systems provide attractive benefits in the form of re-configurable robots that can change and adapt for special tasks. Self-reconfigurable is re-configurable robot with the ability to change their framework for different missions. One way to increase robots capabilities and to achieve self-configurable robots is to develop small, powerful and dexterous modules. In this paper, a new mechanism which uses Shape Memory Alloy (SMA) spring actuators is applied to develop a robotic module. Among the proposed modular systems until now, shape memory alloys especially the spring type are rarely used as actuators. The proposed mechanism is based on antagonistic application of SMA springs which provide faster actuation response. It is shown that the module mechanism is suitable for developing modular robotic systems, such as mobile robots, snake robots, and legged robots. The design of mechanical and electrical hardware of the module in addition to the sensing and actuating system is done talented in an optimum space. The same extendable modules communicate through a common bus in order to develop a distributed system. Consequently a proper module is presented to be applied in different robotic systems. Moreover, an effective non-linear control strategy which is variable structure control is applied for controlling the position of the module. Benefits and suitability of this controller for the module different configurations is verified using simulations and experiments.
Experimental Evaluation of an Adaptive Actuator Control Scheme for Real-Time Tests of Large-Scale Magneto-Rheological Damper Under Variable Current Inputs
Authors: Chen Cheng , Ricles James M.
Published: February 2010

A Magneto-Rheological (MR) fluid damper is a semi-active device for vibration control of engineering structures subjected to dynamic loading. The characteristics of MR dampers vary under different current inputs to achieve optimized vibration control of structural systems. Experimental evaluation of MR dampers under different control laws is necessary before the device can be accepted by the practical design community. Real-time hybrid simulation provides an economical and efficient dynamic testing technique by accounting for the damper rate-dependency and the damper-structure interaction. A successful real-time hybrid simulation requires accurate actuator control to achieve reliable experiment results. A servo-hydraulic actuator usually introduces a time delay due to servo-hydraulic dynamics. The variable current inputs induced by semi-active control laws would pose additional challenges for actuator control by introducing variable delay in a real-time hybrid simulation. In this paper an adaptive compensation technique is experimentally evaluated for real-time hybrid simulation involving an MR damper under variable current inputs. Predefined band-limited white noise is used as the displacement command for the servo-hydraulic actuator and current command for the MR damper. The adaptive compensation scheme is demonstrated to achieve accurate actuator control and therefore shows great potential for real-time hybrid simulation of structural systems with semi-active energy dissipation devices.
Pre-Stressed Piezoelectric Bimorph Micro-Actuators Based on Machined 40-Micron PZT Ceramic Thick Films—Batch Scale Fabrication and Integration With MEMS
Authors: Wilson Stephen , Jourdain Renaud , Owens Sam
Published: February 2010

The projected force-displacement capability of piezoelectric ceramic films in the 20–50μm thickness range suggests that they are well suited to many micro-fluidic and micro-pneumatic applications. Furthermore when they are configured as bending actuators and operated at ∼1V/μm they do not necessarily conform to the high-voltage, very low-displacement piezoelectric stereotype. Even so they are rarely found today in commercial micro-electromechanical devices, such as micro-pumps and micro-valves, and the main barriers to making them much more widely availability would appear to be processing incompatibilities rather than commercial desirability. In particular, the issues associated with integration of these devices into MEMS at the production level are highly significant and they have perhaps received less attention in the mainstream than they deserve. This paper describes a fabrication route based on ultra-precision ceramic machining and full-wafer bonding for cost-effective batch-scale production of thick film PZT bimorph micro-actuators and their integration with MEMS. The resulting actuators are pre-stressed (ceramic in compression) which gives them added performance, they are true bimorphs with bi-directional capability and they exhibit full bulk piezoelectric ceramic properties. The devices are designed to integrate with ancillary systems components using transfer bonding techniques. The work forms part of the European Framework 6 Project ‘Q2M - Quality to Micro’.
Development of a Bio-Inspired Artificial Fish Using Flexible Matrix Composite Actuators
Authors: Zhang Zhiye , Philen Michael , Neu Wayne
Published: February 2010

A bio-inspired prototype fish using the flexible matrix composite (FMC) muscle technology is developed for fin and body actuation. Flexible matrix composite actuators are pressure driven muscle-like actuators capable of large displacements as well as large block forces. An analytical model of the artificial fish using FMC actuators is developed and analysis results are presented. An experimental prototype of the artificial fish having FMC artificial muscles has been completed and tested. Constant mean thrusts have been achieved in the laboratory for a stationary fish for different undulation frequencies around 1 Hz. The experimental results demonstrate that a constant thrust can be achieved through tuning of excitation frequency. Free-swimming results show that the prototype can swim at approximately 0.9 m/s.
Defining and Investigating New Symmetry Classes for the Next Generation of Magnetorheological Elastomers
Authors: von Lockette Paris R. , Lofland Samuel , Biggs Joseph
Published: February 2010

This work addresses the fundamental difference in behavior between magnetorheological elastomers (MREs) formed from soft-magnetic particles, whose behavior is driven by local demagnetizing effects and those formed with hard-magnetic particles that have a preferred magnetic axis and therefore generate magnetic torques at the particle level. This work explores the phenomena by defining and examining four classes of MREs based upon permutations of particle alignment - magnetization pairs, i.e. I-I for magnetically isotropic particles arranged isotropically (randomly, or unaligned), A-A for magnetically anisotropic particles arranged anisotropically (typically aligned in chains), etc. The distinctions are important since the particle-field interactions for each class differ substantially. The behavior of classes I-I and I-A are driven primarily by demagnetizing effects while classes I-A and A-A are driven by the torques produced in the particles. MRE materials made with barium hexaferrite (BaM) (Classes A-A and I-A) and Fe powders (Classes A-I and I-I), aligned and unaligned, served as proxies for each of the four classes in this work. BaM, with saturation magnetization Msat = 4 × 105 A/m and coercive field Hc > 3 × 105 A/m, provided the magnetically anisotropic behavior while iron, with Msat = 1.8 × 106 A/m and Hc < 2 × 103 A/m, provided the soft magnetic behavior. Experiments on materials with 30% v/v particle concentrations showed that under uniform magnetic fields class A-A (aligned BaM) MREs were capable of large deflections in cantilever beam bending (deflections of 12mm for length 50mm and magnetic field 1.2 × 105 A/m) whereas all other classes, including I-A (random BaM) MREs, showed none. Tip deflection varied linearly with applied field strength. Tip blocking-force versus deflection experiments were also conducted on cantilevered A-A specimens. These tests showed that tip force increased with decreasing free deflection and with increasing field strength.
Integrated Structural Damage Assessment, Motion Planning, and Decision-Making for Distressed Aircraft Under Uncertainty
Authors: Lopez Israel , Sarigul-Klijn Nesrin
Published: February 2010

Aircraft navigation can be safely accomplished by properly addressing the following: decision-making, obstacle perception, aircraft state estimation, and aircraft control. To develop a monolithic navigational system is probably an impossible task; instead a hierarchical decomposition is presented, which breaks down the safe recovery and landing of distressed aircraft into sub-problems that maximize the probability that the overall objective is achieved. Navigational performance is often hinder by in-flight damage or failures, which often results in mission failure and an inability to guide the aircraft to a safe landing. Uncertainty is a very important concern in recovery of damaged aircraft since it can cause infeasibilities, false diagnosis and prognosis causing further performance degradation and mission failure. The damaged aircraft is simulated via a simplified kinematic model. The different sources and perspectives of uncertainties in the damage assessment process and post-failure trajectory planning are presented and classified. The decision-making process for an emergency motion planning and landing is developed via the Dempster-Shafer evidence theory. The objective of the trajectory planning is to arrive at a target position while maximizing the safety of the aircraft given uncertain conditions. Simulations are presented for an emergency motion planning and landing that takes into account aircraft dynamics, path complexity, distance to landing site, runway characteristics, and subjective human decision.
Dispersion of Carbon Nanotubes in Cement-Based Composites and Its Influence on the Piezoresistivities of Composites
Authors: Han Baoguo , Yu Xun , Ou Jinping
Published: February 2010

Sodium dodecyl sulfate (SDS) and sodium dodecylbenzene sulfonate (NaDDBS) are used as surfactants to improve the dispersion of multi-walled carbon nanotubes (MWNTs) in cement mortar and fabricate piezoresistive carbon-nanotube/cement mortar composite. The piezoresistivity of carbon-nanotube/cement mortar composite with different content levels of MWNTs and different surfactants were explored under repeated loading and impulsive loading. Experimental results indicate that NaDDBS has higher efficiency than SDS for the dispersion of MWNTs in cement mortar. The response of the electrical resistance of carbon-nanotube/cement mortar composite with NaDDBS to external force is more stable and sensitive than that of carbon-nanotube/cement mortar composite with SDS. These findings indicate that the use of NaDDBS is an effective way for improving the dispersion of MWNTs in cement-based composite and fabricating MWNTs filled cement-based composite with stable and strong piezoresistive response.
Non-Invasive Measurement Techniques for Measuring Bilayers in Droplet-Interface-Bilayers
Authors: Creasy M. Austin , Leo Donald J.
Published: February 2010

Phospholipids and membrane proteins are two of the fundamental building blocks of cell membranes in living organisms. These molecules are amphipathic and synthetic membranes made of phospholipids, called bilayer lipid membranes (BLMs), are used to understand the characteristics of a cell membrane. Studies of these BLMs have been performed on both solid support and liquid support systems. A droplet interface bilayer (DIB) is a liquid support system where a monolayer is formed around a water droplet placed in oil and a bilayer is formed when two of these droplets are placed in contact. For impedance measurements, electrodes are placed in the water on each side of the bilayer. The measurements first insure there is a bilayer and second to obtain information about the bilayer. In a DIB system the electrodes pierce the monolayer surrounding the droplet causing instabilities in the monolayer. This study focuses on a non-invasive technique for measuring the bilayer by using the electrodes to contact the monolayer around the droplets and take impedance measurements without piercing the monolayer.
Ornithopter Flight Maneuver Control
Authors: Dietl John M. , Garcia Ephrahim
Published: February 2010

Ornithopter studies in the past have focused on ornithopter construction, power sources, wing design, maximizing thrust, energy efficiency, steady flight trajectories, and flight stability. The next step is to control unsteady maneuvers: the transition from hovering flight to forward flight, turns, and vertical takeoff and landing. The design of stable trim conditions for forward flight and for hover has been achieved. In forward flight, an ornithopter is configured like a conventional airplane or large bird. Its fuselage is essentially horizontal and the wings heave in a vertical plane. In hover, however, the body pitches vertically so that the wing stroke in the horizontal plane. Thrust directed downward, the vehicle remains aloft while the downdraft envelops the tail to provide enough flow for vehicle control and stabilization. To connect these trajectories dynamically is the goal. This study of the transition from forward flight to hovering uses two approaches: to first achieve adequate trajectories, and then optimal trajectories. The object is to connect an initial state—in this case forward flight—and a final state—a steady hover at a designated point—through a feasible flight trajectory. A simple approach is to immediately switch between feedback controllers that regulate each trajectory. When the forward flight trajectory approaches the desired location, the computer switches to a control law that regulates the desired hovering trajectory, which—barring instability—should cause the vehicle to settle. A second approach is to select a range of intermediate trims to stabilize. Starting with the full forward speed, the controller will successively stabilize a trim with lower forward velocity. After a finite number of controllers, the system will achieve a stable hover. This approach would lessen the jump between trim conditions, increasing the likelihood of a stable transition. A third approach is to establish an open-loop trajectory through a trajectory optimization algorithm—optimized for shortest altitude drop, shortest stopping distance, or lowest energy consumption. This path itself could be stabilized. This serves to establish the feasibility of new maneuvers in mechanical flapping flight. It also will make it easier to perform the maneuvers by computer assisted control or by providing an example for a pilot to use.
Multiscale Modeling of Nafion Mechanical Properties
Authors: Zangrilli Ursula T. , Weiland Lisa M.
Published: February 2010

Multiscale modeling is used to investigate the mechanical characteristics of ionic polymers with the intent of ultimately expanding understanding of the interplay between multiscale stiffness and electromechanical response. Strategies for manipulating electromechanical transduction of ionic polymers include, but are not limited to: variation of hydration and/or the equivalent weight. In general, variations resulting in increased electroactive response also result in decreased mechanical stiffness and can decrease to the point of limiting mechanical integrity. This effort begins with the supposition that a better understanding of the ionic polymer multiscale material stiffness will enable bypass of this perceived trade-off. Rotational Isomeric State (RIS) theory is used to predict the conformation of a typical polymer hydrophobic backbone for a fully hydrated, sodium exchanged, Nafion 1200 EW case. The RIS method generates a large number of crosslink-to-crosslink chain lengths. The distribution is assessed via Johnson distributions and in turn, employed in a Boltzmann statistical thermodynamics framework to assess mechanical stiffness. The approach explores the impact of morphology on stiffness via imposing as assumed morphology a priori.
Enhanced Electromechanical Properties in Poly(Vinylidene Fluoride) (PVDF)-Based Nanocomposites
Authors: Deshmukh Sujay , Ounaies Zoubeida
Published: February 2010

Efforts to enhance the electromechanical properties of Poly(vinylidene fluoride) (PVDF) and its copolymers have been directed at optimizing the molecular chemistry, stretching and poling parameters. This study investigates an alternative approach to enhancing the properties via adding nanoinclusions in PVDF. We investigate the enhanced electrostrictive response in PVDF by adding Single Walled Carbon Nanotubes (SWNTs). We also show the change in the non-polar morphology of “as-is” PVDF to the polar γ phase by adding SWNTs and eventually to the piezoelectric β phase by stretching the nanocomposites.
Durable Biomolecular Assemblies for Protein-Powered Device Concepts
Authors: Sarles Stephen A. , Leo Donald J.
Published: February 2010

Physically encapsulated droplet-interface bilayers are formed by confining aqueous droplets surrounded by lipid mono-layers in connected compartments within a solid substrate. The droplets reside within each compartment and are positioned on fixed electrodes built into the solid substrate. Full encapsulation of the network is achieved with a solid cap that inserts into the substrate to form a closed volume. Encapsulated networks provide increased portability over unencapsulated networks by limiting droplet movement and by integrating the electrodes into the supporting fixture. The formation of encapsulated droplet-interface bilayers is confirmed with electrical impedance spectroscopy and cyclic voltammetry is also used to measure the effect of alamethicin proteins incorporated into the resulting lipid bilayers. The durability of the networks is quantified using a mechanical shaker to oscillate the bilayer in a direction transverse to the plane of the membrane and the results show that single droplet-interface bilayers can withstand several g’s of acceleration. Observed failure modes include both droplet separation and bilayer rupturing, where the geometry of the supporting substrate and the presence of electrodes are key contributors. Physically encapsulated DIBs can be shaken, moved, and inverted without bilayer failure, enabling the creation of portable, protein-powered devices.
Semi-Active Isolation System Using Self-Powered Magnetorheological Dampers
Authors: Choi Young-Tai , Song Hyun Jeong , Wereley Norman M.
Published: February 2010

This study addresses experimental evaluation of a semi-active vibration isolation system using a self-powered magnetorheological (MR) damper. To this end, a self-powered MR damper was constructed by electronically connecting an MR damper with a power harvesting dynamic vibration absorber (DVA) that can convert mechanical energy due to vibration and shock into electrical energy by means of electromagnetic induction. In this study, an MR damper for seat suspensions of the Expeditionary Fighting Vehicle (EFV) was chosen for the application of the self-powered MR damper. The generated voltage, current, and power of the power harvesting DVA were experimentally measured in frequency domain under various acceleration levels of 0.3–1.2 g (where one g = 9.81 m/s2). In addition, damper force testing of the self-powered MR damper (i.e., in this study, a prototype EFV MR damper with the power harvesting DVA) was experimentally conducted in time and frequency domains. To evaluate vibration isolation performance of a semi-active isolation system using the self-powered MR damper, an EFV seat suspension mockup using the self-powered MR damper was constructed. Under eight different representative random excitation accelerations, the vibration isolation performance of the EFV seat suspension mockup using the self-powered MR damper was experimentally evaluated.
On Quantifying Detectable Fatigue Crack Size in Aluminum Beams Using Vibration and Impedance-Based Methods
Authors: Afshari Mana , Butrym Brad A. , Inman Daniel J.
Published: February 2010

This paper looks at the impedance-based and vibration methods used for the structural health monitoring (SHM) of aluminum beams and attempts to quantify the smallest fatigue crack size that is detectable by these two methods. The vibration-based method presented in this paper, uses the recent model of Aydin [1] which is based on a simple Euler-Bernoulli beam model. This method treats cracks as localized reduction in the beam’s stiffness and models them as massless rotational springs at the locations of the cracks. The beam is then considered to be of multiple sections connected by these springs. The beam studied in the present work is assumed to be an aluminum, uniform, Euler-Bernoulli beam having a single fatigue crack and being axially loaded. It is further assumed that frequencies can only be measured to within half a Hertz. This results in formulas that can be used to predict specific detectable sizes of fatigue cracks given specific geometry of the beam. For example for a beam of dimension 240×19.1×4.8 mm, it is found that the fatigue crack must be approximately 12.5% of the beam width in order to induce a frequency shift of 0.5 Hz. In the second part of this paper, different sets of experiments are conducted on aluminum beams. First, saw-cuts are made in the beams and the resultant shift in the beams’ natural frequency is examined to find the minimum detectable cut length. In order to improve this minimum detectable damage size, the beat frequency method is applied, which enhances the minimum detectable frequency shift. These results are then compared to those of the electrical impedance measurements through the HP 4194A Impedance analyzer. At the end, the aluminum beams are being fatigued and by measuring their electrical impedance at different numbers of fatigue cycling, their detectable fatigue crack size is investigated.
An Analytical Method for Vibration Modelling of a Piezoelectric Bimorph Beam for Power Harvesting
Authors: Lumentut Mikail F. , Howard Ian M.
Published: February 2010

This paper presents the development of a mathematical method for modelling a piezoelectric bimorph beam under two input base-transversal and longitudinal excitations. The piezoelectric bimorph beam model was based on the Euler-Bernoulli beam coupled with polarity-electric field for low power harvesting. The piezoelectric bimorph beam with brass centre shim was also coupled to a simple electrical circuit of resistor component. The existence of input base-longitudinal motion can affect the overall strain, polarity and electric field of the cantilevered piezoelectric bimorph, identified to have predominant bending due to input transverse-base motion. The characteristic physical behaviour of the bimorph model for parallel connection can create mode vector configurations of X-poling due to longitudinal extension form and Y-poling due transverse bending form. Conversely, the effect of series connection of the physical bimorph model can create X-poling due to transverse bending and Y-poling due to longitudinal extension forms. A new method of solving the piezoelectric bimorph under two input base-motions using coupling superposition of the elastic-polarity field has been introduced. The governing dynamics equations can be derived analytically using the weak form of Hamiltonian theorem to obtain the constitutive equations. DuBois-Reymond lemma can be used to separate three constitutive dynamic equations based on independent coefficients of the virtual displacement vectors. Furthermore, the solution forms for the three governing dynamics equations were assumed using the three independent normal modes of displacement functions based on the normal modes in the transversal, longitudinal and electric potential mode forms. To this end, the dynamic equations for frequency response, dynamic displacements, accelerations and electric voltage can be further computed analytically according to the suggested formulations.
Dynamics of a Thin Plate With Partly Specified Motion
Authors: Ghasemi AmirHossein , Seigler T. M.
Published: February 2010

The problem considered here is that of determining the precise forcing function that produces specified motion of a deformable structure. While fundamental in nature, the problem is practically important for evaluating actuation requirements for active structures. Our approach to this problem is to apply an existing solution method for finite-dimensional mechanical systems. We evaluate the direct application of this method to the spatially discretized, small strain equations of a thin plate. Several example cases are considered in which the program forces are determined, and then applied in finite element analysis software for verification of the program constraint.
A Wireless Strain Sensor Using Frequency Modulation Technique
Authors: Yoon Hwan-Sik , Khedkar Sanket K.
Published: February 2010

A compact wireless strain sensor using a Frequency Modulation (FM) technique is proposed. The sensor employs a conventional resistive strain gauge such that the resistance changes as the measured structure is mechanically strained. When the strain gauge is connected to a frequency modulation circuit, the change in the resistance appears as a frequency shift in the output signal that is transmitted wirelessly to a remote station. The received signal is then demodulated and the buried strain measurement data can be retrieved. Using this technique, a dynamic strain measurement is possible without any wire connection between the sensing point and the measurement equipment. This type of sensors have numerous applications in the strain or vibration measurement of moving or rotating structures such as fans on a turbine engine. The proposed concept of the wireless strain sensor is experimentally demonstrated by measuring vibration of a cantilevered beam with a wired transmission of the measurement data from the transmitter to the receiver.
Self-Healing in Ceramics Based Nanocomposite
Authors: Nakao Wataru
Published: February 2010

Self-healing is the most valuable phenomenon to overcome the integrity decreases which are caused by the damages in service. Thus, self-healing should be automatically occurred as soon as the damages occur, and the healed zone should have high integrity before damaging. In the case the structural ceramics, the severest flaw is surface cracks which are possible to be introduced by crash, fatigue, thermal shock and corrosion during service. Thus, the self-healing of surface cracks in the structural ceramics is an important issue to ensure the structural integrity of the ceramic components. The present author and coworkers succeeded to endow the excellent self-healing ability to structural ceramics by using the high temperature oxidation of the dispersed silicon carbide particle. In the present paper, the healing mechanism, behavior and advantages will be introduced. Moreover, our latest self-healing ceramics will be also reported.
A Multi-Channel Power Controller for Actuation and Control of Multiple SMA Actuators
Authors: Hangekar Rohan , Seelecke Stefan
Published: February 2010

This paper presents a multi-channel electronic power controller device for Shape Memory Alloy (SMA) actuators. The use of shape memory alloy wires as actuators has been proposed in numerous novel applications such as Smart Inhaler System [1], BAT Micro Air Vehicle [2], etc. These systems have multiple SMA wires for actuation of their mechanisms. The SMA wires can be actuated by controlling the joule heating or the electric power in that wire. This paper describes the development of a multi-channel power device that can control multiple SMA actuators simultaneously. The device presented herewith utilizes a Field Programmable Gate Array (FPGA) board and a custom built electronic device to independently and simultaneously control electric power in three different SMA actuators. The controller adapts to the non linear and hysteretic behavior of the resistance of the SMA actuators and adjusts the pulse width modulated voltage across them to maintain the desired value of power. The controller uses the resistance measurement of the SMA actuators as feedback. With the help of modeling efforts to relate resistance to strain, it is envisioned that feedback position control of these actuators can be implemented without the necessity of a sensor. The device is tested with graphic user interface which enables a user to control various parameters during operation of this device and to monitor the results. The design and implementation of this device is detailed in this paper along with its performance charts. The results relate the input power, observed actuation strokes and measured resistances in the SMA actuators under various conditions. A relevant discussion on implementing position control in Smart Inhaler System using this device is also presented.
A Nonlinear Analytical Model for Magnetorheological Energy Absorbers Under Impact Conditions
Authors: Mao Min , Hu Wei , Wereley Norman M. , Browne Alan L. , Ulicny J. C.
Published: February 2010

Linear stroke magnetorheological energy absorbers (MREAs) can be used to adaptively control load-stroke profiles under impact loads. An appropriate and controllable dynamic range, defined as the ratio of the force at maximum field to the off-state force, as well as the off-state (minimum) damping force, must be specified in order to account for varying payload mass over a wide range of MREA operating velocities. A key challenge when designing MREAs for high speed impact conditions is that the high shaft speeds in linear stroke MREAs induce high Reynolds number flows in the magnetic valve of the MREA, so that high dynamic range canbe a design challenge. Previous studies demonstrated that the dynamic range, D, of an MREA under high speed drop impact test dramatically dropped to D≈1 as velocity rose to 6.6 m/s, where Reynolds number, Re>2000. Also, past research on MREAs typically assumed that the off-state force increases linearly with speed, but at the higher shaft speeds occurring in impact events, the off-state damping exhibits nonlinear velocity squared damping effects. This problem was recognized in our prior work where it was shown that minor losses are important contributing factors to off-state damping. In this study, a nonlinear analytical MREA model, based on the Bingham-plastic nonlinear flow model (BP model), is combined with semi-analytical minor loss factors to develop a BPM model. From this BPM model, an effective design strategy is presented for conventional MREAs and an MREA designed. The BPM model was validated via finite element analysis (FEA), so that MREA performance could be verified before manufacture. The MREA was fabricated and tested up to effective piston velocity of 5 m/s using the high speed drop tower facility at GM R&D Center. Comparison of our analysis with measured data shows that the BPM model can accurately predict off-state (passive) MREA performance under impact conditions, and the effective deign of the MREA using the BPM was validated.
Design of an Intelligent Rotor Blade With a Trailing Edge Flap Manipulated by Piezoelectric Actuators
Authors: Lee JaeHwan , Kim TaeSeong , Shin SanJoon
Published: February 2010

This paper describes a procedure to design and fabricate an intelligent rotor blade with a trailing edge flap called as Seoul National University Flap blade (SNUF blade) manipulated by piezoelectric actuators. To develop a composite blade with a trailing-edge flap, specific design requirements for the SNUF blade are established by an analysis, UMARC (University of Maryland Advanced Rotorcraft Code). An analysis and design of the cross section are conducted first. In this paper, UM/VABS (University of Michigan/Variational Asymptotic Beam Section Analysis) is used for the cross sectional analysis. Prediction on the hinge moment induced in the flap is conducted for selection of the actuator by using FLUENT, a commercial CFD analysis. APA 200M actuator is selected as a candidate actuator to provide an enough stroke in the flap. The design illustrated in this paper includes a procedure only up to a part of the active region. More details of the design will be pursued and described in the final paper.
Actuator Optimization of a Flexible Morphing Wing Mechanism
Authors: O’Grady Brendan , Reich Gregory W. , Westfall James T.
Published: February 2010

This paper investigates the optimization of distributed actuation within a flexible morphing wing structure. The goal is to understand the effect that actuator location, orientation and increased flexibility have on a morphing wing system. This research starts with a single cell of the morphing wing structure, modeled as a four-bar mechanism, and builds a process for modeling, testing and optimization. The flexible skin of the wing is represented by a spring stretched across two vertices of each cell. Both computer analysis and experimentation are performed on the single cell. The computer analysis is done using ADAMS simulation software and the optimization is performed in MATLAB using Sequential Quadratic Programming. The objective of the optimization is to minimize the structural weight and increase the efficiency of the system as the mechanism moves from a starting configuration to an ending configuration. The results of the analysis for the single cell will be compared to the experimental results and used to validate the optimization process developed.
Membrane Modular Structures With Inflatable Tubes and Connective Cables for Future Space Applications
Authors: Katsumata Nobuhisa , Fujii Ryoko , Natori M. C. , Yamakawa Hiroshi
Published: February 2010

Spirally folded hexagonal membrane structures with inflatable tubes and connective cable networks are presented aiming to establish possible construction scenarios of future large space structure systems over hundreds meters scale and corresponding structures based on the hierarchical modular structure concept using deployable membrane modules. Laboratory scale hand-made conceptual models are manufactured, and their deployment experiments are carried out to show their applicability to the hierarchical modular structures systems.
Cancer Sequencing Gets a Little More Personal
Authors: Prokunina-Olsson Ludmila , Chanock Stephen J.
Published: February 2010

Using sophisticated sequencing methods, scientists have begun to catalog genetic fusions in cancer genomes, only to find that most changes are unique to an individual tumor and few are common to many.