bluuebunny/crossref_metadata_2025 huggingface dataset:
Explicit Finite Element Simulation of Granular Flow in an Annular Shear Cell
Authors: Kabir M. A. , Higgs C. F. , Lovell M. R. , Jasti V. , Marinack M. C.
Published: February 2010

Explicit finite element method modeling of granular flow behavior in an annular shear cell has been studied and presented in this paper. The explicit finite element method (FEM) simulations of granular flow in an annular shear cell with around 1633 particles were performed, where the inner wheel rotated at a very high speed and the outer disk remained stationary. The material properties of the particles and the outer wheel were defined as elastic steel whereas the inner wheel was elastic aluminum. In this investigation, the explicit FEM model mimicked granular flow in an experimental set up where the inner wheel was rotated at a speed of 240 rpm. The FEM results for shearing motion and solid fraction were compared with experimental results from a granular shear cell.
An Analytical Model for Predicting Contact Stress and Sliding Wear of a Three-Dimensional Textured Surface
Authors: Terrell Elon J. , Higgs C. Fred
Published: February 2010

In this paper, an analytical model for predicting the contact stress and wear distribution between a textured surface and a compliant flat is presented. The modeling formulation is based upon a two-dimensional stress analysis of the flat, and it allows the contact stress distribution to be found from the distribution of the sample deflection into the flat surface. The wear evolution was calculated from the contact stress.
Voltage Saturation in Electrical Contacts
Authors: Bansal Dinesh G. , Streator Jeffrey L.
Published: February 2010

Electrical contact resistance is important to the performance of electrical switches and other current-carrying interfaces. This study investigates the behavior of electrical contact resistance for an aluminum sphere-on-flat contact as s function of current through the interface. It is observed that the contact resistance may either increase or decrease with increasing current, depending on the current level as well as the current history. At low current levels the voltage drop across the interface increases initially with increasing current until it saturates, after which the voltage level remains constant. If the current is increased beyond the value corresponding to saturation, a subsequent decrease in current yields a corresponding decrease in voltage, so that the associated current cycle shows substantial hysteresis. However, subsequent cycles of current are reversible so long as the voltage remains below the saturation point. Such behavior suggests that irreversible morphological changes occur at the interface when the current exceeds the level associated with the attainment of voltage saturation.
A Coupled Approach for Modelling Rolling Contact Fatigue Cracks Under Elastohydrodynamic Lubrication
Authors: Balcombe R. , Fowell M. T. , Olver A. V. , Dini D.
Published: February 2010

In this paper we present a coupled method for modelling fluid-solid interaction within a crack generated in rolling contact fatigue (RCF) in the presence of lubrication. The technique describes the fluid flow in the contact area and within the crack and explores how this affects the elastic deformation of the solid while the moving load traverses the cracked region. It is argued that this approach sheds light on the instantaneous response of the system, therefore providing a more physically-accurate description of the phenomenon under investigation.
Using Vibration Measurements to Assess Structural Integrity
Authors: Black Jared L.
Published: February 2010

Structural vibration monitoring can aid in assessing offshore platform structural integrity. The method utilizes topside acceleration measurements to detect the platform’s natural periods of vibration; the periods depend only on platform weights (mass) and resistance (stiffness). If the platform’s natural period increases over time, in the absence of a change in mass, it can indicate a loss of structural integrity. The vibration survey utilizes a portable monitoring system, which includes sensitive low frequency accelerometers. The above water monitoring provides information on the below water structural integrity; the method is very low cost when compared to diver or ROV surveys. Examples of structural monitoring surveys are presented, including the following: verification that a platform remained fit for purpose despite having its foundation disturbed by a shallow gas release, two cases of using surveys to confirm jacket stiffness recovery following repairs of structural damage caused by Gulf of Mexico hurricanes and evaluation of a minimal platform after a heavy compressor was installed. The development of a natural period database is reviewed. The database, covering 95 platforms in Asian waters, was developed to reduce inspection costs and aid in life extension reviews, as well as providing quick integrity assessments should a tropical cyclone cross the production area.
Study of Local Vibration Control for the Offshore Platform Based on the Mega-Frame Theory
Authors: Zhao Dong , Tan Hui , Cai Dongmei , Cai Shaoli
Published: February 2010

In order to control the vibration of the W12-1 platform built in the Beibu Gulf, the reduced model of the local platform was made using the finite elements software. Modal analyses showed that the vibration modal shape distortion caused by the insufficient stiffness of local platform was the main reason that caused the whole platform’s vibration. In order to eliminate the distortion, a mega-beam was constructed based on the local platform on which the compressors were installed by increasing the stiffness of beams and changing the position of the inclined struts using the mega-frame theory. Theoretical analysis showed that the mega-beam had the huge holistic stiffness and could remove the vibration modal shape distortion effectively. The computational simulation results showed that the vibration can be restrained effectively. After the anti-vibration method executing, the on-site retesting results showed that the average vibration level of zone I was reduced by 75.08%. The vibration levels of zone II and III were reduced by 49.36% and 49.13% respectively. So, the vibration control methods had the perfect effect on W12-1 platform.
Experimental Investigation of Sloshing Dynamics Coupled With Barge Responses
Authors: Nasar T. , Sannasiraj S. A. , Sundar V.
Published: February 2010

An experimental work has been carried out to study the phenomena of sloshing of liquid in a partially filled tank with aspect ratio (hs/l, where hs is the static liquid depth and l is the tank length) of 0.585. The sloshing tank was rigidly fixed in to a barge and was exposed to regular beam waves. The wave excitation frequencies (fw) ranging from 0.70Hz to 1.54Hz that cover up to the third mode natural sloshing frequency (f3) are considered. The incident wave height (Hi) is 0.10m. The effects of wave excitation frequency and wave height on the sloshing oscillation are studied. Attempts are made to evaluate the harmonics present in the sloshing oscillation and compare with the results of earlier studies. The barge responses such as sway, heave and roll are measured and it is found that the barge responses at their natural frequencies are insensitive to induce sloshing oscillation inside the tank.
Estimation of System Reliability by Monte Carlo Simulation
Authors: Naess A. , Leira B. J. , Batsevych O.
Published: February 2010

A new method for estimating the reliability of structural systems is proposed. The method is based on the use of Monte Carlo simulation. Monte Carlo based methods for system reliability analysis has several attractive features, the most important being that the system failure criterion is usually relatively easy to check almost irrespective of the complexity of the system. The disadvantage of such methods is the amount of computational efforts that may be involved. However, by reformulating the reliability problem to depend on a parameter and exploiting the regularity of the failure probability as a function of this parameter, it is shown that a substantial reduction of the computational efforts involved can be obtained.
Reliability Study of Neka Jack-Up Platform Under SH-Seismic Waves, Sea-Waves and Current With Considering Spud-Can-Soil Interaction
Authors: Emami Azadi M. R.
Published: February 2010

In the present study, the influence of propagating SH-seismic waves under the sea-bed on the overall reliability index of Neka Drilling Jack-up platform is investigated. Neka platform is studied here as a case which is a 3-leg drilling jack-up platform located in a water depth of about 91m in Caspian Sea region. The spud-can-soil interaction has been also taken into account using a plasticity model with Kinematic type hardening. The soil type is varied from loose to dense sand. The effect of bias and COV of the spud-can-soil interaction modeling and also the soil parameters such as effective interface soil friction angle are considered. The influence of seismic SH-wave and sea wave parameters on the overall reliability of the Jack-Up system is also studied. It is found that inclusion of seismic SH-wave as well as wave parameters may have significant effect on the overall reliability of the Jack-Up system compared to the inherent uncertainties involved in the SH-seismic and sea wave parameters. The results have also shown that inclusion of spud-can-soil interaction may have a considerable effect on the reliability of the Jack-up platform. In particular, the bias and COV of soil has shown to have more significant effect on the reliability of jack-up platform in loose sand. It is also found that bias in strength modeling of jack-up itself has less profound effect on the reliability index of the jack-up-foundation-soil system. Importance factors of spud-can-soil modeling are found to be quite considerable.
Reliability-Based Assessment on Stiffened Panel of Deep-Water Platform
Authors: He Yong , Xu Long-kun , Ye Qian , Jiang Yi-hai , Jin Wei-liang
Published: February 2010

Stiffened panel is an important component of floating structures in deep water. This paper analyses of ultimate strength of stiffened panel corresponding to different failure modes. The ultimate limit state (ULS) equations are established. On the base of these equations, the safety assessments of the stiffened panel are conducted by reliability method. The reliability index is compared with the target reliability. The comparison indicates that there is no obvious correlation between different failure modes so that each failure mode could be analyzed individually. In addition, the reliability analysis is more reasonable than deterministic analysis. The method has been illustrated through application to an actual stiffen panel of a Tension Leg Platform. Advantages of the proposed method for assessment the safety of the stiffen panel is also highlighted.
Novel TLP Concept for Ultra-Deepwater Field Development
Authors: Heidari Homayoun
Published: February 2010

The tension leg platform (TLP) is an ideal choice for supporting dry trees in deepwater, mainly due to its favorable motion characteristics and limited stroke requirement for riser tensioners. However, as the developments move into the ultra-deep waters (beyond 2000m), conventional TLP’s begin to show signs of technical and economical disadvantages compared to other floating systems. This is due to the fact that the natural period of the TLP system begins to grow beyond the practical limit (∼4–4.5sec) required to mitigate fatigue problems. SBM Atlantia has developed a new TLP concept, called the Pontoon-less TLP (or PLT), that resolves the above issue in a simple and effective way and enables ultra-deepwater development with TLP technology. The PLT concept eliminates the pontoons from the hull and replaces them with a rigid top-of-the-column frame. This change in the geometry significantly reduces the added mass of, and forcing on, the TLP hull. The resulting improvements are two fold: (1) The natural period of the PLT is reduced into the comfort zone (4–4.5sec), therefore the need for additional tendon steel to adjust the stiffness of the system is minimized (in most cases eliminated); and (2) The dynamic tendon tension is significantly reduced, hence the tendon system is optimized. This paper presents the development of the PLT system with emphasis on the hydrodynamic aspects that are unique to the concept. A case study is presented, where the performance of a dry-tree PLT system designed for ultra-deepwater production is compared to that of a conventional four column TLP system.
Comparison of Golf Ball/Driver Impact Models With Respect to Mechanical Impedance Matching Theory
Authors: Petersen Willem , Salehian Armaghan , McPhee John
Published: February 2010

Three models of a golf ball and a golf clubhead are created to investigate the efficiency of the collision with respect to the theory of mechanical impedance matching, normally derived from oversimplified models. While the results obtained from a lumped-parameter model do validate the mechanical impedance matching theory, the results obtained from a finite element model used to investigate this phenomenon with more fidelity by varying the clubface flexibility disagree. Therefore, a distributed-parameter model is developed. In this model, the clubface is modelled using the Euler-Bernoulli beam equation with clamped-clamped boundary conditions, and the golf ball is modelled using a 3-piece rod with piecewise constant material properties representing the multiple layers of a real golf ball. The number of modes considered in the calculations is varied to determine the influence of the complexity of the model. The results obtained from this model are compared against those from the previous approaches and from the mechanical impedance matching theory.
µ-Synthesis Control of Flexible Modes of AMB Rotor
Authors: Mystkowski Arkadiusz
Published: February 2010

In the paper the optimal robust vibrations control of flexible rotor supported in active magnetic bearings (AMBs) is presented. The purpose of the research is to stabilize the rotate rotor and effective control of rotor vibrations. The noncollocation effect which produce no interlaced of zeros and poles of AMBs system problem stability is investigated. The frequency mode analysis of collocation and noncollocation cases is presented. The μ-Synthesis Control is applied to stabilize the rigid and flexible critical frequency modes of the rotor AMBs. The singular value analysis is used to obtain the robust performances of closed-loop system. The dynamical behaviour of AMBs system in wide range of rotation speed (up 21000 rpm) is investigated. The goal of this paper is also the experimental evaluation of the robust performance. The stable operation, good stiffness of the rotor and robust performances of the closed-loop AMBs systems is reached. Finally, the success of the robust control is demonstrated through results of computer simulations and experimental results.
The Performance Study of Magneto-Rheological Damper
Authors: Chen Shumei , Chen Xiaomei
Published: February 2010

Damper performance is important for the vehicle, especially for the military vehicle. The damper will not only improves driver’s comfort and vehicle safety factor, but also enhances the veracity and the mobility in campaign. Therefore, how to analyze the magneto-rheological damper performance and get more accurate results are extremely important. In this article, first of all, sets up the mathematical model by the desired damper, founds the formula about damping force and simulate analysis by Matlab/Simulink. Then set the relevant parameters and boundary conditions, does the computational fluid dynamics (CFD), numerical analysis of fluid dynamic properties by FLUENT. Manufactured this damper after the optimization design and validated by the test on the experimental platform. The results are shown that this damper’s performance is good for satisfying the actual requests.
Shape Memory-Metal Rubber™ Morphing Aircraft Skins
Authors: Lalli Jennifer H. , Harrison William , Distler Theodore , Bortner Michael , Hill Keith , Dennis Jacob , Davis Bradley , Claus Richard O. , Baur Jeffery W. , Justice Ryan S.
Published: February 2010

This paper discusses electrically conductive, shape changing, elastomeric nanocomposites capable of surviving repeated mechanical strains while remaining highly electrically conductive. Morphing nanocomposites were formed in-situ by chemically reacting monolayers of well defined, electrically conductive, nanostructured constituents with high performance shape memory copolymers. In this study, electrical conductivity was investigated as a function of volume fraction of nanoparticles and processing conditions. It was found that self-assembly processing results in percolation and surface resistivity of <1 Ohm/square with <0.01 volume % of metal nanoparticles. Waveguide measurements verified electrical stability of the thermoresponsive nanocomposites. The conclusion is that ultra-low mass density <0.99 g/cc skins formed via layer-by-layer processing exhibit electromagnetic integrity before, during and after shape change; when simulating disparate configurations that may be required on future morphing unmanned aerial vehicles.
Modelling, Prototype Construction and Testing of Helical Shape Memory Springs With Hollow Cross-Section
Authors: Spinella Igor , Dragoni Eugenio , Stortiero Francesco
Published: February 2010

Shape memory alloys (SMAs) are used in many applications as actuators. The main drawbacks that limit the use of the SMAs in the field of micro-actuation are the low bandwidth and the unsatisfactory stroke. This paper contributes to enhancing the performances of SMA actuators by proposing a new SMA helical spring with hollow section. The hollow spring is modelled, then it is constructed and finally it is tested, comparing its performances with those of a spring with solid cross-section of equal stiffness and strength. Emptied of the inefficient material from its centre, the hollow spring features a lower mass (37% less) and an extremely lower cooling time (four times less). These results demonstrate that helical springs with hollow construction can be successfully exploited to realize SMA actuators with high bandwidth and stroke.
Mode-I Crack Control by SMA Fiber With a Special Configuration
Authors: Jin M.
Published: February 2010

Crack propagation in solid members is an important reason for structure failure. In recent years, many research interests are focused on intelligent control of crack propagation. With the rise in temperature, contraction of prestrained shape memory alloy (SMA) fiber embedded in matrix makes retardation of crack propagation possible. However, with the rise in temperature, separation of SMA fiber from matrix is inevitable. This kind of separation weakens effect of SMA fiber on crack tip. To overcome de-bonding of shape memory alloy (SMA) fiber from matrix, a knot is made on the fiber in this paper. By shape memory effect with the rise in temperature, the knotted SMA fiber generates a couple of recovery forces acting on the matrix at the two knots. This couple of recovery forces may restrain opening of the mode-I crack. Based on Tanaka constitutive law on SMA fiber and complex stress function near an elliptic hole under a point load, a theoretical model on mode-I control is proposed. An analytical expression of relation between stress intensity factor (SIF) of mode-I crack closure and temperature is got. Simulation results show that stress intensity factor of mode-I crack closure decreases obviously with the rise in temperature higher than the austenite start temperature of SMA fiber, and that there is an optimal position for SMA fiber to restrain crack opening, which is behind the crack tip. Therefore the theoretical model supports that prestrained SMA fiber with knots in martensite can be used to control mode-I crack opening effectively because de-bonding between fiber and matrix is eliminated. Specimen of epoxy resin embedded with knotted SMA fiber can be made in experiment and is useful to an analytical study. However, in practical point of view, SMA fiber should be embedded in engineering structure material such as steel, aluminum, etc. The embedding process in these matrix materials should be studied systematically in the future.
Engineered Ion Channels on Synthetic Flexible Membranes: Ion Channel Devices With Focus on Peptides
Authors: Cuppoletti John , Ferrante Christopher J. , Malinowska Danuta H.
Published: February 2010

Recent studies of engineered ion channels on synthetic flexible membranes realized unprecedented materials properties. Starting with ion channels of known sequence and crystal structures, these studies outlined the structural basis for functional and regulatory properties, and developed new computational tools capable of predicting structural and functional properties of the native ion channels as well as native or engineered ion channels that were similar in structure to each other. The approaches taken to prepare the engineered composite membranes and the computational tools are generally applicable to the development, design and prediction of properties of a wide variety of materials such as selectively permeable membranes or functionalized thin films with desired chemical, electrical or optical properties. ClC-2 Cl− transporting channels and related ion channels were used for this work. The following major developments have facilitated this work. First, the X-ray crystal structure of a bacterial ClC Cl− channel was published and our group has been able to use that information in computational studies to develop structures for ClC channels and their transport mechanisms. Recent NMR and X-ray crystal structural studies have given important new information regarding the structure of the intracellular region, and this information helps to explain the structural basis for our findings that this same region is involved in phosphorylation-dependent regulation of the channel. Dissection and reconstitution of this region has already been carried out, raising our level of confidence that we can exploit this regulatory region to develop sensors in future studies. The group was then able to remove those native or engineered ion channels from cells, and place these onto a wide variety of synthetic supports without loss of function. This effort produced unique new materials with the ability to “sense” the environment and at the same time send an electrical signal reporting changes in the chemical or physical environment. These devices can sense chemicals and toxins and even shrink and swell or produce electrical energy from biochemicals. Indeed, the work contributes to a new field of engineering for producing materials with unprecedented properties. These materials can sense and report on chemical, physical and electromagnetic changes in the environment. In living cells, these ion channels other chemi-osmotic transport proteins use electrochemical gradients formed by light and chemical substrates to produce and interconvert energy, mechanical work, electrical work, osmotic work, chemical work and heat. Guided by new predictive computational approaches, these composite materials will do the same.
Development of an Active Squeeze Film Journal Bearing Using High Power Ultrasonic Transducers
Authors: Zhao Su , Mojrzisch Sebastian
Published: February 2010

A novel active squeeze film journal bearing actuated by high power piezoelectric transducers is developed aiming for non-contact suspension of axial rotating member with active error compensation and active axis positioning. A mathematical model based on acoustic radiation pressure theory is developed to predict the levitation force of the proposed bearing system. The levitation force model is then integrated into the model of the electro-mechanical system to describe the total dynamic behavior of the bearing system. Experimental results are carried out using a prototype system, which show good agreement with the calculation.
Deformation Modelling: Embedding a Communication Device in a Polymeric Composite Material
Authors: Sulic Edin , John Sabu , Pell Brendan , Rowe Wayne , Ghorbani Kamran , Gupta Rahul , Zhang Kefei
Published: February 2010

In this paper, an attempt is made to extend the deformation model of a communication device embedded in a viscoelastic thermoset composite polymer commonly known as Sheet Moulding Compound (SMC). The original model takes into account time dependent heat transfer from the mould surface into the SMC charge and the consequent time dependent viscosity propagation during the initial stage of the mould closing and subsequent filling. The required model parameters for viscosity and elasticity have been determined from rheological testing. The extended model will examine the effects of a number of process parameters such as mould closing speed, mould temperature and initial charge temperature. The effect of these parameters on the deformation of the communication device is discussed and is compared to experimental findings.
Characterizing the Effect of Temperature Increase on Polypyrrole Active Strength and Stress Rate
Authors: Keng Yenmei , Pillai Priam V. , Hunter Ian W.
Published: February 2010

Conducting polymers can be utilized as actuators due to the materials’ ability to undergo volumetric change caused by an electrochemical stimulus. Polypyrrole is an attractive electroactive polymer and capable of producing large active stress. Its mechanical performance can be improved by increasing temperature. This work describes a custom built device that is capable of performing dynamic mechanical analyses and electrochemistry simultaneously. In addition, there is a temperature control system that heats (or cools) with Peltier thermoelectric devices controlled by a PID controller. In this study, we characterized the effect of temperature increase on polypyrrole actuation strength and stress rate. For approximately each increment of 10°C from 27–83°C, stiffness measurements and isometric tests in 1-butyl-3-methylimidazolium hexafluorophosphate were done with sample preloaded to about 4 MPa. Results showed that the stiffness decreased by 21% as the temperature was elevated from 25–80°C. The maximum charge per polymer volume increased by 983% as the temperature was increased from 27–75°C and started to level off past 75°C. The peak stress changed with temperature in a similar trend as maximum charge per volume. Peak stress was 0.2 MPa at 27°C and increased to 7 MPa as temperature was increased to 75°C. Moreover, the stress rate increased until 85°C. The results suggest that peak stress depends upon the ionic mobility as opposed to stiffness since both peak stress and charge start to plateau past 75°C.
PVDF Sensor: Design and Development for Use as Intracranial Pressure Monitoring Device
Authors: Vijaywargi V. , Proffitt R. , Mane P. , Mossi K. , Ward K. , Lenhardt M.
Published: February 2010

The brain is surrounded by cerebrospinal fluid, and when a brain tumor or a traumatic brain injury has occurred, intracranial pressure, ICP, is developed. Monitoring ICP non-invasively is a challenge. Currently, a probe is inserted through the skull, running the risk of infection, bleeding, and damage to the brain tissue with residual neurologic effects. A novel method to measure ICP using actuators and sensors has been proposed where the skull is vibrated at high frequencies and the receiving signal is measured at the surface eyelid. A design of experiments approach is used to develop the sensor part of the ICP monitoring device so that gain can be maximized using factors such as area, thickness, electrode, and applied pressure. In addition, sensor packaging is optimized to minimize dampening of the signal and ensure durability, reliability, and repeatability of the measurements. Results of this study showed that for a range of areas and thicknesses with Cu-Ni electrodes packaged with super strength durable tape are the optimum factors for the ICP sensor. These parameters are then incorporated into a design that allows ease of application and consistency of the measurements.
Modeling the Dynamic Behavior of an Inflatable Rigidized Boom in Exposure to Temperature Changes in Space
Authors: Darivandi Neda , Salehian Armaghan
Published: February 2010

During the past few years inflatable technology has received much attention by space industry due to its significantly reduced launch volume and mass. While this technology meets the mass goals, because of being ultra-light the structures become very susceptible to disturbances in space. One of the main sources of disturbances is the abrupt temperature changes for a satellite upon passing the Earth’s shadow. While much research has been carried out on the static thermal loading for such structures, very little is known about their dynamic behavior with respect to temperature changes. The presented work is intended to fill this gap. The frequency response functions for a 3 meter inflatable rigidized boom for various temperatures are studied and compared using FEA models in ABAQUS.
Vertical-Stalk Flapping-Leaf Generator for Wind Energy Harvesting
Authors: Li Shuguang , Lipson Hod
Published: February 2010

We study a parallelized flapping piezo-leaf generator for harvesting ambient wind energy and demonstrate an initial design. We fabricated prototypes in various configurations and performed a series of experiments to study performance trends. We propose a novel vertical-stalk L-shape design that exhibits improved output power density over horizontal piezoelectric configurations. While a significant power density performance gap still exists between the current state of piezoelectric devices and commercial wind turbines, their advantage remains in their robust solid-state, low-cost, low-maintenance and scalable construction.
Control of Shape Memory Alloy (SMA) Actuator Using Series-Parallel Model Reference Adaptive Control (MRAC)
Authors: Kannan Somasundar , Giraud-Audine Christophe , Patoor Etienne
Published: February 2010

In this paper, adaptive predictive control is proposed to control a Shape Memory Alloy (SMA) linear displacement actuator. A Black-Box (BB) model based on a Laguerre filter is used to identify the SMA actuator and the controller in closed loop. This identification is performed online using a recursive least squares (RLS) algorithm, thus providing a linear model which approximate the behaviour of whole system around a working point. Based on this model, a predictor is built and a simple control law is derived. This structure can be cast in the Model Reference Adaptive Control (MRAC) frame and understood as a modified Series-Parallel Model Reference Adaptive control (MRAC) scheme. Experimental results prove that the proposed method combined with an efficient online identification strategy is able to robustly handle both nonlinearities and input constraints.
Design of Highly Integrated Systems on the Basis of Programmed Shape Memory Alloy Components
Authors: Langbein Sven
Published: February 2010

One way to represent the realisation of a system with complex and variable functions is by means of a modular system. Modular systems do not only enable the adoption of the solutions for other applications, but moreover lead to a reduction of the diversity of variants and to a reduction of the development risk. An unsolved problem at modular systems is the increasing system complexity. Additional functions, like the mechanical and electronic coupling of the modules, are responsible for it. Beyond the conventional form of a modular system there is the possibility to create a variable shape memory actuator system only by using the material configuration of one single SMA-component. An emphasizing feature of SMAs is their potential to produce different functional effects, for example thermal shape memory or superelasticity, in one component. Separated from the former point of view a new perspective with extreme integral and standardised set up is opened up. Here it is merely required to complete the structuring and dimensioning of SMA components with function “material programming”. The SMA-component can therefore especially be programmed functionally for the scheduled use case. This programming can be reversible or not reversible in consideration of different configuration possibilities. The structure of such a variable SMA-component can be understood as a “one module” modular system. The components are endued with different regional operating spheres. One area of the various function spheres represents one module. This is an equivalent to the modular system in common design. Through an activation or a setup process the superelastic behaviour can as well as the thermal shape memory be optionally adjusted. Therefore “material programming” can be installed in order to implement active actuators, passive superelastic structures (usable for hinges, clips or dampers) and even a combination of both. Furthermore the transformation with several stages can be implemented by adjusting different transformation temperatures in one specific element. On the one hand the aim of this study is to show a way to develop such components. On the other hand the study gives a review in “one-module” component designs.
Thermal Control of the Wrinkling Effect Using NiTi Thin Film
Authors: Seong Myunghoon , Lee Dong-Gun , Mohanchandra K. P. , Carman Gregory P.
Published: February 2010

This paper presents modeling and testing results for membrane wrinkling control using material’s property changes produced by a 1st order phase transformation. ANSYS® is utilized to determine the membrane’s length and width as well as thickness to produce wrinkling in a test sample. Test results conducted on a NiTi 20.9mm×10.8mm×5.5μm sample produce wrinkling at approximately 1% strain, which is the critical strain (εcr). Using the phase transformation properties and corresponding stiffness change, we demonstrated that wrinkling control (i.e. turning it on and off) is possible simply by changing the temperature through the phase transformation. The maximum amplitude of the wrinkles was 46.5 ± 5.4μm and the wavelength was 2.05 ± 0.40mm.
Comparison of Novel Conductive Open- and Closed-Porous PPy-PLA Composites
Authors: Chan Christine , Chan Ellen , Zhang Weijia , Naguib Hani E.
Published: February 2010

This study compared the fabrication techniques and characterization of novel open- and closed-porous structures in PPy-PLA conductive composites. For the open-porous composites, PLA samples were fabricated using compression molding and salt leaching with varying salt-to-polymer mass ratios, which were subsequently coated with PPy by in situ polymerization of pyrrole and iron (III) chloride. For the closed-porous composites, a patterned structure of PPy within PLA was created using compression molding of PPy-coated PLA pellets, followed by gas saturation and foaming techniques in order to create the closed pores. Characterization of both porous composites included their physical, mechanical, and electrical properties. Results showed that the modulus increased with increasing relative density and decreasing open porosity. The open-porous composites had lower relative density values but higher open porosities compared to the closed-porous composites. The average size of the closed pores was approximately an order of magnitude larger than the open pores. Lastly, the open-porous composites had higher conductivity values than the closed-porous composites due to the greater surface area of the continuous conductive pathway. The comparisons between open- and closed-porous composites established their characteristic properties for their future development in applications.
Development of a Multi-Function Sensors
Authors: Seeley Charles E. , Sarva Sai S.
Published: February 2010

Sensors are increasingly used to determine the operational and environmental state of aerospace structures while in service. Typically, each sensor is tasked with a single function. The measurement of multiple physical quantities is usually associated with multiple sensors. The number of sensors on a structure may become prohibitive due to cost, weight or power constraints. This paper investigates the development and application of a multi-functional sensor where a single sensor performs multiple functions. A flexible MFC based piezoelectric sensor is embedded in a corrugated composite plate to determine the state of stress, temperature and vibration, all from the same device. Development of the sensor and preliminary test results are discussed in detail.
A Phase Field Analysis of Thermomechanically Coupled Liquid Crystal Elastomers
Authors: Wang Hongbo , Oates William S.
Published: February 2010

A nonlinear phase field approach is developed to investigate micron scale liquid crystal structure evolution within an elastomer network. The polymer network is described by hyperelastic constitutive relations while a set of configurational forces are introduced to simulate the liquid crystals. A general theoretical framework is given which illustrates coupling between the liquid crystal domains and elastomer without introducing explicit phenomenological coupling constants. The model is implemented numerically using a finite element phase field approach. Problems involving thermal gradients are reviewed to illustrate bending behavior due to liquid crystal reorientation. This is shown to also have implications on photomechanical liquid crystal elastomers.
Crack Detection and Monitoring Using Passive Wireless Sensor
Authors: Deshmukh Srikar , Mohammad Irshad , Tentzeris Manos , Wu Terence , Huang Haiying
Published: February 2010

This paper presents an antenna sensor that can detect and monitor crack remotely and passively. Since this antenna sensor does not need electric wires for power supply and data transmission, it has great potential to be implemented as large area sensor skin with high spatial resolution, simple configuration and remote-interrogation capability. The sensor fabrication, the sensor characterization procedure and the non-contact interrogation technique are presented. The experimental results demonstrated that the antenna sensor is sensitive to crack growth and can be interrogated remotely.
Developing a Piezoelectric Active Sensor SHM System for Satellites
Authors: Zagrai Andrei , Gigineishvili Vlasi , Brown Jacob , Doyle Derek , Gardenier Hugh , Arritt Brandon
Published: February 2010

Structural Health Monitoring (SHM) is a valuable tool for in-service assessment of structural condition. Despite a broad use in many engineering fields, SHM has seen limited application to space systems. The paper explores specifics of SHM applied to space systems and satellites in particular. It is suggested that SHM may be considered for aiding rapid assembly of satellite components, monitoring system dynamics during launch and assessing in-service variation of structural properties suitable for model updating. In this paper, we present a discussion of factors affecting realization of the SHM system for satellites and provide recommendations for the system configuration and its practical use. The SHM system design based on a network of piezoelectric active sensors is considered. Piezoelectric sensors were selected due to availability of both active and passive operation modes. The passive SHM mode may find applications related to spaceship launch process and on-orbit structural monitoring. It is anticipated that the active structural assessment may be exercised during satellite pre-launch qualification and possible on-orbit characterization. Hence, the present contribution focuses on SHM of improperly tightened bolts as one of major satellite integrity concerns and embedded material characterization techniques. The developed SHM method utilizes the acousto-elastic effect manifested through the elastic wave phase shift caused by stress-induced localized changes in the sound speed. Experiments aimed at improving fundamental understanding of this technique are discussed and applicability of the technique to realistic structures is investigated. The methodology for in-situ material characterization is tested on structural elements of simple geometry and extension to complex structural systems is suggested. Synergistic use of the same hardware for acoustoelastic and material characterization methods is recommended and further system integration options are proposed.
Characterization of Magnetoelectric Cantilever for Use as an Ablation Tool in Minimally Invasive Surgery
Authors: Sundaresan Vishnu Baba , Atulasimha Jatulasimha
Published: February 2010

Despite great strides in materials science and control, an automated surgical tool is still in the fiction pages due to the lack of a surgical tool employing a self-sensing actuator. In an attempt to fill this void, we present magnetoelectric materials as a solution for designing surgical tools. This paper discusses our ongoing work to model the dynamics of the magnetoelectric material for use in a control loop. The surgical tool is a two-segment magnetoelectric cantilever in which one of the two magnetoelectric segments is attached to a fixed support called the base. A floating segment called the cutting tip is attached to the base using a flexible hinge. The two-segment tool is placed in a remote magnetic field to generate the cutting force in the magnetoelectric tip. Displacement in the tip generates a proportional electrical response from the piezoelectric layer and serves as the self-sensing signal. The self-sensing signal from the two segments is used for operating the tool in closed loop operation. The dynamic characterization of the magnetoelectric cantilever in bending is derived from constitutive equations for the magnetoelectric material. The strain terms in the constitutive equation is expressed using generalized coordinates in the shape function for the cantilever in bending mode. The equivalent stiffness of the magnetoelectric cantilever is derived using variational principles for calculating the tip displacement in the cantilever.
Magnetolectric Cantilever for Collocated Actuation and Sensing Applications: Experimental Study, Model and Scaling Laws
Authors: Atulasimha Jayasimha , Wang Yezuo , Sundaresan Vishnu Baba
Published: February 2010

The magneto-electro-mechanical behavior of cantilevers is modeled with two novel applications in mind: micro-surgical ablation tools and larger actuators such as cutting tools for machining applications. By uniquely combining a energy based non-linear magnetostrictive model with Euler-Bernoulli structural model and a linear piezoelectric constitutive model, a modeling tool is developed to predict the deflections and electric responses of such cantilevers under different loading conditions and magnetic field. A reduced version of this model is validated with experimental data of a magnetostrictive cantilever in bending mode. Further a simple scaling law is developed to calculate the actuating forces that can be produced when the dimensions of the cantilever is changed.
A Magnetorheological Mount for Hydraulic Hybrid Vehicles
Authors: Nguyen The , Elahinia Mohammad , Ciocanel Constantin
Published: February 2010

Advanced vehicular technologies have been increasingly popular since they improve fuel economy. Automobiles with variable cylinder management are capable of turning on/off the cylinders in order to optimize the fuel consumption. Hybrid vehicles such as hybrid electric vehicles (HEVs) or hydraulic hybrid vehicles (HHVs) allow the engines to operate in the most efficient region. Besides, the hybrid technology includes capturing the braking energy, otherwise wasted as heat, to aid the acceleration. However, the enhancement in fuel efficiency comes with unbalance, shock and wider range of frequency vibration. Noise and vibration is actually one of the main obstacles in commercializing the HHV technology. This study is to design a vibration isolator to work for HHVs effectively and economically. The vibration profile of HHVs is proven to include both shock load at the switches of power sources and wide frequency range of vibration. That the HHV’s engine is turned on/off frequently and the hydraulic pumps/motors operate between 0 and 2000RPM, corresponding to 0–300Hz, poses difficult challenges for the isolation system. Rubber mounts are cheap, but only good for static load support and suitable for low power engine. Passive hydraulic mounts are only effective for conventional engines with unvarying working schedules. On the other hand, the active mounts are responsive for any condition, but too costly for commercial vehicles. Semi-active mounts with magnetorheological fluid (MRF) have been researched and recognized as a highly potential solution for hydraulic hybrid vehicles. The semi-active MRF mount is constructed very similar to a conventional hydraulic mount. However, the working fluid is an MRF which can quickly change its characteristics when the magnetic field is present. The main features of the MRF mount include multiple controllable MR valves, utilizing the flow (valve) mode, to connect the top and bottom fluid chambers. In addition, the mount is also capable of employing the fluid in squeeze mode. The structure of the MRF mount allows the stiffness and damping to be controlled in real time. The controllability makes the mount tunable to particularly fit the requirements of the HHVs. In this study, a mathematical model was constructed to predict the performance of the mount. The parameters were tuned so that the mount is effective within the whole operating frequency range of the HHV’s vibration.
Modeling NiTi Superelastic-Shape Memory Antagonistic Beams: A Finite Element Analysis
Authors: Tabesh Majid , Elahinia Mohammad , Pourazady Mehdi
Published: February 2010

Shape memory alloys (SMA) have received widespread attention from researchers in various fields of engineering sciences due to their exceptional properties of shape memory and superelasticity. NiTi equiatomic alloys among other SMA, show acceptable biocompatibility to be implemented in biomedical applications. Applications of NiTi in biomedical areas specifically orthopedics, demonstrate its unique performance which is not achievable with conventional materials. Pedicle screws, which are used as an anchoring point for implanting spinal instrumentations in spinal fracture and deformity treatments, entail a major drawback; i.e. loosening and back-out. The strength of screw contact with the surrounding bone diminishes as the bone degrades due to osteoporosis. A “Smart” pedicle screw design was developed to address this issue which uses NiTi superelastic-shape memory coils wrapped around it. The smart assembly consists of external superelastic tubing which is responsible for expanding the designed protrusions when they reach body temperature; also an internal shape memory wire inserted into the tubing is sought to retract the assembly when locally heated to above body temperature. The whole assembly was modeled as a beam structure in COMSOL Multiphysics Finite Element software. The behavior of shape memory alloy was defined in the software via its Partial Differential Equation (PDE) module. The SMA model has is a Tanaka-based model and is capable of capturing shape memory effect, superelasticity and hysteresis behavior, and partial transformation in both positive and negative directions. This 1D model was further modified to be included in a 3D framework such that it makes it possible for simulation of a beam under bending. The functionality of the smart screw design can be studied via this FEM model as a future work and the outcomes of the simulation can be compared with experimental tests on the prepared sample of the screw comprising NiTi tubing and wires.