bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrasonic Welding Simulations of Multiple, Thin and Dissimilar Metals for Battery Joining
Authors: Lee Dongkyun , Kannatey-Asibu Elijah , Cai Wayne
Published: July 2013

Ultrasonic welding is a solid-state bond created using ultrasonic energy. It has been used in the semiconductor industry for several decades, and more recently, in the automotive industry such as for battery welding. Even though there existed several numerical simulations on ultrasonic welding, the models were too simplistic, in both theory and welding configuration, to present the multiple sheet, dissimilar metal ultrasonic welding. In this study, theories and a finite element procedure for the ultrasonic welding process are developed. The procedure invokes both Abaqus/Standard and Abaqus/Explicit to simulate the mechanical-thermal coupled phenomena over the entire weld duration with moderate computational cost. The procedure is verified and used to simulate selected specific cases involving multiple sheets and dissimilar materials, i.e., copper and aluminum. The simulation procedure demonstrates its capability to predict welding energy and temperature distribution of the workpieces, towards the goal of improving welding quality.
Electric Vehicle Drivetrain Development in China
Authors: Yuan Yiqing , Wu Guoqiang , He Xiangyan , Song Yanda , Zhang Xuewen
Published: July 2013

Despite great progress recently made on applications of in-wheel motors in electric vehicles, almost all production or near-production electric vehicles still utilize mechanical speed reduction systems for transferring torque from the traction motor to wheels for the purposes of torque augmentation and speed reduction. These systems in general fall into three categories, i.e. fixed ratio, stepped variable ratio, or continuously variable ratio.

In China, most electric cars retrofitted from internal combustion engine propelled vehicle models use gear reduction systems of a fixed speed ratio, in order to minimize the time to market. Typically a conversion is made to the original 5-speed manual transmission by taking out a few unused gear sets. With the rapid growth in electric vehicle industry, some gearboxes of fixed speed have been engineered and they typically have a layshaft configuration. Most of them still do not come with a “park” gear due to a lack of understanding on customer’s needs. As an exception, a transmission of fixed speed ratio dedicated for electric vehicle applications has been developed at the Electric Vehicle R&D Center, Chinese Academy of Sciences (UCAS).

Among electric vehicles announced by domestic vehicle manufacturers in China, some employ 5-speed manual transmissions (MTs) or automatic transmission (ATs) that typically found in traditional vehicles. From the driving convenience, transmission efficiency, or cost standpoints, these transmissions are, in general, not appropriate for applications in electric vehicles. The “misusage” of these transmissions has often something to do with their availability rather than suitability. A great deal of effort has been put into the research and development of automated mechanical transmissions (AMTs) in China to date. Significant progress has been made to the reduction of shift time, improvement of shift quality, and optimization of the mechanical components.

Continuously variable transmission (CVT) is considered to be an important trend in drivetrain technology. However, the pulley-belt types of CVT commonly seen in traditional vehicles are not proper for electric vehicle applications. An EVT dedicated for electric vehicles is under development at UCAS, in which the power from an electric motor of dual-rotors is coupled by means of a planetary gear set, allowing continuous variable of the output speed.

In summary, the electric vehicle drivetrain technology in China is undergoing rapid advances, which will impact the development of electric vehicle industry at home and abroad.
Verification of Scheduling Efficiency of an Autonomous Assembly System Using the Multi-Agent Manufacturing Simulator
Authors: Sudo Yasuhiro , Kasiwase Keisuke , Matsuda Michiko
Published: July 2013

This study is an examination of the effect of agent-based autonomous production scheduling, using the virtual factory on multi-agent simulation system. In the autonomous manufacturing system, a production plan is generated autonomously and dynamically, using communication and negotiation between agents that correspond to factory components. As infrastructure software for agent based manufacturing, the artisoc(c) is used as multi-agent simulator system. In this virtual factory, three types of agents are equipped. Users can operate a configuration such as input new jobs, adjusting a machine setting, etc, with monitoring conditions of agents. Additionally, this simulator has capability of input and output files such as assembly process schedules and logs of practical operations. As a result, by adjustment of the agent’s behavior with factory floor detail, the assembly schedule becomes more effective. The experiment was carried out to show that local negotiations contribute to global optimization when resources in the factory are effectively distributed and shared.
Hierarchical Optimal Force–Position Control of Complex Manufacturing Processes
Authors: Zomorodi Moghadam Hesam , Landers Robert G. , Balakrishnan S. N.
Published: July 2013

A hierarchical optimal controller is developed to regulate the cutting force and tool position, simultaneously, in a micro end milling process. The process is divided into two levels of decision making. The bottom level includes the measurable states, which in this work comprise the servomechanism positions. The top level includes the higher order objectives which can be derived from the bottom level objectives by an aggregation relationship. In this work the top level objective is concerned with cutting force regulation. The aggregation relations are linearized to fit into a linear optimal control problem to reduce the computational efforts. Reference velocity is calculated based on the force model, using the desired depth-of-cut and spindle speed. The proposed method is compared to a normal optimal controller without considering the top level objectives. Comparison between the two methods reveals the advantages of considering the top level objectives.
FEM Modeling of Effect of Cutting Speeds and Tool-Chip Frictional Coefficients in Orthogonal Machining of Titanium Alloy (Ti-6Al-4V)
Authors: Ma Jeff
Published: July 2013

Titanium alloys are classified as hard-to-cut materials due to high chemical reactivity and low thermal conductivity. In this paper, the Finite Element Method (FEM) is used to model and simulate effects of cutting speeds and too-chip frictional coefficients in orthogonal machining of Titanium alloy (Ti-6Al-4V). Johnson-Cook plastic model is used to model the workpiece due to its capability of modeling large strains, high strain rates, and temperature dependent visco-plasticity. The tool material is Carbide. Three different cutting speeds (70m/min, 150m/min, and 190m/min) and four different frictional coefficients (0.3, 0.5, 0.7, and 1.0) are used to explore the effects of the cutting speeds and frictional coefficients on the cutting temperature, cutting forces, and chip morphology. This model provides fundamental understanding of cutting mechanics of the orthogonal cutting of Titanium alloy (Ti-6Al-4V).
Self-Organizing Map (SOM) in Wind Speed Forecasting: A New Approach in Computational Intelligence (CI) Forecasting Methods
Authors: Esmaeili Mohammad Amin , Twomey Janet
Published: July 2013

While wind energy has been reported as the fastest growing among different sources of renewable energy, two critical issues are how to make wind energy cost effective and how to integrate it into electricity grids properly. The ability to predict power generated by wind not only allows the most effective integration of wind power into electricity grid but also makes it possible to have an optimal maintenance scheduling that can reduce cost significantly. This research investigates the practical use of Self Organizing Map (SOM) as a special type of neural network based forecasting method. In this paper, forecasting the average, maximum and minimum of one-day-ahead wind speed based on the past wind speed states of the previous 24 hours is the objective.
Experimental Study of Data Transmission Performance for Rotating Wireless Sensors Using Automatic Repeat Request
Authors: Yang Fan , Wang Kuang-Ching , Huang Yong
Published: July 2013

IEEE 802.15.4 wireless sensor radios have limited resources, resulting in a higher probability of transmission errors in monitoring fast rotating structures such as the machinery spindle. To achieve reliable data transmission with wireless sensors, one feasible approach is to use automatic repeat request (ARQ) where packets that are not acknowledged are retransmitted immediately after timeout. The objective of this paper is to experimentally study the ARQ-based data transmission performance of IEEE 802.15.4 wireless sensor radios on a mechanical rotation apparatus. Using a specially designed rotation apparatus, the ARQ-based data transmission performance has been studied in terms of the data throughput and packet error rate (PER). It is found that ARQ is able to improve the data throughput performance and decrease the cycle PER at the cost of degrading the transmission energy efficiency. A throughput model is further proposed and validated for rotating wireless sensors when ARQ is implemented.
Signal Integrity Analysis of Battery Management System for Electric Vehicles
Authors: Wang Dalong , Wu Zhengbin , Zhu Honglei , Cai Chun , Lu Fanshui
Published: July 2013

Battery management system (BMS) takes a key role in battery health management and life extension of electric vehicles. It contains various analogue-digital hybrid circuits above the frequency range of several hundred mega-Hertz, where the signal integrity and system stability are probably affected by certain issues of circuit design. In this report, the signal reflections along the transmission lines in a BMS are theoretically simulated and analyzed. The performance of the system is compared to that after optimization both in theory and measurement. The simulation and experimental results verify that electrical impedance matching is most crucial to the signal integrity and system stability in the system design.
Functional Silver Nanoink for Direct Write Applications
Authors: Bai Zongwu , Wilks Garth B. , Tandon Gyaneshwar P. , Yocum Brandon J. , Justice Ryan S.
Published: July 2013

Direct write (DW) technology offers a simple method of rapid manufacturing technology for printing electronic, optoelectronic devices, and complex functional devices. The key component of DW technology is the functional inks, which are colloidal suspensions of functional nanoparticles in various solvents such as aerosol or liquid form. With a DW approach, patterns or structures can be easily deposited on flexible substrates such as paper, plastics, and composites, once the solvent volatilizes or is driven off via conventional, laser, or microwave sintering. In this work, polymer-assisted silver (Ag) nanoinks were synthesized by silver salt and polymer in the water solution at relatively high silver precursor concentrations and relatively low concentration of polymers. The silver nanoparticle dispersion and morphology was examined by dynamic light scattering (DLS) and transmission electron microscopy (TEM). The results showed that the size of Ag nanoparticles was in nanoscale (∼20 nm) with a narrow distribution of Ag nanoparticle sizes. The viscosity and thermal properties of synthesized silver nanoinks were characterized to determine their applicability and the lifetime. It has been shown that the synthesized silver nanoink can be printed on a flexible plastic substrate or glass substrate. The morphology of the Ag nanoink line printed on the substrate was observed by optical microscopy and scanning electron microscopy (SEM) to understand the relationship between the microstructure and wettability. Uniaxial tension tests of silver nanoink line on a Kapton film indicate that the ink can be stretched ∼20% without failure. The resistance of silver nanoink line printed on the Kapton films was also measured by four probe conductivity measurement system to assess the electrical performance. The resistivity is about 7.5 × 10−5 Ω-cm by thermal treatment at 250°C for 30 min, which is about half that of bulk silver (1.6 × 10−6 Ω-cm). Overall, the performance of the synthesized silver nanoink is comparable to a commercially available ink with lower Ag weight content at relatively low cost.
Processing and Characterization of Novel Bismaleimide-Based Shape Memory Polymer Composites
Authors: Tandon G. P. , Gibson T. , Shumaker J. , Coomer R. , Baur J. , Justice R. S.
Published: July 2013

In the present study, a series of novel linear polyaspartimide-based silane endcapped (cross-linked) polymers are synthesized using 4-4′ bismaleimidodiphenylmethane, Jeffamine D-400 (BMI-JA-400), and (3-Aminopropyl) trimethoxysilane. To add strength to these systems, the trimethoxysilane moiety is cross-linked with the addition of water to create a thermosetting material with both improved toughness and variable cross-link densities. Thermal analysis is done to evaluate the developed shape-memory polymer (SMP) resin for composite processing feasibility. The solvent content in the resin and thermal stability is monitored using thermogravimetric analysis (TGA) while advanced rheometric expansion system (ARES) with parallel plate geometry is used to measure viscosity variation with temperature.

The resin BMI-JA-400-Si-70/30 is chosen for making the composite based on its viscosity, weight change, and kinetic results. Differential scanning calorimetry (DSC) is performed to determine the cure kinetics including the temperatures at which the cure reaction initiates and completes in order to develop the cure cycle for composite fabrication. The selected SMP resin is hand-impregnated with T-300 plain-weave and T-700 uni-weave carbon fabric. Six-ply composites are successfully fabricated with < 2% void content using both fabric weaves. The thermo-mechanical properties of the SMP resin are measured using dynamic mechanical analysis (DMA). In addition, the shape memory cycle with free recovery is conducted on the SMP resin and composites.
Shape Characterization of a Simply Supported Beam in Morphing
Authors: Motlagh Amin Mohaghegh , Clark William W.
Published: July 2013

Rather than address morphing in the conventional way of applying forces to a fixed-compliance structure, this work addresses morphing in a structure that can exhibit variable compliance. Specifically, this work addresses the shape morphing of a simply-supported elastic beam from a forward approach perspective, that is, determining beam shape due to applied forces. The focus on this study is on the spatial distribution of the structure due to local/total modulus change in its steady state condition. The resulting morphed shapes are quantified in terms of the characteristic parameters, such as spatial distribution of the peaks of the shapes, deviation from the axis of the symmetry and, in case of flat-top shapes, the width of the flat portion.
Modelling of Broadband Piezoelectric Energy Harvesters
Authors: Zhou Shengxi , Cao Junyi , Lin Jing , Ma Chengbin
Published: July 2013

A nonlinear magnetic coupling model for piezoelectric energy harvesting systems is proposed in this paper. For the purpose of enhancing harvesting efficiency from wide-spectrum vibrations, a magnetic coupling structure of piezoelectric cantilevers is presented. However, the nonlinear dynamic of broadband piezoelectric energy harvesters could not be adequately described due to complex nonlinear magnetic force. Furthermore, the broken frequency can not be predicted using the designed dimensionless model. In order to solve those issues, the nonlinear magnetic force is established using polynomial equation. Based on Hamilton principle and finite element theory, a nonlinear model of the standard piezoelectric cantilever with magnetic coupling is established. Frequency sweeping experiments with various excitation are carried out. The results show that the output characteristic of the proposed model is approximate to that of experimental system under the same condition, and also their broken frequency is very close.
Air-Brushed Carbon Nanotube (CNT) and Inkjet-Printed Silver and PEDOT:PSS Layer as Alternative Electrodes for Piezoelectric Polymer Transducer
Authors: Seidel Sven-Oliver , Fischer Bert , Stahlberg Nicole , Wegener Michael
Published: July 2013

Different routes for electrode processing which fulfill the requirements of piezoelectric transducer will be presented. One attempt is the electrode deposition via inkjet printing, another is the deposition via an air-brush technique. For the preparation of electrodes via inkjet printing, different inks such as a silver composite or the semiconducting poly(3,4-ethylene-dioxythiophene): polystyrenesulfonate (PEDOT:PSS) are used. A further attempt is the deposition of carbon nano tubes (CNT’s) via an air-brush technique. For all three systems the ink or solution formulation, the deposition techniques, suitable parameter and partly additional encapsulation steps will be discussed in detail accompanied by a description of electrode properties, e.g. the conductivity, as well as by the characterization of the materials poling behavior in particular.
Bending Analysis of Textured Polycrystalline Shape Memory Alloy Beams
Authors: Mirzaeifar Reza , DesRoches Reginald , Yavari Arash , Gall Ken
Published: July 2013

In this paper a micro-mechanical model that incorporates single crystal constitutive relationships is used for studying the pseudoelastic response of polycrystalline shape memory alloy beams subjected to bending. In the micro-mechanical framework, the stress-free transformation strains of all the 24 correspondence variant pairs (CVPs) obtained from the crystallographic data of NiTi are used, and the overall transformation strain is obtained by defining a set of martensitic volume fractions corresponding to active CVPs during a phase transformation. A three-dimensional finite element model is used and a polycrystalline beam is modeled based on Voronoi tessellations. The effect of crystallographic texture and the tension-compression asymmetry on the bending response of superelastic beams is studied. The results of texture measurements are used to assign appropriate crystal orientations to the grains in the model. By considering various combinations of crystal orientations, the effect of preferred crystallographic texture on the bending response is studied. The size effect is also studied by considering two polycrystal structures with different number of grains.
Synthesis and Characterization of PVDF-Based SWNT/GO Hybrid Films
Authors: Sigamani Nirmal Shankar , Ounaies Zoubeida , Sodano Henry
Published: July 2013

Hybrid nanocomposites with single walled carbon nanotubes (SWNT) and graphene oxide (GO) as nanofillers and polyvinylidene fluoride (PVDF) as a polymer were synthesized as potential electronic active polymers (EAPs) with high breakdown strength. A co-solvent method was developed to achieve exfoliation and dispersion of GO in PVDF. The microstructure of the PVDF was found to be predominantly γ phase. Percent crystallinity of PVDF increased due to the addition of the hybrid nanofillers. And, at room temperature, the storage modulus is increased by 56.26% over the pure PVDF. The dielectric constant increased from ∼7 to ∼25 for the hybrid nanocomposites as compared to pure PVDF at 1KHz measurement frequency. Dielectric loss of the hybrid nanocomposite is found less than 0.6 for the frequency range from 20 Hz–1MHz. Electrical conductivity of the hybrid nanocomposite increase by nearly two orders of magnitude at 1KHz when compared to pure PVDF. The effect of the presence of these hybrid nanofillers on microstructure and properties of PVDF are discussed.
Optical Fibre Sensing of High Order Lamb Waves for Structural Health Monitoring
Authors: Rosalie Cedric , Norman Patrick , Smithard Joel , Davis Claire , Rajic Nik
Published: July 2013

Lamb waves provide arguably the best prospect for achieving a structural health monitoring (SHM) capability with broad diagnostic coverage at sensor densities that are not impractically high. The traditional approach in Lamb wave SHM is to employ a single mode, typically one of the fundamental modes, in a non-dispersive and easily excited regime, which is done largely to simplify the interpretation of the elastic wave dynamics. However, the diagnostic value of an interrogation conducted using only the fundamental modes is limited. In general, higher order modes offer potential for greater sensitivity to structural damage and greater scope for discriminating between different failure mechanisms. This paper reports on experimental work demonstrating an in-situ fibre Bragg grating (FBG) sensing capability for Lamb waves at frequencies of up to 2MHz, an achievement that represents an important step toward developing a more robust and versatile approach to Acousto-Ultrasonic SHM.
Strain Actuation Behavior of Barium Titanate Single Crystal Loaded Electromechanically in Non-Variant [110] Direction
Authors: Shieh Jay , Lin Yen-Nan , Shu Yi-Chung
Published: July 2013

Strain hysteresis evolution of a (001)-oriented 5 × 5 × 2 mm3 cuboidal barium titanate (BaTiO3) single crystal during a combined electromechanical loading sequence in the non-variant [110] direction is investigated. The goal is to compare the strain behaviors of the BaTiO3 single crystal subjected to loading in the variant [001] and non-variant [110] directions. The simultaneous application of compressive stress and electric field in the [110] direction was achieved by machining the square cuboid crystal into a hexagonal prism and applying the loads parallel to the hexagonal side faces of the prism (i.e., perpendicular to the [001] and 45° to the [100] and [010] directions). The room temperature strain hystereses show that the maximum total electro strains produced from loading and measuring in the [110] and [001] directions (denoted as ε[110],max,RT and ε[001],max,RT, respectively, where the last term of the subscript describes the testing temperature) are 0.20% at 3.0 MPa and 0.45% at 2.7 MPa, respectively. The ratio between ε[110],max,RT and ε[001],max,RT is 0.44, which is in good agreement with the ratio, predicated by the analytical calculations. Factors which may influence the strain behavior, such as the bias stress level, depolarization field and switching coercivities, are examined by repeating the loading experiment at 55 °C. The strain hystereses measured at 55 °C show that ε[110],max,55 is 0.19% at 11.9 MPa — this maximum [110] strain is similar to the one obtained at room temperature, but is only achieved with a much larger bias stress. When the out-of-plane depolarization field and the in-plane switching coercivities are reduced at 55 °C, more domains are randomized in the in-plane variant directions during electric field unloading by the depolarization fields. Therefore, a much larger bias stress is required at 55 °C to switch a sufficient number of domains to the out-of-plane variant directions at small electric fields, which can then be switched back to the in-plane variant directions at high electric fields, producing strain in the [110] direction. The strain hysteresis study has revealed that the combined effect of the depolarization field and switching coercivity is a critical factor governing the strain behavior of the BaTiO3 single crystal.
New Ferromagnetic Shape Memory Alloy Production and Actuator Concepts
Authors: Pagounis Emmanouel , Laufenberg Markus
Published: July 2013

Over the past decade ferromagnetic shape memory alloys (FSMA) have been the subject of intensive R&D work due to their potential in actuators, sensors, and intelligent systems. These smart materials can elongate and contract up to 10% when subjected to moderate magnetic fields, generating thus motion and force. Typically FSMA materials are alloys of Ni-Mn-Ga with various off-stoichiometric compositions. A new production approach based on commercially available machinery is introduced in this paper. Large single crystals have been produced demonstrating homogeneous structure and excellent magneto-mechanical properties. The properties of actuator elements (sticks) are presented as well as the influence of the alloy microstructure. The FSMA elements are used to develop prototype actuator and sensor devices for industrial and automotive applications. In this respect a benchmark between an FSMA actuator and a commercially available solenoid actuator has indicated that the FSMA technology offers potential to replace several of today’s electromagnetic actuators by advanced FSMA solutions, especially when temperature requirements are met.
Wing Rotation and Lift Modeling and Measurement in SUEX Flapping Wing Mechanisms
Authors: Mateti Kiron , Byrne-Dugan Rory A. , Tadigadapa Srinivas A. , Rahn Christopher D.
Published: July 2013

This paper presents detailed modeling and experimental testing of wing rotation and lift in the LionFly, a flapping wing mechanism powered by piezoelectric bimorph actuators fabricated using SUEX dry film. The goal of this paper is to understand the flapping and rotation dynamics and the lift-producing mechanisms in this device. A linear vibrational model is developed and augmented with nonlinear aerodynamic forces using the blade element method. Experimental testing using a laser vibrometer in air and in vacuum characterizes small amplitude flapping and rotation. Strobe photography and high definition image processing measures high amplitude wing trajectories. A lift measurement system using a force transducer is designed and used to measure average lift in the LionFly. The LionFly produces 46° peak flapping and 44° peak rotation resulting in lift of 71 μN at 37 Hz.
The Study of Fluid Structure Interactions of an Electroactive Membrane Wing
Authors: Hays Michael R. , Hart Adam , Oates William S. , Ukeiley Lawrence
Published: July 2013

Active materials, due to their intrinsic multi-functional material characteristics, have shown great promise for the improvement of agility and the mitigation of adverse turbulence effects for micro-air-vehicles (MAVs). One such subsection of active materials known as dielectric elastomers have demonstrated this multifunctional role by functioning as the wing surface and a boundary layer control device. In the past this material has shown that an increase in overall lift of 20% is possible and has the ability to delay stall by up to 5 degrees for an elliptical wing at a chord based Reynolds number of 63000. In order to better understand the effect of these fluid structure interactions, simultaneous time dependent structural deformation, aerodynamic loads, and flow velocities were measured and compared. These responses showed direct correlation between the applied electric field on the membrane wing and the aerodynamic loads and flow responses.
Design of a Morphing Skin by Optimizing a Honeycomb Structure With a Two-Phase Material Infill
Authors: Puttmann John , Beblo Richard , Joo James , Smyers Brian , Reich Gregory
Published: July 2013

For morphing wing skin applications, low in-plane stiffness is advantageous to reduce the cost of actuation and high out-of-plane stiffness is required to withstand the aerodynamic loads. A proposed solution is to engineer a composite material made of a honeycomb support combined with a multi-state infill that can reduce the Young’s modulus for a low in-plane stiffness. Assuming thin beam theory and using the potential energy formulation, equivalent in-plane Young’s moduli can be calculated for a range of honeycomb cell geometries. The out-of-plane deflection of a representative plate fixed on all edges is calculated using flat plate theory and used to assess the performance of the skin system. To optimize the cell geometry for a given application, the out-of-plane deflection is constrained and the honeycomb cell geometry varied to investigate the design space. Results show that a skin can be designed to have in-plane Young’s moduli similar to the polymer infill and still have a low out-of-plane deflection. However, these results come at the expense of increased skin weight. Further analysis to obtain a more realistic design is done by imposing weight and geometric constraints.
Actuation Behavior in Patterned Magnetorheological Elastomers: Simulation, Experiment, and Modeling
Authors: von Lockette Paris
Published: July 2013

Magnetorheological elastomers (MREs) are an emerging class of smart materials whose mechanical behavior varies in the presence of a magnetic field. Historically MREs have been comprised of soft-magnetic iron particles in a compliant matrix such as silicone elastomer. Numerous works have experimentally cataloged the MRE effect, or increase in shear stiffness, versus the applied field. Several other researchers have derived constitutive models for the large deformation behavior of MREs. In almost all cases the arrays of embedded particles, and or the particles themselves, are assumed magnetically symmetric with respect to the external magnetic field, i.e. the bulk materials exhibit magnetic symmetry in the given experimental or analytical configuration.

In this work the author presents results of dynamic shear experiments, Lagrangian dynamic analysis, and static shear simulations on MRE material systems that exhibit broken magnetic symmetry. These new materials utilize barium hexaferrite powder as the magnetically anisotropic filler combined with a compliant silicone elastomer matrix. Simulations of representative laminate structures comprised of varied arrays of magnetic particles exhibit novel actuation behaviors including reversible shearing deformation, variable magnetostriction, and most surprisingly, piezomagnetism. Results of dynamic shear experiments and analytical modeling support predicted shearing actuation responses in MREs having broken symmetry and only in those systems.
Electroelastic Modeling and Experimental Validation of Piezoelectric Energy Harvesting From Broadband Random Vibrations
Authors: Zhao Sihong , Erturk Alper
Published: July 2013

Energy harvesting from ambient environment has received increasing attention over the last decade due to the need for minimizing the dependence on conventional batteries in wireless applications. Among the methods of vibration-to-electricity conversion, piezoelectric transduction has been investigated by numerous research groups due to the ease of application and high power density offered by piezoelectric materials. Electromechanical modeling efforts of piezoelectric energy harvesters have been mostly focused on deterministic forms of excitation input, as in the typical case of harmonic excitation. In most practical applications, however, ambient vibrational energy is often stochastic with broad frequency content. This paper presents analytical and numerical modeling, simulations, and experimental validations of piezoelectric energy harvesting from broadband random vibrations. The models employed herein are based on distributed-parameter electroelastic solution to ensure that the effects of higher vibration modes are included. The goal is to predict the expected value of the power output in terms of the given power spectral density (PSD) or time history of the random vibration input. The analytical estimations are based on the PSD of broadband random base excitation and distributed-parameter frequency response functions (FRFs) of the coupled voltage and vibration response. The numerical simulations use the Fourier series representation of base acceleration history in an ordinary differential equation solver that employs first-order electroelastic equations. The simulations are compared against the experiments for a brass-reinforced PZT-5H bimorph under different random excitation levels. The analytical and numerical simulations exhibit very good agreement with the experimental measurements. Soft and hard ceramic and single crystal bimorphs (made of PZT-5H, PZT-8, PMN-PZT, and PMN-PZT-Mn) are compared for broadband random excitation through a theoretical case study.
Thermodynamic Modeling of Ionic Polymer-Metal Composite Beams
Authors: Arumugam Jayavel , Srinivasa Arun
Published: July 2013

A thermodynamically consistent model to simulate the electromechanical response of ionic polymer-metal composite (IPMC) beams has been developed based on Euler-Bernoulli beam theory. Appropriate assumptions have been made and suitable forms for the Helmholtz free energy and the rate of dissipation have been chosen. The governing equations, describing the actuation and sensing behavior of IPMC strips in air, have been formulated using a set of kinematic assumptions, the power theorem, and the maximum rate of dissipation hypothesis, neglecting inertial effects. The model has been extended to solve for large deformations in IPMC cantilevers with certain loading conditions. The model has been shown to simulate the electromechanical responses of both Nafion and Flemion based IPMC strips. This includes the initial overshoot followed by a gradual back-relaxation observed in the tip deflection measurements of Nafion based IPMC strips under the application of a step voltage. It has been shown that a coupled convective heating term in the rate of dissipation function is crucial for simulating this overshoot and the back relaxation.
Application of Shape Memory Alloys in Locking Devices
Authors: Theiß Ralf , Lichte Daniel , Wolf Kai-Dietrich
Published: July 2013

Networked and automated locking systems are an easy to use and to administer solution for governmental and commercial use, especially in combination with advanced authentication technologies like RFID-based keys. Regardless of the advances of authentication technologies locking systems still use electric motor transmission units, which are controlled by an authentication and control unit. From an economic and an engineering point of view this approach has significant weaknesses. The main issue is the transformation of the rotational movement generated by the motor into a translational movement, which is necessary for locking applications. This leads to the implementation of a complex transmission and an inappropriate and inefficient mode of operation for the used electric motors, inflicting the reliability and increasing the overall cost as well as the required building space of the system. Consequently, there is a need to reduce the complexity and the cost of locking systems by optimizing the actuator and the mechanical components.

An alternative approach for actuators is usable with Shape Memory Alloys (SMA) and the Shape Memory Effect. Components made from SMA can return after a deformation into a pre-trained shape under certain thermal and mechanical conditions. SMA-based components can provide mechanical work as well as high forces while returning to their previous shape. Common SMA-based actuators have the form wire and provide significant pull forces when activated thermally. So it becomes possible to replace conventional electric motors and the necessary transmission with SMA-based wire actuator.

The article provides an overview of the requirements and restrictions for the application of SMA in locking systems, illustrating the issues of existing locking system designs and an approach to overcome their limitations with a system based on SMA. After a short introduction chapter two introduces SMA as an alternative approach for actuators. Chapter three focuses on the main issues of locking systems and explains the requirements for the development of new actuators for locking devices. Chapter 4 describes the conceptual development of an approach for a SMA-based locking system illustrating security issues. The article concludes with a summery and an outlook.
Characterization of Mechanically-Equivalent Amplifiers and Frequency Modulating Concepts for Energy Harvesting Devices
Authors: Lajnef Nizar , Burgueño Rigoberto , Borchani Wassim , Sun Yi , Heeringa Annelise
Published: July 2013

One of the major obstacles that are limiting the development of deployable integrated sensing and actuation solutions is the scarcity of power. Converted energy from ambient loading in civil and mechanical structures is typically used as an alternative solution. Although, piezoelectric vibration harvesters have been widely used, these elements exhibit a narrow natural frequency response range, thus considerably limiting the levels of harvestable power. Most of the previously used methods focus only on modifying the transducer’s properties and configurations. These techniques do little to modify the stimuli from the source. In contrast, this work proposes to focus on the input signal generated within the structure by inducing amplified response amplitude and a frequency up-conversion toward the harvesters’ natural response spectrum. This paper introduces the concept of using mechanically-equivalent frequency modulators that can transform the low-amplitude and low-rate service and ambient deformations into an amplified input to the piezoelectric transducer. The introduced methods will allow energy generation and conversion for loads within the unexplored quasi-static frequency range (<< 1 Hz). The post-buckling behavior of bilaterally restrained columns and bistable plates is used for frequency up-conversion. A bimorph cantilever PVDF piezoelectric beam, attached to the columns and plates, are used for energy conversion. Experimental prototypes were built and tested to validate the introduced concept. The levels of extractable power are evaluated for different cases under varying input frequencies. Finally, numerical simulations provide insight into the scalability and performance of the developed concepts.
Experimental Validation of Simultaneous Gust Alleviation and Energy Harvesting for Multifunctional Composite Wing Spars
Authors: Wang Ya , Inman Daniel J.
Published: July 2013

Vibration suppression in flexible structures is becoming an important design problem to develop energy-autonomous systems powered using the harvested ambient energy. Reduced energy control laws are developed to address the trend towards autonomous ultra-light weight aerospace structures with limited energy supply. Experiments build upon recent advances in harvester, sensor and actuator technology that have resulted in thin, light-weight multi-layered composite wing spars. These beam like multifunctional spars are designed to be capable of alleviating wind gust of small Unmanned Aerial Vehicles (UAVs) using the harvested energy. Experimental results are presented for cantilever wing spars with micro-fiber composite transducers controlled by reduced energy controllers with a focus on two vibration modes. A reduction of 16dB and 11dB is obtained for the first and the second mode using the harvested ambient energy. This work demonstrates the use of reduced energy control laws for solving gust alleviation problems in small UAVs, provides the experimental verification details, and focuses on applications to autonomous light-weight aerospace systems.
Lamb Wave Instantaneous Phase Based Method for Quantitative Level of Delamination Damage in Composite Structures
Authors: Samaratunga Dulip , Wang Ruisheng , Jha Ratneshwar
Published: July 2013

In this study, we investigate the interactions of Lamb wave A0 mode with different sizes of delaminations in composites using finite element code Abaqus®. According to Lamb wave dispersion curves, the group velocity of A0 mode increases rapidly as the frequency-thickness increases in the relatively low frequency region. In the delamination region, the frequency-thickness product decreases compared to the healthy laminate since the damage causes ply separation at the lamina interface. In the current study this observation is investigated in detail using finite element simulations. The resulting phase delay is analyzed by Empirical Mode Decomposition (EMD) and instantaneous phase approach. Finite element simulations are performed using Abaqus® and signal processing is performed in joint time-frequency domain using Hilbert-Huang Transform (HHT) method. The unwrapped instantaneous phase difference is correlated with the extent of delamination (quantitative level of damage).
Computational Design of a Reconfigurable Origami Space Structure Incorporating Shape Memory Alloy Thin Films
Authors: Hartl Darren , Lane Kathryn , Malak Richard
Published: July 2013

The subject of origami design is garnering increased attention from the science, mathematics, and engineering communities. However, relatively little research exists on understanding the behavioral aspects of the material system undergoing the folding operations. This work considers the design and analysis of a novel concept for a self-folding structure. It consists of an active, self-morphing laminate that includes thermally actuated shape memory alloy (SMA) layers and a compliant passive layer. Multiple layers allow folds in both the positive and negative directions relative to the laminate normal. The layers are configured to allow continuously variable folding operations based only on which regions are heated. For the purposes of demonstration, an example problem is considered whereby a thin structure is designed that can be stored in a flat sheet configuration and then morph using sets of folds toward two distinct shapes. We examine the effects of fold width, layer thicknesses, and activation power history on the geometric configurations that can be obtained. The design efforts are supported by a comprehensive and accurate three-dimensional constitutive model for SMAs implemented into a finite element analysis (FEA) framework. Shell elements and laminate theory are used to increase the computational efficiency of the analysis. Discussion of the complex effects of active folding in an SMA laminate sheet with in-plane homogeneity, including transient effects, are discussed.
Development of Multi-DOF Active Microvibration Emulator
Authors: Park Geeyong , Lee Dae-Oen , Han Jae-Hung , Goo Nam Seo
Published: July 2013

Recently, some components and payload systems installed in satellites are exposed to various disturbance sources, such as the reaction wheel assembly, the control moment gyro, coolers, and others. Because there is low damping in space, the continuous microvibration causes the degradation of the performance of various payload systems. Therefore, the development of a practical isolation system that shields against microvibration are very important and the author is on the way to developing the microvibration isolation system for the improvement on the performance of the optical payload. In order to develop appropriate microvibration isolation device for a specific payload, it is necessary to understand vibration characteristics of the main disturbance sources; modeling and analysis of disturbance sources including reaction wheel assembly and control moment gyros have been studied by many researchers. However, there are practical difficulties to obtain and perform an experiment with real flight model (FM) reaction wheel assembly and control moment gyros because of expensive price and security reasons. Generally, the disturbance characteristics of a prototype of the reaction wheel assembly or control moment gyros are significantly different from those of FM ones even when the reaction wheel type, size and wheel speed are the same.

Therefore, in order to facilitate the microvibration isolation experiment during the satellite development process, this paper proposes a microvibration emulator that could generate the real disturbance spectrums of FMs. Note that the disturbance profiles are quite complex, consisting of several higher harmonics, and also changing for varying operational wheel speeds. The disturbance characteristics of FMs are typically measured in advance. First an analytical model for the RWA is presented and the development procedure for the emulator is also described. The performance of the first prototype emulator is demonstrated.
Seizures in patients with high-grade glioma: a serious challenge in the end-of-life phase
Authors: Sizoo Eefje M , Koekkoek Johan A F , Postma Tjeerd J , Heimans Jan J , Pasman H Roeline W , Deliens Luc , Taphoorn Martin J B , Reijneveld Jaap C
Published: July 2013

Background

To analyse the prevalence of seizures and use of antiepileptic drugs (AEDs) in the end-of-life (EOL) phase of patients with high-grade glioma (HGG) and to identify patient characteristics associated with the occurrence of seizures in the last week of life.

Methods

Patients were recruited from a cohort of adults with HGG diagnosed in 2005 and 2006 in three tertiary referral centres for patients with brain tumour. Physicians involved in the EOL care of patients who had HGG and had died were asked to fill in a questionnaire regarding seizures and antiepileptic treatment in the last 3 months and in the last week of life. Data on seizures and use of AEDs before the EOL phase were obtained from medical correspondence and hospital medical charts.

Results

Out of 155 patients who had died, data for 92 patients were eligible for analysis. Twenty-nine percent of these 92 patients had seizures during the last week of life; 33% of patients had a history of seizures and 22% did not. Besides a history of status epilepticus (p=0.047), we identified no other significant risk factors for developing seizures in the last week of life. Seventy percent of all patients used AEDs before the last week of life. In 35% of patients in whom AEDs were tapered, seizures occurred in the last week of life.

Conclusions

Our results demonstrate that seizures are a common symptom in patients with HGG during the last week of life and emphasise the importance of adequate AED treatment throughout the EOL phase.
Characterizing heterogeneity in a glaciofluvial deposit using architectural elements, Limehouse, Ontario, Canada
Authors: Slomka J.M. , Eyles C.H.
Published: July 2013

Major hydrocarbon and groundwater reservoirs are commonly hosted within coarse-grained alluvial deposits that contain a high degree of sedimentary heterogeneity. This paper presents a detailed characterization of the sedimentary heterogeneity of fluvial–deltaic deposits using architectural element analysis (AEA). Sedimentological data collected from outcrop faces exposing Late Quaternary glaciofluvial deposits in southern Ontario, Canada, is recorded in 31 sedimentary logs. These logs are used to identify nine different facies types, including gravel facies (Gm, Gp, Gt), sand facies (Sr, Sp, St, Ss), and fine-grained facies (Fl and Fd). Variations in facies associations and geometries are defined by five architectural elements (AEs): sand complex (SC), gravel sheet (GS), fine-grained sheet (FS), gravel foreset body (GFB), and concave fill (CF) elements. The spatial arrangement of bounding surfaces (first- to fifth-order) and AEs allows the classification of six EAs, which, in this study, are defined as the largest-scale architectural subunits that allow for architectural-based mapping over a large area. EAs delineated in this study are sandy braided-river (EA1), delta-front (EA2), gravelly braided-river to delta-top (EA3), delta-front to lacustrine (EA4), braided-river to deltaic (EA5), and sand-dominated fluvial (EA6). AEA is utilized here to capture three levels of heterogeneity, which allow detailed reservoir characterization based on geometric objects and can be readily used for computer-based modelling. Outcrop analogue studies such as this one provide insight to the geometries of more deeply buried coarse-grained deposits that form potential reservoirs and enhance paleoenvironmental reconstruction of subsurface alluvial deposits in Canada and elsewhere.