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Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T02A008, September 15, 2020
Paper No: SMASIS2020-2390
Abstract
Composites can be tailored to specific applications by adjusting process variables. These variables include those related to composition, such as volume fraction of the constituents and those associated with processing methods, methods that can affect composite topology. In the case of particle matrix composites, orientation of the inclusions affects the resulting composite properties, particularly so in instances where the particles can be oriented and arranged into structures. In this work, we study the effects of coupled electric and magnetic field processing with externally applied fields on those structures, and consequently on the resulting material properties that arise. The ability to vary these processing conditions with the goal of generating microstructures that yield target material properties adds an additional level of control to the design of composite material properties. Moreover, while analytical models allow for the prediction of resulting composite properties from constituents and composite topology, these models do not build upward from process variables to make these predictions. This work couples simulation of the formation of microscale architectures, which result from coupled electric and magnetic field processing of particulate filled polymer matrix composites, with finite element analysis of those structures to provide a direct and explicit linkages between process, structure, and properties. This work demonstrates the utility of these method as a tool for determining composite properties from constituent and processing parameters. Initial particle dynamics simulation incorporating electromagnetic responses between particles and between the particles and the applied fields, including dielectrophoresis, are used to stochastically generate representative volume elements for a given set of process variables. Next, these RVEs are analyzed as periodic structures using FEA yielding bulk material properties. The results are shown to converge for simulation size and discretization, validating the RVE as an appropriate representation of the composite volume. Calculated material properties are compared to traditional effective medium theory models. Simulations allow for mapping of composite properties with respect to not only composition, but also fundamentally from processing simulations that yield varying particle configurations, a step not present in traditional or more modern effective medium theories such as the Halpin Tsai or double-inclusion theories.
Proceedings Papers
A Two Dimensional Finite Element Model for Prestress Effects on Magnetoelectric Laminated Composites
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T02A004, September 15, 2020
Paper No: SMASIS2020-2244
Abstract
Magnetoelectric (ME) composites are viable candidates for use in numerous applications owing to their multifunctional capabilities. These composites develop voltages across the piezo-electric phase under external magnetic fields. Numerous models available in literature consider the magnetostriction under pure magnetic loading. However, fabrication of ME composites results in development of compressive stresses on the magnetostrictive layer, which leads to a poor ME response and hence an initial effective tensile prestress to the magnetostrictive phase is required to either compensate or enhance the ME coupling. In this work, the ME response of an unsymmetric laminate is predicted using a finite element procedure based on Mindlin plate theory, giving due consideration the magnetostrictive nonlinearity, the direction of the applied field and the effect of the stress state on the magnetostrictive response. The model predicts that initial shear stresses, positive or negative, provide the best enhancement to the ME coupling.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T03A012, September 9–11, 2019
Paper No: SMASIS2019-5708
Abstract
Current wearable technologies strive to incorporate more medical functionalities in wearable devices for tracking health conditions and providing information for timely medical treatments. Beyond tracking of a wearer’s physical activities and basic vital signs, the advancement of wearable healthcare devices aspires to continuously monitor health parameters, such as cardiovascular indicators. To properly monitor cardiovascular health, the wearables should accurately measure blood pressure in real-time. However, current devices on the market are not validated for continuous monitoring of blood pressure at a clinical level. To develop wearable healthcare devices such applications, they must be validated by considering various parameters, such as the effects of varying skin properties. Being located between the blood vessel and the wearable device, the skin can affect the sensor readings of the device. The primary goal of this study is to investigate the effect of skin property on the radial pulse measurements. To this end, a range of artificial vein-inserted skin samples with varying properties is fabricated using Magneto-Rheological Elastomers (MRE), materials whose mechanical properties can be altered by external magnetic fields. The samples include layers to simulate the structure of skin and a silicone vein for the pulse to pass through. Note that they are not intended to represent real human skin-vein properties but created to vary a range of stiffness properties to carry out the study. Experiments are performed using a cam system capable of generating realistic human pulse waveforms to pass through the samples. During the indentation testing, the sample is compressed using a dynamic mechanical analyzer (DMA) to record experienced surface pressure, allowing the pulse patterns to be studied. Various samples are used to probe the effects of base resin hardness, iron content, and magnetic field. A pressure sensor incorporated in the cam simulator is used to benchmark the internal pulse pressure of the vein while the DMA indents the sample in order to note the pulse pressures being passed through the sample. Test results show that the properties of the skin influence the resulting pulse behaviors, particularly the ratio of the recorded pulse pressures from the sensor and the DMA.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T02A001, September 9–11, 2019
Paper No: SMASIS2019-5501
Abstract
Recently NRL researchers have embarked on a basic research effort “Tuning Giant Magnetoelectric Properties in Phase Transformation Multiferroics” focused on multifunctional materials for energy transduction and conversion. Multiferroic materials combine at least two coupled ferroic properties and are used in multiple applications including magnetic field sensors, energy harvesting devices, non-volatile memory and antennas. There are very few single phase multiferroic materials, and they normally have relatively low magnetoelectric (ME) coupling coefficient. In contrast, engineered materials such as ME composites fabricated from piezoelectric and magnetostrictive materials can show multiple orders of magnitudes increase in the ME coupling coefficient. The optimal design of ME composites would lead to conditions of maximum response (strain, induced voltage, or field) with minimum applied electric or magnetic fields, providing advanced materials for transduction, sensing, energy harvesting and other applications. That is why NRL researchers are working on piezoelectric materials with enhanced properties due to a phase transformation that would minimize the stimuli needed to achieve large strains. Key to the successful design and fabrication of ME composites is an understanding of interface characteristics as well as individual material components. In this paper we will review the current status of work at NRL on engineered multiferroic composites comprised of piezoelectric and magnetostrictive materials coupled through strain. There are still many open questions about the interfacial properties as well as the individual component materials. Details will be presented from recent work on material characterization under repetitive cycling, interface characteristics, and stress/electric/thermal effects on driving the phase transition in a relaxor ferroelectric single crystal.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T01A016, September 10–12, 2018
Paper No: SMASIS2018-8080
Abstract
The orientation and spatial distribution of magnetic particles in smart mechano-magnetic composites are key to enhancing their actuation capability. In this study, we present a new experimental approach to tune the orientation and assembly of barium hexaferrite (BHF) micro-platelets in liquid polymers by applying uniform magnetic and alternating current (AC)-electric fields. First, we investigated the assembly of BHFs under different electric field amplitudes and frequencies in the silicone elastomer. After establishing the optimum parameters for electric and magnetic alignment, four different microstructures are fabricated namely (a) random (b) electrically aligned (c) magnetically aligned and (d) simultaneously electrically and magnetically aligned. Finally, microstructural and property characterizations are performed using OM, XRD, SEM, and VSM measurements. Our findings demonstrate that a variety of microstructures can be obtained depending on the nature of the applied external field: in the absence of any field, BHF platelets are organized as small stacks, owing to their intrinsic magnetic polarization. In contrast, application of an electric field creates chain-like structures where the orientation of the BHF stacks inside the chains is random. Application of a magnetic field enhances rotation of the BHF stacks, which are found to rotate inside the chain in directions dictated by the magnetic field. Finally, by applying simultaneous electric and magnetic fields while also tuning the processing parameters, BHF-composite film with a squareness ratio of 0.92 is obtained. In order to further extend the actuation capability of resulting composites, we will also experiment with electroactive polymer matrices such as P(VDF–TrFE–CTFE) terpolymer to fabricate a multiferroic material that can actuate under both electric and magnetic field.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T01A010, September 10–12, 2018
Paper No: SMASIS2018-8016
Abstract
Liquid crystalline (LC) behaviors of cellulose nanocrystal (CNC), derived from wood, cotton or other cellulose-based biopolymers, have been actively investigated due to their unique optical properties and their superb mechanical properties, which open up potential applications in bioelectronics and biomedical engineering. In particular, many attempts have been made to control phase and orientation of LC-CNCs because they are critical factors deciding optical and mechanical properties, and electromechanical performances. Through the applications of mechanical force, electric field and magnetic field, some degree of success has been achieved; however, realizing homogeneous arrangements of CNCs that can be exploited at the macroscale is still elusive, owing to a variety of intermolecular interactions. The characterizations of the LC phase and orientation of CNCs are also challenging due to their complex biological structures. In this report, we introduce approaches to control the phase and orientation of LC-CNCs through the self-assembly, mechanical force and electric field. The liquid crystalline behaviors of CNCs in polar solvents and at the air/water interface are discussed. Translational and rotational behaviors of CNCs under DC electric field are also investigated as a function of their surface charge and dipole moment. In addition, we introduce a nonlinear optical process, namely, sum frequency generation (SFG) spectroscopy, for the structural characterization of LC-CNCs. Using SFG, we can analyze not only crystal phase and structure, but also polar ordering of CNCs which plays a key role in determining their electromechanical performances. Development of cellulose-based smart materials will expand the spectrum of available functional materials that are lightweight, flexible, mechanically tough, and thermally stable at moderately high temperatures (up to 300°C).
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T01A001, September 10–12, 2018
Paper No: SMASIS2018-7911
Abstract
Localized reinforcement of composites employed to manufacture parts for the transport industries is making possible the lightweighting of components that have a much sought-after effect in the reduction of CO 2 and NO x emissions. However, its realization, through the removing of mass where it is not required and reinforcement added to areas more prone to stress from working loads, relies on the development of novel manufacturing processes that can create structures whose performance is on a par with their solid counterparts, but at a fraction of the weight and at an affordable production cost. In this work we exploit the use of a very weak and safe magnetic field to control the location and orientation of functionalized discontinuous carbon fibers within a polymeric structural (polyurethane) foam to create performance-optimized composites. Two wet-chemistry methods (i.e. in-situ precipitation-deposition and amine-co-adjuvated electrodeposition of magnetite) to transform commercial carbon fiber into a magnetically active form were explored. The resulting fibers were analyzed and characterized through a set of physico-chemical tests. The functionalized fibers were then embedded at 3 different %vol contents in the polymeric matrix at given locations and with a desired alignment. Their mechanical performance (incl. compression, tension) was assessed and benchmarked against both a similar %volumetric content but non-functionalized-reinforcement (i.e. randomly distributed) composites and to non-reinforced matrices. In the two sets of reinforced composites (random and aligned) there is a positive correlation between stiffness, yield strength and strain with increasing %vol content. Both sets outperformed the non-reinforced matrix, demonstrating good fiber adhesion within the matrix and successful load transfer from matrix to fiber. The magnetically aligned composites generally outperformed the non-functionalized ones in terms of stiffness and strength at yield.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T01A011, September 10–12, 2018
Paper No: SMASIS2018-8033
Abstract
This study aims to investigate the influence of temperature on the linear and nonlinear rheological behavior of a MR fluid, MRF 132DG, using a rotational rheometer. The experiments were designed to obtain properties of the fluid under oscillatory shear strain in the amplitude and frequency sweep modes, while maintaining different constant temperatures (−5, 0, 20 and 50 °C). The data were used to evaluate the storage and loss moduli under different levels of magnetic flux density considering the linear as well as nonlinear viscoelastic regions. The critical strain amplitudes were further obtained. Results showed enhanced linear viscoelastic region with increasing magnetic field density. Moreover, the effects of temperature and magnetic field on the frequency dependency of the fluid properties are illustrated for small and large amplitudes of shear strains.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T03A008, September 10–12, 2018
Paper No: SMASIS2018-8015
Abstract
Artificial and synthetic skins are widely used in the medical field; used in applications ranging from skin grafts to suture training pads. There is a growing need for artificial skins with tunable properties. However, current artificial skins do not take into account the variability of mechanical properties between individual humans as well as the age-dependent properties of human skin. Furthermore, there has been little development in artificial skins based on these properties. Thus, the primary purpose of this research is to develop variable stiffness artificial skin samples using magnetorheological elastomers (MREs) whose properties that can be controlled using external magnetic fields. In this study, multiple MRE skin samples were fabricated with varying filler particle volume contents. Using a precision dynamic mechanical analyzer, a series of indenting experiments were performed on the samples to characterize their mechanical properties. The samples were tested using a spherical indenter that indented a total depth of 1 mm with a speed of 0.01 mm/s and unloaded at the same rate. The results show that the modulus or stiffness increases significantly as the iron percent (w/w) in the sample increases. Additionally, the stiffness of the sample increases proportional to the intensity of the applied external magnetic field. To assess the MRE samples’ variability of properties, the testing results were compared with in vivo human skin testing data. The results show the MRE samples are feasible to represent the age-dependent stiffness demonstrated in in vivo human skin testing. The MRE materials studied will be further studied as a variable-stiffness skin model in medical devices, such as radial pulse simulators.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V002T07A002, September 10–12, 2018
Paper No: SMASIS2018-7958
Abstract
This paper presents mathematical modeling of an energy harvester (EH) for a wireless structure health monitoring (SHM) system in wind turbine blades. The harvester consists of a piezoelectric energy harvester (PEH) beam, a gravity-induced disk, and magnets attached to both the beam and the disk. An electromechanical model of the proposed EH is developed using the energy method with repelling magnetic force considered. The three coupled equations — the motion of the disk, the vibration of the beam, and the voltage output — are derived and solved using ODE45 in MATLAB software. The result showed the blade rotation speed affects the output angular velocity of disk and the output PEH voltage. That is, as the blade speed increases, the disk angular velocity becomes nonlinear and chaotic which is more beneficial to generate larger power.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V002T07A003, September 10–12, 2018
Paper No: SMASIS2018-7967
Abstract
This paper presents a special piezoelectric energy harvester system which is obtained by separating the end of the upper piezoelectric layer of the traditional piezoelectric cantilever beam from its basic layer. A mass I is located at the end of the separated upper piezoelectric layer (SUPL), a mass II and a permanent magnet I are located at the end of the separated lower piezoelectric beam (SLPB) and a permanent magnet II is added in the opposite position of the permanent magnet I and they face each other with same polarities. A nonlinear magnetic force which can broaden the frequency bandwidth of the system is generated mutually on the two permanent magnets. Studies find that this special piezoelectric energy harvester has extremely high energy capture efficiency. In order to further explore the reason of high efficiency, experimental research on its dynamic behavior is carried out. The experimental results show that the vibrations of the SUPL and the SLPB are relatively simple. The dynamic behaviors of the SUPL, the SLPB and the unseparated part are different. The unseparated part of the piezoelectric shows relatively complex nonlinear phenomenon due to the interaction of nonlinear magnetic force and the collision. With the increase of the external excitation frequency, period doubling motion and almost periodic motion appear alternately.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T01A006, September 18–20, 2017
Paper No: SMASIS2017-3850
Abstract
Active origami designs, which incorporate smart materials such as electroactive polymers (EAPs) and magnetoactive elastomers (MAEs) into mechanical structures, have shown good promise in engineering applications. In this study, finite element analysis (FEA) models are developed using COMSOL Multiphysics software for two configurations that incorporate a combination of active and passive material layers, namely: 1) a single-notch unimorph folding configuration actuated using only external electric field and 2) a bimorph configuration which is actuated using both electric and magnetic (i.e. multifield) stimuli. Constitutive relations are developed for both electrostrictive and magnetoactive materials to model the coupled behaviors directly. Shell elements are adopted for their capacity of modeling thin films, reduction of computational cost and ability to model the intrinsic coupled behaviors in the active materials under consideration. A microstructure-based constitutive model for electromechanical coupling is introduced to capture the nonlinearity of the EAP’s relaxor ferroelectric response; the electrostrictive coefficients are then used as input in the constitutive modeling of the coupled behavior. The magnetization of the MAE is measured by experiment and then used to calculate magnetic torque under specified external magnetic field. The objective of the study is to verify the effectiveness of the constitutive models to simulate multi-field coupled behaviors of the active origami configurations. Through quantitative comparisons, simulation results show good agreement with experimental data, which is a good validation of the shell models. By investigating the impact of material selection, location, and geometric parameters, FEA can be used in design, reducing trial-and-error iterations in experiments.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T02A006, September 18–20, 2017
Paper No: SMASIS2017-3909
Abstract
Magnetic shape memory alloys (MSMAs) exhibit recoverable strains of up to 10% due to reorientation of their martensitic tetragonal unit cell. A stress or magnetic field applied to the material will cause the short side of the unit cell (which is approximately aligned with the magnetic easy axis) to align with the input to the material, resulting in an apparent plastic strain. This strain can be fully recovered by an applied stress or magnetic field in a perpendicular direction. When the martensitic variants reorient, twin boundaries, which separate the different variants, form and move throughout the specimen. A number of models have been proposed for MSMAs and many of these models are homogenized, i.e. the models do not account for twin boundaries, but rather account for the volume fraction of material in each variant. These types of models often assume that the MSMA is subject to a uniform field so that there is no appreciable difference in the volume fraction of variants in each location. In this work, we address the issue of how these models can be used when the field is not uniform. In particular, we look at the experiments from Feigenbaum et al., in which a MSMA trained to accommodate three variants, was subject to 3-dimensional magneto-mechanical loading. Due to experimental constraints, the field applied to the MSMA was not uniform. In this work, to understand the actual field distribution during experiments, we performed a high-resolution 3-dimensional finite element analysis (FEA) of the magnetic field experienced by the MSMA sample. The FEA allowed us to determine how non-uniform the experimentally applied field was and the differences between the applied field and the field experienced by the MSMA. Furthermore, we use the FEA to determine the average field experienced by the MSMA, and identify an equivalent uniform applied field that could serve as input for the model. For the latter, we seek a uniform magnetic field which gives similar magnetic field within the MSMA specimen as the true experimental conditions.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T06A009, September 18–20, 2017
Paper No: SMASIS2017-3841
Abstract
A recent achievement in the droplet interface bilayer (DIB) technique is the ability to link multiple lipid-encased aqueous droplets in an oil medium to construct a membrane-based network. Highly flexible, efficient and durable compared to other lipid bilayer modeling techniques, these systems establish a framework for the creation of biocompatible and stimuli-responsive smart materials with applications ranging from biosensing to reliable micro-actuation. Incorporating ferrofluids droplets into this platform has proven to accelerate the networks’ building mechanism through remote magnetic-control of the droplets movement and has reduced the likelihood of failure during the pre-network-completion phase. Additionally, ferrofluid drops may be placed in the final network structure as they are macroscopically homogenous and behave as single phased liquids. Due to their paramagnetic characteristics, no residual magnetization is observed in the ferrofluid upon removal of the external magnetic field, allowing for simple control of the magnetically responsive droplets. Aside from the ferrofluids reliability in contact-free manipulation of bilayer networks, this work shows a different feature of having such hybrid ferrofluid-water DIB networks: magnetic-sensibility and actuation. Once pre-structured mixed networks are formed, a magnetic source is used to generate various magnetic fields in the vicinity of the DIB webs; changes in structural responses are then observed and used to induce protein channel gating in DIB networks channeling the functionality of a switch. Tailored architectures are accordingly evaluated and their suitability for the creation of microfluidic-magneto sensors and actuators is assessed.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T01A015, September 18–20, 2017
Paper No: SMASIS2017-3988
Abstract
In this study, we demonstrate the electric and magnetic manipulation of nanoscale M-type Barium Hexaferrite (nBF) in polydimethylsiloxane (PDMS) to engineer a multifunctional nanocomposite with improved dielectric and magnetic properties. First, we synthesized the single crystal nBF via the hydrothermal synthesis route. The hydrothermal temperature, duration, and surfactant conditions were optimized to improve the magnetic properties of the nBFs, with further improvement achieved by post-annealing. The annealed nBFs were aligned dielectrophoretically (DEP) in the polymer matrices by applying an AC electric field. Under the influence of this electric field, nBFs were observed to rotate, align and form chains within the polymer matrix. Optical microscopy (OM) imaging was used to determine the electrical alignment conditions (duration, magnitude, and frequency) and these parameters were used to fabricate the composites. A Teflon setup with Indium Tin Oxide (ITO) coated Polyethylene Terephthalate (PET) was used, where the ITO coatings act as electrodes for the electric field-manipulation. To simultaneously apply the magnetic field, this Teflon setup is placed between two permanent magnets capable of generating a 0.6 T external magnetic field. Along with electric and magnetic fields, concurrent heating was applied to cure the PDMS and freeze the microstructure formed due to electric and magnetic fields. Upon completion of the curing step, parallel chain formation is observed under OM. The X-Ray Diffraction (XRD) results also confirm that the particles are magnetically oriented in the direction of the magnetic field within the chain. Vibrating Sample Magnetometry (VSM) measurements and dielectric spectroscopy are used to characterize the extent of anisotropy and improvement in dielectric and magnetic properties compared to random composites. We find that simultaneous electric and magnetic field alignment improves the dielectric properties by 12% compared to just magnetic alignment. We also observe 19% improved squareness ratio when both fields are applied. The possibility of simultaneous electrical and magnetic alignment of magnetic nanoparticles will open up new doors to manipulate and design particle-modified polymers for various applications.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T01A008, September 18–20, 2017
Paper No: SMASIS2017-3868
Abstract
Magneto-Active elastomers (MAEs) and magneto-rheological elastomers (MREs) are smart materials that consist of hard and soft magnetic particles, respectively, embedded in a flexible matrix. Their actuation capabilities are dependent on the arrangement of particles achieved during the fabrication process. Previous works have shown varying degrees of particle alignment and / or agglomeration as a function of fabrication process variable, most notably volume fraction of the particulates, their magnetic material type (hard vs soft), and the strength of the external field applied during curing. In this work, we simulated the dynamics of magnetic particles suspended in a fluid matrix to predict the evolution of microstructures resulting from these varying process conditions. The simulations accounted for the magnetic interaction of all particles using standard dipole-dipole interaction potentials along with dipole-field potentials developed from the Zeeman Energy. Additionally, the field local to each particle, on which magnetization depends, was determined by the sum of the external fields generated by each member of the ensemble and their demagnetizing fields. Fluid drag forces and short range particle-particle repulsion (non-overlapping) were also considered. These interactions determined the body forces and torques acting on each particle that drove the system of equations of motions for the ensemble of particles. The simulation was carried out over a nearest neighbor periodic unit cell using an adaptive time stepping numerical integration scheme until an equilibrium structure was reached. Structural parameters, related to the magnetic energy, spatial distribution, spatial alignment, and orientation alignments of the particle distributions were defined to characterize the simulated structures. The effect of volume fraction and intensity of the external magnetic field on the achieved particle distributions were studied. At low external field strengths, the particles formed long entangled chains that had very low alignment with the applied field. The remnant magnetic potential energy of these configurations was also significantly low. As the field is increased the length of the chains reduced and the alignment increased. The corresponding change in magnetic potential energy of the system with an increase in the applied field was found to follow a power law fit that spanned a wide range of magnetic field strengths. At low volume fractions the particles aligned rapidly with the field and formed short chains. As the volume fraction of the samples increased the chains grew longer and closer to each other, and magnetic potential of the structure became lower. Results of the simulations suggest that it is possible to tailor the microstructure and thus affect remanent magnetization and magnetization anisotropy, by judicious control of process parameters. This ability could have implications for newly emerging additive manufacturing techniques utilizing suspensions of magnetic particulates.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T01A001, September 18–20, 2017
Paper No: SMASIS2017-3732
Abstract
In this study, 3D printed magnetorheological (MR) elastomer has been characterized through a force vibration testing. The 3D printed MR elastomer is a composite consisting three different materials, magnetic particles and two different elastomers. The MR elastomers were printed layer-by-layer by encapsulating MR fluid within the polymeric elastomer and then allowed to cure at room temperature. The 3D printing allowed to print various patterns of magnetic particles within the elastomeric matrix. In the presence of an external magnetic field, both elastic and damping properties of the 3D printed MR elastomers were changed. Natural frequency, stiffness, damping ratio, damping coefficient, and shear modulus were increased with increasing magnetic field. For the single degree-of-freedoms system, shear mode MR elastomers suppressed the transmitted vibration amplitude up to 31.4% when the magnetic field was 550 mT. The results showed that the 3D printed MR elastomer could be used as a tunable spring element for vibration absorption or isolation applications. However, further optimization of the magnetic particles’ configurations should be performed to obtain the higher MR effect.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T02A001, September 18–20, 2017
Paper No: SMASIS2017-3774
Abstract
Magneto-rheological fluids (MRF) are commonly applied in MRF brakes and vibration damping. The apparent viscosity dependence with respect to the magnetic field has been addressed in detail in the state of the art. The aim of this paper is to experimentally study the vibration effects on the particle chain-like structures and, as a consequence, the shear stress variation applied to the fluid. Three vibration configurations have been applied to a ferromagnetic cylinder rotating between two magnetic poles filled with MRF a “Z-vibration” where the generated displacement is along the rotation axis of the shearing cylinder, a “θ-vibration”, tangential to the cylinder, and an “R-vibration”, normal to the cylinder surface. First we focus on the vibration mode characterisation in free air, and then when plunged in the fluid. In a second step, we measure the reactive torque generated on the clutch under different magnetic field intensities with different rotation speeds and vibration amplitudes. It appears that the “R-vibration” configuration is providing the most influence, up to 20% of torque reduction observed at moderate B field. The “Z-vibration” and the “θ-vibration” configurations respectively have less influence on the torque, nevertheless vibrations always tend to decrease the corresponding yield stress in the MRF.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 1: Development and Characterization of Multifunctional Materials; Mechanics and Behavior of Active Materials; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V001T07A010, September 18–20, 2017
Paper No: SMASIS2017-3860
Abstract
There is a growing interest to convert ambient mechanical energy to electrical energy by vibration energy harvesters. Realistic vibrations are random and spread over a large frequency range. Most energy harvesters are linear with narrow frequency bandwidth and show low performance, which led to creation of nonlinear harvesters that have larger bandwidth. This article presents a simulation study of a nonlinear energy harvester that contains two cantilever beams coupled by magnetic force. One of the cantilever beam is covered partially by piezoelectric material, while the other beam is normal to the first one and is used to create a variable potential energy function. The variable double-well potential function enables optimum conversion of the kinetic energy and thus larger output. The system is modeled by coupled Duffing oscillator equations. To represent the ambient vibrations, the response to Gaussian random input signal (generated by Shinozuka formula) is studied using power spectral density. The effects of different parameters on the system are also investigated. The results show that the double cantilever harvester has a threshold distance, where the harvester can perform optimally regardless of the excitation level. This observation is opposite to that of the conventional fixed magnet cantilever system where the optimal distance varies with the excitation level. Results of this study can be used to enhance energy efficiency of vibration energy harvesters.
Proceedings Papers
Proc. ASME. SMASIS2017, Volume 2: Modeling, Simulation and Control of Adaptive Systems; Integrated System Design and Implementation; Structural Health Monitoring, V002T03A030, September 18–20, 2017
Paper No: SMASIS2017-3893
Abstract
This manuscript investigates one way sound propagation in Magnetorheological fluids (MRF) using spatio-temporal modulation of the applied magnetic field. One-way propagation of waves in a structure can have potential technological applications such as sound isolation, filtering and echo suppression. Several experimental works in the literature have shown that elastic properties of MRF’s (local speed of sound, in particular) are dependent on the applied magnetic field. Therefore, several fascinating possibilities regarding the manipulation of sound waves in MRF, by tailoring the applied magnetic field, exist. A effective medium approximation (previously used in literature) is used to analyze sound propagation in a MRF composed of hydrogen-reduced Iron particles suspended in pure glycerine. Floquet-Bloch theory is used to obtain a quadratic eigenvalue problem that gives the band structure as a function of the material and modulation parameters. When the applied magnetic field is allowed to vary only in space, regular bandgaps are obtained as a result of Bragg scattering. In contrast, the temporal variation of the magnetic field to induce a traveling wave like variation of the modulated parameters, breaks the symmetry of the Brilloouin zones and we obtain directional bandgaps. The theoretical band structure is validated by numerical band diagrams obtained using a Finite Element code. This research has important applications in active sound manipulation.