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Author: Ashkan Dargahi
Publisher:
ISBN:
Category :
Languages : en
Pages : 126
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Book Description
Magnetorheological elastomers (MREs) are a novel class of magneto-active materials comprised of an elastomeric matrix impregnated by micron-sized ferromagnetic particles, which exhibit adjustable mechanical properties such as stiffness and damping coefficient in a reversible manner under the application of an external magnetic field. MREs are solid state of magnetorheological (MR) materials. In contrast to MR fluids, which provide field-dependent apparent viscosity, MREs, being a smart viscoelastic material, are capable of providing controlled field dependent moduli. Yet having a solid grasp of highly complex behavior of this active composite is a fundamental necessity to design any adaptive structure based on the MRE. This study is concerned with investigation of the static and dynamic behavior of the magnetorheological elastomers. To this end, six different types of MREs with varying contents of the rubber matrix as well as ferromagnetic particles are fabricated and characterized statically in the shear mode as a function of the magnetic field intensity. The MRE containing the highest percentage of iron particles (40% volume fraction) exhibited a notable relative MR effect of 555% with 181.54 KPa increase in the MRE shear modulus. This particular MRE was then chosen for subsequent dynamic characterization. The dynamic responses of magnetorheological elastomers revealed strong dependence on the strain and strain rate as well as the applied magnetic field intensity. Dynamic characterization is performed in shear mode under harmonic excitations under the broad ranges of shear strain amplitude (2.5-20%), frequency (0.1-50 Hz) and magnetic field intensity (0-450 mT). The strain softening, strain stiffening, strain rate stiffening and the magnetic field stiffening phenomena are identified as the nonlinear properties of MRE stress-strain hysteresis loops. Subsequently, an operator-based Prandtl-Ishlinskii (PI) phenomenological model is developed to predict the nonlinear hysteresis behavior of the MREs as functions of strain, strain rate and field intensity. The stop-operator-based classical PI model using only 10 hysteresis operators provided very accurate predictions, and it involved identification of only four parameters, which were dependent on the loading conditions. The validity of the developed Classical Prandtl-Ishlinskii model is assessed using the laboratory-measured data for MRE over a wide range of inputs. The proposed model is further generalized to predict the dynamic behavior of MRE independent of the loading conditions, which could be beneficial for controlling the MRE-based adaptive devices in real time. The results demonstrated that the proposed generalized model could accurately characterize the nonlinear hysteresis properties of MRE under a wide range of loading conditions and applied magnetic fields.
Author: Ashkan Dargahi
Publisher:
ISBN:
Category :
Languages : en
Pages : 126
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Book Description
Magnetorheological elastomers (MREs) are a novel class of magneto-active materials comprised of an elastomeric matrix impregnated by micron-sized ferromagnetic particles, which exhibit adjustable mechanical properties such as stiffness and damping coefficient in a reversible manner under the application of an external magnetic field. MREs are solid state of magnetorheological (MR) materials. In contrast to MR fluids, which provide field-dependent apparent viscosity, MREs, being a smart viscoelastic material, are capable of providing controlled field dependent moduli. Yet having a solid grasp of highly complex behavior of this active composite is a fundamental necessity to design any adaptive structure based on the MRE. This study is concerned with investigation of the static and dynamic behavior of the magnetorheological elastomers. To this end, six different types of MREs with varying contents of the rubber matrix as well as ferromagnetic particles are fabricated and characterized statically in the shear mode as a function of the magnetic field intensity. The MRE containing the highest percentage of iron particles (40% volume fraction) exhibited a notable relative MR effect of 555% with 181.54 KPa increase in the MRE shear modulus. This particular MRE was then chosen for subsequent dynamic characterization. The dynamic responses of magnetorheological elastomers revealed strong dependence on the strain and strain rate as well as the applied magnetic field intensity. Dynamic characterization is performed in shear mode under harmonic excitations under the broad ranges of shear strain amplitude (2.5-20%), frequency (0.1-50 Hz) and magnetic field intensity (0-450 mT). The strain softening, strain stiffening, strain rate stiffening and the magnetic field stiffening phenomena are identified as the nonlinear properties of MRE stress-strain hysteresis loops. Subsequently, an operator-based Prandtl-Ishlinskii (PI) phenomenological model is developed to predict the nonlinear hysteresis behavior of the MREs as functions of strain, strain rate and field intensity. The stop-operator-based classical PI model using only 10 hysteresis operators provided very accurate predictions, and it involved identification of only four parameters, which were dependent on the loading conditions. The validity of the developed Classical Prandtl-Ishlinskii model is assessed using the laboratory-measured data for MRE over a wide range of inputs. The proposed model is further generalized to predict the dynamic behavior of MRE independent of the loading conditions, which could be beneficial for controlling the MRE-based adaptive devices in real time. The results demonstrated that the proposed generalized model could accurately characterize the nonlinear hysteresis properties of MRE under a wide range of loading conditions and applied magnetic fields.
Author: Armin Rasooli
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Semi-active tunable vibration absorbers (SATVAs) have recently received growing interest due to their energy efficiency, simple structure and optimal performance under a wide frequency-bandwidth. SATVAs generally consist of elements with variable stiffness to allow for optimal performance under a wide frequency range compared with their passive analogues which are typically tuned at a particular frequency. Magnetorheological elastomers (MREs) are unique smart materials which can serve as the variable-stiffness elements in SATVAs. MREs are basically the solid state of the well-known magnetorheological (MR) fluids, which in contrast to MR fluids, their stiffness (storage modulus) can be continuously changed rapidly through the application of an external magnetic field. The present research study is concerned with the modeling, fabrication and control of a novel SATVA based on MRE-filled sandwich structures. To this end, a novel five-layered beam-shape sandwich structure was designed using MREs as core layers, reinforced with thin elastic plates on top, middle and bottom. To provide for a suitable and controllable magnetic field a set of U-shaped electromagnets were also designed. A specific two-node adaptive sandwich beam element has been developed to derive the governing dynamic equations of the MRE-based sandwich beam in the finite element (FE) form. The developed finite element model of the MRE-based sandwich beam together with the developed magnetic finite element of the electromagnets have then been effectively utilized to identify the suitable design parameters for the proposed SATVA to meet the geometrical and mechanical requirements. Experimental tests have been designed to acquire the magnetic permeability and the storage modulus of the fabricated MREs required for the modeling. Next the proposed SATVA was fabricated and subsequently tested using an electrodynamic shaker to evaluate its vibration performance and also to validate the developed FE models. The results indicate that the fabricated SATVA, provides an approximately 9% shift in the natural frequency. The validated FE models were subsequently utilized to conduct systematic sensitivity analysis to investigate the effect of different design parameters including the thickness of elastic layers and the position of electromagnets. The experimental results were also used to developed an equivalent lumped mass model for the proposed SATVA. Finally, a phased-based control strategy using the full-state adaptive Kalman filter (AKF) observer has been developed to adaptively tune the natural frequency of the absorber to the varying excitation conditions. It is expected that the present research dissertation provides an essential guidance for the future development of light-weight adaptive vibration absorbers.
Author: Mostafa Asadi Khanouki
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Multi-functional magnetorheological elastomers (MREs) with magnetic-controlled properties offer great potential for enabling new technologies in a diverse range of industry sectors, such as automotive, aerospace, civil, and biomedical applications. The main objective of this research dissertation is to develop analysis models for magneto-mechanical properties of smart MREs and to propose design optimization strategies to optimally design a novel sandwich beam-type MRE-based adaptive tuned vibration absorber. The dissertation comprises three major interrelated parts. In the first part, a quasi-static microstructure-based model has been proposed to investigate the magneto-elastic properties of MREs. The elastic response of the MREs at zero magnetic field is initially studied by comparing the results of three hyperelastic material models. Then, a microscale model is developed for predicting the quasi-static response of MREs under an external magnetic field. The model considers magnetic interaction between particles distributed in the carrier elastomeric matrix according to regular lattice models for isotropic MREs and according to chain-like structure for anisotropic MREs. Several lattice models are proposed, and performance of each lattice is compared with their counterparts. Detailed explanation is provided on the characteristics of the proposed lattices and on the resulting changes in the microstructure properties of the MREs. The simulation results for different lattice models are then compared with the experimental measurements for both isotropic and anisotropic MRE samples using an advanced rheometer equipped with a magnetorheological (MR) device. In the second part, the dynamic magneto-mechanical properties of MREs are investigated. For this purpose, a dynamic physic-based model considering the microstructure of MREs is developed to accurately predict the frequency- and field-dependent linear viscoelastic properties of the material. The proposed model considers a cubic particle network in which magnetic particles are located at the junctures and connected with elastic springs. Using Langevin dynamics, the governing equations of motion of particles are derived to evaluate the relaxation spectrum associated with particles' motion in parallel and normal directions with respect to the applied magnetic field. A dipole magnetic saturation model is also implemented to derive the storage and loss moduli of the MREs in terms of frequency and magnetic flux density. The material parameters in the proposed dynamic microstructure-based model have been identified using experimental tests. For this purpose, oscillatory shear tests were performed using the magneto-rheometer in linear viscoelastic region under a wide range of excitation frequency varying from 2 Hz to 100 Hz in presence of various levels of applied magnetic fields ranging from 0.0 T to 1.0 T. The viscoelastic properties, namely storage and loss moduli of both isotropic and anisotropic MREs, were subsequently measured and compared with those obtained using the developed model to quantitatively evaluate its performance. The third part of the present dissertation aims to investigate the application of MREs in developing a novel sandwich beam-shaped MRE-based adaptive tuned vibration absorber (MRE-ATVA). An MRE-ATVA comprised of a light-weight sandwich beam treated with an MRE core layer and two electromagnets installed at both free ends is proposed. The MRE-ATVA is designed to have a lightweight and compact structure and the electromagnets provide the magnetic field required to activate the MRE layer while also act as the resonator of the absorber. The finite element (FE) model of the proposed MRE-ATVA and magnetic model of the electromagnets with three different potential designs are developed and combined to evaluate the frequency range of the absorber under varying magnetic field intensity. The results of the developed models are validated in multiple stages with available analytical and simulation data. The developed models are then utilized to formulate the multidisciplinary design optimization problem to maximize the operating frequency range of the MRE-ATVA while respecting constraints of weight, size, mechanical stress, and sandwich beam deflection. The optimization problem is solved combining the gradient based sequential quadratic programming (SQP) technique and stochastic based genetic algorithm (GA) to accurately obtain the global optimum solution. The performance of the optimal MRE-ATVAs with three potential designs are finally compared.
Author: Anna Boczkowska
Publisher: BoD – Books on Demand
ISBN: 9535107399
Category : Science
Languages : en
Pages : 416
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Book Description
This book provides an extensive overview of current trends in the area of elastomers and their composites from the chapters contributed by internationally recognized specialists. The book deals with novel synthesis, modelling and experimental methods in elastomers. Contents include: new approach to crosslinking, liquid crystal elastomers, nanocomposites, smart elastomers, elastomers in microelectronics and microfluidics, elastomers in cement concrete and mortar, experimental testing and modelling. Each section demonstrates how enhancements in materials, processes and characterization techniques can improve performance in the field of engineering. The book provides a unique opportunity to discover the latest research on elastomer advances from laboratories around the world. This book addresses to industrial and academic researchers in the fields of physical, chemical, biological sciences and engineering.
Author: Nader Mohseni Ardehali
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Magnetoactive elastomers also known as Magnetorheological elastomers (MREs) are solid analogue of the well-known magnetorheological (MR) fluids. MREs are smart composite materials made of elastomeric medium embedded with micron-sized ferromagnetic particles. Unlike MR fluids which can mainly provide variable damping, MREs can provide simultaneous variations in damping as well as stiffness properties. Moreover, MREs do not exhibit limitation of MR fluids such as sedimentation of iron particles and leakage. Hard magnetorheological elastomers (H-MREs) are MREs in which the soft magnetic particles in conventional MREs are replaced by hard micron-sized permanent magnetic particles which provide magnetic poles inside the elastomeric medium. By applying the magnetic field in the same or opposite direction of the magnetic poles, respectively, the stiffness of the H-MREs can be increased or decreased. While conventional MREs have been widely studied during the past decade, very limited studies exist to demonstrate the response behavior of H-MREs. The objectives of the present research thesis are to 1- experimentally characterize the viscoelastic properties of H-MREs under varying operating conditions and applied magnetic field, 2- develop simple phenomenological models to predict the viscoelastic response behavior of MREs, 3- explore the potential application of H-MREs in an adaptive vibration isolator. For this purpose, H-MREs with 15% volume fraction of neodymium-iron-boron (NdFeB) magnetic particles have been fabricated and then tested under oscillatory shear motion using a rotational magneto-rheometer to investigate their viscoelastic behavior under varying excitation frequency and magnetic flux density. The influence of the shear strain amplitude and driving frequency are also examined under various levels of applied magnetic field ranging from -0.2 T to 1.0 T. Moreover, field-dependent phenomenological models have been proposed to predict the variation of storage and loss moduli of H-MREs under varying excitation frequency and applied magnetic flux density. The results show that the proposed model can accurately predict the viscoelastic behavior of H-MREs under various fields and operating conditions. Finally, a tunable vibration isolator based on H-MRE is developed and the influence of applying positive and negative magnetic fields on the transmissibility of the HMRE-based isolator is investigated.
Author: Bilen Emek Abali
Publisher: Springer
ISBN: 3030133079
Category : Science
Languages : en
Pages : 586
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Book Description
This book presents a liber amicorum dedicated to Wolfgang H. Müller, and highlights recent advances in Prof. Müller’s major fields of research: continuum mechanics, generalized mechanics, thermodynamics, mechanochemistry, and geomechanics. Over 50 of Prof. Müller’s friends and colleagues contributed to this book, which commemorates his 60th birthday and was published in recognition of his outstanding contributions.
Author: Norman Wereley
Publisher: Royal Society of Chemistry
ISBN: 1849736677
Category : Science
Languages : en
Pages : 410
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Book Description
Leading experts provide a timely overview of the key developments in the physics, chemistry and uses of magnetorheological fluids.
Author: Hal F. Brinson
Publisher: Springer
ISBN: 1489974857
Category : Science
Languages : en
Pages : 488
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Book Description
This book provides a unified mechanics and materials perspective on polymers: both the mathematics of viscoelasticity theory as well as the physical mechanisms behind polymer deformation processes. Introductory material on fundamental mechanics is included to provide a continuous baseline for readers from all disciplines. Introductory material on the chemical and molecular basis of polymers is also included, which is essential to the understanding of the thermomechanical response. This self-contained text covers the viscoelastic characterization of polymers including constitutive modeling, experimental methods, thermal response, and stress and failure analysis. Example problems are provided within the text as well as at the end of each chapter. New to this edition: · One new chapter on the use of nano-material inclusions for structural polymer applications and applications such as fiber-reinforced polymers and adhesively bonded structures · Brings up-to-date polymer production and sales data and equipment and procedures for evaluating polymer characterization and classification · The work serves as a comprehensive reference for advanced seniors seeking graduate level courses, first and second year graduate students, and practicing engineers
Author: Seung-Bok Choi
Publisher: Materials, Circuits and Device
ISBN: 1785617702
Category : Technology & Engineering
Languages : en
Pages : 443
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Book Description
This book introduces magnetorheological fluids and elastomers, and explores their material properties, related modelling techniques and applications in turn. The book offers insights into the relationships between the properties and characterisation of MR materials and their current and future applications.
Author: P. M. Visakh
Publisher: Springer Science & Business Media
ISBN: 3642209254
Category : Technology & Engineering
Languages : en
Pages : 497
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Book Description
This is the first volume of a two-volume work which summarizes in an edited format and in a fairly comprehensive manner many of the recent technical research accomplishments in the area of Elastomers. “Advances in Elastomers” discusses the various attempts reported on solving these problems from the point of view of the chemistry and the structure of elastomers, highlighting the drawbacks and advantages of each method. It summarize the importance of elastomers and their multiphase systems in human life and industry, and covers all the topics related to recent advances in elastomers, their blends, IPNs, composites and nanocomposites. This first volume focuses on advances on the blends and interpenetrating networks (IPNs) of elastomers.
