Dynamics of viscoelastic-magnetorheological sandwich structures: multiphysics analysis

A fundamental aim of many industrial sectors is the reduction of structural vibration in order to increase the service life of mechanical components and diminish noise radiation. Viscoelastic sandwiches have been widely applied to attenuate structural vibration as they are cost-effective and simple to employ. However, the constantly increasing requirements for vibration control have made the latest research move towards smart structures able to adapt to random vibrations in real time. Magnetorheological materials are a class of smart materials able to modify their rheological properties in response to magnetic fields. Thus, they offer attractive features for constructing smart sandwich structure with enhanced vibration control. The present thesis studies the dynamics of thin viscoelastic-magnetorheological sandwich structures. These sandwiches are analogous to thin viscoelastic sandwiches in the absence of a magnetic field, whereas when magnetic fields are applied their dynamic behaviour is modified as a result of the coupling of multiple physical phenomena generated in their skins and core. The dynamic behaviour of thin viscoelastic sandwiches was analysed as a way of studying the behaviour of thin viscoelastic-magnetorheological sandwiches in the absence of a magnetic field. To that end, sandwiches of different compositions were characterized and numerical models were defined. From the joint analysis of the experimental and numerical results, the influence of the nature and thickness of both viscoelastic adhesive and metallic skins on the dynamic properties of the sandwich were determined. The phenomenon of eddy currents generated in metallic skins was studied in order to determine its influence on the dynamic behaviour of viscoelasticmagnetorheological sandwiches. To do this, an experimental modal analysis with a metallic beam, with and without induced eddy currents, was carried out. Then, in view of the damping capacity of eddy currents, a new hybrid sandwich structure combining viscoelastic and eddy current damping was proposed. Afterwards, a new inverse method was developed to estimate and model the influence of eddy currents. The phenomena generated in the viscoelastic-magnetorheological core, the magnetorheological effect and magnetic force, were studied. To that end, a magneto-dynamic model of viscoelastic-magnetorheological sandwiches including both phenomena was proposed and validated with experimental results. Finally, the dynamic behaviour of a thin viscoelastic-magnetorheological sandwich was analysed experimentally, and the influence of the magnetic particles and the intensity and position of the magnetic field was studied. The knowledge acquired in the course of this research enables determining the physical phenomena governing the dynamics of thin viscoelastic-magnetorheological sandwiches and explain the experimentally observed magneto-dynamic behaviour.Sektore industrial askoren helburua egiturazko bibrazioak murriztea da, honela, osagai mekanikoen bizitza erabilgarria luzatu eta erradiazio akustikoa murrizten baita. Sandwich biskoelastikoak oso erabiliak izan dira egiturazko bibrazioak moteltzeko, izan ere, inplementatzeko errazak eta kostu baxukoak baitira. Gaur egun, gero eta bibrazio-kontrol efikazagoa eskatzen denez, denbora errealean ausazko bibrazioetara egokitzeko gai diren estruktura adimendunetan ardaztu dira azken ikerketak. Material magnetoerreologikoak material adimendunak dira, zeinen propietate erreologikoak eremu magnetiko baten bidez aldatu daitezkeen. Hortaz, ohiko sandwichen nukleoa material magnetoerreologikoekin ordezkatu daiteke, sandwich estruktura adimenduak sortzeko. Tesi doktoral honen helburu nagusia sandwich biskoelastiko-magnetoerreologiko meheen dinamika aztertzea da. Eremu magnetikorik aplikatu ezean, sandwich hauen izaera dinamikoa sandwich biskoelastikoen bera da. Eremu magnetikoak aplikatzean, berriz, sandwichen izaera dinamikoa aldatu egiten da, beraien azal eta nukleoetan sortzen diren fenomeno ezberdinen akoplamenduagatik. Lehenik, sandwich biskoelastiko meheen jokaera dinamikoa aztertu da, sandwich biskoelastiko-magnetoerreologikoen jokaera eremu magnetikorik gabe analizatzeko asmoz. Horretarako, konposizio ezberdineko sandwich biskoelastikoak karakterizatu eta zenbakizko ereduak definitu dira. Itsasgarri biskoelastikoek eta azal metalikoek sandwicharen propietate dinamikoetan duten eragina zehaztu da emaitza esperimental eta zenbakizkoei esker. Azal metalikoetan sortutako Foucault-en korronteen fenomenoa ere aztertu da, korronte hauek sandwich biskoelastiko-magnetorreologikoen jokaera dinamikoaren gain duten eragina zehazteko. Horretarako, metalezko habe baten analisi modal esperimentala gauzatu da, habeak Foucault-en korronteak induzituta eta induzitu gabe dituelarik. Jarraian Foucault-en korronteen moteltze-gaitasuna ikusirik, sandwich hibrido berria proposatu da, zeinak moteltze biskoelastikoa eta Foucault-ena batzen dituen. Ondoren, metodo alderantzikatu berria garatu da, korronte hauen eragina zenbatetsi eta modelatzeko. Nukleo biskoelastiko-magnetoerreologikoetan sortutako fenomenoak ere aztertu dira, hau da, efektu magnetoerreologikoa eta indar magnetikoa. Horretarako, bi fenomeno hauek kontutan hartzen dituen sandwich biskoelastikomagnetoerreologikoen eredu dinamikoa proposatu eta emaitza esperimentalekin egiaztatu da. Azkenik, sandwich biskoelastiko-magnetoerreologiko meheen jokaera dinamikoa esperimentalki ebaluatu da. Partikula magnetikoek eta eremu magnetikoaren intentsitateak eta posizioak sandwicharen propietate dinamikoetan duten eragina aztertu da. Tesi doktoral honetan zehar sortutako ezagutzak, sandwich hauen erantzun magnetodinamikoa gidatzen duten fenomeno fisikoak ezagutzea ahalbidetu du.En la actualidad, numerosos sectores industriales tienen como objetivo disminuir la amplitud de las vibraciones con el fin de alargar la vida útil de los componentes y reducir la radiación acústica. Con este propósito se utilizan sándwich viscoelasticos, ya que son sencillos de implementar, de bajo coste y eficaces en la atenuación de vibraciones estructurales. Sin embargo, estos sándwich no tienen la capacidad de adaptarse en tiempo real a las condiciones de trabajo, por lo que las últimas investigaciones en control de vibraciones se centran en estructuras inteligentes. Los materiales magnetorreológicos son capaces de modificar sus propiedades reológicas en respuesta a campos magnéticos externos, y por tanto son idóneos para fabricar estructuras sándwich inteligentes. El objetivo principal de la presente tesis doctoral es conocer la respuesta dinámica de sándwich viscoelasticos-magnetorreológicos finos. En ausencia de campo magnético el comportamiento dinámico de estos sándwich es análogo al de los sándwich viscoelasticos, sin embargo al aplicar un campo magnético su comportamiento dinámico se modifica como resultado del acoplamiento de múltiples fenómenos físicos generados en las pieles y en el núcleo. Se ha analizado el comportamiento dinámico de los sándwich viscoelasticos finos para entender la respuesta de los sándwich viscoelasticos-magnetorreológicos en ausencia de campo magnético. Para ello, se han caracterizado sándwich de diferentes composiciones y se han generado modelos numéricos. Con estos análisis se ha establecido la influencia de la composición y del espesor tanto del adhesivo viscoelastico, como de las pieles metálicas en las propiedades dinámicas del sándwich. Se han estudiado las corrientes de Foucault que se generan en las pieles metálicas de los sándwich. Dada la capacidad de amortiguación de estas corrientes, se ha propuesto un nuevo sándwich híbrido que combina el amortiguamiento viscoelastico, con las corrientes de Foucault. Además, se ha desarrollado un nuevo método inverso que estima la influencia de este fenómeno en la respuesta dinámica de los sándwich. En el núcleo viscoelastico-magnetorreológico concurren dos fenómenos: el efecto magnetorreológico, propio de la inteligencia del núcleo, y la fuerza magnética que se origina por el acoplamiento de las vibraciones del núcleo magnetizado con el campo magnético aplicado. Ambos fenómenos se han incluido en un nuevo modelo numérico, que se ha validado con resultados experimentales, y se ha establecido su influencia en la dinámica del sándwich. Por último, se ha estudiado experimentalmente la influencia de las partículas magnéticas, y de la intensidad y posición del campo magnético en el comportamiento dinámico de los sándwich viscoelastico-magnetorreológico finos. El conocimiento adquirido con esta tesis, ha permitido determinar los fenómenos físicos que rigen la dinámica del sándwich viscoelastico-magnetorreológico y explicar el comportamiento magneto-dinámico experimental observado

Enhancement of Shock Absorption Using Hybrid SMA-MRF Damper by Complementary Operation

A hybrid damper concept is presented here using a combination of a Magnetorheological (MR) Fluid (MRF) and Shape Memory Alloy (SMA)-based energy dissipation. A demonstration is performed utilizing the shear operating mode of the MRF and the one-way effect of the SMA. The damping performance of different MRF-SMA configurations is investigated and the corresponding energy consumption is evaluated. We demonstrate that the operation of MRF and SMA dampers complement each other, compensating for each other’s weaknesses. In particular, the slow response from the MR damper is compensated by passive SMA damping using the pseudoplastic effect of martensite reorientation, which can dissipate a significant amount of shock energy at the beginning of the shock occurrence. The MR damper compensates for the incapability of the SMA to dampen subsequent vibrations as long as the magnetic field is applied. The presented hybrid SMA-MR damper demonstrates superior performance compared to individual dampers, allowing for up to five-fold reduction in energy consumption of the MR damper alone and thereby opening up the possibility of reducing the construction volume of the MR damper

Dynamics research of a flywheel shafting with PMB and a single point flexible support

Flywheel energy storage system (FESS) is new advanced machinery which is intended for electric power storage and release. A FESS, which is suitable for the small flywheel, was developed with a permanent magnet bearing (PMB) and a single point flexible support, and its friction loss is very low. By means of the Lagrange theory, a dynamic model was established. The Campbell diagram, mode shapes, modal damping ratios and critical speeds were designed after the flywheel data at different operating speeds was obtained by numerical simulation. Based on the excitation test and single freedom vibration theory, the stiffness and damping coefficient of the upper and lower damper was measured. The influences of damper dynamic parameters on modes of flywheel rotor bearing system were discussed in detail. The comparison between the calculated unbalance response and the experimental response indicates that the dynamic model is appropriate. The results showed that the lower damper absorbed vibration energy of the flywheel rotor, which increased vibration of the damping body. And the bigger damping coefficient had better vibration absorption effect. The developed FESS is simple, stable and efficient in structure

Dual Purpose Tunable Vibration Isolator Energy Harvester: Design, Fabrication, Modeling and Characterization

This dissertation is focused on design, fabrication, characterization, and modeling of a unique dual purpose vibration isolation energy harvesting system. The purpose of the system is to, simultaneously, attenuate unwanted vibrations and scavenge kinetic energy available in these vibrations. This study includes theoretical modeling and experimental work to fully characterize and understand the dynamic behavior of the fabricated dual purpose system. In the theoretical study, both numerical (Runge-Kutta) and analytical (Harmonic Balance Method, HBM) methods are used to obtain the dynamic behavior of the system. The system features a combination of mechanical and electromagnetic components to facilitate its dual functionality. The system consists of a magnetic spring, mechanical flat spring, and dampers. The combination of negative stiffness of the magnetic spring with positive stiffness of the mechanical spring results in lowering the cut off frequency of the system. Lowering the cut off frequency improves the device’s ability to operate in a wider range of frequencies. Results from dynamic measurements and model simulation confirm the ability of the device to function in both vibration isolation and energy harvesting modes simultaneously. The dual-purpose device is able to attenuate vibrations higher than 12.5 [Hz]. The device also produces 26.8 [mW] output power at 1g [m/s2] and 9.75 [Hz]. Performance metrics of the device including displacement transmissibility and energy conversion efficiency are formulated. Results show that for low acceleration levels, lower damping values are desirable and yield higher energy conversion efficiencies and improved vibration isolation. At higher acceleration, there is a trade-off where lower damping values worsen vibration isolation but yield higher conversion efficiencies

Development of Hybrid Electromagnetic Dampers for Vehicle Suspension Systems

Vehicle suspension systems have been extensively explored in the past decades, contributing to ride comfort, handling and safety improvements. The new generation of powertrain and propulsion systems, as a new trend in modern vehicles, poses significant challenges to suspension system design. Consequently, novel suspension concepts are required, not only to improve the vehicle’s dynamic performance, but also to enhance the fuel economy by utilizing regeneration functions. However, the development of new-generation suspension systems necessitates advanced suspension components, such as springs and dampers. This Ph.D. thesis, on the development of hybrid electromagnetic dampers is an Ontario Centres of Excellence (OCE) collaborative project sponsored by Mechworks Systems Inc. The ultimate goal of this project is to conduct feasibility study of the development of electromagnetic dampers for automotive suspension system applications. With new improvements in power electronics and magnetic materials, electromagnetic dampers are forging the way as a new technology in vibration isolation systems such as vehicle suspension systems. The use of electromagnetic dampers in active vehicle suspension systems has drawn considerable attention in the recent years, attributed to the fact that active suspension systems have superior performance in terms of ride comfort and road-handling performances compared to their passive and semi-active counterparts in automotive applications. As a response to the expanding demand for superior vehicle suspension systems, this thesis describes the design and development of a new electromagnetic damper as a customized linear permanent magnet actuator to be used in active suspension systems. The proposed electromagnetic damper has energy harvesting capability. Unlike commercial passive/semi-active dampers that convert the vibration kinetic energy into heat, the dissipated energy in electromagnetic dampers can be regenerated as useful electrical energy. Electromagnetic dampers are used in active suspension systems, where the damping coefficient is controlled rapidly and reliably through electrical manipulations. Although demonstrating superb performance, active suspensions still have some issues that must be overcome. They have high energy consumption, weight, and cost, and are not fail-safe in case of a power break-down. Since the introduction of the electromagnetic dampers, the challenge was to address these drawbacks. Hybrid electromagnetic dampers, which are proposed in this Ph.D. thesis, are potential solutions to high weight, high cost, and fail-safety issues of an active suspension system. The hybrid electromagnetic damper utilizes the high performance of an active electromagnetic damper with the reliability of passive dampers in a single package, offering a fail-safe damper while decreasing weight and cost. Two hybrid damper designs are proposed in this thesis. The first one operates based on hydraulic damping as a source of passive damping, while the second design employs the eddy current damping effect to provide the passive damping part of the system. It is demonstrated that the introduction of the passive damping can reduce power consumption and weight in an active automotive suspension system. The ultimate objective of this thesis is to employ existing suspension system and damper design knowledge together with new ideas from electromagnetic theories to develop new electromagnetic dampers. At the same time, the development of eddy current dampers, as a potential source for passive damping element in the final hybrid design, is considered and thoroughly studied. For the very first time, the eddy current damping effect is introduced for the automotive suspension applications. The eddy current passive damper, as a stand-alone unit, is designed, modeled, fabricated and successfully tested. The feasibility of using passive eddy current dampers for automotive suspension applications is also studied. The structure of new passive eddy current dampers is straightforward, requiring no external power supply or any other electronic devices. Proposed novel eddy current dampers are oil-free and non-contact, offering high reliability and durability with their simplified design. To achieve the defined goals, analytical modeling, numerical simulations, and lab-based experiments are conducted. A number of experimental test-beds are prepared for various experimental analyses on the fabricated prototypes as well as off-the-shelf dampers. Various prototypes, such as eddy current and electromagnetic dampers, are manufactured, and tested in frequency/time domains for verification of the derived analytical and numerical models, and for proof of concept. In addition, fluid and heat transfer analyses are done during the process of the feasibility study to ensure the durability and practical viability of the proposed hybrid electromagnetic dampers. The presented study is only a small portion of the growing research in this area, and it is hoped that the results obtained here will lead to the realization of a safer and more superior automotive suspension system

Self-Tuning Algorithm for Tuneable Clamping Table for Chatter Suppression in Blade Recontouring

The production and repair of blades for aerospace engines and energy turbines is a complex process due their inherently low stiffness and damping properties. The final recontouring operation is usually performed by milling operations where regenerative chatter is one of the main productivity limiting factors. With the objective of avoiding specific stiffening fixtures for each blade geometry, this paper proposes a semi-active tuneable clamping table (TCT) based on mode tuning for blade machining. The active mode of the device can be externally controlled by means of a rotary spring and eddy current damping modules. Its in-series architecture allows damping to be introduced to the critical mode of the thin-walled part without any direct contact in the machining area and enables a more universal clamping. Its chatter suppression capabilities are maximized by means of a novel self-tuning algorithm that iteratively optimizes the tuning for the measured chatter frequency. The benefits of the iterative algorithm are validated through semidiscretization and initial value time-domain simulations, showing a clear improvement in blade recontouring stability compared to regular broad-bandwidth tuning methods.This project has been funded by the MIRAGED: Posicionamiento Estratégico en Modelos Virtuales y Gemelos Digitales para una Industria 4.0 (CER-20191001), supported by CDTI-Acreditación y Concesión de Ayudas Destinadas a Centros Tecnológicos de Excelencia Cervera; the Hungarian NKFI FK 124361 and the TiMachina project (IDI-201904196) from the International Technological Corporation, and by R+d projects program of the Spanish Centre for the Development of Industrial Technology (CDTI)

Invited Review: Recent developments in vibration control of building and bridge structures

This paper presents a state-of-the-art review of recent articles published on active, passive, semi-active and hybrid vibration control systems for structures under dynamic loadings primarily since 2013. Active control systems include active mass dampers, active tuned mass dampers, distributed mass dampers, and active tendon control. Passive systems include tuned mass dampers (TMD), particle TMD, tuned liquid particle damper, tuned liquid column damper (TLCD), eddy-current TMD, tuned mass generator, tuned-inerter dampers, magnetic negative stiffness device, resetting passive stiffness damper, re-entering shape memory alloy damper, viscous wall dampers, viscoelastic dampers, and friction dampers. Semi-active systems include tuned liquid damper with floating roof, resettable variable stiffness TMD, variable friction dampers, semi-active TMD, magnetorheological dampers, leverage-type stiffness controllable mass damper, semi-active friction tendon. Hybrid systems include shape memory alloys-liquid column damper, shape memory alloy-based damper, and TMD-high damping rubber

Hybrid Electromagnetic Vibration Isolation Systems

Traditionally, dynamic systems are equipped with passive technologies like viscous shock absorbers and rubber vibration isolators to attenuate disturbances. Passive elements are cost effective, simple to manufacture, and have a long life span. However, the dynamic characteristics of passive devices are fixed and tuned for a set of inputs or system conditions. Thus in many applications when variation of input or system conditions is present, sub-optimal performance is realized. The other fundamental flaw associated with passive devices is that they expel the undesired kinetic energy as heat. Recently, the introduction of electromagnetic technologies to the vibration isolation systems has provided researchers with new opportunities for realizing active/semi-active vibration isolation systems with the additional benefit of energy regeneration (in semi-active mode). Electromagnetic vibration isolators are often suffer from a couple of shortcomings that precludes their implementations in many applications. Examples of these short comings include bulky designs, low force density, high energy consumption (in active mode), and fail-safe operation problem. This PhD research aims at developing optimal hybrid-electromagnetic vibration isolation systems to provide active/semi-active and regenerative vibration isolation for various applications. The idea is to overcome the aforementioned shortcomings by integrating electromagnetic actuators, conventional damping technologies, and stiffness elements into single hybrid packages. In this research, for both semi-active and active cases, hybrid electromagnetic solutions are proposed. In the first step of this study, the concept of semi-active hybrid damper is proposed and experimentally tested that is composed of a passive hydraulic and a semi-active electromagnetic components. The hydraulic medium provides a bias and fail-safe damping force while the electromagnetic component adds adaptability and energy regeneration to the hybrid design. Based on the modeling and optimization studies, presented in this work, an extended analysis of the electromagnetic damping component of the hybrid damper is presented which can serve as potent tool for the designers who seek maximizing the adaptability (and regeneration capacity) of the hybrid damper. The experimental results (from the optimized design) show that the damper is able to produce damping coefficients of 1300 and 0-238 Ns/m through the viscous and electromagnetic components, respectively. In particular, the concept of hybrid damping for the application of vehicle suspension system is studied. It is shown that the whole suspension system can be adjusted such that the implementation of the hybrid damper, not only would not add any adverse effects to the main functionally of the suspension, but it would also provide a better dynamics, and enhance the vehicle fuel consumption (by regenerating a portion of wasted vibration energy). In the second step, the hybrid damper concept is extended to an active hybrid electromagnetic vibration isolation systems. To achieve this target, a passive pneumatic spring is fused together with an active electromagnetic actuator in a single hybrid package. The active electromagnetic component maintains a base line stiffness and support for the system, and also provides active vibration for a wide frequency range. The passive pneumatic spring makes the system fail-safe, increases the stiffness and support of the system for larger masses and dead loads, and further guarantees a very low transmissibility at high frequencies. The FEM and experimental results confirmed the high force density of the proposed electromagnetic component, comparing to a voice coil of similar size. In the proposed design, with a diameter of ~125 mm and a height of ~60 mm, a force variation of ~318 N is obtained for the currents of I=±2 A. Furthermore, it is demonstrated that the proposed actuator has a small time constant (ratio of inductance to resistance for the coils) of less than 5.2 ms, with negligible eddy current effect, making the vibration isolator suitable for wide bandwidth applications. According to the results, the active controllers are able to enhance the performance of the passive elements by up to 80% and 95% in terms of acceleration and force transmissibilities, respectively

Simulation studies of vibration isolation using electromagnetic damper

This paper presents the review of electromagnetic damper as a vibration/isolation material. A bunch of articles about vibration and suspension system was reviewed and the key factors that contribute to electromagnetic damper was identified. Electromagnetic damper has been given special attention from many researchers and thus being among the important research area in vibration system. Vibration concept of electromagnetic damper has been elucidated by referring to several paper that demonstrate the usage of electromagnetic damper. Finite element magnetic method (FEMM) software has been used in order to identify the best configuration of geometry in the system. A simulation in Matlab was done by considering a quarter car model with a theoretical value from the Faraday’s Law equation involved in electromagnetic damper. The slotted and cylindrical geometry configurations have been simulated using FEMM and the result clearly shows that the slotted configuration has a better effect on the electromagnetic damper system