Vibration control and magnetostrictive composite materials

Smart structures are a result of effective integration of control system design and signal processing with the structural systems to maximally utilize the new advances in materials for structures, actuation and sensing to obtain the best performance for the application at hand. The research in smart structures is constantly driving towards attaining self adaptive and diagnostic capabilities that biological systems possess. This has been manifested in the number of successful applications in many areas of engineering such as aerospace, civil and automotive systems. Instrumental in the development of such systems are smart materials such as piezo-electric, shape memory alloys, electrostrictive, magnetostrictive and fiber-optic materials and various composite materials for use as actuators, sensors and structural members. The need for development of control systems that maximally utilize the smart actuators and sensing materials to design highly distributed and highly adaptable controllers has spurred research in the area of smart structural modeling, identification, actuator/sensor design and placement, control systems design such as adaptive and robust controllers with new tools such a neural networks, fuzzy logic, genetic algorithms, linear matrix inequalities and electronics for controller implementation such as analog electronics, micro controllers, digital signal processors (DSPs) and application specific integrated circuits (ASICs) such field programmable gate arrays (FPGAs) and Multichip modules (MCMs) etc. In this paper, we give a brief overview of the state of control in smart structures. Different aspects of the development of smart structures such as applications, technology and theoretical advances especially in the area of control systems design and implementation will be covered.

This article presents a review of recent-important developments in the field of intelligent material and fluid systems. Intelligent material and fluid systems, sometimes referred to as smart materials and fluids, can adjust their behavior to changes of external or internal parameters analogously to biological systems. In these systems, sensors, actuators and controllers are seamlessly integrated with structural materials at the macroscopic or mesoscopic level. In general, sensors and actuators are made of functional materials and fluids such as piezoelectric materials, magnetostrictive materials, shape memory alloys, polymer hydrogels, electro- and magneto-rheological fluids and so on. This article is specifically focused on the design of intelligent material and fluid systems used to control the deformation, vibration and fracture of composite materials and structures.

Energy dissipation devices have been accepted as a promising alternative to dissipate the energy that earthquakes induce in structures; therefore, reducing displacement demands. A large number of new or retrofitted buildings are equipped with fluid dampers or other energy dissipation devices which are expected to suppress earthquake induced shaking. They can be incorporated in the isolation system of a building 2 . or within the skeleton of a structure. When structures are built near a potential fault, the expected displacement demands in the structure are large and there is a tendency to equip structures with supplement damping - in most cases of nearly viscous type 2 .. On the other hand, near source ground motions usually contain one or more distinct and coherent pulses; and it is known that for pulse motions the efficiency of viscous damping in reducing displacement demands is limited when the system is highly damped 1.4 . In a recent paper, the senior author showed that plastic damping is more efficient than viscous damping in reducing the response of a SDOF structure when subjected to pulse motion represented by cycloidal fronts with duration close to the natural period of the structure 5 . Recent developments on controllable fluid dampers showed that both electrorheological (ER) and magnetrorheological (MR) dampers are capable of delivering the desirable plastic or viscoplastic behavior. In this paper an analytical study on the response of a 2 DOF isolated structure equipped with controllable fluid damper subjected to a variety of near source earthquakes is presented in order to understand the difference between viscous and friction damping, and to investigate possible advantages of controllable fluid dampers. The isolated structure is considered to be supported either on elastomeric bearings or sliding bearings.

In this paper the fabrication process for ascreen-printable magnetostrictive thick-film material based upon thegiant magnetostrictive material, Terfenol-D, is reported. Factorsaffecting the magnetostriction of the printed thick film have beenidentified, and suitable parameters selected to yield a functionalthick film. The evaluation process used to compare themagnetostrictive thick films is also detailed and a magnetostrictionof 4.4 ppm for an excitation field of 11.5 kA m-1 is recorded.This value is compared to other composite materials, and potentialroutes for improvement of the magnetostrictive thick-film materialidentified.

Paper shows study on the magnetoelectric composite material placed in an external magnetic field with changing magnetic field vecotr. An experimental setup for investigation of magnetoelectric properties of magnetostrictive-piezoelectric material was prepared. The hybrid structure is made of magnetostrictive composite (based on Terfenol-D) and piezoelectric material. Experimental results shown the response of prepared hybrid material to the rate of changes of direction of magnetic field vector. Investigation were mainly focused on possibility of generating of electric power from prepared material. It was found that the prepared hybrid material exhibits magnetoelectric effect in the case of work when direction of magnetic field vector was changing. This effect might be use in Energy Harvesting applications.

This paper focuses on the preparation and characterization of 2 new Fe-Ga-based alloys: (i) 3-D shaped Fe100-x(Ga,Al)x polycrystalline magnetostrictive alloys, and (ii) Fe100-x(Ga,Al)x composite materials, consisting of nano-and micropowders of active material embedded into a polymer matrix. Thin plates have been prepared by Cu mould casting technique, and magnetostriction has been measured by the electrical resistance strain gauge technique.

This chapter will provide an insight into smart materials, which are a class of materials that can change their physical properties, such as shape, size, stiffness, color, or electrical conductivity, in response to external stimuli, such as temperature, pressure, light, humidity, magnetic, or electric fields. Various types of smart materials like shape memory alloys (SMAs), electroactive polymers (EAPs), piezoelectric materials, magnetostrictive materials, and thermoelectric materials were discussed in this chapter, along with their properties and applications. Nevertheless, the advantages of smart materials over the conventional materials along with the challenges were also discussed. Also, the possibility of integrating these materials with the existing systems was discussed.

A smart structure involves distributed actuators and sensors, and one or more microprocessors that analyze the responses from the sensors and use distributed-parameter control theory to command the actuators to apply localized strains to minimize system response. A smart structure has the capability to respond to a changing external environment (such as loads or shape change) as well as to a changing internal environment (such as damage or failure). It incorporates smart actuators that allow the alteration of system characteristics (such as stiffness or damping) as well as of system response (such as strain or shape) in a controlled manner. Many types of actuators and sensors are being considered, such as piezoelectric materials, shape memory alloys, electrostrictive materials, magnetostrictive materials, electro- rheological fluids and fiber optics. These can be integrated with main load-carrying structures by surface bonding or embedding without causing any significant changes in the mass or structural stiffness of the system. Numerous applications of smart structures technology to various physical systems are evolving to actively control vibration, noise, aeroelastic stability, damping, shape and stress distribution. Applications range from space systems, fixed-wing and rotary-wing aircraft, automotive, civil structures and machine tools. Much of the early development of smart structures methodology was driven by space applications such as vibration and shape control of large flexible space structures, but now wider applications are envisaged for aeronautical and other systems. Embedded or surface-bonded smart actuators on an airplane wing or helicopter blade will induce alteration of twist/camber of airfoil (shape change), that in turn will cause variation of lift distribution and may help to control static and dynamic aeroelastic problems. Applications of smart structures technology to aerospace and other systems are expanding rapidly. Major barriers are: actuator stroke, reliable data base of smart material characteristics, non-availability of robust distributed parameter control strategies, and non-existent mathematical modeling of smart systems. The objective of this paper is to review the state-of-the-art of smart actuators and sensors and integrated systems and point out the needs for future research.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Vibration control of offshore jacket platforms through shape memory alloy pounding tuned mass damper (SMA-PTMD)

Smart materials such as piezoceramics, magnetostrictive materials, and shape memory alloys exhibit significant hysteresis, especially when driven with large input signals. Hysteresis can lead to unwanted harmonics, inaccuracy in open loop control, and instability in closed loop control. The Preisach independent domain hysteresis model has been shown to capture the major features of hysteresis arising in ferromagnetic materials. Noting the similarity between the microscopic domain kinematics that generate static hysteresis effects in ferromagnetics, piezoceramics, and shape memory alloys, we apply the Preisach model for the hysteresis in piezoceramic and shape memory alloy materials. This paper reviews the basic properties of the Preisach model, discusses control-theoretic issues such as identification, simulation, and inversion, and presents experimental results for piezoceramic sheet actuators bonded to a flexible aluminum beam, and a Nitinol SMA wire muscle that applies a bending force to the end of a beam.

The microstructure, preferred orientation and magnetostriction of Y doped Fe-Ga magnetostrictive composite materials

Recently, there has been substantial research on the development of a hybrid hydraulic pump driven by various smart materials. Piezo-hydraulic actuators have already been developed for potential use in smart rotor applications. However, at high actuation frequencies, piezo-stacks generate significant heat mainly due to the hysteresis losses that can deteriorate their performance and permanently damage the piezo material. In contrast, magnetostrictive materials are more robust than piezostacks, especially at high temperatures, while offering almost the same bandwidth and higher maximum induced strain when compared with piezoelectric stacks. Also, the magnetostrictive material usually has a particular frequency range where the hysteretic losses taking place are minimum and consequently the operation results in least heat generation. As a result, to operate the pump with higher flow rate with minimum heat generation and maximum efficiency, we need to know the system resonance. Moreover, the hybrid pump with smart material is mechanically more complex than a single rod actuator; consequently, it can have more than one resonant frequency depending on the number of degrees of freedom of the system. A hybrid pump using the magnetostrictive material Terfenol-D has been developed in our laboratory with hydraulic oil as the working fluid. Several key design parameters, which include output cylinder size, diaphragm thickness, reed valve thickness and tubing diameter, along with operational conditions, like input current and bias pressure within the fluid, have been varied to identify a set of optimum driving conditions. Tests at no-load have been carried out for unidirectional motion of the output piston. In this paper, we develop a dynamic model of the hydraulic hybrid actuator to show the basic operational principle and compare the simulated data with test results. The final target of this study is to find optimal operational frequency to get highest performance and also to predict the pump sizing for a desired output velocity and load lifting capability.

Vibration is an essential subject for the design of rotordynamic systems, being responsible for compromising the integrity and causing risks to operational functioning. This work deals with an experimental investigation of the semi-active vibration controller for a rotordynamic system using shape memory alloy (SMA) elements. SMAs are smart materials that present thermomechanical coupling represented by solid phase transformations that promote either stiffness change or hysteretic dissipation. In this regard, they are useful in controllers employing thermal actuation from electric current through the Joule effect. This paper presents a proof of concept of a controller using SMA elements. An experimental apparatus is proposed considering a typical rotor system using SMA wires at the bearings. In this regard, proper temperature variations allow the system to cross critical resonant conditions.

Shape Memory Alloy (SMA) based composites are unique because their static and dynamic characteristics can be controlled. Active modal modification and active strain energy tuning are two common techniques used to control the dynamics of SMA based composite materials. Using Active Modal Modification Technique (AMMT), the stiffness of the SMA composite can be modified by changing the temperature of the SMA. The stiffness change is a result of a reversible phase transformation, which is tempeature activated. The Active Strain Energy Tuning Method (ASETM) takes advantage of the SMA’s ability to impart forces to the structure thereby changing the stored strain energy within the composite. The result is a change in the modal characteristics of the composite material. This paper will present the results of the application of an AMMT used to modify the dynamic characteristics of an SMA composite. A rectangular example of quasi-isotropic SMA composite was used in this study. As a result of a temperature change, the stiffness of the composite changed. This change is stiffness altered the dynamic responses such as the resonant frequency of the composite. Time Average Opto-Electronic Holography (TAOEH) [6] was used to monitor the dynamic behavior of the structure. Analytical modeling was used along with the experimental results to obtain the temperature history of the composite as a result of the activation of the SMA.

To unlock the lock of futuristic developments, nowadays shape memory alloys (SMAs) are acting as key by outnumbering the existing smart materials in view of new design competence, innovative techniques, enhanced technologies, and meeting the dire need according to the demand of ongoing scientific and industrial progress. Undoubtedly, it can be worthy to associate SMAs with the term polymorphism, as they possess unique capability to encapsulate multitudinous inherent characteristics under their name. Shape memory effect, superelasticity, and damping are there to name a few among many others, as prime indicators. The exhibition of these characteristics of SMAs is due to the transformation that takes place between austenite phase and martensite phase which is achieved either by temperature or stress variation. The fascinating characteristics they possess enable them to attract researchers and designers toward their potential applications in diverse domain as smart and multi-functional materials. The present work focuses on the review of research works accomplished in the recent 5 years pertaining to modeling and applications of shape memory alloys in distinct domains. Under the topic of modeling, a look into the research carried out on a variety of SMA structures—like functionally graded SMAs, SMA springs, porous SMAs, novel SMA actuators—is presented. In addition to this, the work carried out to represent SMAs with large strains and large rotations and to model polycrystalline SMAs is also covered. This is supplemented by application-oriented domains, each of which disseminates the attributes of SMAs that are self-sufficient to express what factors make SMAs more prominent. It is believed that the foregoing works comprehensively detailed in this review article will certainly lay a solid platform for the future investigations that are going to take place in time to come.