Showing papers on "Smart material published in 1993"
TL;DR: A smart material is one that can perform both sensor and actuator functions as mentioned in this paper, which allows for some flexibility in deciding how to qualify a material as "smart", since the fun damental mechanisms of operation may differ greatly between types of smart materials.
Abstract: A smart material is one that can perform both sensor and actuator functions. This definition allows for some flexibility in deciding how to qualify a material as "smart", since the fun damental mechanisms of operation may differ greatly between types of smart materials. From the point of view of an electroceramist, piezoelectric materials, which show reversible electromechan ical coupling, may be thought of as "naturally" smart materials since the same piezoelectric material may act as a sensor and/or an actuator. Piezoelectric single crystals, polymers, and poled poly crystalline ceramics all show good electromechanical coupling. In addition, they may be combined in a composite material that exaggerates their beneficial properties by eliminating their detrimental properties. Some common piezoelectric materials are reviewed, along with some examples of smart materials that incorporate piezoelectric ceramics.
64 citations
TL;DR: In this article, the bending beam method was used to detect the presence of certain gases, including ammonia gas and iodine vapor, by observing the bending behavior of the strips, which can be used to study in situ conformational change or phase transition in conjugated polymers during gas doping or undoping.
50 citations
TL;DR: In this article, a review of sensor and actuator types for smart materials is presented, including multilayer and multifunctional ceramics, complex device designs based on biological analogs, emphasis on nonlinear materials with tunable properties, and integration of the active ceramic elements with control circuitry.
Abstract: Electroceramic materials offer an extensive array of sensing and actuating functions that can be incorporated into designs for smart materials. While sophisticated sensing systems have already reached some high-volume applications (including the automotive one) it is expected that the field of smart materials will grow rapidly as additional industrial and consumer markets are tapped. In this paper, a review of ceramic sensor and actuator types was presented. Future developments in this area are expected to include increased use of multilayer and multifunctional ceramics, complex device designs based on biological analogs, emphasis on nonlinear materials with tunable properties, and integration of the active ceramic elements with control circuitry.
47 citations
TL;DR: In this paper, hollow porous fibers filled with a chemical that is released into the matrix at appropriate times, or over time, are designed to address some issues of material performance, namely, cracking, corrosion, en ergy absorption and change in dynamic modulus.
Abstract: Materials containing various types of hollow porous fibers filled with a chemical that is released into the matrix at appropriate times, or over time, are designed to address some issues of material performance, namely, cracking, corrosion, en ergy absorption and change in dynamic modulus (Dry, 1991a, 1991b).
23 citations
TL;DR: In this article, a special issue on actuators is presented, with articles on piezoelectric, electrostrictive, magnetostrictive and shape memory materials.
Abstract: One of the qualities that distinguishes living systems from inanimate matter is the ability to adapt to changes in the environment. Smart materials have the ability to perform both sensing and actuating functions and are, therefore, capable of imitating this rudimentary aspect of life. Poled piezoelectric ceramics, for instance, are capable of acting as both sensor and actuator. External forces are detected through the direct piezoelectric effect, and a response is elicited through the converse piezoelectric effect, in which a voltage of suitable phase, frequency, and amplitude is applied to the same ceramic.In this special issue, emphasis is placed on actuators, with articles on piezoelectric, electrostrictive, magnetostrictive, and shape memory materials. This is not to say that sensor materials are any less important; it is simply a matter of space. Optical fiber sensors, chemical sensors, thermistors, micromachined semiconductors, and other smart materials deserve special issues of their own.Smart materials can be conveniently subdivided into passively smart materials that respond to external change without assistance, and actively smart materials that utilize a feedback loop enabling them to both recognize the change and initiate an appropriate response through an actuator circuit.Zinc oxide varistors are passively smart materials capable of self-protection against high voltage breakdown. When struck by lightning, the ceramic varistor loses most of its electrical resistance, and the current is bypassed to ground. The resistance change is reversible, and acts as a standby protection phenomenon.
18 citations
22 Jul 1993
TL;DR: In this paper, the authors describe in an expository fashion one such technique which has been applied in several instances especially related to certain alloys or other crystalline materials, and describe how to successfully describe these systems.
Abstract: The smartness of a shape-memory material is a consequence of its ability to form a flexible variant structure at one temperature while recognizing only a homogeneous equilibrium at a different temperature. The fine scale morphology or microstructure of this variant structure has a clear role in the macroscopic behavior of the material. To investigate these phenomena, two issues are paramount. First, the presence of several stable variants at a given temperature reflects a complicated potential well structure for the free energy of the material. Second, the presence of spatially oscillatory behavior at the small scale suggests competition between the free energy of the material and loading or other environmental effects. Both of these features represent highly nonlinear processes and thus it is to nonlinear analysis we turn for methods to successfully describe these systems. In this report we describe in an expository fashion one such technique which has been applied in several instances especially related to certain alloys or other crystalline materials.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
18 citations
23 Jul 1993
TL;DR: In this paper, a dual macroscopic theory is proposed for the nonhomogeneous reversible large deformations of ionic polymeric gels in the presence of both a pH field and an electric field.
Abstract: Based on recent experimental observations on the behavior of ionic polymeric gels in the presence of pH and electric fields performed in our laboratories, a dual macroscopic theory is proposed for the nonhomogeneous large deformations of such gels. The proposed theory presents two distinct mechanisms for the nonhomogeneous reversible large deformations and in particular bending of strips of ionic polymeric gels in the presence of both a pH field and an electric field. It is concluded that direct voltage control of such nonhomogeneous large deformations in ionic polymeric gels is possible. These electrically controlled deformations may find unique applications in robotics, artificial muscles, large motion actuator designs, drug delivery systems and smart materials, adaptive structures and systems.
16 citations
01 Jan 1993
TL;DR: In this paper, the authors propose a feedback loop which allows active materials to recognize the change and initiate an appropriate response through an actuator circuit, which is similar to the one described in this paper.
Abstract: “Smart” materials have the ability to perform both sensing and actuating functions. Passively smart materials respond to external change in a useful manner without assistance, while actively smart materials have a feedback loop which allows them to both recognize the change and initiate an appropriate response through an actuator circuit.
14 citations
23 Jul 1993
TL;DR: In this article, the bias conductors are incorporated as an integral component of a new microwave material called an effective surface, which is the two dimensional equivalent of an effective media, and the surface impedance of the treatment satisfies an impedance boundary condition to allow the processor to use an efficient electromagnetic computational code.
Abstract: Versatile control of the microwave signature of a complex object under the command of a central/local processor(s) requires a bias/communications network to be embedded in a smart surface treatment and distributed over distances small compared to the shortest wavelength of interest. One requirement of the system is that the bias and microwave signal paths be isolated for all configurations of the smart surface. It is also required that the surface impedance of the treatment satisfy an impedance boundary condition to allow the processor to use an efficient electromagnetic computational code. A design approach that accommodates these requirements incorporates the bias conductors as an integral constituent of a new smart microwave material called an `effective surface;' the two dimensional equivalent of an effective media.
13 citations
01 Jan 1993
TL;DR: A brief summary of recent results of some importance in mathematical and computational issues that are fundamental to the development of smart material technology and an example of a clamped beam with piezoceramic actuators.
Abstract: An emerging technology for the 90s that offers new challenges for the distributed parameter control community involves the design, development and use of smart material structures. These structures may involve one or more of several materials such as shape memory alloys, piezoceramics, magnetostrictives, or electrorheological fluids. In this paper, we present a brief summary of recent results of some importance in mathematical and computational issues that are fundamental to the development of smart material technology. To illustrate certain ideas and findings, we apply these results to a specific example of a clamped beam with piezoceramic actuators. We emphasize that such a structure is not a “smart material” (usually defined as one with combined sensing and actuation units embedded along with control elements) but that with proper circuitry (to render the piezoceramic element a “self-sensing actuator” (see [16])) such a structure could be an example of a smart material beam.
08 Sep 1993
TL;DR: In this article, two applications of piezoelectric and electrostrictive materials are proposed that generate both micro and macro positioning control, and an overview of these smart materials and their properties is given.
Abstract: While many new smart materials have been developed over the last few years, the integration of these materials into useful systems must be exploited if this emerging technology is to become viable. Two applications of piezoelectric and electrostrictive materials are proposed that generate both micro and macro positioning control. Additionally, an overview of these smart materials and their properties is given. Precise micro positioning devices have applications to adaptive optical systems. A NASA project called Space Laser Energy (SELENE) involves such a system. This project proposes to control the surface of a power transmission dish comprised of several thousands of small lenses or lenslets. A major objective of the dish is to increase efficiency by compensating for atmospheric disturbances. A second application of piezoelectric materials is presented for micro and macroscopic one dimensional motion. Specifically, a novel design of an inchworm device is presented. This device has the ability to generate macroscopic motion from microscopic piezoelectric expansions and contractions, the frequency of these expansion/contraction cycles should allow the motor to move for significant distances as well as provide incremental micro positioning.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
15 Dec 1993
TL;DR: In this article, a theoretical approach is introduced to establish the shape design for piezoelectric materials to make them to perform as distributed controllers in active damping and stabilization of flexible structures.
Abstract: A natural control synthesis for distributed parameter systems (DPS) consists of distributed controllers which can adequately manipulate and force every point of the spatial domain to conform to the desired function. The traditional actuators and sensors such as shakers and accelerometers are localized (point-wise) devices. New sensors/actuators made of smart materials such as piezoelectric ceramic or PVDF have been proposed as alternatives for traditional controllers. In this paper a theoretical approach is introduced to establish the shape design for these materials to make them to perform as distributed controllers in active damping and stabilization of flexible structures. Based on the dissipativity of energy functional, a criteria for the design of the shape of piezoelectric material or electrode, which can achieve the task of distributed control, is derived. Unlike previous efforts, which could find piezoelectric shape for dissipativity of one mode, it is proved that the suggested shape guarantees the dissipativity of energy function for all modes of the system. >
01 Jan 1993
TL;DR: The feasibility studies of a new solution for the individual blade control aiming at helicopter vibration reduction are performed in this article, where adaptive material actuators are installed at the blade root to induce both a constant pitch, and a constant flap angle in the structure.
Abstract: The feasibility studies of a new solution for the individual blade control aiming at helicopter vibration reduction are performed. Adaptive material actuators are installed at the blade root to induce both a constant pitch, and a constant flap angle in the structure. The results indicate that small angles compatible with the present technology of smart materials are sufficient to produce a significant attenuation in the dynamic response of a typical rotor in forward flight.
23 Jul 1993
TL;DR: In this article, the authors use the lower skin of the radome as a substrate on which the radiator can be made using standard photolithography, thick film, or LTCC techniques.
Abstract: Using smart materials and skins, one could design a smart structure with suitable feedback system architecture. This paper is designed to address some technical advances and applications of smart materials, smart skins and coatings covering a broad spectrum of electromagnetic fields. The Smart Skin Antenna Technology Program's objectives are to (1) use smart skin technologies to develop an antenna system architecture which is structurally integratable, wideband, and embedded/conformal; (2) design, develop, and fabricate a thin, wideband, conformal/arrayable radiator that is structurally integratable and which uses advanced Penn State dielectric and absorber materials to achieve wideband ground planes, and together with low RCS, wideband radomes; (3) implement a smart skin antenna system architecture. Traditional practice has been to design radome and antenna as separate entities and then resolve any interface problems during an integration phase. A structurally integratable conformal antenna, however, demands that the functional components be highly integrated both conceptually and in practice. Our concept is to use the lower skin of the radome as a substrate on which the radiator can be made using standard photolithography, thick film, or LTCC techniques.
01 Sep 1993
TL;DR: In this paper, the current status and maturity of smart structures technology is assessed and a strategic research and development plan is suggested for the Air Force. And eleven specific problems with Air Force aircraft structure and weapons systems are identified which have the potential for being alleviated or reduced by application of Smart structures technologies.
Abstract: : This report assesses the current status and maturity of smart structures technology. The report contains sections on smart materials, neural networks, health monitoring, and smart structures component technologies such as actuators, sensory elements, control methodologies and algorithms, controller architecture and implementation hardware, and signal conditioning and power amplification. A strategic research and-development plan is suggested for the Air Force. Eleven specific problems with Air Force aircraft structure and weapons systems are identified which have the potential for being alleviated or reduced by application Of Smart structures technologies.
23 Jul 1993
TL;DR: In this paper, the microstructural characteristics for three surface-mounted optical fiber sensors bonded to structural composites for high temperature applications were investigated, and it was determined that the plasma spray system was severely micro-cracked, as a result of the fabrication process, prior to any thermal cycling.
Abstract: This paper describes an investigation of the microstructural characteristics for three surface-mountedoptical fiber sensors bonded to structural composites for high temperature applications. The primaryobjective was to identify defect generation mechanisms that occur during thermal cycling and to makeprocessing and testing recommendations that would optimize their measurement performance.A secondobjective was to identify areas of microstructural research that would have the most significant impact onthe development of high temperature smart materials.The three high temperature smart material systems investigated were: (1) a silica optical fiber sensorbonded to a titanium-matrix composite (TMC) using a nickel-base plasma spray, (2) a silica optical fibersensor bonded to a TMC using a ceramic cement, and (3) a sapphire optical fiber sensor bonded to a car-bon-carbon composite (CCC) using a ceramic cement. The microstructure of each system was character-ized in terms of morphology and fracture mechanisms using conventional microscopic, metallographicand analytical techniques.It was determined that the plasma spray system was severely micro-cracked, as a result of the fabricationprocess, prior to any thermal cycling. Combined with a distribution of non-metallic spheroidal inclusionsin the matrix, this provided a crack growth mechanism for disbonding of the optical fiberand loss of sen-sor performance. A high degree of porosity in both ceramic cements significantly reduced the initerfacialcontact area which, combined with inherent brittleness caused disbonding of the optical fibers in the lattertwo sensor systems.
12 Jul 1993
TL;DR: In this article, a modified version of an existing finite element program is used to numerically simulate a laminated plate under a low velocity impact and calculate the electric field generated by the in-plane strains on the piezoelectric plies.
Abstract: The desire to counteract impact loads on laminated structures in order to reduce ply damage has recently led to research using smart materials in laminated composites. The ability to sense the onset of these impact loads using piezoelectric material is the first step in the damage control process. This research focuses on smart laminated plates under impact and the electric field created by piezoelectric patches in the structure. A modified version of an existing finite element program is used to numerically simulate a laminated plate under a low velocity impact. Linear constitutive relations are used in the program which calculate the electric field generated by the in-plane strains on the piezoelectric plies. Several studies are made comparing the electric field generated by patches of piezoelectric material of varying size, shape, and location within the plate. The average electric field generated by larger patches which contain more oscillations of electric field filters the high frequency components. The distance between the impacting point and the piezoelectric sensor is found to be directly related to the lag time between the impact and generation of an electric field.
12 Jul 1993
TL;DR: In this article, the authors proposed a method for the integration of optical fiber waveguides and cable assemblies onto and into materials and structures, and evaluated the effect of the optical fiber and coatings on the survivability of the fiber.
Abstract: Optical fibers are attractive candidates for sensing applications in near-term smart materials and structures, due to their inherent immunity to electromagnetic interference and ground loops, their capability for distributed and multiplexed operation, and their high sensitivity and dynamic range. These same attributes also render optical fibers attractive for avionics busses for fly-by-light systems in advanced aircraft. The integration of such optical fibers with metal and composite aircraft and aerospace materials, however, remains a limiting factor in their successful use in such applications. This paper first details methods for the practical integration of optical fiber waveguides and cable assemblies onto and into materials and structures. Physical properties of the optical fiber and coatings which affect the survivability of the fiber are then considered. Mechanisms for the transfer of the strain from matrix to fiber for sensor and data bus fibers integrated with composite structural elements are evaluated for their influence on fiber survivability, in applications where strain or impact is imparted to the assembly.
08 Sep 1993
TL;DR: In this article, a new concept for automotive active suspension has been developed using smart structures featuring piezoceramics, and a candidate design is analytically investigated for performance.
Abstract: Smart structures are being increasingly applied in active vibration control. Typically, motion ranges produced in such systems are in the micro-range. This work proposes a mechanism to accomplish macro-motion ranges using smart materials. A new concept for automotive active suspension has been developed using smart structures featuring piezoceramics. A candidate design is analytically investigated for performance. The work presented in this paper includes the concept, its illustration, development of a design geometry based on this concept, and its finite element analysis and results. It is shown that by a proper synthesis of smart structure, macro-motion outputs needed for this application are possible.
25 May 1993
TL;DR: In this article, a design technique for optimal control in active structural vibration damping using smart materials is described, where the vibration of a cantilever beam is stabilized by using distributed sensors and actuators.
Abstract: We describe a design technique for optimal control in active structural vibration damping using smart materials. The vibration of a cantilever beam is stabilized by using distributed sensors and actuators. We model the beam by the Timoshenko beam model together with the distributed sensors and actuators. A control law using the weighted integration of vibration velocity is incorporated in the closed loop system. We propose a method to find the optimal layout design of the smart material so as to maximize the damping effect. An objective functional is defined based on the vibration energy of the system. The optimal shapes of the sensor and actuator are determined through minimizing the energy functional of the beam over the admissible shape function space subject to certain geometric constraints. An algorithm has been developed to determine the optimal sensor and actuator layout. This method can be generalized to the plate damping problem and more complicated structures as well.
23 Jul 1993
TL;DR: In this article, it was shown that amorphous thin films of TiNi and BaTiO3 can be crystallized simultaneously by air annealing at 600 degree(s)C.
Abstract: Smart materials composed of ferroelastic and ferroelectric materials are described for damping of mechanical waves. These heterostructures using active and adaptive materials will likely be represented by heterostructures of several types of thin and thick films. In this investigation, deposition and processing of thin film ferroelastic TiNi and thin film ferroelectric BaTiO3 and Pb(Zr,Ti)O3 are discussed. Growth conditions as well as the thermodynamic conditions for successful synthesis are described. it was found that amorphous thin films of TiNi and BaTiO3 can be crystallized simultaneously by air annealing at 600 degree(s)C. Onto bulk TiNi samples, PZT was synthesized successfully, with good mechanical bonding.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
03 Jun 1993
TL;DR: In this article, the authors suggest the following definition of smart materials/structures: Smart Materials/Structures (SMS): Structural systems based upon materials with the ability to sense their own response to environmental and operational stimuli, and modify that response in such a way as to maintain or optimize structural performance, utilizing embedded sensors and actuators interfaced with closed-loop adaptive control systems based on system stimulus response models.
Abstract: : 'Smart' Materials and Structure have the capability to respond to their environment to a significant degree, by virtue of intrinsic properties and/or built-in sensor/ actuator systems. The words 'smart' or 'intelligent' as applied to materials/structures are used in an idealistic and imprecise way to indicate an analogy with the integrated sensor/actuator/control systems evolved by living beings. The programatic objectives of this proposal suggest the following definition of Smart Materials/ Structures (SMS): Smart Materials / Structures (SMS) Structural systems based upon materials with the ability to SENSE their Own response to environmental and operational stimuli, and modify that response in such as way as to maintain or optimize structural performance, utilizing embedded sensors and actuators interfaced with closed-loop adaptive control systems based on system stimulus-response models. In this effort, BDM federal, Inc., a subsidiary of BDM International, Inc. (BDM) conducted a technical analysis of Smart Materials and Structures in order to assist DARPA in planning a future initiative in this area.
08 Sep 1993
TL;DR: In this article, the authors report the results of an ongoing experimental program for damage assessment and mitigation of composite structures using smart materials using modal analysis which can be carried out using piezoelectric films as both sensor and actuator on the structure member.
Abstract: This paper reports the results of an ongoing experimental program for damage assessment and mitigation of composite structures using smart materials. One consequence of all damage to a composite structure is a change in its stiffness. This change in stiffness is measured by modal analysis which can be carried out using piezoelectric films as both sensor and actuator on the structure member. It is shown that the presence of damage can be detected by the change in natural frequencies and the location of the damage can be detected from the ratio of changes in frequencies between two successive modes.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
22 Jul 1993
TL;DR: In this paper, two different approaches to computing twinned configurations are discussed, a variation on the conjugate gradient method applied to computing approximate minimizers of a model of the material energy for a shape memorsy material in the martensitic phase, and a multigrid based approach, averaging the approximate minimizer to include a probability distribution of the various orientations within the solution.
Abstract: One feature of shape memory alloys and other smart materials is the formation of fine-scale arrangements (microstructures) as a response to external stimuli. In shape memory materials there is twinning, where the material forms narrow bands in its interior, where in each band the material has a uniform orientation, but in adjacent bands it takes on different but symmetry-related orientations. In this paper, we discuss two different approaches to computing twinned configurations. The first is a variation on the conjugate gradient method applied to computing approximate minimizers of a model of the material energy for a shape memorsy material in the martensitic phase. This energy functional is not convex so special considerations are needed to assure that the method does not get stuck in the many local minima. The second method uses a multigrid based approach, averaging the approximate minimizers to include a probability distribution of the various orientations within the solution, i.e., it uses a Young measure to compute the minimizer.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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01 Jan 1993
01 Jan 1993
TL;DR: The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical as discussed by the authors.
Abstract: Embedded optical fibers allow not only the cure-monitoring and in-service lifetime measurements of composite materials, but the NDE of material damage and degradation with aging. The capabilities of such damage-detection systems have been extended to allow the quantitative determination of 2D strain in materials by several different methods, including the interferometric and the numerical. It remains to be seen, what effect the embedded fibers have on the strength of the 'smart' materials created through their incorporation.
08 Sep 1993
TL;DR: In this article, the energy dissipation characteristics of smart cantilever beam specimens were measured, and the relationship between the particle concentration of the suspension with damping ratio of the smart beam and the electric field intensity imposed on the beam was investigated.
Abstract: This experimental investigation is focused on characterizing a class of electro-rheological (ER) fluids and also characterizing a class of smart structures featuring this class of suspensions. These studies involved the imposition of different applied voltages on the ER fluid domain and various concentrations of the suspension particles. Electro-rheological fluids belong to a class of colloidal suspensions whose global characteristics can be controlled by the imposition of an appropriate external electric field upon the fluid domain. Therefore, when these fluids are embedded within a smart beam-like structure, the global properties of the beam, and hence its vibrational response, can also be controlled. In this work, the energy dissipation characteristics of smart cantilever beam specimens were measured. Different ER fluid smart beam specimens with various concentrations were employed in these investigations to provide insight on the relationship between the particle concentration of the suspension with damping ratio of the smart beam and the electric field intensity imposed on the beam. The coupled electrical and mechanical dynamic properties of smart materials featuring hydrous ER fluids were experimentally studied using a Rheometrics RMS 800 mechanical spectrometer to gain insight into their effectiveness in vibration control applications. THe experimental results demonstrate the non-Newtonian rheological behavior of ER fluids, and the ability of this class of smart beams to dissipate energy increases with the increase of particulate concentration and also the applied electric field.