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smart structures and materials 1995: Passive Damping

作者： Clark, Peter W. Aiken, Ian D. Kelly, James M. Higashino, Masahiko Krumme, Robert Univ. of California/Berkeley Earthquake Engineering Research Cent. Richmond CA USA

ISBN: (纸本)0819417947

In the wake of damaging earthquakes in both the United States and Japan over the past year, the performance of structures, in addition to traditional life-safety concerns, has become an important issue for designers and owners. Many possible approaches to enhancing the seismic performance of structures have been proposed, and one promising family of solutions which is receiving attention today is passive damping devices. The work presented here is part of an ongoing experimental and analytical study of the applicability of one particular type of damping device for controlling the response of civil structures. Two different types of reduced-scale dampers using shape memory alloys have been tested over a range of strain amplitudes, loading frequencies, and temperatures. The purpose of the tests was to thoroughly characterize an alloy and examine variations in device design and installation configurations that could lead to a number of different hysteretic shapes. The ultimate behavior of the devices was also examined. Parallel to the device development and testing, a series of analyses of a steel frame building incorporating shape memory alloys has been undertaken to quantify the benefits of using these devices in an actual structure. Preliminary results of these analyses are presented.

关键词： Shape memory effect

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Multidisciplinary research in smart structures: a survey

Multidisciplinary research in smart structures: a survey

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American control Conference (ACC)

作者： J. Chandra V. Rao R. Butler R. Damle Mathematical and Computer Science Division Army Research Office NC USA Department of Electrical Engineering and Intelligent Systems Center University of Missouri Rolla MO USA

The field of smart structures encompasses a large number of engineering disciplines. A clear understanding of the concepts of smart structures depends on in depth knowledge of mechanics of materials, mechanical vibrations, structural analysis, sensors and actuators and control theory. This field is truly multidisciplinary in nature and promises many technological innovations. A brief survey of multidisciplinary research in smart structures is provided in this paper.

关键词： Intelligent structures Intelligent actuators Intelligent sensors Force control Temperature Vibration control Shape memory alloys Piezoelectric materials Magnetic materials Heating

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smart skis and other adaptive structures

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MECHANICAL ENGINEERING 1995年第11期117卷 76-81页

作者： Ashley, S

A radical new ski design developed by K2 of Vashon, Wash., uses smart material technology to create a versatile 'all-mountain' expert ski that can thrive in just about any kind of snow. Embedded in the laminated body of the K2 Four smart Ski are piezoelectric ceramic elements that first detect and then dampen shocks and vibrations. The active vibration-attenuation module improves control on fast downhill runs by keeping the specially sculpted ski in contact with the snow. The smart Ski is among the first mainstream consumer products to benefit from the use of piezoelectric smart materials in a large-scale adaptive structure. The piezoelectric technology is being developed for vibration damping, noise attenuation, and device actuation in skis, cars, submarines, and aircraft.

关键词： Intelligent materials

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Development and testing of an improved viscous fluid damping device for appendage damping and component isolation

Development and testing of an improved viscous fluid damping...

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smart structures and materials 1995: Passive Damping

作者： Morgenthaler, Daniel R. Martin Marietta Astronautics Denver CO USA

ISBN: (纸本)0819417947

The requirements for spacecraft and launch vehicles have driven numerous investigations of vibration suppression techniques and devices. Appendages on spacecraft and component vibrations on launch vehicles are common problems for which vibration attenuation is beneficial or necessary. This paper documents the hardware development and component and system level demonstration of a viscous fluid damper design in a very low frequency appendage application. The resulting design has significant advantages over state-of-the-art viscous damper designs and can meet the requirements of many future systems. Potential applications include damping struts, isolation systems, and tuned dampers. Advantages of the design include excellent predictability and linearity, the capability for high forces and displacements, high hydraulic stiffness, the absence of elastomeric seals and the potential for passive control of damper property variations with temperature.

关键词： Vibration control

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Transducer tolerance theory for structural control

Transducer tolerance theory for structural control

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smart structures and materials 1995: smart structures and Integrated Systems

作者： Burke, Shawn E. Clark, Robert L. Boston Univ. Boston MA USA

ISBN: (纸本)0819417920

An expression for the mean and variance of a transducer array's modal coefficients is developed to quantify the effect of spatial errors on the transducer structural coupling, and on the transducer augmented plant's input/output frequency response. Transducer elements are modeled spatially via their position, aperture, and shading (e.g., spatial gain weighting). Each of these spatial parameters can be statistically modeled in terms of their mean and variance, assuming statistical independence. Modal coefficients are described via composition integrals of the transducer spatial kernel and the plant mode shapes. The probability density function of each parameter is then assumed to be unimodal, with characteristic scale smaller than any corresponding spatial scale of the modal coefficient's dependence on the parameter. Consequently, the mean values of the modal coefficients are the values of the corresponding integrals evaluated at the mean transducer position, aperture, and shading. The variance of the modal coefficients, derived via a Taylor series expansion to second order about their mean values, is expressed in terms of the partial derivatives of the modal coefficient with respect to the uncertain spatial parameters. This suggests that transducers whose shadings consist of low- order generalized function or modal expansions are less sensitive to spatial parameter variations. Variations in the modal coefficients are mapped to expressions for the mean and variance of transducer-augmented plant transfer functions. Simulation examples are presented that model variations in the input/output transfer functions characteristics of a flexible beam with a mis- registered point actuator, and a mis-registered modally-weighted piezo film sensor distribution. For even slight aperture mis- registrations - 0.26% of the beam's length - the modal sensors no longer perfectly `sift out' non-targeted modes, and off-mode contributions grow by nearly an order of magnitude.

关键词： Structural analysis

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Shape control of plates using piezoceramic elements

Shape control of plates using piezoceramic elements

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Active materials and smart structures

作者： Ghosh, K. Batra, Romesh C. Univ. of Missouri/Rolla Rolla MO USA

ISBN: (纸本)0819417750

We use the first-order shear deformation theory to study quasistatic deformations of a plate with piezoceramic elements (PZTs) mounted symmetrically on its top and bottom surfaces. The Galerkin formulation of the problem is derived. After having validated the computer code, the voltage to be applied to the PZTs in order to nullify the deflection of preassigned points of a plate deformed quasistatically is determined. It is shown that the deflections of the centerline of a simply supported plate and the tip deflection of a cantilever plate can be controlled by applying suitable voltages to the PZTs. The voltage to be applied to the actuators as a function of the surface area covered by them in the former case, and as a function of their distance from the fixed end for the latter case is depicted graphically.

关键词： Shape memory effect

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Shape memory alloys for damage-resistant composite structures

Shape memory alloys for damage-resistant composite structure...

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Active materials and smart structures

作者： Paine, Jeffrey S. Rogers, Craig A. Virginia Polytechnic Inst. and State Univ. Blacksburg VA USA

ISBN: (纸本)0819417750

Shape memory alloy (SMA) materials such as nitinol have unique properties associated with the shape recovery effect and the material's phase changes that have been used in a variety of actuator and sensing applications. By embedding SMA elements into host composite materials, control or modification of the SMA hybrid composite's structural properties can be accomplished in-service, thereby increasing the hybrid composite's structural functionality. Utilizing the SMA's substantial capacity to dissipate strain energy to increase the hybrid composite's static functionality is addressed herein. Specific applications of SMA hybrid composites for improving polymer matrix composite material's impact damage resistance is presented. Hybridizing composites with nitinol improves their impact resistance because of nitinol's tremendous capacity to dissipate impact strain energy through the stress-induced martensitic phase transformation. The amount of impact damage is reduced and the material's resistance to impact perforation at various velocities is improved. The experimental response of nitinol hybrid composites to low and high velocity impact perforation is presented. The unique toughness and resistance to permanent deformation that is a result of the stress-induced martensitic phase transformation enables the nitinol to dissipate on the order of 4 times the strain energy of high alloy steel and 16 times that of many graphite/epoxy composites.

关键词： Shape memory effect

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smart structure obtained by implementation of adaptive controlled columns

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smart materials and structures 1995年第1 A期4卷 A25-A31页

作者： Hirsch, Gerhard H. Jozsa, Maria R. Univ of Technology Germany

This paper opens with a comparison of several methods of active control concepts from the engineering point of view. Consequently, it introduces intelligent columns, adaptively controlling substructures in the sense of base isolation. Concerning the verification of this concept relating to hardware and software, a collaborative research project between Aachen University and the University of Southern California is proposed. Here a wide-band spectrum of different loading tests will be prepared. The programme schedule consisting of the experimental model, analytical and experimental studies is presented in detail.

关键词： Intelligent structures

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BENDING AND TWISTING VIBRATION control OF A CANTILEVER PLATE VIA ELECTROMECHANICAL SURFACE DAMPING

BENDING AND TWISTING VIBRATION CONTROL OF A CANTILEVER PLATE...

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Conference on Passive Damping

作者： GHONEIM, H ROCHESTER INST TECHNOL DEPT MECH ENGNROCHESTERNY 14623

ISBN: (纸本)0819417947

The electromechanical surface damping technique (EMSD) is applied to suppress the bending and twisting peak vibration amplitudes of a cantilever plate. The technique is a combination of the constrained layer damping (CLD) and the shunted piezoelectric methods in which the constraining layer of the CLD is replaced by a shunted piezoelectric ceramic. The frequency responses, to a white noise random base excitation, of the EMSD-treated plate at the vicinity of the first and second bending and twisting resonant frequencies are determined and compared with the corresponding responses of the CLD-treatment. It is shown that, in general, the EMSD treatment provides more suppression of the bending and twisting peak vibration amplitudes than the conventional CLD treatment. The EMSD treatment, however, is more effective at higher frequencies and lower temperatures, which suggests that the EMSD method can be applied to extend the effective range of frequencies and/or temperatures of the conventional CLD method. The work presented is primarily analytical, however crude and preliminary experimental results are presented in order to demonstrate the feasibility of the EMSD technique.

关键词： Ceramics Vibration control Temperature metrology Aluminum Calcium Capacitance Mechanical engineering Actuators Mathematical modeling Reliability

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Active control of the lateral buckling of nitinol-reinforced composite beams

Active control of the lateral buckling of nitinol-reinforced...

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Active materials and smart structures

作者： Baz, Amr M. Chen, T. Catholic Univ. of America Washington DC USA

ISBN: (纸本)0819417750

The lateral buckling characteristics of flexible composite beams are actively controlled by activating sets of shape memory alloy (NITINOL) fibers which are embedded along the mid- plane of these beams. With such active control capabilities, the beams can be manufactured from light weight sections without compromising their elastic stability. This feature will be invaluable in building light weight structures that have high resistance to failure due to buckling. Finite element models are developed to analyze the mechanical and thermal characteristics of the composite beams. The models account for the individual contributions of the matrix, the NITINOL fibers and the shape memory effect to the overall performance of the composite beams. A closed-loop computer-controlled system is built to validate the finite element model. The system is used to control the lateral buckling of a composite beam which is 40.6 cm long, 5.1 cm wide and .25 cm thick which is reinforced with two NITINOL-55 fibers that are 0.55 mm in diameter. The results obtained confirm the validity of the developed theoretical model and indicate that the buckled beams can be brought back completely to their unbuckled configuration by proper activation of the shape memory effect. Also, the results obtained suggest that reinforcing the beams with NITINOL fibers is effective in enhancing their lateral buckling characteristics.

关键词： Beams and girders

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