In order to advance safety of some important structures that will be required to perform under increasingly stringent conditions,it will be necessary to use materials that are lighter weight,have superior strength and...
详细信息
This paper focuses on the curriculum development portion of an ongoing project whose goal is to integrate research results with curriculum development in the area of smartstructures. These courses are intended for se...
详细信息
This paper focuses on the curriculum development portion of an ongoing project whose goal is to integrate research results with curriculum development in the area of smartstructures. These courses are intended for seniors and graduate students in Electrical, Mechanical and Aerospace Engineering and Engineering Mechanics. Two courses, each with a laboratory component, have been developed and taught during the spring and fall semesters in 1994. The topics covered include some review in mechanics of materials and linear system theory, sensors, actuators, advanced topics in vibrations, control, system identification, and composite materials in the first course. The second course treats structural control techniques, active and passive damping using piezoceramic actuators, modeling and control of distributed systems, and neural networks for smartstructures. Both courses are team-taught by two instructors, one from the Department of Electrical Engineering and one from the Department of Mechanical and Aerospace Engineering.
Fiber optic sensors (FOS) for vibration monitoring of smartstructures have certain advantages over conventional strain gage based sensors due to electromagnetic environment insensitivity and high response bandwidth. ...
详细信息
ISBN:
(纸本)0819417920
Fiber optic sensors (FOS) for vibration monitoring of smartstructures have certain advantages over conventional strain gage based sensors due to electromagnetic environment insensitivity and high response bandwidth. During the present study, a spatially integrating fiber optic sensor was used for vibration monitoring. It is based on the concept that the optimal placement of the sensing element can be sought by using a priori knowledge of the mode shapes of the structure. The applicability of this approach to polarimetric optical fibers is described. The acquired integrating FOS signal was used to sense and control the vibration of an electrorheological adaptive structure subjected to a random external excitation.
The main theme of this research project has been to analytically develop a proof-of-concept design to demonstrate the effectiveness of a smart material actuator employing ETREMA TERFENOL-DTM for helicopter rotor servo...
详细信息
ISBN:
(纸本)0819417920
The main theme of this research project has been to analytically develop a proof-of-concept design to demonstrate the effectiveness of a smart material actuator employing ETREMA TERFENOL-DTM for helicopter rotor servoflap control. This design enables the control of the rotor blade flap with an actuator embedded in the blade itself. By moving the control to the rotor blades, the swashplate system could be eliminated. Requirements such as applied load and motions were the key issues that needed to be accounted for in order to achieve a successful design employing the `giant' magnetostrictive material. A series of loading conditions characterized by an additive process of Steady-State. Cyclic, and Active control functions were considered for Sustained flight. Optimization of the overall system gave rise to a system gain of 3.7 for Sustained motion. At this same optimal gain value, and using an ETREMA TERFENOL- DTM rod length of at least 22.7 inches, a net peak-to-peak displacement of as high as 42 mils (1.07 mm) was obtained.
The proceedings contains 34 papers. Some of the specific topics discussed are: passive damping technology demonstration;integral passive damping for aircraft fuselage structure;particle beam damper;effect of radiation...
详细信息
ISBN:
(纸本)0819417947
The proceedings contains 34 papers. Some of the specific topics discussed are: passive damping technology demonstration;integral passive damping for aircraft fuselage structure;particle beam damper;effect of radiation and creep on viscoelastic damping materials;dynamic scaling of viscoelastic elements;and vibration control of plates with active constrained-layer damping.
In this paper, a macro-scale, phenomenological constitutive model for shape memory alloys is used in conjunction with energy balance equations to study the temperature profile and hence deformation profile seen in SMA...
详细信息
ISBN:
(纸本)0819417750
In this paper, a macro-scale, phenomenological constitutive model for shape memory alloys is used in conjunction with energy balance equations to study the temperature profile and hence deformation profile seen in SMA wires under specific boundary conditions. The general, fully coupled thermo-mechanical problem is formulated, but analytical solutions are determined only for the decoupled case. Results for two specific boundary value problems are presented here: (1) resistive heating of an SMA wire--initial detwinned martensite leads to strain recovery (contraction) on heating; (2) deformation migration in semi-infinite SMA wire cooled at the boundary--deformation zone propagates and expands as initially austenitic wire transforms to martensite (expansion). In both cases, the region and extent of transformation is identified, indicating the magnitude of actuation obtained. Implications of the modeling for active control of structures are discussed.
This paper presents some findings from work in progress to investigate the efficacy of using active materials to control mechanical vibrations. The device under study is designed to be useful for a range of precision ...
详细信息
ISBN:
(纸本)0819417963
This paper presents some findings from work in progress to investigate the efficacy of using active materials to control mechanical vibrations. The device under study is designed to be useful for a range of precision positioning, force cancellation, and vibration isolation tasks typically associated with spacecraft environments. It incorporates shape-memory-alloy springs to provide an adaptive-passive isolator stage, and multilayer electrostrictive ceramic actuators for precise positioning and canceling transmitted forces across a support interface. Device performance in each of these three modes is explored by simulations incorporating characterized properties of the individual active material components.
Future advanced fixed and rotary-wing aircraft, launch vehicles, and spacecraft will incorporate smart MEMS devices to monitor structural integrity and manage overall structural health. These smartstructures will be ...
详细信息
ISBN:
(纸本)0819417971
Future advanced fixed and rotary-wing aircraft, launch vehicles, and spacecraft will incorporate smart MEMS devices to monitor structural integrity and manage overall structural health. These smartstructures will be capable of assessing vehicle structural damage in real time and ultimately reconfiguring the vehicle flight control to prevent catastrophic failures. This paper describes an overview of Honeywell's MEM technology for new and aging aircraft applications to assess preflight readiness, in- flight structural integrity, and postflight time-based maintenance. Honeywell's MEMS approach combines silicon micromachining, free-space optical waveguides, high-speed optical interconnects, and supervisory sensor management to monitor structural integrity and health. A unique second-generation polysilicon resonance microbeam sensor is described. It incorporates a micron-level vacuum-encapsulated microbeam to optically sense structural-integrity parameters such as acoustic- mission, strain, and to optically power the sensor pickoff. Its principle of operation and significant payoffs and benefits are summarized.
Theory and experiments to control the static shape of flexible structures by employing internal translational actuators are summarized and plants to extend the work to adaptive wings are presented. Significant reducti...
详细信息
ISBN:
(纸本)0819417963
Theory and experiments to control the static shape of flexible structures by employing internal translational actuators are summarized and plants to extend the work to adaptive wings are presented. Significant reductions in the shock-induced drag are achievable during transonic- cruise by small adaptive modifications to the wing cross-sectional profile. Actuators are employed as truss elements of active ribs to deform the wing cross section. An adaptive-rib model was constructed, and experiments validated the shape-control theory. Plans for future development under an ARPA/AFWAL contract include payoff assessments of the method on an actual aircraft, the development of inchworm TERFENOL-D actuators, and the development of a method to optimize the wing cross-sectional shapes by direct-drag measurements.
This paper describes experimental work on the semi-active control of structural modal energy by dynamically controlling structural stiffness. Stiffness adjustment of the structure is achieved by engaging or disengagin...
详细信息
ISBN:
(纸本)0819417920
This paper describes experimental work on the semi-active control of structural modal energy by dynamically controlling structural stiffness. Stiffness adjustment of the structure is achieved by engaging or disengaging `relaxed' control elements, thus changing local stiffness and changing the global eigenstructure without the introduction of energy into the system. Experiments on a three story laboratory model are described. control experiments when the model is subjected to sinusoidal and random excitations demonstrate feasibility.
暂无评论