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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Timoshenko beam theory is applied to beams with multiple layers of piezoelectric material attached. The model is developed using a Hamiltonian approach, and includes the external electrical circuit as well as a complete set of boundary conditions. Resistors are added to the sensor layers for passive damping. The resulting model is then formulated in state space.
The results of the Independent Orbiter Assessment (IOA) of the Failure Modes and Effects Analysis (FMEA) and Critical Items List (CIL) are presented. The IOA effort first completed an analysis of the Elevon Subsystem hardware, generating draft failure modes, and potential critical items. To preserve independence, this analysis was accomplished without reliance upon the results contained within the NASA FMEA/CIL documentation. The IOA results were then compared to the NASA FMEA/CIL baseline with proposed Post 51-L updates included. A resolution of each discrepancy from the comparison is provided through additional analysis as required. This report documents the results of that comparison for the Orbiter Elevon hardware. The IOA product for the Elevon analysis consisted of 25 failure mode worksheets that resulted in 17 potential critical items being identified. Comparison was made to the NASA FMEA/CIL, which consisted of 23 FMEAs and 13 CIL items. This comparison produced agreement on all CIL items. Based on the Pre 51-L baseline, all non-CIL FMEAs were also in agreement.
The paper models the effects of dynamic coupling between a structure and an electrical network through the piezoelectric effect. The coupled equations of motion of an arbitrary elastic structure with piezoelectric elements and passive electronics are derived. State space models are developed for three important cases: direct voltage driven electrodes, direct charge driven electrodes, and an indirect drive case where the piezoelectric electrodes are connected to an arbitrary electrical circuit with embedded voltage and current sources. The equations are applied to the case of a cantilevered beam with surface mounted piezoceramics and indirect voltage and current drive. The theoretical derivations are validated experimentally on an actively controlled cantilevered beam test article with indirect voltage drive.
The active control of flexural power flow in both semiinfinite and finite elastic beams is experimentally investigated. The experimental results demonstrate that piezoceramic transducers when used in conjunction with an adaptive least mean squares controller, can effectively control flexural power flow in thin beam systems. The piezoceramic transducers offer distinct size and weight advantages over conventional transducers. The experiments also demonstrate the use of an axial scanning laser vibrometer to determine out of plane velocity and power flow.
Prosthetic hand attached to end of remaining part of forearm and to upper arm just above elbow. Pincerlike fingers pushed apart to degree depending on rotation of forearm. Simpler in design, simpler to operate, weighs less, and takes up less space.
Flow-control valve varies cross-sectional area with drop in pressure. Conceived for controlling flow of oxidizing fluid in rocket engine, concept applicable to other situations necessary to vary flows over wide ranges. In rocket-engine application, fluid liquid or gaseous, depending on chosen operating conditions.
A prosthetic device has been developed for below-the-elbow amputees. The device consists of a cuff, a stem, a housing, two hook-like fingers, an elastic band for holding the fingers together, and a brace. The fingers are pivotally mounted on a housing that is secured to the amputee's upper arm with the brace. The stem, which also contains a cam, is rotationally mounted within the housing and is secured to the cuff, which fits over the amputee's stump. By rotating the cammed stem between the fingers with the lower arm, the amputee can open and close the fingers.
This paper describes a design for fiber-optic sensing and control in advanced aircraft Electronic Engine Control (EEC). The recommended architecture is an on-engine EEC which contains electro-optic interface circuits for fiber-optic sensors. Size and weight are reduced by multiplexing arrays of functionally similar sensors on a pairs of optical fibers to common electro-optical interfaces. The architecture contains interfaces to seven sensor groups. Nine distinct fiber-optic sensor types were found to provide the sensing functions. Analysis revealed no strong discriminator (except reliability of laser diodes and remote electronics) on which to base a selection of preferred common interface type. A hardware test program is recommended to assess the relative maturity of the technologies and to determine real performance in the engine environment.
A computer program has been developed that improves the efficiency of wind tunnel model leak checking. The program uses a voice recognition unit to relay a technician's commands to the computer. The computer, after receiving a command, can respond to the technician via a voice response unit. Information about the model pressure orifice being checked is displayed on a gas-plasma terminal. On command, the program records up to 30 seconds of pressure data. After the recording is complete, the raw data and a straight line fit of the data are plotted on the terminal. This allows the technician to make a decision on the integrity of the orifice being checked. All results of the leak check program are stored in a database file that can be listed on the line printer for record keeping purposes or displayed on the terminal to help the technician find unchecked orifices. This program allows one technician to check a model for leaks instead of the two or three previously required.
Timoshenko beam theory is applied to beams with multiple layers of piezoelectric material attached. The model is developed using a Hamiltonian approach, and includes a model of the external electrical circuits to which the piezoelectric layers are attached, as well as a complete set of boundary conditions. The resulting model is then formulated in state space, and compared to a state space model of the standard Timoshenko beam.
Analysis of complex configurations using structured grids virtually demands multiple blocks of grids. To facilitate calculations involving multiple blocks, a geneal grid-block patching algorithm based on generalized coordinate inerpolation has been developed. The computational grid may contain as many arbirarily shaped blocks as required to make the grid generation problem tractable and to accurately model the fow features. Results are presented for several test cases as well as for the F-18 forebody control strake. The methodology developed has application to overlapped or embedded grids.
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The active control of acoustic pressure in a 2-D cavity with a flexible boundary (a beam) is considered. Specifically, this control is implemented via piezoceramic patches on the beam which produces pure bending moments. The incorporation of the feedback control in this manner leads to a system with an unbounded input term. Approximation methods in this manner leads to a system with an unbounded input term. Approximation methods in the context of linear quadratic regulator (LQR) state space control formulation are discussed and numerical results demonstrating the effectiveness of this approach in computing feedback controls for noise reduction are presented.
A high temperature, flexible brush seal comprises a bundle of fibers or bristles held tightly together and secured at one end with a backing plate. The assembly includes a secondary spring-clip having one end anchored to the brush seal backing plate. An alternate embodiment of the seal utilizes a metal bellows containing coolant holes. Another embodiment of the seal uses non-circular cross-sectional fibers which may be square, rectangular or hexagonal in cross section.
Equations for the force produced by an air core electromagnet on a permanent magnet core as a function of the coil height, coil inner and outer radii, and core displacement are developed. The magnetization vector of the permanent magnet core is assumed to be aligned with the central axis of the electromagnet and the forces which are produced lie along the same axis. Variations in force due to changes in electromagnet parameters and core displacement are investigated and parameter plots which should be useful for coil design are presented.
Electrostriction, which exists in all materials, exhibits many potential applications in electronic and optically controlled systems. Few materials, however, possess electrostrictive effects large enough to be of practical usefulness. The development of materials with high electrostrictive coefficients has been a major impetus of much research in this area. The Pb(x)Ba(1 - x)(Zr(y)Ti(1 - y))O3 (PBZT) ceramic system appears to be a very promising candidate because of the electrostrictive coefficients, Q(sub 11) and Q(sub 12), are among the highest discovered today. In this paper, we describe the preparation and sintering of the PBZT(73/37) ceramic, and the effect of some sintering conditions on sintered samples. The results on the measurement of the electrostrictive and related properties are presented. In addition, a brief discussion of characteristics of PBZT ceramics is provided.
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