Mechanical Components

Using a Steering Shaping Function to Improve Human Performance in By-Wire Vehicles

Currently, there is a performance issue regarding vehicle control at higher speeds for some indirect-vision, by-wire military vehicles; that is, those vehicles in which mechanical links between the driver and control devices are replaced by electronic or computerized signals. Work has been performed to assess the current state of knowledge regarding the shaping function. The overall goal was to identify design parameters critical to improving the current by-wire implementation for military tactical vehicles, and to ultimately optimize system (i.e., human-vehicle) performance for the execution of secure mobile operations.

Posted in: Briefs, Mechanical Components, Steer-by-wire, Human machine interface (HMI), Military vehicles and equipment, Vehicle dynamics
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Sensing for Controls and Propulsion Health Management in Turbine Engines

Advances in engine performance and reliability require sensor components that operate reliably under extreme engine operating conditions (e.g., takeoff, max thrust) and in harsh environments (e.g., high temperature and radiation). The design of advanced controls and Propulsion Health Man agement (PHM) also depend on the use of components with increased susceptibility to atmospheric radiation. Current and future engine operating temperature environments that provide major challenges in sensor design for control and propulsion health management are being explored.

Posted in: Briefs, Mechanical Components, Sensors and actuators, Diagnostics, Gas turbines, Durability, Reliability
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Water Mist System for Shipboard Machinery Space Fires

Water mist has been determined to be a preferred alternative to Halon 1301 total flooding to extinguish fires occurring in ship machinery spaces and pump rooms, because it is toxicologically and physiologically inert. Water mist systems produce a drop size distribution with a range of drop sizes under 1000 μm, while the more conventional sprinkler systems produce much coarser particles. The smaller particle sizes have greater cooling efficiencies because evaporation and cooling are controlled by surface area, and the surface area of a large number of small droplets is greater than that of a small number of large droplets of the same total volume.

Posted in: Briefs, Mechanical Components
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Axial Field Electric Motor

An axial field electric motor comprises one or more elements such as a rotor mounted for rotation and multiple axial flux permanent magnets carried by the rotor. The axial flux permanent magnets are oriented such that an associated magnetic flux produced thereby is at least substantially axially oriented. The axial flux permanent magnets are positioned around the rotor with alternating orientations of flux direction so that a flux direction of adjacent magnets is at least substantially axially oriented but opposite in direction. The radial flux permanent magnets are also carried by the rotor and oriented so that an associated magnetic flux produced is at least substantially radially oriented.

Posted in: Briefs, Mechanical Components
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SparkJet Actuators for Controlling Flows

SparkJet actuators are under investigation as means of controlling flows — especially supersonic and hypersonic flows. In one important class of potential applications, SparkJet actuators would be used to effect rapid and flexible steering of advanced aerospace vehicles. Effective manipulation of flow fields in aerospace systems could afford significant benefits, including increases in performance, maneuverability, payload, and range, as well as reductions in overall costs. These macro-scale benefits would be achieved through the use of SparkJet actuators to alter such phenomena as laminar-to-turbulent transition, turbulence, and flow separation on a micro scale.

Posted in: Briefs, Mechanical Components
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Stability of Rotors Supported by Hydrodynamic Film Bearings

The document, "Hydrodynamic Fluid Film Bearings and Their Effect on the Stability of Rotating Machinery" represents a lecture in a series "Design and Analysis of High-Speed Pumps," held in 2006 under the auspices of the North Atlantic Treaty Organization. The document introduces the basic principles of hydrodynamic lubrication and the fundamental equation of classical lubrication theory, then proceeds through derivation of the static and dynamic performance characteristics of short cylindrical journal bearings, with application to the dynamic forced performance of a rigid rotor supported on plain bearings. The Sommerfeld number is introduced and shown to define the relation among load, speed, and equilibrium eccentricity of a journal within a radial bearing. Rotordynamic force coefficients (direct and cross-coupled stiffnesses) are introduced and the relationships between them and instabilities of the rotor-and-bearing system are thoroughly discussed. The relationship between the whirl frequency ratio (the ratio between the frequency of undesired orbital rotor motion about the nominal journal axis and the frequency of rotation) and the threshold rotational frequency for instability is discussed. The document concludes with a review of practical journal-bearing configurations, including summaries of their major advantages and disadvantages and brief descriptions of typical applications.

Posted in: Briefs, Mechanical Components
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Prototype Rocket Engine for a Nanosat Launch Vehicle

A paper discusses a prototype rocket engine for a suborbital Reusable Nanosat Launch Vehicle (RNLV). The engine must operate with thrust levels from 3,000 to 5,000 lbf. The engine is comprised of three major subassemblies: the injector, igniter, and the combustion chamber nozzle. Propellants are introduced and mixed in the combustion chamber utilizing a combination of triplet and unlike doublet injector elements. In addition, film cooling is provided in order to extend the life of the ablative chamber. Ignition is accomplished with solid propellant ports mounted on the side of the chamber.

Posted in: Briefs, Mechanical Components
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Biaxial and Shear Testing Apparatus With Force Controls

An apparatus for in-plane biaxial tension/compression and in-plane shear testing of fabrics, other flexible sheet materials, or relatively rigid thin plate materials has been invented. The apparatus is capable of applying, to a sheet material specimen, a controlled tensile or compressive force along each of two directions in the plane of the specimen. The force along each direction can differ from the force along the other direction. The directions of the applied forces can be orthogonal or can be set at an oblique angle, depending on the combination of stresses required to be applied to the specimen. Thus, depending on the angle between the applied-force directions, the sense (tensile or compressive) of each applied force, and the magnitude of each force, the specimen can be subjected to almost any combination of in-plane shear and biaxial tension/compression loading.

Posted in: Briefs, Mechanical Components
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MEMS Offset-Beam Torsional Electrothermal Actuators

Prototypes of microelectromechanical system (MEMS) rotational actuators based on a principle of torsion induced by thermal expansion of electrically heated offset beams have been designed, fabricated, and tested. It is envisioned that after further development, these actuators might be used to satisfy stringent competing requirements for smaller, larger-force, largerdisplacement actuators in increasingly complex MEMS systems. Until now, MEMS thermal actuators have been regarded as inefficient and capable of producing, variously, either large forces and small displacements or small forces and large displacements. The actuators of the present type are intended to overcome some of the deficiencies heretofore attributed to MEMS thermal actuators by producing medium displacements and medium forces.

Posted in: Briefs, Mechanical Components, Microelectricmechanical device, Sensors and actuators
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Tethered, Remotely Operated Miniature Submarine

A tethered, remotely operated, armed underwater vehicle has been conceived to satisfy a need for an uninhabited vehicle for Navy missions in which positive identification of targets is needed. Examples of such missions include those involving detection of swimmers and neutralization of mines. Unarmed versions of the vehicle might also be useful in civilian applications involving underwater inspections under hazardous conditions.

Posted in: Briefs, Mechanical Components
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