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  • Other Sources  (858)
  • NASA Technical Reports  (858)
  • MECHANICAL ENGINEERING  (858)
  • 1980-1984  (858)
  • 1955-1959
  • 1935-1939
  • 1
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    Improved techniques of parallel gap welding and monitoring (1984)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: Welding programs which show that parallel gas welding is a reliable process are discussed. When monitoring controls and nondestructive tests are incorporated into the process, parallel gap welding becomes more reliable and cost effective. The panel fabrication techniques and the HAC thermal cycling test indicate reliable product integrity. The design and building of automated tooling and fixturing for welding are discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Space Photovoltaic Res. and Technol. 1983; p 228-234
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  • 2
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    Variable polarity plasma arc welding on the Space Shuttle external tank (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Variable polarity plasma arc (VPPA) techniques used at NASA's Marshall Space Flight Center for the fabrication of the Space Shuttle External Tank are presentedd. The high plasma arc jet velocities of 300-2000 m/s are produced by heating the plasma gas as it passes through a constraining orifice, with the plasma arc torch becoming a miniature jet engine. As compared to the GTA jet, the VPPA has the following advantages: (1) less sensitive to contamination, (2) a more symmetrical fusion zone, and (3) greater joint penetration. The VPPA welding system is computerized, operating with a microprocessor, to set welding variables in accordance with set points inputs, including the manipulator and wire feeder, as well as torch control and power supply. Some other VPPA welding technique advantages are: reduction in weld repair costs by elimination of porosity; reduction of joint preparation costs through elimination of the need to scrape or file faying surfaces; reduction in depeaking costs; eventual reduction of the 100 percent-X-ray inspection requirements. The paper includes a series of schematic and block diagrams.
    Keywords: MECHANICAL ENGINEERING
    Type: Welding Journal (ISSN 0043-2296); 63; 27-35
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  • 3
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    An analysis of temperature effect in a finite journal bearing with spatial tilt and viscous dissipation (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The analysis presented herein deals with the evaluation of the pressure, velocity, and temperature profiles in a finite-length plane journal bearing. The geometry of the case under study consists of a spatially tilted shaft. The two-dimensional Reynolds equation accounts for the variation of the clearance gap h with x and z and is used to model the pressure field. The latter is solved for a variety of shaft tilt angles and then used to calculate the two-dimensional flow field. Finally, the flow field is used in the energy equation to solve for the film temperature profile, when the effect of viscous dissipation is taken into account.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions; 27; 405-412;
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  • 4
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    Special cases of friction and applications (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Two techniques for reducing friction forces are presented. The techniques are applied to the generalized problem of reducing the friction between kinematic pairs which connect a moveable link to a frame. The basic principles are: (1) Let the moveable link be supported by two bearings where the relative velocities of the link with respect to each bearing are of opposite directions. Thus the resultant force (torque) of friction acting on the link due to the bearings is approximately zero. Then, additional perturbation of motion parallel to the main motion of the moveable link will require only a very small force; (2) Let the perturbation in motion be perpendicular to the main motion. Equations are developed which explain these two methods. The results are discussed in relation to friction in geared couplings, gyroscope gimbal bearings and a rotary conveyor system. Design examples are presented.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME; 256-260
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  • 5
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    Why ceramic engines? (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Oil is still a problem for the U.S. and its allies. Transportation uses 61 percent of U.S. oil and its share is increasing, so more efficient technology should be concentrated there. Trucks' share of oil use is increasing because they are already much more efficient than autos. The primary truck opportunities are streamlining, more efficient engines, and shifting freight to railroads. More efficient engines are possible using ceramics to allow elimination of cooling systems and better use of waste exhaust heat. A 60 percent improvement seems possible if ceramics can be made tough enough and durable enough.
    Keywords: MECHANICAL ENGINEERING
    Type: Ceramic Engineering and Science Proceedings (ISSN 0196-6219); 5; 281-284
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  • 6
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    NASA transmission research and its probable effects on helicopter transmission design (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Transmissions studied for application to helicopters in addition to the more conventional geared transmissions include hybrid (traction/gear), bearingless planetary, and split torque transmissions. Research is being performed to establish the validity of analysis and computer codes developed to predict the performance, efficiency, life, and reliability of these transmissions. Results of this research should provide the transmission designer with analytical tools to design for minimum weight and noise with maximum life and efficiency. In addition, the advantages and limitations of drive systems as well as the more conventional systems will be defined.
    Keywords: MECHANICAL ENGINEERING
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  • 7
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    Feasibility analysis of a spiral groove ring seal for counter-rotating shafts (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Keywords: MECHANICAL ENGINEERING
    Type: Journal of Aircraft (ISSN 0021-8669); 21; 618-622
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  • 8
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    Pivoting and slip in an angular contact bearing (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Pivoting slips are calculated for the ball-race and ball-ball contacts in a retainerless bearing. The calculation is kinematic, ignoring all inertial loadings. Pure spin and uniform precession of the balls are considered. Pivoting slip magnitudes are compared with several other kinds of slip which were previously reported in an R4 size bearing. Previously announced in STAR as N83-26079
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions; 27; 259-262
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  • 9
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    Elastic model of the traction behavior of two traction lubricants (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: In the analysis of rolling-sliding concentrated contacts, such as gears, bearings and traction drives, the traction characteristics of the lubricant are of prime importance. The elastic shear modulus and limiting shear stress properties of the lubricant dictate the traction/slip characteristics and power loss associated with an EHD contact undergoing slip and/or spin. These properties can be deducted directly from the initial slope m and maximum traction coefficient micron of an experimental traction curve. In this investigation, correlation equations are presented to predict m and micron for two modern traction fluids based on the regression analysis of 334 separate traction disk machine experiments. The effects of contact pressure, temperature, surface velocity, ellipticity ratio are examined. Problems in deducing lubricant shear moduli from disk machine tests are discussed. Previously announced in STAR as N83-20116
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions; 27; 129-137;
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  • 10
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    Dynamic stiffness characteristics of high eccentricity ratio bearings and seals by perturbation testing (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The complex behavior of cylindrical bearings and seals that are statically loaded to eccentricities in excess of 0.7 are examined. The stiffness algorithms as a function of static load are developed from perturbation methodology by empirical modeling.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 481-501
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  • 11
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    Damping capacity of a sealed squeeze film bearing (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The advantages of incorporating an open-ended or weakly-sealed squeeze-film bearing in a flexible support structure simulating an aero-engine assembly were examined. Attention is given to empirically modelling the hydrodynamics of the more usual tightly-sealed squeeze-film bearing, with a view to assessing its damping performance.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 407-428
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  • 12
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    Influence of stationary components on unsteady flow in industrial centrifugal compressors (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An experimental investigation was performed to determine the characteristics of the onset and the growth of rotating nonuniform flow in a standard low specific speed stage, normally utilized in high pressure applications, in relation to change of stationary component geometry. Four configurations, differing only in the return channel and crossover geometry were tested on an atmospheric pressure open loop test rig. Experimental results make conspicious the effect of return channel geometry and give the possibility of shifting the unstable zone onset varying such geometry. An attempt was made to interpret the experimental results in the Emmons - Stenning's rotating stall theory.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 429-480
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  • 13
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    Squeeze-film dampers for turbomachinery stabilization (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A technique for investigating the stability and damping present in centrally preloaded radially symmetric multi-mass flexible rotor bearing systems is presented. In general, one needs to find the eigenvalues of the linearized perturbation equations, though zero frequency stability maps may be found by solving as many simultaneous non-linear equations as there are dampers; and in the case of a single damper, such maps may be found directly, regardless of the number of degrees of freedom. The technique is illustrated for a simple symmetric four degree of freedom flexible rotor with an unpressurized damper. This example shows that whereas zero frequency stability maps are likely to prove to be a simple way to delineate multiple solution possibilities, they do not provide full stability information. Further, particularly for low bearing parameters, the introduction of an unpressurized squeeze film damper may promote instability in an otherwise stable system.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 391-406
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  • 14
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    Design of electromagnetic bearing for vibration control of flexible transmission shaft (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Recently magnetic bearings were proposed by several researchers and shown to be viable on a variety of rotor assemblies. The design and construction of such a bearing, which employs features hitherto not used by other workers is examined. These include an original approach to the design of the electromagnets and their amplifiers, and to software in a digital control system, to condition the control signals so as to make the magnets appear to be linear and uncoupled. The resulting system is used to control a rotor-bearing assembly, whose speed range covers two flexural-critical speeds.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 351-364
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  • 15
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    Effects of fluid inertia and turbulence on force coefficients for squeeze film dampers (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effects of fluid inertia and turbulence on the force coefficients of squeeze film dampers are investigated analytically. Both the convective and the temporal terms are included in the analysis of inertia effects. The analysis of turbulence is based on friction coefficients currently found in the literature for Poiseuille flow. The effect of fluid inertia on the magnitude of the radial direct inertia coefficient (i.e., to produce an apparent added mass at small eccentricity ratios, due to the temporal terms) is found to be completely reversed at large eccentricity ratios. The reversal is due entirely to the inclusion of the convective inertia terms in the analysis. Turbulence is found to produce a large effect on the direct damping coefficient at high eccentricity ratios. For the long or sealed squeeze film damper at high eccentricity ratios, the damping prediction with turbulence included is an order of magnitude higher than the laminar solution.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 365-390
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  • 16
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    Analysis for leakage and rotordynamic coefficients of surface roughened tapered annular gas seals (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: In order to soften the effects of rub, the smooth stators of turbine gas seals are sometimes replaced by a honeycomb surface. This deliberately roughened stator and smooth rotor combination retards the seal leakage and may lead to enhanced rotor stability. However, many factors determine the rotordynamic coefficients and little is known as to the effectiveness of these honeycomb seals under various changes in the independent seal parameters. An analytical-computational method to solve for the rotordynamic coefficients of this type of compressible-flow seal is developed. The governing equations for surface roughned tapered annular gas seals are based on a modified Hirs' turbulent bulk flow model. A perturbation analysis is employed to develop zeroth and first-order perturbation equations. These equations are numerically integrated to solve for the leakage, pressure, density, and velocity for small motion of the shaft about the centered position. The resulting pressure distribution is then integrated to find the corresponding rotor-dynamic coefficients.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 341-350
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  • 17
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    Analysis and testing for rotordynamic coefficients of turbulent annular seals with different, directionally homogeneous surface-roughness treatment for rotor and stator elements (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A theory is presented, based on a simple modification of Hirs' turbulent lubrication equations, to account for different but directionally-homogeneous surface roughness treatments for the rotor and stator of annular seals. The theoretical results agree with von Pragenau's predictions that a damper seal which uses a smooth rotor and a rough stator yields more net damping than a conventional seal which has the same roughness for both the rotor and stator. Experimental results for four stators confirm that properly-designed roughened stators yield higher net damping values and substantially less leakage than seals with smooth surfaces. The best seal from both damping and leakage viewpoints uses a round-hole-pattern stator. Initial results for this stator suggest that, within limits, seals can be designed to yield specified ratios of stiffness to damping.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 313-340
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  • 18
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    Identification of dynamic coefficients of annular turbulent seals (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An identification procedure to determine dynamic coefficients of annular turbulent seals in turbopumps is presented. Measurements were carried out at a built test rig with two symmetrical arranged seals. A rigid rotating shaft is surrounded by an elastically supported housing, which is excited by impact forces. The relative radial motion between the rotating parts and the housing, respectively between the seal surfaces, is measured by displacement pick-ups and from the time signals complex frequency response functions can be calculated. Finally an analytical model, depending on the seal parameters, is fitted to the measured data, to find the dynamic coefficients.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 295-312
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  • 19
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    Preliminary investigation of labyrinth packing pressure drops at onset of swirl-induced rotor instability (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Backward and forward subsynchronous instability was observed in a flexible model test rotor under the influence of swirl flow in a straight-through labyrinth packing. The packing pressure drop at the onset of instability was then measured for a range of operating speeds, clearances and inlet swirl conditions. The trend in these measurements for forward swirl and forward instability is generally consistent with the short packing rotor force formulations of Benchert and Wachter. Diverging clearances were also destabilizing and had a forward orbit with forward swirl and a backward orbit with reverse swirl. A larger, stiff rotor model system is now being assembled which will permit testing steam turbine-type straight-through and hi-lo labyrinth packings. With calibrated and adjustable bearings in this new apparatus, direct measure of the net destabilizing force generated by the packings can be made.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 281-294
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  • 20
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    An iwatsubo-based solution for labyrinth seals - comparison with experimental results (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The basic equations are derived for compressible flow in a labyrinth seal. The flow is assumed to be completely turbulent in the circumferential direction where the friction factor is determined by the Blasius relation. Linearized zeroth and first-order perturbation equations are developed for small motion about a centered position by an expansion in the eccentricity ratio. The zeroth-order pressure distribution is found by satisfying the leakage equation while the circumferential velocity distribution is determined by satisfying the momentum equation. The first-order equations are solved by a separation of variables solution. Integration of the resultant pressure distribution along and around the seal defines the reaction force developed by the seal and the corresponding dynamic coefficients. The results of this analysis are compared to published test results.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 257-280
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  • 21
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    Prediction of force coefficients for labyrinth seals (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The development of a linear model for the prediction of labyrinth seal forces and on its comparison to available stiffness data is presented. A discussion of the relevance of fluid damping forces and the preliminary stages of a program to obtain data on these forces are examined. Fluid-dynamic forces arising from nonuniform pressure patterns in labyrinth seal glands are known to be potentially destablizing in high power turbomachinery. A well documented case in point is that of the space Shuttle Main Engine turbopumps. Seal forces are also an important factor for the stability of shrouded turbines, acting in that case in conjunction with the effects of blade-tip clearance variations.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 235-256
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  • 22
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    Analysis of dynamic characteristics of fluid force induced by labyrinth seal (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Flow patterns of the labyrinth seal are experimentally investigated for making a mathematical model of labyrinth seal and to obtain the flow induced force of the seal. First, the flow patterns in the labyrinth chamber are studied on the circumferential flow using bubble and on the cross section of the seal chamber using aluminum powder as tracers. And next, the fluid force and its phase angle are obtained from the measured pressure distribution in the chamber and the fluid force coefficients are derived from the fluid force and the phase angle. Those are similar to the expression of oil film coefficients. As a result, it is found that the vortices exist in the labyrinth chambers and its center moves up and down periodically. The pressure drop is biggest in the first stage of chambers and next in the last stage of chambers.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 211-234
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  • 23
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    Experimental investigation of lateral forces induced by flow through model labyrinth glands (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The lateral forces induced by flow through model labyrinth glands were investigated. Circumferential pressure distributions, lateral forces and stiffness coefficients data obtained are discussed. The force system is represented as a negative spring and a tangential force orthogonal to eccentricity. The magnitude of these forces are dependent on eccentricity, entry swirl, rotor peripheral velocity and seal size. A pressure equalization chamber at midgland tests should in significantly reduced forces and stiffness coefficients.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 187-210
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  • 24
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    Theoretical approach to labyrinth seal forces - cross-coupled stiffness of a straight-through labyrinth seal (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two kinds of three dimensional flows in a labyrinth seal, a jet flow and a core flow, are considered and theoretical equations are set up concerning the motion of each flow. The pressure distribution within the labyrinth is calculated, when the rotor shaft makes a small displacement from the center line of the casing, keeping parallel with it. The theoretical values of cross coupled stiffness obtained by integrating the pressure under different labyrinth geometries and operating conditions through these formulas are compared with the experimental data.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 173-186
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  • 25
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    Two-dimensional unsteady analysis of fluid forces on a whirling centrifugal impeller in a volute (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Destabilizing fluid forces on a whirling centrifugal impeller rotating in a volute were observed. A quasisteady analysis neglecting shed vorticity or an unsteady analysis without a volute does not predict the existence of such destabilizing fluid forces on a whirling impeller. The effects of a volute and the shed vorticity are considered. We treat cases when an impeller with an infinite number of vanes rotates with a constant velocity omega and its center whirls with a constant eccentric radius epsilon and a constant whirling velocity psi. It is assumed that: (1) the number of the vanes is so large that the impeller can be treated as an actuator impeller in which the flow is perfectly guided; (2) flow is inviscid, incompressible and two dimensional; (3) the eccentricity epsilon is so small that unsteady components can be linearized; (4) vorticity is transported on a prescribed mean flow, the operating point is near design flow rate; and (5) the volute can be represented by a curved plate.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 161-172
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  • 26
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    Hydrodynamic impeller stiffness, damping, and inertia in the rotordynamics of centrifugal flow pumps (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The lateral hydrodynamic forces experienced by a centrifugal pump impeller performing circular whirl motions within several volute geometries were measured. The lateral forces were decomposed into: (1) time averaged lateral forces and (2) hydrodynamic force matrices representing the variation of the lateral forces with position of the impeller center. It is found that these force matrices essentially consist of equal diagonal terms and skew symmetric off diagonal terms. One consequence of this is that during its whirl motion the impeller experiences forces acting normal and tangential to the locus of whirl. Data on these normal and tangential forces are presented; it is shown that there exists a region of positive reduced whirl frequencies, within which the hydrodynamic forces can be destablizing with respect to whirl.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 137-160
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  • 27
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    Hydraulic forces on a centrifugal impeller undergoing synchronous whirl (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: High speed centrifugal rotating machinery with large vibrations caused by aerodynamic forces on impellers was examined. A method to calculate forces in a two dimensional orbiting impeller in an unbounded fluid with nonuniform entering flow was developed. A finite element model of the full impeller is employed to solve the inviscid flow equations. Five forces acting on the impeller are: Coriolis forces, centripetal forces, changes in linear momentum, changes in pressure due to rotation and pressure changes due to linear momentum. Both principal and cross coupled stiffness coefficients are calculated for the impeller.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 123-136
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  • 28
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    Lateral fluid forces acting on a whirling centrifugal impeller in vaneless and vaned diffuser (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Fluid forces on a rotating centrifugal impeller in whirling motion were studied. A two dimensional impeller installed in a parallel-walled vaneless and vaned diffuser whirled on a circular orbit with various positive and negative angular velocities. It is shown that the fluid forces exert a damping effect on the rotor in most operating conditions, but become excitatory when the impeller operates at very low partial discharge while rotating far faster than the whirl speed. The fluid forces were expressed in terms of mass, damping and stiffness matrices. Impellers with the same geometry and whirl condition are calculated. Quantitative agreement is obtained especially in positive whirl.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 109-122
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  • 29
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    Internal hysteresis experienced on a high pressure syn gas compressor (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: A vibration instability phenomenon experienced in operating high pressure syn gas centrifugal compressors in two ammonia plants is described. The compressors were monitored by orbit and spectrum analysis for changes from baseline readings. It is found that internal hysteresis was the major destabilizing force; however, the problem was further complicated by seal lockup at the suction end of the compressor. A coupling lockup problem and a coupling fit problem, which frettage of the shaft, are also considered as contributors to the self excited vibrations.
    Keywords: MECHANICAL ENGINEERING
    Type: Rotordynamic Instability Problems in High-Performance Turbomachinery; p 97-108
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  • 30
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    Experimental on-stream elimination of resonant whirl in a large centrifugal compressor (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Resonant whirl condition during operation of a multi-stage centrifugal compressor at higher than anticipated speeds and loads was reported. The condition was diagnosed by a large scale computerized Machinery Condition Monitoring System (MACMOS). This computerized system verified that the predominant subsynchronous whirl frequency locked in on the first resonant frequency of the compressor rotor and did not vary with compressor speed. Compressor stability calculations showed the rotor system had excessive hearing stiffness and inadequate effective damping. An optimum bearing design which was developed to minimize the unbalance response and to maximize the stability threshold is presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 81-95
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    Control of rotordynamic instability in a typical gas turbine's power system (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The effect of rotor internal friction on the system's stability was studied when operated above the first critical speed. This internal friction is commonly caused by sliding press fits or sliding splines. Under conditions of high speed and low bearing damping, these systems will occassionally whirl at a frequency less than the shaft's rotational speed. This subsynchronous precession is a self excited phenomenon and stress reversals are created. This phenomenon was observed during engine testing. The reduction of spline friction and/or the inclusion of squeeze film damping have controlled the instability. Case history and the detail design of the squeeze film dampers is discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 53-80
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  • 32
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    Experiences with nonsynchronous forced vibration in centrifugal compressors (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The high subsynchronous vibrations which are often forced vibrations caused by flow instabilities, such as stage stall were examined. Modifications to improve the rotor stability by changing the bearings or seals have little effects on the subsynchronous vibrations. Understanding of the differences between forced vibrations and self excited vibrations to properly diagnose the problem and to correct it, is recommended. A list of characteristics of the two types of subsynchronous vibration is presented.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 37-52
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  • 33
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    Subsynchronous vibrations in a high pressure centrifugal compressor: A case history (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Two distinct aerodynamically excited vibrations in a high pressure low flow centrifugal compressor are documented. A measured vibration near 21% of running speed was identified as a nonresonant forced vibration which results from rotating stall in the diffuser; a measured vibration near 50% of running speed was identified as a self excited vibration sustained by cross coupling forces acting at the compressor wheels. The dependence of these characteristics on speed, discharge pressure, and changes in bearing design are shown. The exciting mechanisms of diffuser stall and aerodynamic cross coupling are evidenced. It is shown how the rotor characteristics are expected to change as a result of modifications. The operation of the compressor after the modifications is described.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 17-36
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  • 34
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    Full load testing in the platform module prior to tow-out: A case history of subsynchronous instability (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An electric motor driven centrifugal compressor to supply gas for further compression and reinjection on a petroleum production platform in the North Sea was examined. The compressor design, raised concerns about susceptibility to subsynchronous instability. Log decrement, aerodynamic features, and the experience of other compressors with similar ratios of operating to critical speed ratio versus gas density led to the decision to full load test. Mixed hydrocarbon gas was chosen for the test to meet discharge temperature restrictions. The module was used as the test site. Subsynchronous vibrations made the compressor inoperable above approximately one-half the rated discharge pressure of 14500 kPa. Modifications, which includes shortening the bearing span, change of leakage inlet flow direction on the back to back labyrinth, and removal of the vaned diffusers on all stages were made simultaneously. The compressor is operating with satisfactory vibration levels.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Lewis Research Center Rotordynamic Instability Problems in High-Performance Turbomachinery; p 1-16
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  • 35
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    Structural Optimization in automotive design (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Although mathematical structural optimization has been an active research area for twenty years, there has been relatively little penetration into the design process. Experience indicates that often this is due to the traditional layout-analysis design process. In many cases, optimization efforts have been outgrowths of analysis groups which are themselves appendages to the traditional design process. As a result, optimization is often introduced into the design process too late to have a significant effect because many potential design variables have already been fixed. A series of examples are given to indicate how structural optimization has been effectively integrated into the design process.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Langley Research Center Recent Experiences in Multidisciplinary Analysis and Optimization, Part 1; 16 p
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  • 36
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    Inherent Problems in Designing Two-Failure Tolerant Electromechanical Actuators (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An electromechanical ac-powered rotary actuated four-bar linkage system for rotating the Shuttle/Centaur deployment adapter is described. The essential features of the deployment adapter rotation system (DARS) are increased reliability for mission success and maximum practical hazard control for safety. The requirements, concept development, hardware configuration, quality assurance provisions, and techniques used to meet two-fault tolerance requirements are highlighted. The rationale used to achieve a degree of safety equivalent of that of two-failure tolerance is presented. Conditions that make this approach acceptable, including single failure point components with regard to redundancy versus credibility of failure modes, are also discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 155-170
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  • 37
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    Design and test of a low-temperature liner driver/rate controller (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design and testing of a force/rate control device used to deploy an Earth shield on an orbiting satellite is described. Test experience, failure modes, and applications are emphasized.
    Keywords: MECHANICAL ENGINEERING
    Type: The 18th Aerospace Mech. Symp.; p 65-77
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  • 38
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    A passively controlled appendage deployment system for the San Marco D/L spacecraft (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The analytical simulation of deployment dynamics of these two axis concepts as well as the evolution of practical designs for the add on deployable inertia boom units is described. With the boom free to swing back in response to Coriolis forces as well as outwards in response to centrifugal forces, the kinematics of motion are complex but admit the possibility of absorbing deployment energy in frictional or other damping devices about the radial axis, where large amplitude motions can occur and where the design envelope allows more available volume. An acceptable range is defined for frictional damping for any given spin rate. Inadequate damping allows boom motions which strike the spacecraft; excessive damping causes the boom to swing out and latch with damaging violence. The acceptable range is a design parameter and must accommodate spin rate tolerance and also the tolerance and repeatability of the damping mechanisms.
    Keywords: MECHANICAL ENGINEERING
    Type: The 18th Aerospace Mech. Symp.; p 29-48
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  • 39
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    Evolution from a hinge actuator mechanism to an antenna deployment mechanism for use on the European large communications satellite (L-SAT/OLYMPUS) (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The evolution of an Antenna Deployment Mechanism (ADM) from a Hinge Actuator Mechanism (HAM) is described as it pertains to the deployment of large satellite antennas. Design analysis and mechanical tests are examined in detail.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 79-91
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  • 40
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    Status of Understanding for Seal Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Material selection for mainshaft face and ring seals, labyrinth seals, accessory gearbox face seals, and lip seals are discussed in light of tribology requirements and a given seal application. Carbon graphite has been found to be one of the best sealing materials and it is widely used in current gas turbine mainshaft and accessory gearbox seals. Its popularity is due to its unique combination of properties which consists of dimensional stability, corrosion resistance, low friction, good self lubricating characteristics, high thermal conductivity and low thermal expansion, the latter two properties combining to provide good thermal shock resistance. A brief description of the seals and the requirements they must meet are discussed to provide insight into the limitations and advantages of the seals in containing the lubricant. A forecast is made of the operational requirements of main shaft and gearbox seals for advanced engines and candidate materials and coatings that may satisfy these advanced engine requirements.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 811-829
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  • 41
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    Status of Understanding for Gear Materials (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: A wide variety of gear materials is available today for the gear designer. The choice of which material to use should be based on the requirements of the application and will include the operating conditions of load, speed, and temperature in addition to reliability, weight, noise limitation, accuracy, and cost. In aircraft applications such as helicopters, V/STOL aircraft, and turboprops, the dominant factors to be considered are reliability and weight. The following gear materials are reviewed herein with an emphasis upon mechanical properties, cost, and durability: plastics, nonferrous metals, copper alloys, iron alloys, metal powders, and steels.
    Keywords: MECHANICAL ENGINEERING
    Type: Tribology in the 80's, vol. 2; p 795-809
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  • 42
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    Sputtering as a Technique for Applying Tribological Coatings (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Friction and wear-induced mechanical failures may be controlled to extend the life of tribological components through the interposition of selected solid materials between contacting surfaces. Thin solid films of soft and hard materials are appropriate to lower friction and enhance the wear resistance of precision tribo-elements. Tribological characteristics of thin hard coats deposited on a variety of ferrous and non-ferrous substrates were tested. The thin hard coats used were titanium nitride films deposited by reactive magnetron sputtering of metallic titanium. High contact stress, low speed tests showed wear rate reductions of one or more magnitude, even with films a few micrometers in thickness. Low contact stress, high speed tests carried out under rather severe test conditions showed that thin films of TiN afforded significant friction reduction and wear protection. Thin hard coats were shown to improve the friction and wear performance of rolling contacts. Satisfactory film-to-substrate adhesion strengths can be obtained with reactive magnetron sputtering. X-ray diffraction and microhardness tests were employed to assess the effectiveness of the sputtering technique.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 753-772
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  • 43
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    Micro-elastohydrodynamic Lubrication (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Conventional elastohydrodynamics, which is based on assumption of smooth surfaces, is reviewed to show its insufficiency for explaining the failure processes in these contacts. For conditions approaching failure, lubrication breakdown occurs locally at asperity contacts where the lubrication behavior is controlled by microelastohydrodynamic lubrication (micro-EHL). The film formation mechanisms in micro-EHL conjunctions is described. The level of film thickness due to normal approach and sliding of a single asperity and due to asperity-asperity collision between two asperities is assessed. Possible influence of the micro-EHL to incipient scuffing failure, surface crack propagation and wear are discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 615-639
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  • 44
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    Transient EHL Effects in Starved Ball Bearings (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The independent variables used in most calculations for EHL film thickness in ball bearings involve lubricant properties, contact elasticity, load, and bearing kinematics. The calculations are for steady state, and they give a time constant film thickness. Four distinct processes in starved ball bearings which are explained by assuming a time varying film thickness are shown. The four processes and another transient EHL effect which does not involve the thickness of the film are described. A simple model allows direct calculation of several of the thickness transients.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 641-649
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  • 45
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    Real Surface Effects in Elastohydrodynamic Lubrication (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The real effects in electrohydrodynamic lubrication (EHL,) are discussed and the role of stochastic roughness superimposed on the nominal solid boundaries is considered. The full film EHL regime where incipient asperity contact bears a negligible fraction of the load is analyzed. Flow, from which an averaged Reynolds equation can be formed, is nonetheless modified by the amplitude and texture of the roughness patterns. It is found that only two extra parameters are needed, the rms surface height and the ratio of the correlation lengths in the two principal roughness directions. In a lowest order perturbation expansion of these flow factors in powers of the ratio of rms roughness to nominal film thickness, no other properties of the roughness appear. The factors describing Poiseuille flow are separable into the sum of two single surface flow factors which means that a combination of a single equivalent rough surface versus an ideal smooth surface is found. For flow entrained by slip velocity the factors separate instead into a difference of single surface factors and it becomes significant which of the two surfaces carries the equivalent roughness. Applications of the averaged Reynolds equation based on the flow factor method to the EHL line contact problem are discussed. The partial EHL regime is considered where comparable load fractions are carried by the hydrodynamic film and by incipient mechanical contact. An extension of the method into this regime by combining it with asperity contact models appears most encouraging.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 595-614
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  • 46
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    Non-steady State Effects in EHL (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Lubricated machine elements are subjected to cyclic variations of load and speed, particularly in reciprocating machinery. Squeeze film action plays an important role in preserving satisfactory lubricating films in many cases in which the entraining velocities fall to zero during each cycle, as in the reciprocating seal and synovial joints. The essential features of combined entraining and normal motion for hydrodynamic and elastohydrodynamic conditions are described. It is shown that very small squeeze film velocities lead to substantial hydrodynamic action. A squeeze film lubrication between spheres or cylinders and a plane is reviewed by an analysis of ankle joint lubrication. It is shown that elastohydrodynamic lubrication might be encountered in the conjunction between a piston ring and cylinder liner and that combined entraining and squeeze film action is important. The 2 stroke Diesel engine shows that variations in squeeze film velocity throughout the conjunction, associated with time rates of change of elastic deformation, must be considered in a full elastohydrodynamic lubrication analysis.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 579-592
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  • 47
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    Lubricant Rheology in Concentrated Contacts (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Lubricant behavior in highly stressed situtations shows that a Newtonian model for lubricant rheology is insufficient for explanation of traction behavior. The oil film build up is predicted by using a Newtonian lubricant model except at high slide to roll ratios and at very high loads, where the nonNewtonian behavior starts to be important already outside the Hertzian contact area. Static and dynamic experiments are reported. In static experiments the pressure is applied to the lubricant more than a million times longer than in an EHD contact. Depending on the pressure-temperature history of the experiment the lubricant will become a crystallized or amorphous solid at high pressures. In dynamic experiments, the oil is in an amorphous solid state. Depending on the viscosity, time scale, elasticity of the oil and the bearing surfaces, the oil film pressure, shear strain rate and the type of lubricant, different properties of the oil are important for prediction of shear stresses in the oil. The different proposed models for the lubricant, which describe it to a Newtonian liquid, an elastic liquid, a plastic liquid and an elastic-plastic solid.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 555-572
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  • 48
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    Elastohydrodynamic Lubrication. Status of Understanding (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The development of elastohydrodynamic lubrication which was divided into three main stages is discussed. The first stage is the development of the idealized form of elastohydrodynamic lubrication, where the surfaces are smooth, the fluid behavior is assumed to be Newtonian, and isothermal considerations are assumed. The complete spectrum of contact geometries contact materials and lubricant availability are presented. The second state of development incorporates the effects of a nonNewtonian fluid model, thermal effects, and surface roughness effects into the elastohydrodynamic lubrication model developed in stage one. Recent developments in this stage are presented. The third stage considers the items considered in stage two, the lubrication of real surfaces in their operating environments is examined.
    Keywords: MECHANICAL ENGINEERING
    Type: Tribology in the 80's, vol. 2; p 507-531
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  • 49
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    Temperature Effects in Elastohydrodynamically Lubricated Contacts (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Thermal phenomena in elastohydrodynamic contacts are reviewed. Measured temperatures are presented for representative conditions and ranges of operating parameters. Temperatures can range from bulk ambient temperature to several hundred degrees centigrade in fully separated elastohydrodynamic films. The mixed elastohydrodynamic films are outlined. These mixed conditions are common in tribological systems and conditions that border on unsuccessful run-in and failure of the elastohydrodynamic contact. In mixed film conditions local hot spots can have temperatures of the order of 1000 C which cause increased reactivity of the surfaces with surrounding materials and changes of the surface physical properties so important to the operation of concentrated contacts. The bulk system thermal transients which occur in tribological systems is discussed. These transients are frequently long in duration and have a direct bearing on the elastohydrodynamic film thickness and traction.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's, vol. 2; p 533-548
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  • 50
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    Antiwear Additive Mechanisms in Sliding Contacts (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The possible mechanisms associated with wear in a sliding contact and how an oil and antiwear additive can mitigate wear or prevent catastropic seizure of the contacting parts was examined. The various load and temperature regimes are examined and the mechanisms which are predominant under these conditions are determined. The critical mechanism(s) depend on the test parameters, particularly load and temperature, although sliding speed is also a factor. Different ways to improve the efficiency of antiwear additives are suggested.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 391-413
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  • 51
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    Considerations in Friction and Wear (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The abrasion of ceramic materials is discussed. The friction and wear properties of ceramics which arise primarily from adhesion between sliding surfaces in contact was examined. The role of chemical bonding in adhesion and friction and the influence of surface films, temperature, and crystallographic orientation effects on tribological response with respect to adhesion, friction, and wear are discussed. The complex interaction of various deformation and fracture mechanisms in ceramics, the effect of crystallographic orientation on abrasion, friction, and fracture behavior is addressed.
    Keywords: MECHANICAL ENGINEERING
    Type: Tribology in the 80's. Vol. 1; p 291-320
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  • 52
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    Importance of Properties of Solids to Friction and Wear Behaviour (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: The main properties of solids which influence friction and wear are discussed and published rules which relate material properties to friction and wear are considered. In addition, recent experimental results on the tribological behaviour of metals and polymers illustrating the effect of some important interaction characteristics on friction and wear are presented. Finally, a framework for the systematic compilation and documentation of relevant tribological parameters in experimental friction and wear investigations is given.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 71-106
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  • 53
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    Future Directions of Research in Adhesion and Friction. Status of Understanding (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-11
    Description: Four main classes of materials are covered: metals, ceramics, elastomers and polymers. In dealing with adhesion a distinction is drawn between adhesion (which often involves thermodynamic concepts) and the observed adhesive strength, here designated as the pull-off force. With metals the level of understanding of the interfacial bond is well understood theoretically and was elegantly studied experimentally. However the role of surface roughness and especially ductility needs to be incorporated into an overall view of metallic adhesion. The effect of contaminant films has not gone far beyond purely descriptive language. The friction of metals is understood in terms of surface topography, adhesion and deformation and there are now promising solutions using slipline-field theory. These do not however, cope very satisfactorily with work hardening. For surfaces sliding at higher speeds there are now good models which deal with asperity instabilities produced by frictional heating.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 119-139
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  • 54
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    Frictional and morphological properties of Au-MoS2 films sputtered from a compact target (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: AuMoS2 films 0.02 to 1.2 microns thick were sputtered from target compacted from 5 wt pct. Au + 95 wt pct. MoS2, to investigate the frictional and morphological film growth characteristics. The gold dispersion effects in MoS2 films are of interest to increase the densitification and strengthening of the film structure. Three microstructural growth stages were identified on the nano-micro-macrostructural level. During sliding both sputtered Au-MoS2 and MoS2 films have a tendency to break within the columner region. The remaining or effective film, about 0.2 microns thick, performs the lubrication. The Au-MoS2 films displayed a lower friction coefficient with a high degree of frictional stability and less wear debris generation as compared to pure MoS2 films. The more favorable frictional characteristics of the Au-MoS2 films are attributed to the effective film thickness and the high density packed columner zone which has a reduced effect on the fragmentation of the tapered crystallites during fracture.
    Keywords: MECHANICAL ENGINEERING
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  • 55
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    Substrate heating rates for planar and cylindrical-post magnetron sputtering sources (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Results are presented for the substrate heating energy/atom required in the planar magnetron sputtering of Al, Cr, Ni, Cu, Mo, In, Ta, W, and Pt in Ar, as well as Al and Cr in O2. Data are also obtained for cylindrical magnetron sputtering of Nb, Ag, Ta, W, and Pb-Sn in Ar, and Mo sputtered in Ne, Ar, Kr, and Xe. Planar and cylindrical magnetron heating rates were comparable. Special experiments were conducted to examine the contributions to substrate heating of plasma species and ion neutralization and reflection at the cathode; the results obtained indicate that charged plasma species do not significantly contribute to the heating, but that neutralized and reflected ions play a significant role in the planar as well as cylindrical cases despite the differences in cathode geometry.
    Keywords: MECHANICAL ENGINEERING
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  • 56
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    Vibration of a hydrostatic gas bearing due to supply pressure oscillations (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating supply pressure is investigated. Both angular and radial vibration modes are analyzed. The time-dependent Reynolds equation governing the pressure distribution between the oscillating journal and the sleeve is solved numerically together with the journal equation of motion to obtain the response characteristics of the bearing. The Reynolds equation and the equation of motion are simplified by applying regular perturbation theory for small displacements. The results presented include Bode plots of bearing oscillation gain and phase for a particular bearing configuration for various combinations of parameters over a range of frequencies, including the resonant frequency. The results are compared with the results of an earlier study involving the response of a similar bearing to oscillating exhaust pressure.
    Keywords: MECHANICAL ENGINEERING
    Type: Wear (ISSN 0043-1648); 95; 199-212
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  • 57
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    Formation and destruction of vortices in a motored four-stroke piston-cylinder configuration (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Previously cited in issue 05, p. 652, Accession no. A83-16749
    Keywords: MECHANICAL ENGINEERING
    Type: AIAA Journal (ISSN 0001-1452); 22; 948
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  • 58
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    Dynamic characteristics of a hydrostatic gas bearing driven by oscillating exhaust pressure (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Vibration of a statically loaded, inherently compensated hydrostatic journal bearing due to oscillating exhaust pressure is investigated. Both angular and radial vibration modes are analyzed. The time-dependent Reynolds equation governing the pressure distribution between the oscillating journal and sleeve is solved together with the journal equation of motion to obtain the response characteristics of the bearing. The Reynolds equation and the equation of motion are simplified by applying regular perturbation theory for small displacements. The numerical solutions of the perturbation equations are obtained by discretizing the pressure field using finite-difference aproximations with a discrete, nonuniform line-source model which excludes effects due to feeding hole volume. An iterative scheme is used to simultaneously satisfy the equations of motion for the journal. The results presented include Bode plots of bearing-oscillation gain and phase for a particular bearing configuration for various combinations of parameters over a range of frequencies, including the resonant frequency.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Tribology (ISSN 0742-4787); 106; 477-483
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    A device for applying plastic film antireflection coatings to optical elements (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: To simplify the process of thermally bonding thin plastic films to optical elements and to help eliminate the source of the flaws, a film-application device (FAD) is developed. Any plastic film may be used to make the coatings, but thin polyethylene is particularly useful for this application since it is readily available. If more than one layer of polyethylene is required, several layers may be applied, one layer at a time. The coatings may be used for protecting optical elements or to reduce surface reflection of radiation with wavelengths greater than 20 microns. When the FAD is used without the central plate it may be used to stretch single sheets of plastic material to make pellicles or beam-splitters for many applications.
    Keywords: MECHANICAL ENGINEERING
    Type: Infrared Physics (ISSN 0020-0891); 24; 567-569
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  • 60
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    Frictional and morphological properties of Au-MoS2 films sputtered from a compact target (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: AuMoS2 films 0.02 to 1.2 microns thick were sputtered from target compacted from 5 wt percent Au + 95 wt percent MoS2, to investigate the frictional and morphological film growth characteristics. The gold dispersion effects in MoS2 films are of interest to increase the densification and strengthening of the film structure. Three microstructural growth stages were identified on the nano-micro-macrostructural level. During sliding both sputtered Au-MoS2 and MoS2 films have a tendency to break within the columner region. The remaining or effective film, about 0.2 microns thick, performs the lubrication. The Au-MoS2 films displayed a lower friction coefficient with a high degree of frictional stability and less wear debris generation as compared to pure MoS2 films. The more favorable frictional characteristics of the Au-MoS2 films are attributed to the effective film thickness and the high density packed columner zone which has a reduced effect on the fragmentation of the tapered crystallites during fracture.
    Keywords: MECHANICAL ENGINEERING
    Type: Thin Solid Films (ISSN 0040-6090); 118; 375-384
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    Elastohydrodynamic lubrication of line contacts (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An isothermal elastohydrodynamically lubricated rectangular contact was evaluated numerically. This required the simultaneous solution of the elasticity and Reynolds equations. In the elasticity analysis the contact zone was divided into equal rectangular areas, and it was assumed that a uniform pressure was applied over each area. The elastohydrodynamic lubrication theory thus developed was used to investigate the influence of the dimensionless speed, load, and materials parameters on minimum film thickness. Ten cases were used in obtaining the minimum film thickness formula. Plots are shown that indicate the details of the pressure distribution, film shape, and flow. The characteristic pressure spike is clearly in evidence as is the parallel film shape through the central portion of the contact, with a minimum film thickness occurring near the outlet of the contact.
    Keywords: MECHANICAL ENGINEERING
    Type: ASLE Transactions; 27; 275-286;
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    Two-region analysis of interface shape in continuous casting with superheated liquid (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A slab ingot is being formed as a continuous casting by withdrawal from a mold with parallel walls. The sides of the ingot below the mold are cooled to remove heat of fusion and energy transferred to the solidification interface by superheated liquid metal in the mold. A two-region analysis is made to determine the non-uniform heat conduction from the liquid metal to the interface, and then from the interface to the cooled ingot sides. The solidification interface shape is found that is compatible with the removal of fusion energy and nonuniform heating from the liquid. The solution is obtained by two applications of a Cauchy boundary value method.
    Keywords: MECHANICAL ENGINEERING
    Type: ASME, Transactions, Journal of Heat Transfer (ISSN 0022-1481); 106; 506-511
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    Overview of Advanced Stirling and Gas Turbine Engine Development Programs and Implications for Solar Thermal Electrical Applications (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The DOE automotive advanced engine development projects managed by the NASA Lewis Research Center were described. These included one Stirling cycle engine development and two air Brayton cycle development. Other engine research activities included: (1) an air Brayton engine development sponsored by the Gas Research Institute, and (2) plans for development of a Stirling cycle engine for space use. Current and potential use of these various engines with solar parabolic dishes were discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: JPL Proc. of the 5th Parabolic Dish Solar Thermal Power Program; p 49
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    Design of a precision etalon position control system for a cryogenic spectrometer (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Upper Atmosphere Research Satellite (UARS) will be launched in 1988 to study the distribution of a series of trace elements in the upper atmosphere and to study atmospheric dynamics. The UARS carries on board a cryogenically cooled infrared spectrometer to measure the concentration of a series of chemical species that are important for understanding the ozone layer in the stratosphere. This device, known as the Cryogenic Limb Array Etalon Spectrometer (CLAES), uses a multiposition filter wheel combined with tilt-scanned Fabry Perot etalons to obtain the high resolution required for these experiments. The CLAES optical system is sealed in a dewar where it is maintained at cryogenic temperatures by a supply of solid hydrogen. Operating temperatures for CLAES range from 130 K at the entrance aperture to 13 K at the focal plane. The design and test of a special control system using a unique actuator concept to provide position and can control for the CLAES etalon are described. Results of performance tests at cryogenic temperatures simulating the CLAES on-orbit environment are discussed.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 243-262
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    The design and development of a release mechanism for space shuttle life-science experiments (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design, development, and testing of a release mechanism for use in two life science experiments on the Spacelab 1, 4, and D1 missions is described. The mechanism is a self latching ball lock device actuated by a linear solenoid. An unusual feature is the tapering of the ball lock plunger to give it a near constant breakout force for release under a wide range of loads. The selection of the design, based on the design requirements, is discussed. A number of problems occurred during development and test, including problems caused by human factors that became apparent after initial delivery for crewtraining sessions. These problems and their solutions are described to assist in the design and testing of similar mechanisms.
    Keywords: MECHANICAL ENGINEERING
    Type: The 18th Aerospace Mech. Symp.; p 1-14
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  • 66
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    Load positioning system with gravity compensation (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A load positioning system with gravity compensation has a servomotor, position sensing feedback potentiometer and velocity sensing tachometer in a conventional closed loop servo arrangement to cause a lead screw and a ball nut to vertically position a load. Gravity compensating components comprise the DC motor, gears, which couple torque from the motor to the lead screw, and constant current power supply. The constant weight of the load applied to the lead screw via the ball nut tend to cause the lead screw to rotate, the constant torque of which is opposed by the constant torque produced by the motor when fed from the constant current source. The constant current is preset as required by the potentiometer to effect equilibration of the load which thereby enables the positioning servomotor to see the load as weightless under both static and dynamic conditions. Positioning acceleration and velocity performance are therefore symmetrical.
    Keywords: MECHANICAL ENGINEERING
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  • 67
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    Separator plugs for liquid helium (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Work performed during Summer 1984 (from June to Sept. 30) in the area of porous media for use in low temperature applications is discussed. Recent applications are in the area of vapor - liquid phase separation, pumping based on the fountain effect and related subsystems. Areas of potential applications of the latter are outlined in supplementary work. Experimental data have been developed. The linear equations of the two-fluid model are inspected critically in the light of forced convection evidence reported recently. It is emphasized that the Darcy permeability is a unique throughput quantity in the porous media application areas whose use will permit meaningful comparisons of data not only in one lab but also within a group of labs doing porous plug studies.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-176545 , NAS 1.26:176545 , UCLA-ENG-8436
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  • 68
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    Design and performance analysis of gas sorption compressors (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Compressor kinetics based on gas adsorption and desorption processes by charcoal and for gas absorption and desorption processes by LaNi5 were analyzed using a two-phase model and a three-component model, respectively. The assumption of the modeling involved thermal and mechanical equilibria between phases or among the components. The analyses predicted performance well for compressors which have heaters located outside the adsorbent or the absorbent bed. For the rapidly-cycled compressor, where the heater was centrally located, only the transient pressure compared well with the experimental data.
    Keywords: MECHANICAL ENGINEERING
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  • 69
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    Magnetic Refrigeration Development (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-12
    Description: Magnetic refrigeration is being developed to determine whether it may be used as an alternative to the Joule-Thomson circuit of a closed cycle refrigerator for providing 4 K refrigeration. An engineering model 4-15 K magnetic refrigerator has been designed and is being fabricated. This article describes the overall design of the magnetic refrigerator.
    Keywords: MECHANICAL ENGINEERING
    Type: The Telecommun. and Data Acquisition Rept.; p 49-58
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  • 70
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    Status and Direction of Tribology as a Science in the 80's. Understanding and Prediction (1984)
    In:  CASI
    Details
    Publication Date: 2014-09-10
    Description: The most challenging research problems in tribology for the next decade or beyond are classified horizontally into two categories: (1) understanding of basic mechanisms and (2) prediction of practical performance. Vertical classifications are in terms of particular themes or fields of interest. Areas where more fundamental work is required are: adhesion and friction of clean and contaminated surfaces; lubrication; new materials; surface characterization at the engineering level (topography) and at the atomic levels (various spectroscopies); and wear.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA Lewis Research Center Tribology in the 80's. Vol. 1; p 1-17
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  • 71
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    The electron Echo 6 mechanical deployment systems (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The Echo 6 sounding rocket payload was flown on a Terrier boosted Black Brant vehicle on March 30, 1983. The experiment requirements resulted in the new design of a rocket propelled Throw Away Detector System (TADS) with onboard Doppler radar, a free-flyer forward experiment designated the Plasma Diagnostic Package (PDP), and numerous other basic systems. The design, developmental testing, and flight preparations of the payload and the mechanical deployment systems are described.
    Keywords: MECHANICAL ENGINEERING
    Type: The 18th Aerospace Mech. Symp.; p 263-276
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    Antenna tracking mechanism for geostationary satellites (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The design and development of a continuous duty cycle antenna tracking mechanism (ATM) for geostationary communications satellites is described. The FACC requirements for an ATM and description of the development mechanism designed and built for the program are presented. The mechanism mechanical configuration and component performance is documented along with its launch and operational constraints. The proposed development tests and the results of computer simulations are discussed. The advantages of this mechanism are its simplicity with inherent reliability, low mass, high stiffness, and ability to accurately point a wide range of antenna sizes.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 203-214
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    The design and development of a solar tracking unit (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The solar tracking unit was developed to support the Laser Heterodyne Spectrometer (LHS) airborne instrument, but has application to a general class of airborne solar occultation research instruments. The unit consists of a mirror mounted on two gimbals, one of which is hollow. The mirror reflects a 7.6 cm (3.0 in.) diameter beam of sunlight through the hollow gimbal into the research instrument optical axis. A portion of the reflected sunlight is directed into a tracking telescope which uses a four quadrant silicon detector to produce the servo error signals. The colinearity of the tracker output beam and the research instrument optical axis is maintained to better than + or - 1 arc-minute. The unit is microcomputer controlled and is capable of stand alone operation, including automatic Sun acquisition or operation under the control of the research instrument.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 187-201
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  • 74
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    The design and development of two-failure tolerant mechanisms for the Spaceborne Imaging Radar (SIR-B) antenna (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The performance requirements, design constraints, and design qualification status of the mechanisms necessary to restrain, deploy, and stow the Spaceborne Imaging Radar (SIR) B antenna experiment on the Shuttle Orbiters are described.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 131-154
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    The importance of thermal-vacuum testing in achieving high reliability of spacecraft mechanisms (1984)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The work performed on thermal vacuum testing of complex mechanisms is described. The objective of these tests is to assess the mechanism reliability by monitoring performance in an environment that closely resembles the environment that will occur during flight. To be both valid and cost effective, these tests are performed in a detailed, formally controlled manner. A review of the major test observations is given, during which time some failure modes are detected. Full confidence now exists in many mechanism and component designs, and much valuable data obtained.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA. Goddard Space Flight Center The 18th Aerospace Mech. Symp.; p 93-109
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    Solid lubrication desgin methodology (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-01-25
    Keywords: MECHANICAL ENGINEERING
    Type: Society of Automotive Engineers, Inc. Proc. of the 21st Automotive Technol. Develop. Contractors' Meeting; p 241-252
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  • 77
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    Advanced on-board storage concepts for compressed natural gas fueled automotive vehicles (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Keywords: MECHANICAL ENGINEERING
    Type: Society of Automotive Engineers, Inc. Proc. of the 21st Automotive Technol. Develop. Contractors' Meeting; p 377-382
    Format: text
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  • 78
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    NASA welding assessment program (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A long duration test has been conducted for comparing various methods of attaching electrical interconnects to solar cells for near Earth orbit spacecraft. Representative solar array modules have been thermally cycled for 36,000 cycles between -80 and +80 C on this JPL and NASA Lewis Research Center sponsored work. This test simulates the environmental stress of more than 6 years on a near Earth spacecraft as it cycles in and out of the Earth's shadow. Evaluations of the integrity of these modules were made by visual and by electrical examinations before starting the cycling and then at periodic intervals during the cycling tests. Modules included examples of parallel gap and of ultrasonic welding, as well as soldering. The materials and fabrication processes are state of the art, suitable for forming large solar arrays of spacecraft quality. The modules survived his extensive cycling without detectable degradation in their ability to generate power under sunlight illumination.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-175682 , JPL-9950-1069 , NAS 1.26:175682
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  • 79
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    Development of robots and application to industrial processes (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An algorithm is presented for using a robot system with a single camera to position in three-dimensional space a slender object for insertion into a hole; for example, an electrical pin-type termination into a connector hole. The algorithm relies on a control-configured end effector to achieve the required horizontal translations and rotational motion, and it does not require camera calibration. A force sensor in each fingertip is integrated with the vision system to allow the robot to teach itself new reference points when different connectors and pins are used. Variability in the grasped orientation and position of the pin can be accomodated with the sensor system. Performance tests show that the system is feasible. More work is needed to determine more precisely the effects of lighting levels and lighting direction.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-175754 , NAS 1.26:175754
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  • 80
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    Arc-driven rail gun research (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The equations describing the performance of an inductively-driven rail gun are analyzed numerically. Friction between the projectile and rails is included through an empirical formulation. The equations are applied to the experiment of Rashleigh and Marshall to obtain an estimate of energy distribution in rail guns as a function of time. The effect of frictional heat dissipation on the bore of the gun is calculated. The mechanism of plasma and projectile acceleration in a dc rail gun is described from a microscopic point of view through the establishment of the Hall field. The plasma conductivity is shown to be a tensor indicating that there is a small component of current parallel to the direction of acceleration. The plasma characteristics are evaluated as a function of plasma mass through a simple fluid mechanical analysis of the plasma. By equating the energy dissipated in the plasma with the radiation heat loss, the properties of the plasma are determined.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-174816 , NAS 1.26:174816
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  • 81
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    NASA welding assessment program (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A long duration test was conducted for comparing various methods of attaching electrical interconnects to solar cells for near Earth orbit spacecraft. Representative solar array modules were thermally cycled for 36,000 cycles between -80 and +80 C. The environmental stress of more than 6 years on a near Earth spacecraft as it cycles in and out of the earth's shadow was simulated. Evaluations of the integrity of these modules were made by visual and by electrical examinations before starting the cycling and then at periodic intervals during the cycling tests. Modules included examples of parallel gap and of ultrasonic welding, as well as soldering. The materials and fabrication processes are state of the art, suitable for forming large solar arrays of spacecraft quality. The modules survived this extensive cycling without detectable degradation in their ability to generate power under sunlight illumination.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-175512 , NAS 1.26:175512
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  • 82
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    Ingot slicing machine and method (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An improved method for simultaneously slicing one or a multiplicity of boules of silicon into silicon wafers is described. A plurality of vertical stacks of horizontal saw blades of circular configuration are arranged in juxtaposed coaxial alignment. Each blade is characterized by having a cutting diameter slightly greater than the cutting diameter of the blade arranged immediately above, imparting a simultaneous rotation to the blades.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:NPO-15483-1
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    Connection system (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A mechanical connection system comprises a first body defining a receptable and a second body defining a pin matingly receivable in the receptacle by relative movement in a first directional mode. A primary latch is engagable between the two bodies to retain the pin in the receptacle. The primary latch is reciprocable in a second directional mode transverse to the first directional mode. A lock member carried by one of the bodies is operatively associated with the primary latch and movable, transverse to the second directional mode, between a locking position maintaining engagement of the primary latch and a releasing position permitting release of the primary latch. The lock includes an operator portion engagable to move the lock member from its locking position to its releasing position. The operator is located internally of the first body. An actuator is selectivity insertable into and disengagable from the first body. The actuator is movable relative to the first body when it is inserted for engagement with and operation of the operator.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:MSC-20319-1
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  • 84
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    Materials testing of the IUS techroll seal material (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: As a part of the investigation of the control system failure Inertial Upper Stage on IUS-1 flight to position a Tracking and Data Relay Satellite (TDRS) in geosynchronous orbit, the materials utilized in the techroll seal are evaluated for possible failure models. Studies undertaken included effect of temperature on the strength of the system, effect of fatigue on the strength of the system, thermogravimetric analysis, thermomechanical analysis, differential scanning calorimeter analysis, dynamic mechanical analysis, and peel test. The most likely failure mode is excessive temperature in the seal. In addition, the seal material is susceptible to fatigue damage which could be a contributing factor.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-86462 , NAS 1.15:86462
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  • 85
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    Thermal analysis of a planetary transmission with spherical roller bearings operating after complete loss of oil (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Planetsys and Spherbean, two computer programs developed for the analysis of rolling element bearings, were used to simulate the thermal performance of an OH-58 helicopter main rotor transmission. A steady state and a transient thermal analysis were made and temperatures thus calculated were compared with experimental data obtained from a transmission that was operated to destruction, which occurred about 30 min after all the oil was drained from the transmission. Temperatures predicted by Spherbean were within 3% of the corresponding measured values at 15 min elapsed time and within 9% at 25 min. Spherbean also indicates a potential for high bearing cage temperatures with misalignment and outer ring rotation.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2367 , E-2008 , NAS 1.60:2367
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  • 86
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    Radial SI latches vibration test data review (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Dynamic testing of the Space Telescope Scientific Instrument Radial Latches was performed as specified by the designated test criteria. No structural failures were observed during the test. The alignment stability of the instrument simulator was within required tolerances after testing. Particulates were discovered around the latch bases, after testing, due to wearing at the B and C latch interface surfaces. This report covers criteria derivation, testing, and test results.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-86454 , NAS 1.15:86454
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  • 87
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    Testing and evaluation of Vespel up to 450 deg F when used in nuts and bolts as a self-locking element (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The object of this investigation was to evaluate Vespel for potential application on the Solid Rocket Booster to replace all-metal deformed self-locking nuts and anchor nuts and be used as self-locking elements for bolts and screws. The Vespel self-locking elements were tested for prevailing torque retention at room temperature, after heating to 450 F and exposure for 3 hr, breakaway torque at 450 F and for vibration at a level consistent with the maximum expected on the SRB at lift-off and reentry. The investigation revealed Vespel has properties that can provide a self-locking capability for threaded fasteners up to 450 F and it can be used in nuts and anchor nuts for installation on the SRB. Vespel elements in bolts did not meet all our SRB requirements for reuse, however, we have defined a design for Vespel elements in nuts/anchor nuts that fully meets all requirements. It is recommended that No. 1, 1/4 in. and 5/16 in. nuts/anchor nuts be procured for use on the SRB. This system will eliminate the galling problems now encountered and achieve a much higher reuse life than the present deformed nut design.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TM-86456 , NAS 1.15:86456
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  • 88
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    Operating characteristics of a three-piece-inner-ring large-bore roller bearing to speeds of 3 million DN (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A 118 mm bore roller bearing with a three piece inner ring ran successfully at 300,000 DN for 20 hr. Provisions were made for lubrication and cooling through the inner ring. In some tests the outer ring was also cooled. Power loss within the bearing increased with both speed and total oil flow rate to the inner ring. Outer ring temperature decreased by as much as 22 K (40 F) when outer ring cooling was employed whereas inner ring temperature remained essentially constant. Cage slip was greatly reduced or even eliminated by using a bearing with a very tight clearance at operating speed. A three piece inner ring bearing had higher inner ring temperatures and less temperature difference between the inner and outer rings than a conventional one piece inner ring bearing.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2355 , E-1806 , NAS 1.60:2355
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  • 89
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    Tubing and cable cutting tool (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A hand held hydraulic cutting tool was developed which is particularly useful in deactivating ejection seats in military aircraft rescue operations. The tool consists primarily of a hydraulic system composed of a fluid reservoir, a pumping piston, and an actuator piston. Mechanical cutting jaws are attached to the actuator piston rod. The hydraulic system is controlled by a pump handle. As the pump handle is operated the actuator piston rod is forced outward and thus the cutting jaws are forced together. The frame of the device is a flexible metal tubing which permits easy positioning of the tool cutting jaws in remote and normally inaccessible locations. Bifurcated cutting edges ensure removal of a section of the tubing or cable to thereby reduce the possibility of accidental reactivation of the tubing or cable being severed.
    Keywords: MECHANICAL ENGINEERING
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  • 90
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    Directional gear ratio transmissions (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Epicyclic gear transmissions which transmit output at a gear ratio dependent only upon the input's direction are considered. A transmission housing envelops two epicyclic gear assemblies, and has shafts extending from it. One shaft is attached to a sun gear within the first epicyclic gear assembly. Planet gears are held symmetrically about the sun gear by a planet gear carrier and are in mesh with both the sun gear and a ring gear. Two unidirectional clutches restrict rotation of the first planet gear carrier and ring gear to one direction. A connecting shaft drives a second sun gear at the same speed and direction as the first planet gear carrier while a connecting portion drives a second planet gear carrier at the same speed and direction as the first ring gear. The transmission's output is then transmitted by the second ring gear to the second shaft. Input is transmitted at a higher gear ratio and lower speed for all inputs in the first direction than in the opposite direction.
    Keywords: MECHANICAL ENGINEERING
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  • 91
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    Workpiece positioning vise (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A pair of jaw assemblies simultaneously driven in opposed reciprocation by a single shaft has oppositely threaded sections to automatically center delicate or brittle workpieces such as lithium fluoride crystal beneath the blade of a crystal cleaving machine. Both jaw assemblies are suspended above the vise bed by a pair of parallel guide shafts attached to the vise bed. Linear rolling bearings, fitted around the guide shafts and firmly held by opposite ends of the jaw assemblies, provide rolling friction between the guide shafts and the jaw assemblies. A belleville washer at one end of the drive shaft and thrust bearings at both drive shaft ends hold the shaft in compression between the vise bed, thereby preventing wobble of the jaw assemblies due to wear between the shaft and vise bed.
    Keywords: MECHANICAL ENGINEERING
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  • 92
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    Apparatus for and method of compensating dynamic unbalance (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An apparatus to stabilize a fine platform that carries a parabolic reflecting dish, utilized in connection with the large aperture, multichannel microwave radiometer, is discussed. It provides compensation for dynamic unbalance imparted to a fixed body by a shaft about which the rotating body rotates. Force components exerted on the fixed body by the rotating body in a plane at right angles to the axis are determined. In response to the determined force components, the rotational speed and effective direction of mass means mounted on the rotating body are controlled. The mass means has an effective axis of rotation in a plane at right angles to the longitudinal axis.
    Keywords: MECHANICAL ENGINEERING
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  • 93
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    Centrifugal-reciprocating compressor (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A centrifugal compressor is described which includes at least one pair of cylinders arranged in coaxial alignment and supported for angular displacement about a common axis of rotation normally disecting a common longitudinal axis of symmetry for the cylinders. The cylinders are characterized by ported closures located at the mutually remote ends thereof through which the cylinders are charged and discharged, and a pair of piston heads seated within the cylinders and supported for floating displacement in compressive strokes in response to unidirectional angular displacement imparted to the cylinders.
    Keywords: MECHANICAL ENGINEERING
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  • 94
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    Research study for effects of case flexibility on bearing loads and rotor stability (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods to evaluate the effect of casing flexibility on rotor stability and component loads were developed. Recent Rocketdyne turbomachinery was surveyed to determine typical properties and frequencies versus running speed. A small generic rotor was run with a flexible case with parametric variations in casing properties for comparison with a rotor attached to rigid supports. A program for the IBM personal computer for interactive evaluation of rotors and casings is developed. The Root locus method is extended for use in rotor dynamics for symmetrical systems by transforming all motion and coupling into a single plane and using a 90 degree criterion when plotting loci.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-171147 , NAS 1.26:171147 , RI/RD84-191
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  • 95
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    Diesel engine catalytic combustor system (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A low compression turbocharged diesel engine is provided in which the turbocharger can be operated independently of the engine to power auxiliary equipment. Fuel and air are burned in a catalytic combustor to drive the turbine wheel of turbine section which is initially caused to rotate by starter motor. By opening a flapper value, compressed air from the blower section is directed to catalytic combustor when it is heated and expanded, serving to drive the turbine wheel and also to heat the catalytic element. To start, engine valve is closed, combustion is terminated in catalytic combustor, and the valve is then opened to utilize air from the blower for the air driven motor. When the engine starts, the constituents in its exhaust gas react in the catalytic element and the heat generated provides additional energy for the turbine section.
    Keywords: MECHANICAL ENGINEERING
    Type: NAS 1.71:LEW-12995-1
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  • 96
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    Characterization of erosion of metallic materials under cavitation attack in a mineral oil (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Cavitation erosion and erosion rates of eight metallic materials representing three crystal structures were studied using a 20-kHz ultrasonic magnetostrictive oscillator in viscous mineral oil. The erosion rates of the metals with an fcc matrix were 10 to 100 times higher than that of an hcp-matrix titanium alloy. The erosion rates of iron and molybdenum, with bcc matrices, were higher than that of the titanium alloy but lower than those of the fcc metals. Scanning electron microscopy indicates that the cavitation pits are initially formed at the grain boundaries and precipitates and that the pits that formed at the triple points grew faster than the others. Transcrystalline craters formed by cavitation attack over the surface of grains and roughened the surfaces by multiple slip and twinning. Surface roughness measurements show that the pits that formed over the grain boundaries deepended faster than other pits. Computer analysis revealed that a geometric expression describes the nondimensional erosion curves during the time period 0.5 t(0) t 2.5 t(0), where t(0) is the incubation period. The fcc metals had very short incubation periods; the titanium alloy had the longest incubation period.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2368 , E-2049 , NAS 1.60:2368
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  • 97
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    Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The reusable design of the Space Shuttle requires a target life of 7.5 hours for the turbopumps of the Space Shuttle main engine (SSME). This large increase from the few hundred seconds required in single-use rockets has caused various problems with the bearings of the turbopumps. The berings of the high pressure oxygen turbopump (HPOTP) were of particular concern because of wear, spalling, and cage failures at service time well below the required 7.5 hours. Lubrication and wear data were developed for the bearings. Since the HPOTP bearings operate in liquid oxygen, conventional liquid lubricants cannot be applied. Therefore, solid lubricant coatings and lubricant transfer from the polytetrafluorethylene (FTFE) cage were the primary lubrication approaches for the bearings. Measurements were made using liquid nitrogen in a rolling disk machine to determine whether usable elastohydrodynamic films could be generated to assist in the bearing lubrication.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-171008 , NAS 1.26:171008
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  • 98
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    Effects of bearing deadbands on bearing loads and rotor stability (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A generic model of a turbopump, simplified to bring out these effects is examined. This model demonstrates that bearing deadbands which are of the same order of magnitude or larger than the center-of-mass offset of a rotor due to mass imbalances cause significantly different dynamic behavior than would be expected of a linear, dynamical system. This fundamentally nonlinear behavior yields altered stability characteristics and altered bearing loading tendencies. It is shown that side forces can enhance system stability in the small, i.e., as long as the mass imbalance does not exceed some thresholds value or as long as no large, impulsive disturbances cause the motion to depart significantly from the region of stability. Limit cycles are investigated in this report and techniques for determining these limit cycles are developed. These limit cycles are the major source of bearing loading and appear in both synchronous and nonsynchronous forms. The synchronous limit cycles are driven by rotor imbalances. The nonsynchronous limit cycles (also called subsynchronous whirls) are self-excited and are the sources of instability.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-170986 , NAS 1.26:170986
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  • 99
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    High pressure oxygen turbopump bearing cage stability analyses (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The low service life of the high pressure oxygen turbopump (HPOTP) bearings used in the space shuttle main engine was examined by use of the Battelle "BASDAP' bearing computer stability model. The dynamic instability of the bearing cage resulted in excessive wear and eventual failure of the unit. By maintaining a cage/race clearance of no more than 0.25 millimeters (0.010 inches), ball/pocket clearance of no less than 0.54 millimeters (0.025 inches), dynamic balancing of the cages, and maintaining adequate lubricant films between the balls and races, cage instability and subsequent bearing degradation can be reduced.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-CR-170991 , NAS 1.26:170991
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  • 100
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    Comparison of predicted and experimental thermal performance of angular-contact ball bearings (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Predicted bearing heat generation and bearing temperature were verified by experimental data for ball bearings over a range of sizes, shaft speeds, and lubricant flow rates. The computer program Shaberth requires, as input, a factor which describes the air-oil mixture in the bearing cavity for calculation of the ball drag contribution to bearing heat generation. An equation for this lubricant percent volume in the bearing cavity was derived and appears to be valid over the range of test conditions including bearing bore sizes from 35 to 167 mm and shaft speeds from 1.0 to 3.0 million DN.
    Keywords: MECHANICAL ENGINEERING
    Type: NASA-TP-2275 , E-1751 , NAS 1.60:2275
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