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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

The noncavitating performance and life of a small vane-type positive displacement pump in liquid hydrogen

The low flow rate and high head rise requirements of hydrogen/oxygen auxiliary propulsion systems make the application of centrifugal pumps difficult. Positive displacement pumps are well-suited for these flow conditions, but little is known about their performance and life characteristics in liquid hydrogen. An experimental and analytical investigation was conducted to determine the performance and life characteristics of a vane-type, positive displacement pump. In the experimental part of this effort, mass flow rate and shaft torque were determined as functions of shaft speed and pump pressure rise. Since liquid hydrogen offers little lubrication in a rubbing situation, pump life is an issue. During the life test, the pump was operated intermittently for 10 hr at the steady-state point of 0.074 lbm/sec (0.03 kg/sec) flow rate, 3000 psid (2.07 MPa) pressure rise, and 8000 rpm (838 rad/sec) shaft speed. Pump performance was monitored during the life test series and the results indicated no loss in performance. Material loss from the vanes was recorded and wear of the other components was documented. In the analytical part of this effort, a comprehensive pump performance analysis computer code, developed in-house, was used to predict pump performance. The results of the experimental investigation are presented and compared with the results of the analysis. Results of the life test are also presented.

Ulbricht, T. E.↗
NASA NTRS1986

Flight test of a displacement sidearm controller

A six-axis displacement-stick sidearm controller was developed to enable single-handed control of remote manipulator operations in space. With a working model available, piloted evaluation became possible in a fly-by-computer variable-stability research aircraft, originally a Bell 205 helicopter. The original mechanization was limited to three rotational axes and a linear one, analogous to the collective stick. A newly designed short stickgrip was mounted and the spring force pattern adjusted to suit the helicopter flight control environment. A standard set of test maneuvers was flown by four experimental pilots with conventional helicopter flight controls and with sidearm controllers equipped with two different handgrips. Existing data from flight tests with an isometric-stick controller were added to complete the comparison. The displacement controller consistently achieved a rating of 3.0 to 3.5 on the Cooper-Harper scale, on par with the conventional controls. The same basic controller design was tested in spacecraft and remote manipulator simulations with very promising results. In each application operator/system integration was rapid and positive. The results demonstrate feasibility and support the design philosphy of using deflection as well as force to generate proprioceptive feedback.

Lippay, A. L.↗
NASA NTRS1985

Finite elements based on consistently assumed stresses and displacements

Finite element stiffness matrices are derived using an extended Hellinger-Reissner principle in which internal displacements are added to serve as Lagrange multipliers to introduce the equilibrium constraint in each element. In a consistent formulation the assumed stresses are initially unconstrained and complete polynomials and the total displacements are also complete such that the corresponding strains are complete in the same order as the stresses. Several examples indicate that resulting properties for elements constructed by this consistent formulation are ideal and are less sensitive to distortions of element geometries. The method has been used to find the optimal stress terms for plane elements, 3-D solids, axisymmetric solids, and plate bending elements.

Pian, T. H. H.↗
NASA NTRS1987

The development of laser speckle or particle image displacement velocimetry. Part 1: The role of photographic parameters

One of the difficult problems in experimental fluid dynamics remains the determination of the vorticity field in fluid flows. Recently, a novel velocity measurement technique, commonly known as Laser Speckle or Particle Image Displacement Velocimetry became available. This technique permits the simultaneous visualization of the 2 dimensional streamline pattern in unsteady flows and the quantification of the velocity field. The main advantage of this new technique is that the whole 2 dimensional velocity field can be recorded with great accuracy and spatial resolution, from which the instantaneous vorticity field can be easily obtained. A apparatus used for taking particle displacement images is described. Local coherent illumination by the probe laser beam yielded Young's fringes of good quality at almost every location of the flow field. These fringes were analyzed and the velocity and vorticity fields were derived. Several conclusions drawn are discussed.

Lourenco, L. M. M.↗
NASA NTRS1986

KI-solutions for single edge notch specimens under fixed end displacements

The KI solution for a finite length single-edge notch specimen loaded under fixed-end displacements is derived using a crack compliance analysis. Numerical and experimental checks of the KI solution are provided. Good agreement between the experimental and numerical solutions is observed. The applicability of conventional fracture mechanics to correlate crack growth data generated under displacement control is discussed.

Marchand, N.↗
NASA NTRS1986

Crack-surface displacements for two symmetric cracks emanating from a circular hole in an infinite plate

An analytical model is presented for the surface displacement associated with two symmetric cracks radiating from a circular hole in a plate undergoing remote uniform stress. The model equations account for the stress intensity factor (Kic), the boundary conditions enveloping the hole, and the effects of symmetric forces concentrated around the hole. The displacement(s) of the surface are calculated at a given distance from the hole along the crack(s).

Mall, S.↗
NASA NTRS1986

The noncavitating performance and life of a small vane-type positive displacement pump in liquid hydrogen

The low flow rate and high head rise requirements of hydrogen/oxygen auxiliary propulsion systems make the application of centrifugal pumps difficult. Positive displacement pumps are well-suited for these flow conditions, but little is known about their performance and life characteristics in liquid hydrogen. An experimental and analytical investigation was conducted to determine the performance and life characteristics of a vane-type, positive displacement pump. In the experimental part of this effort, mass flow rate and shaft torque were determined as functions of shaft speed and pump pressure rise. Since liquid hydrogen offers little lubrication in a rubbing situation, pump life is an issue. During the life test, the pump was operated intermittently for 10 hr at the steady-state point of 0.074 lbm/sec (0.03 kg/sec) flow rate, 3000 psid (2.07 MPa) pressure rise, and 9000 rpm (938 rad/sec) shaft speed. Pump performance was monitored during the life test series and the results indicated no loss in performance. Material loss from the vanes was recorded and wear of the other components was documented. In the analytical part of this effort, a comprehensive pump performance analysis computer code, developed in-house, was used to predict pump performance. The results of the experimental investigation are presented and compared with the results of the analysis. Results of the life test are also presented.

Ulbricht, T. E.↗
NASA NTRS1986

Topographic effect on tilt, strain, and displacement measurements

An approximate analytical method is used to give simple expressions for the effect of arbitrarily shaped topography on vertical, horizontal and surface tilt measurements. Corrections to tilt fields are found to be directly proportional to the local slope of the topography. Comparison is made between expressions for tilt and those for strain and displacement. Although the topographic effects on secular tilt, strain, and vertical displacement are not yet measurable, the topographic effect on precision tidal tilt and strain measurements can be significant.

Meertens, Charles M.↗
NASA NTRS1987

Displacements of the earth's surface due to atmospheric loading - Effects of gravity and baseline measurements

Atmospheric mass loads and deforms the earth's crust. By performing a convolution sum between daily, global barometric pressure data and mass loading Green's functions, the time dependent effects of atmospheric loading, including those associated with short-term synoptic storms, on surface point positioning measurements and surface gravity observations are estimated. The response for both an oceanless earth and an earth with an inverted barometer ocean is calculated. Load responses for near-coastal stations are significantly affected by the inclusion of an inverted barometer ocean. Peak-to-peak vertical displacements are frequently 15-20 mm with accompanying gravity perturbations of 3-6 micro Gal. Baseline changes can be as large as 20 mm or more. The perturbations are largest at higher latitudes and during winter months. These amplitudes are consistent with the results of Rabbel and Zschau (1985), who modeled synoptic pressure disturbances as Gaussian functions of radius around a central point. Deformation can be adequately computed using real pressure data from points within about 1000 km of the station. Knowledge of local pressure, alone, is not sufficient. Rabbel and Zschau's hypothesized corrections for these displacements, which use local pressure and the regionally averaged pressure, prove accurate at points well inland but are, in general, inadequate within a few hundred kilometers of the coast.

Van Dam, T. M.↗
NASA NTRS1988

Fiber-optic displacement sensor with temporally separated signal and reference channels

A fiber-optic displacement sensor with temporally separated signal and reference channels is proposed. The sensing technique used is based on determining the relative amplitude of the signal and reference pulses that together form a double pulse. The relative amplitude of the pulses in the double pulse is a function of the displacement. A setup to generate the double pulse with individual pulses of 5-ns duration and 10-ns delay is described. A novel signal processing technique, used to determine the relative amplitude of such pulses in the double pulse by analyzing different portions of the signal spectrum, is explained. Experimental data are also provided.

Adamovsky, Grigory↗
NASA NTRS1988

Vertical displacement threshold sensitivity along the horizontal meridian as a function of stimulus rate, duration, and length

Four independent variables of visual perception during binocular viewing were studied. In 24 observers, the vertical displacement threshold (DT) sensitivity along the horizontal meridian was determined as a function of the rate, duration, and length of the stimulus. It was found that the DT increases with an increased angular separation of the stimulus image from the fovea (i.e., the stimulus must move farther in order to be correctly discriminated as having moved). In addition, it was found that the sensitivity to the stimulus displacement increases with increasing of the stimulus length, duration, and/or angular rate. These findings are related to the design optimization of dynamic attitude displays and symbology for aircraft.

Haines, Richard F.↗
NASA NTRS1989

Capacitive Displacement Sensor With Frequency Readout

Simple displacement-measuring circuit senses capacitance between two parallel conducting plates and produces output signal, with frequency proportional to distance between plates. Principle of circuit provides advantages over other methods because of frequency-encoded output and high linearity. Used to measure displacements.

Fritsch, Klaus↗
NASA NTRS1989

An interferometric strain-displacement measurement system

A system for measuring the relative in-plane displacement over a gage length as short as 100 micrometers is described. Two closely spaced indentations are placed in a reflective specimen surface with a Vickers microhardness tester. Interference fringes are generated when they are illuminated with a He-Ne laser. As the distance between the indentations expands or contracts with applied load, the fringes move. This motion is monitored with a minicomputer-controlled system using linear diode arrays as sensors. Characteristics of the system are: (1) gage length ranging from 50 to 500 micrometers, but 100 micrometers is typical; (2) least-count resolution of approximately 0.0025 micrometer; and (3) sampling rate of 13 points per second. In addition, the measurement technique is non-contacting and non-reinforcing. It is useful for strain measurements over small gage lengths and for crack opening displacement measurements near crack tips. This report is a detailed description of a new system recently installed in the Mechanisms of Materials Branch at the NASA Langley Research Center. The intent is to enable a prospective user to evaluate the applicability of the system to a particular problem and assemble one if needed.

Sharpe, William N., Jr.↗
NASA NTRS1989

Nonlinear strain-displacement relations and flexible multibody dynamics

Dynamics of chains of flexible bodies undergoing large rigid body motions, but small elastic deflections are considered. The role of nonlinear strain-displacement relations in the development of the motion equations correct to first order in elastic deflections is investigated. The general form of these equations linearized only in the small elastic deflections is presented, and the relative significance of various nonlinear terms is studied both analytically and through the use of the numerical simulations. Numerical simulations are performed for a two link chain constrained to move in the plane, subject to hinge torques. Each link is modeled as a thin beam. Slew maneuver simulation results are compared for models with and without properly modeled kinematics of deformation. The goal of this case study is to quantify the importance of the terms in the equations of motion which arise from the inclusion of nonlinear strain-displacement relations. It is concluded that unless the consistently linearized equations in elastic deflections and speeds are available and necessary, the inconsistently (prematurely) linearized equations should be replaced in all cases by ruthlessly linearized equations: equations in which all nonlinear terms involving the elastic deflections and speeds are ignored.

Padilla, Carlos E.↗
NASA NTRS1989

Nonlinear finite element formulation for the large displacement analysis in multibody system dynamics

A total Lagrangian finite element formulation for the deformable bodies in multibody mechanical systems that undergo finite relative rotations is developed. The deformable bodies are discretized using finite element methods. The shape functions that are used to describe the displacement field are required to include the rigid body modes that describe only large translational displacements. This does not impose any limitations on the technique because most commonly used shape functions satisfy this requirement. The configuration of an element is defined using four sets of coordinate systems: Body, Element, Intermediate element, Global. The body coordinate system serves as a unique standard for the assembly of the elements forming the deformable body. The element coordinate system is rigidly attached to the element and therefore it translates and rotates with the element. The intermediate element coordinate system, whose axes are initially parallel to the element axes, has an origin which is rigidly attached to the origin of the body coordinate system and is used to conveniently describe the configuration of the element in undeformed state with respect to the body coordinate system.

Rismantab-Sany, J.↗
NASA NTRS1990

Particle displacement tracking for PIV

A new Particle Imaging Velocimetry (PIV) data acquisition and analysis system, which is an order of magnitude faster than any previously proposed system has been constructed and tested. The new Particle Displacement Tracing (PDT) system is an all electronic technique employing a video camera and a large memory buffer frame-grabber board. Using a simple encoding scheme, a time sequence of single exposure images are time coded into a single image and then processed to track particle displacements and determine velocity vectors. Application of the PDT technique to a counter-rotating vortex flow produced over 1100 velocity vectors in 110 seconds when processed on an 80386 PC.

Wernet, Mark P.↗
NASA NTRS1991

Software manual for operating particle displacement tracking data acquisition and reduction system

The software manual is presented. The necessary steps required to record, analyze, and reduce Particle Image Velocimetry (PIV) data using the Particle Displacement Tracking (PDT) technique are described. The new PDT system is an all electronic technique employing a CCD video camera and a large memory buffer frame-grabber board to record low velocity (less than or equal to 20 cm/s) flows. Using a simple encoding scheme, a time sequence of single exposure images are time coded into a single image and then processed to track particle displacements and determine 2-D velocity vectors. All the PDT data acquisition, analysis, and data reduction software is written to run on an 80386 PC.

Wernet, Mark P.↗
NASA NTRS1991

Computer animation of NASTRAN displacements on IRIS 4D-series workstations: CANDI/ANIMATE postprocessing of NASHUA results

The capabilities of the postprocessing program CANDI (Color Animation of Nastran DIsplacements) were expanded to accept results from axisymmetric analysis. An auxiliary program, ANIMATE, was developed to allow color display of CANDI output on the IRIS 4D-series workstations. The user can interactively manipulate the graphics display by three-dimensional rotations, translations, and scaling through the use of the keyboard and/or dials box. The user can also specify what portion of the model is displayed. These developments are limited to the display of complex displacements calculated with the NASHUA/NASTRAN procedure for structural acoustics analysis.

Fales, Janine L.↗