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Results for “INTERNAL PRESSURE”

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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A fuselage/tank structure study for actively cooled hypersonic cruise vehicles: Structural analysis

The effects of fuselage cross-section (circular and elliptical) and structural arrangement (integral and nonintegral tanks) on the performance of actively cooled hypersonic cruise vehicles was evaluated. It was found that integrally machined stiffening of the tank walls, while providing the most weight-efficient use of materials, results in higher production costs. Fatigue and fracture mechanics appeared to have little effect on the weight of the three study aircraft. The need for thermal strain relief through insulation is discussed. Aircraft size and magnitude of the internal pressure are seen to be significant factors in tank design.

Baker, A. H.↗
NASA NTRS1974

A novel negative-limited sealed nickel-cadmium cell

The use of negative-limited nickel-cadmium cells with adequate charge control is shown to provide an effective means for controlling internal pressure. Cycle test data show that negative-limited cells have somewhat higher ampere-hour degradation rates at higher operating temperatures. The most important advantages of these cells are: (1) lesser heat generation during operation; (2) longer separator life, as a result of operation at lower temperatures; (3) decreased stresses on cell seals due to lower operating pressures; and (4) significant weight savings.

Juvinall, G. L.↗
NASA NTRS1975

Elliptical cutouts in cylindrical shells

The stress concentrations due to an elliptical cutout in a shallow cylindrical shell are determined by means of a system of singular integral equations, solved numerically. Three loading conditions are considered: tension, and internal pressure. Results confirm those obtained by previous authors by other methods and extend the range of parameters over which results are available.

Tsai, C.-J.↗
NASA NTRS1975

Noise addendum experimental clean combustor program, phase 1

The development of advanced CTOL aircraft engines with reduced exhaust emissions is discussed. Combustor noise information provided during the basic emissions program and used to advantage in securing reduced levels of combustion noise is included. Results are presented of internal pressure transducer measurements made during the scheduled emissions test program on ten configurations involving variations of three basic combustor designs.

Sofrin, T. G.↗
NASA NTRS1975

Measurements of farfield sound generation from a flow-excited cavity

Results of 1/3-octave-band spectral measurements of internal pressures and the external acoustic field of a tangentially blown rectangular cavity are compared. Proposed mechanisms for sound generation are reviewed, and spectra and directivity plots of cavity noise are presented. Directivity plots show a slightly modified monopole pattern. Frequencies of cavity response are calculated using existing predictions and are compared with those obtained experimentally. The effect of modifying the upstream boundary layer on the noise was investigated, and its effectiveness was found to be a function of cavity geometry and flow velocity.

Block, P. J. W.↗
NASA NTRS1976

Symmetric stiffness matrix for incompressible hyperelastic materials

Symmetric structure matrices are derived for solving plane strain and axisymmetric problems involving incompressible hyperelastic materials. An infinite hollow cylinder subjected to internal pressure is considered as an example. Displacement and hydrostatic pressure profiles are calculated using the Newton-Raphson iteration technique. The results are in good agreement with the exact curves.

Takamatsu, T.↗
NASA NTRS1976

Fluid-plasticity of thin cylindrical shells

Dynamic plastic response of a thin cylindrical shell, immersed in a potential fluid initially at rest and subjected to internal pressure pulse of arbitrary shape and duration, is examined. The shell is assumed to respond as a rigid-perfectly plastic material while the fluid is taken as inviscid and incompressible. The fluid back pressure is incorporated into the equation of motion of the shell as an added mass term. Since arbitrary pulses can be reduced to equivalent rectangular pulses, the equation of motion is solved only for a rectangular pulse. The influence of the fluid in reducing the final plastic deformation is demonstrated by a numerical example.

Krajcinovic, D.↗
NASA NTRS1977

Finite element stress analysis of the human left ventricle whose irregular shape is developed from single plane cineangiocardiogram

The three-dimensional left ventricular chamber geometrical model is developed from single plane cineangiocardiogram. This left ventricular model is loaded by an internal pressure monitored by cardiac catheterization. The resulting stresses in the left ventricular model chamber's wall are determined by computerized finite element procedure. For the discretization of this left ventricular model structure, a 20-node, isoparametric finite element is employed. The analysis and formulation of the computerised procedure is presented in the paper, along with the detailed algorithms and computer programs. The procedure is applied to determine the stresses in a left ventricle at an instant, during systole. Next, a portion (represented by a finite element) of this left ventricular chamber is simulated as being infarcted by making its active-state modulus value equal to its passive-state value; the neighbouring elements are shown to relieve the 'infarcted' element of stress by themselves taking on more stress.

Ghista, D. N.↗
NASA NTRS1978

An investigation of mercury hollow cathode phenomena

An experimental investigation is described in which measurements were made of plasma properties and other physical parameters upstream and downstream of the orifice plate of an operating mercury hollow cathode. These measurements included plasma property profiles, internal surface temperatures, internal pressure, and spectroscopic data of the external discharge. The results show the plume-to-spot mode transition to be characterized by significant changes in the plasma properties downstream of the cathode orifice, including the disappearance of an apparent electron free-fall region which is found to be present in the plume mode. The results also indicate the existence of a very dense plasma (10 to the 10th to 10 to the 14th electrons/cu cm) with steep electron density gradients in the region upstream of the orifice. The upstream data is found to correlate well with a modified form of the Saha equation. The related analysis indicates that the heavy particles approach thermal equilibrium with the electrons in the region of the orifice and that the ionization fraction in the orifice is very high - 80 to 100%.

Siegfried, D. E.↗
NASA NTRS1978

On the masses of giant molecular cloud complexes

A method of mass estimation for molecular clouds is presented which is based on approximate balance in the outer cloud layers between the cloud's gravitation, the galactic tide, and internal pressure. The largest observed clouds, which have greatest linear extents of 100 pc, are found to have masses of at least 200,000 solar masses. The cloud masses cannot exceed this lower limit by more than a factor of 3, or the velocity distributions of disk stars would be more relaxed than is actually observed. This implied upper limit to cloud masses combined with the galactic tide may be related to the absence of clouds at galactocentric radii less than 4 kpc. If Sagittarius B2 is bound, its mass must be more than 50 million solar masses.

Stark, A. A.↗
NASA NTRS1978

Development of long life lightweight nickel-cadmium cells and batteries

The paper describes the development of a high-specific energy Ni-Cd cell for a lightweight battery. After preliminary cycling tests on laboratory and commercial cells, a cell was produced that features electrochemically impregnated positive and negative electrodes, a single terminal, and increased amount of electrolyte. This cell weighed an average of 948 g and had a measured specific energy of over 50 Wh/kg at a C/2 discharge to 1.0 V. The epoxy graphite case capable of withstanding internal pressures in excess of 300 psig represents a 35% weight reduction from a lightweight 0.30 mm Ni-Cd case. A pack of these cells was cycled at 70% maximum depth of discharge beyond 10 simulated geosynchronous orbit-eclipse seasons, and high end-of-charge voltages were obtained. A prototype battery consisting of 14 such cells was fabricated and has a measured specific energy of 46 Wh/kg.

Ritterman, P. F.↗
NASA NTRS1979

Initial wind tunnel tests at Mach 4 and 7 of a hydrogen-burning, airframe-integrated scramjet

A research investigation of a new, fixed-geometry, hydrogen-burning scramjet engine concept, designed for total airframe integration, is currently in progress. Two heavily instrumented engine models incorporate inlet and combustor designs developed previously in component tests. Initial tests of these subscale engine models are being conducted in ground facilities at conditions simulating flight at Mach numbers 4 and 7. The scramjet test results which are presented include inlet performance, ignition/reaction aids, inlet-combustor interactions, and engine performance in terms of thrust balance measurements and internal pressure and heating rate distributions. The relationship of these results to flight engine performance is discussed.

Guy, R. W.↗
NASA NTRS1980

Composite materials research and education program: The NASA-Virginia Tech composites program

Major areas of study include: (1) edge effects in finite width laminated composites subjected to mechanical, thermal and hygroscopic loading with temperature dependent material properties and the influence of edge effects on the initiation of failure; (2) shear and compression testing of composite materials at room and elevated temperatures; (3) optical techniques for precise measurement of coefficients of thermal expansion of composites; (4) models for the nonlinear behavior of composites including material nonlinearity and damage accumulation and verification of the models under biaxial loading; (5) compressive failure of graphite/epoxy plates with circular holes and the buckling of composite cylinders under combined compression and torsion; (6) nonlinear mechanical properties of borsic/aluminum, graphite/polyimide and boron/aluminum; (7) the strength characteristics of spliced sandwich panels; and (8) curved graphite/epoxy panels subjected to internal pressure.

Herakovich, C. T.↗
NASA NTRS1979

Manufacturing methods of a composite cell case for a Ni-Cd battery

Basic manufacturing method refinements for using graphite epoxy material for a nickel cadmium battery cell case were performed to demonstrate production feasibility. The various facets of production scale-up, i.e., process and tooling development, together with material and process control, were integrated into a comprehensive manufacturing process that assures production reproducibility and product uniformity. Test results substantiate that a battery cell case produced from graphite epoxy pre-impregnated material, utilizing the internal pressure bag fabrication method, is feasible.

Bauer, J. L.↗
NASA NTRS1980

Implementation of a trapezoidal ring element in NASTRAN for elastic-plastic analysis

The explicit expressions for an elastic-plastic trapezoidal ring element are presented and implemented in NASTRAN computer program. The material is assumed to obey the von Mises' yield criterion, isotropic hardening rule and the Prandtl-Reuss flow relations. For the purpose of demonstration, two elastic-plastic problems are solved and compared with previous results. The first is a plane-strain tube under uniform internal pressure and the second, a finite-length tube loaded over part of its inner surface. A very good agreement was found in both test problems.

Chen, P. C. T.↗
NASA NTRS1980

Elastic-plastic analysis using a triangular ring element in NASTRAN

An elastic plastic triangular ring element is implemented in NASTRAN computer program. The plane strain problem of partially plastic thick walled cylinder under internal pressure is solved and compared with the earlier finite difference solution. A very good agreement has been reached. In order to demonstrate its application to more general problems, an overloaded thread problem for the British Standard Buttress is examined. The maximum axial and principal stresses are located and their values are determined as functions of loadings.

Chen, P. C. T.↗
NASA NTRS1979

Manufacturing methods of a composite cell case for a Ni-Cd battery

Graphite epoxy material for a nickel cadmium battery cell case has been evaluated and determined to perform in the simulated environment of the battery. The basic manufacturing method requires refinement to demonstrate production feasibility. The various facets of production scale-up, i.e., process and tooling development together with material and process control, have been integrated into a comprehensive manufacturing process that assures production reproducibility and product uniformity. Test results substantiate that a battery cell case produced from graphite epoxy pre-impregnated material utilizing internal pressure bag fabrication method is feasible.

Bauer, J. L.↗