Results for “simplified analysis” — Page 2

NASA NTRS1973

Simplified photoionization analysis of quasar emission spectra.

Simplified photoionization calculations, considering quasar emission lines with ultraviolet rest-wavelengths, can be made including only hydrogen, helium, and carbon ions. With plausible assumptions about the helium abundance and ionizing spectral slope, estimates of the (radiation/gas) pressure ratio and carbon abundance are possible. Proportionality relations, showing the dependences of line ratios upon assumed parameters, may be useful in considering differences between individual spectra.

Davidson, K.↗

NASA NTRS1983

Simplified method for nonlinear structural analysis

A simplified inelastic analysis computer program was developed for predicting the stress-strain history of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a simulated plasticity hardening model. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, and different materials and plasticity models. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

Kaufman, A.↗

NASA NTRS1930

Simplified aerodynamic analysis of the cyclogiro rotating wing system

A simplified aerodynamic theory of the cyclogiro rotating wing is presented herein. In addition, examples have been calculated showing the effect on the rotor characteristics of varying the design parameters of the rotor. A performance prediction, on the basis of the theory here developed, is appended, showing the performance to be expected of a machine employing this system of sustentation. The aerodynamic principles of the cyclogiro are sound; hovering flight, vertical climb, and a reasonable forward speed may be obtained with a normal expenditure of power. Auto rotation in a gliding descent is available in the event of a power-plant failure.

Wheatley, John B↗

NASA NTRS1977

Analytical procedure for evaluating speckle-effect instrumentation

A general analysis suitable for developing speckle effect instruments and a simplified analysis suitable for evaluating laser speckle instrumentation are presented. The simplified analysis is summarized as a list of equations. Several sample applications are discussed.

Decker, A. J.↗

NASA NTRS1978

Simplified contact analysis

A simple and straightforward method for calculating the elastic deformation at the center of contact between two solids with different radii of curvature is proposed instead of the conventional contact deformation analysis for ball bearings, gears, and cams, which usually involves tedious iterative procedures or the use of design charts. Ellipticity of the contact is approximated from a least-squares power fit. Simplified expressions are derived which allow rapid calculation of deformation from the material properties and geometry of the contacting elements.

Brewe, D. E.↗

NASA NTRS1984

A simplified method for elastic-plastic-creep structural analysis

A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

Kaufman, A.↗

NASA NTRS1985

A simplified method for elastic-plastic-creep structural analysis

A simplified inelastic analysis computer program (ANSYPM) was developed for predicting the stress-strain history at the critical location of a thermomechanically cycled structure from an elastic solution. The program uses an iterative and incremental procedure to estimate the plastic strains from the material stress-strain properties and a plasticity hardening model. Creep effects are calculated on the basis of stress relaxation at constant strain, creep at constant stress or a combination of stress relaxation and creep accumulation. The simplified method was exercised on a number of problems involving uniaxial and multiaxial loading, isothermal and nonisothermal conditions, dwell times at various points in the cycles, different materials and kinematic hardening. Good agreement was found between these analytical results and nonlinear finite element solutions for these problems. The simplified analysis program used less than 1 percent of the CPU time required for a nonlinear finite element analysis.

Kaufman, A.↗

NASA NTRS1973

A simplified signal analysis technique for obtaining optimal estimates of system dynamics

A procedure is presented which provides an algorithm for the special case where the unknown system has n inputs, and n finite length realizations for each of the n input signals are available. Given an n input system and n experimental records for each input, it is shown that the optimum Wiener filter is easily computed using only the experimental data. No assumptions concerning the analytical structure of the spectral matrix are necessary.

Whitbeck, R. F.↗

NASA NTRS1976

COMMAND: A FORTRAN program for simplified composite analysis and design

A FORTRAN program is presented for preliminary analysis and design of multilayered composite panels subjected to inplane loads. All plys are of the same material. The composite is assumed symmetric about the midplane, but need not be balanced. Failure criterion includes limit ply strains and lower bounds on composite inplane stiffnesses. Multiple load conditions are considered. The required input data is defined and examples are provided to aid the use in making the program operational. Average panel design times are two seconds on an IBM 360/67 computer. Results are compared with published literature. A complete FORTRAN listing of program COMAND is provided. In addition, the optimization program CONMIN is required for design.

Vanderplaats, G. N.↗

NASA NTRS1988

Simplified Drag Analysis For Nozzles

Measurements, graphs and calculations combined to give realistic and convenient estimates. Pitot-tube measurements made at various distances from wall to obtain pressure distribution in viscous boundary layer. Pressure readings converted to mach numbers, and analytical expressions for mach-number profile of boundary layer fitted to mach numbers derived from pressure by adjusting shape factor. Applied to jet-expansion devices in turbines, compressors, and variety of other equipment.

Wagner, W. R.↗

NASA NTRS2010

Innovative Techniques Simplify Vibration Analysis

In the early years of development, Marshall Space Flight Center engineers encountered challenges related to components in the space shuttle main engine. To assess the problems, they evaluated the effects of vibration and oscillation. To enhance the method of vibration signal analysis, Marshall awarded Small Business Innovation Research (SBIR) contracts to AI Signal Research, Inc. (ASRI), in Huntsville, Alabama. ASRI developed a software package called PC-SIGNAL that NASA now employs on a daily basis, and in 2009, the PKP-Module won Marshall s Software of the Year award. The technology is also used in many industries: aircraft and helicopter, rocket engine manufacturing, transportation, and nuclear power."

Source record↗

NASA NTRS1951

Combustion Instability in an Acid-Heptane Rocket with a Pressurized-Gas Propellant Pumping System

Results of experimental measurements of low-frequency combustion instability of a 300-pound thrust acid-heptane rocket engine were compared to the trends predicted by an analysis of combustion instability in a rocket engine with a pressurized-gas propellant pumping system. The simplified analysis, which assumes a monopropellant model, was based on the concept of a combustion the delay occurring from the moment of propellant injection to the moment of propellant combustion. This combustion time delay was experimentally measured; the experimental values were of approximately half the magnitude predicted by the analysis. The pressure-fluctuation frequency for a rocket engine with a characteristic length of 100 inches and operated at a combustion-chamber pressure of 280 pounds per square inch absolute was 38 cycles per second; the analysis indicated. a frequency of 37 cycles per second. Increasing combustion-chamber characteristic length decreased the pressure-fluctuation frequency, in conformity to the analysis. Increasing the chamber operating pressure or increasing the injector pressure drop increased the frequency. These latter two effects are contrary to the analysis; the discrepancies are attributed to the conflict between the assumptions made to simplify the analysis and the experimental conditions. Oxidant-fuel ratio had no apparent effect on the experimentally measured pressure-fluctuation frequency for acid-heptane ratios from 3.0 to 7.0. The frequencies decreased with increased amplitude of the combustion-chamber pressure variations. The analysis indicated that if the combustion time delay were sufficiently short, low-frequency combustion instability would be eliminated.

Tischler, Adelbert O.↗

NASA NTRS1985

On local total strain redistribution using a simplified cyclic inelastic analysis based on an elastic solution

Strain redistribution corrections were developed for a simplified inelastic analysis procedure to economically calculate material cyclic response at the critical location of a structure for life prediction purposes. The method was based on the assumption that the plastic region in the structure is local and the total strain history required for input can be defined from elastic finite element analyses. Cyclic stress-strain behavior was represented by a bilinear kinematic hardening model. The simplified procedure has been found to predict stress-strain response with reasonable accuracy for thermally cycled problems but needs improvement for mechanically load cycled problems. This study derived and incorporated Neuber type corrections in the simplified procedure to account for local total strain redistribution under cyclic mechanical loading. The corrected simplified method was exercised on a mechanically load cycled benchmark notched plate problem. Excellent agreement was found between the predicted material response and nonlinear finite element solutions for the problem. The simplified analysis computer program used 0.3 percent of the CPU time required for a nonlinear finite element analysis.

Hwang, S. Y.↗

NASA NTRS1985

On local total strain redistribution using a simplified cyclic inelastic analysis based on an elastic solution

Strain redistribution corrections were developed for a simplified inelastic analysis procedure to economically calculate material cyclic response at the critical location of a structure for life prediction purposes. The method was based on the assumption that the plastic region in the structure is local and the total strain history required for input can be defined from elastic finite element analyses. Cyclic stress-strain behavior was represented by a bilinear kinematic hardening model. The simplified procedure has been found to predict stress-strain response with reasonable accuracy for thermally cycled problems but needs improvement for mechanically load cycled problems. This study derived and incorporated Neuber type corrections in the simplified procedure to account for local total strain redistribution under cyclic mechanical loading. The corrected simplified method was exercised on a mechanically load cycled benchmark notched plate problem. Excellent agreement was found between the predicted material response and nonlinear finite element solutions for the problem. The simplified analysis computer program used 0.3 percent of the CPU time required for a nonlinear finite element analysis.

Hwang, S. Y.↗

NASA NTRS1980

Simplified fatigue life analysis for traction drive contacts

A simplified fatigue life analysis for traction drive contacts of arbitrary geometry is presented. The analysis is based on the Lundberg-Palmgren theory used for rolling-element bearings. The effects of torque, element size, speed, contact ellipse ratio, and the influence of traction coefficient are shown. The analysis shows that within the limits of the available traction coefficient, traction contacts exhibit longest life at high speeds. Multiple, load-sharing roller arrangements have an advantageous effect on system life, torque capacity, power-to-weight ratio and size.

Rohn, D. A.↗

NASA NTRS1980

Simplified fatigue life analysis for traction drive contacts

A simplified fatigue life analysis for traction drive contacts of arbitrary geometry is presented. The analysis is based on the Lundberg-Palmgren theory used for rolling-element bearings. The effects of torque, element size, speed, contact ellipse ratio, and the influence of traction coefficient are shown. The analysis shows that within the limits of the available traction coefficient, traction contacts exhibit longest life at high speeds. Multiple, load-sharing roller arrangements have an advantageous effect on system life, torque capacity, power-to-weight ratio and size.

Rohn, D. A.↗

NASA NTRS1973

Aeroelastic effects on space shuttle dynamics

A simplified analysis procedure for determining static and dynamic aeroelastic loads for the space shuttle and space shuttle configuration is presented. A computer program, originally developed for the Atlas launch vehicle, was modified for simplifying the turbulence response analysis approach. This approach is compared with a more detailed and time consuming approach to space shuttle response to turbulence which was developed earlier. The simplification in going from interference to lumped aerodynamic data was found to give adequate results for preliminary design aeroelastic analysis. Gust loads were found to be approximately 50% of the maximum static aeroelastic loads. The autopilot became unstable when ten elastic modes were included. Elastic effects were found to be less than 3% in the static aeroelastic analysis.

Source record↗

NASA NTRS1987

A simplified computer solution for the flexibility matrix of contacting teeth for spiral bevel gears

A computer code, FLEXM, was developed to calculate the flexibility matrices of contacting teeth for spiral bevel gears using a simplified analysis based on the elementary beam theory for the deformation of gear and shaft. The simplified theory requires a computer time at least one order of magnitude less than that needed for the complete finite element method analysis reported earlier by H. Chao, and it is much easier to apply for different gear and shaft geometries. Results were obtained for a set of spiral bevel gears. The teeth deflections due to torsion, bending moment, shearing strain and axial force were found to be in the order 10(-5), 10(-6), 10(-7), and 10(-8) respectively. Thus, the torsional deformation was the most predominant factor. In the analysis of dynamic load, response frequencies were found to be larger when the mass or moment of inertia was smaller or the stiffness was larger. The change in damping coefficient had little influence on the resonance frequency, but has a marked influence on the dynamic load at the resonant frequencies.

Hsu, C. Y.↗