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Empirical Correlation of Excitation Environment and Structural Parameters with Flight Vehicle Vibration Response
Report Number: AFFDL TR 64-160
Author(s): R. W. White; D. J. Bozich; K. M. Eldred
Corporate Author: Northrup Corporation
Laboratory: AF Flight Dynamics Laboratory
Publication Date: 12/1/1964
Pages: 140
Contract: AF 33(657)-8218
Project: 1370
Task: 137005
AD Number: AD0610482
Abstract Text:
The design of fatigue resistant structures for high speed aircraft and aerospace vehicles depends largely on the prediction of realistic acoustic, fluctuating aerodynamic, and engine vibration environments and on the estimation of the attendant vibration levels of structural components and attached equipment. The practical engineering limitations on the mathematical and numerical analyses required to treat such structures rigorously by classical dynamics necessitate studies of alternate, approximate methods. In the report, a definitive statement is presented of the empirical approach for determining correlations between the excitation environment and the vibration response of typical flight vehicle structures by means of statistical analyses of measured vibration data. The various aspects of the vibration prediction problem and the general philosophy motivating research in the area of empirical correlation are discussed. Specific treatment is given to the effects of bandwidth, modal density, and surface pressure spacecorrelation on the crosscorrelation of energy transmitted along various structural transmission paths in complex linear structures.
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High Temperature Investigation of Various Crew Escape Concepts for the Reentry Flight Regime
Report Number: AFFDL TR 64-161
Author(s): C. J. Cohan, G. Campbell, W. Herman, W. Nugent and J. Heathman
Corporate Author: General Dynamics Corporation
Laboratory: Air Force Flight Dynamics Laboratory
Publication Date: 11/1/1964
Pages: 300
Features: + Foldout(s)
Contract: AF 33(615)-1131
Project: 1362
Task: 136203
AD Number: AD0461713
Photo Enhancement: Not Needed
Abstract Text:
This report presents the results of an analysis of escape system separation techniques from a maximum heating re-entry trajectory. Four escape capsule concepts applicable to a lifting type flight vehicle were considered. These are (1) a separable-noise ballistic body; (2) a separablenose lifting body; (3) a pod capsule; (4) a turnaround capsule. The objective of the study was to determine the applicability of these capsules and various thermal protection schemes to providing escape capability from the maximum heating point of a typical lifting re-entry trajectory. The compatibility of escape techniques developed at the maximum heating point with providing escape capability throughout the complete mission profile was also investigated. It was determined that all concepts except the turnaround capsule could provide escape capability throughout the mission.
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Lithium Spray Structural Cooling
Report Number: AFFDL TR 64-169
Author(s): Andrew L. Mistretta
Corporate Author: Bell Aerosystems Company
Laboratory: AF Flight Dynamics Laboratory
Publication Date: 11/1/1964
Pages: 130
Features: + Foldout(s)
Contract: AF 33(657)-8386
Project: 1368
Task: 136804
AD Number: AD0451274
Photo Enhancement: Complete
Abstract Text:
The objective of this program was to demonstrate the feasibility of an open cycle lithium spray absorptive cooling system for nose cap applications and to determine maximum heat flux capability of the system. Test specimens were designed and fabricated. The experimental program which was established demonstrated the feasibility of the lithium spray system. While subjected to a heat flux of 600 BTU/sq ft-sec, equivalent to a radiation equilibrium temperature of about 5800 F, specimen surface temperature did not exceed 2200 F. Instrumentation difficulties precluded tests at higher heat fluxes; therefore, the maximum potential of the system could not be determined experimentally. Approximate analytical estimates indicate a minimum potential capability of 3000 BTU/sq ft-sec.
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Transducers for Sonic Fatigue Measurements
Report Number: AFFDL TR 64-171
Author(s): Ronald D. Kelly
Corporate Author: Measurement Analysis Corporation
Laboratory: Air Force Flight Dynamics Laboratory
Publication Date: 2/1/1965
Pages: 120
Contract: AF 33(615)-1314
Project: 4437
Task: 443706
AD Number: AD0613946
Photo Enhancement: Not Needed
Abstract Text:
The report discusses the machine errors of transducer systems used for the measurement of dynamic input and response data during sonic fatigue testing. The specific types of transducers covered are accelerometers, microphones, and strain gages. The basic operating principles, intrinsic inaccuracies, environmentally related inaccuracies, and usage inaccuracies are described. These inaccuracies are broken down into errors occurring in the transducer, cabling, and signal conditioner, as well as those due to system operation. In addition, methods for minimizing these errors are given.
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An Investigation of Hypersonic Flow Separation and Control Characteristics
Report Number: AFFDL TR 64-174
Author(s): Louis G. Kaufman II; Lawrence Meckler; Stavros A. Hartofilis; Daniel Weiss
Corporate Author: Grumman Aircraft Engineerign Corporation
Laboratory: Air Force Flight Dynamics Laboratory
Publication Date: 1/1/1965
Pages: 125
Contract: AF 33(616)-8130
Project: 8219
Task: 821902
AD Number: AD0611272
Photo Enhancement: Complete
Abstract Text:
Hypersonic flow separation and its effects on control characteristics were investigated analytically and experimentally. Included are conclusions drawn from extensive test data for hypersonic flows over 'basic' geometries and over 'typical' flight configurations with aerodynamic controls. The basic flow geometries discussed include: separation on flat plates ahead of ramps (flaps); flows over sharp expansion corners; 'breakaway' separation; and fin plate interactions. Force data and limited pressure and heating rate distributions are presented for the flight configurations for various trailing edge flap settings. As a supplement to this work, available sources of pertinent hypersonic controls data are tabulated.
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Research on Accelerated Reliability Testing Methods Applicable to Non-Electronic Components of Flight Control Systems
Report Number: AFFDL TR 64-181
Author(s): W. F. Johnson, et al
Corporate Author: Curtiss-Wright Corporation
Laboratory: AF Flight Dynamics Laboratory
Publication Date: 3/1/1965
Pages: 207
Features: + Foldout(s)
Contract: AF 33(657)-11080
Project: 8225
Task: 822502
AD Number: AD0617567
Photo Enhancement: Complete
Abstract Text:
The study is concerned with the development of techniques for the testing of electromechanical components in time compressed form. The motivating basis for this work is that presently used statistical testing methods require large numbers of samples and long testing periods to compile meaningful MTBF data. The approach employed herein included: System failure mode analysis, Classification and ranking of failure modes in terms of influence and frequency of occurrence, Physics of failure analysis at part and material levels. 'Measured weakening' (pre-cracking) technique was developed and applied to the most predominate failure parts to generate failures in reasonably short test times. In addition, extraneous or unwanted failures were not produced, which is frequently the case when 'over load' testing is employed. An all mechanical position servo unit was selected as a typical energy conversion flight control system component on which tests were conducted to verify the developed techniques for accelerating reliability testing. The tests results indicated that 'measured weakening' of mechanical parts can be employed to reduce the number of samples required and the test time involved to perform reliability testing.
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Theoretical Investigations of Boundary Layer Stability
Report Number: AFFDL TR 64-184
Author(s): Gibbs S. Raetz; W. Byron Brown
Corporate Author: Northrop Corporation
Laboratory: Air Force Flight Dynamics Laboratory
Publication Date: 9/1/1966
Pages: 142
Contract: AF 33(657)-11618
Project: 1366
Task: 136612
AD Number: AD0809388
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Abstract Text:
The mathematical analysis underlying a Fortran program for calculating the proper solutions of the Orr-Sommerfeld system with sufficient accuracy and economy for applying the resonance theory of transition is described. This program covers spacewise growths, rather than timewise growths as in previous computations, of mainly two-dimensional Fourier components of the motion. It employs various innovations providing as much accuracy from efficient single-precision arithmetic as would be obtained from awkward multiple-precision arithmetic in previous calculation schemes. The source programs and some sample calculations, for the proncipal mode of oscillation of the Blasius boundary layer, are included. The Lees-Lin stability equation for compressible flow have been extended to include the terms involving the component of the mean boundary layer flow perpendicular to the flat plate. At Mach 5 this more than doubled the critical Reynolds number. Allowance was then made for the three-dimensional aspect of the disturbance velocity. The final result was to give good agreement with observed data in the lower branch of the neutral stability curve at Mach 2.2 and Mach 5, fair agreement with the upper branch at Mach 2.2 and large discrepancies with the data in the upper branch at Mach 5. Comparison of experimental determined neutral stability curves with those computed by simplified approximations have disagreed considerably at high Mach numbers on the upper branch, even when agreement was fairly good on the lower branch.
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The Effects of Active Cooling on the Aerodynamic and Aerothermodynamic Characteristics of Slender Bodies of Revolution
Report Number: AFFDL TR 64-187
Author(s): B. M. Leadon; Jan. Rosciszeski; W. H. Gallaher; W. R. Holst; W. V. Carter
Corporate Author: General Dynamics/Convair
Laboratory: AF Flight Dynamics Laboratory
Publication Date: 12/1/1964
Pages: 106
Contract: AF 33(657)-11679
Project: 1366
Task: 136607
AD Number: AD0615471
Photo Enhancement: Not Needed
Abstract Text:
A new self consistent method has been developed for calculation of boundary layer with mass injection. The system of partial differential equations is reduced to a system of ordinary differential equations by integration over different strips. The velocity and enthalpy profiles are assumed to be expressed by series of error functions. A method of calculating the initial velocity and enthalpy profiles, based on an analysis of singularity, is presented herein. The calculation of the initial profiles is reduced to the solution of a system of transcendential equations. The initial derivatives are calculated from linearlized equations near the singular points and provide a smooth start of integration of the downstream equations. The present method was applied to the cases of a sharp edged body and a blunt body. In addition to the velocity and enthalpy profiles, the pressure distribution and shock layer thickness can be calculated from generalized Newtonian expressions developed as a part of this effort.
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Active Control of Booster Elasticity
Report Number: AFFDL TR 64-189
Author(s): Robert L. Swaim
Corporate Author: Air Force Flight Dynamics Laboratory
Laboratory: Air Force Flight Dynamics Laboratory
Publication Date: 4/1/1965
Pages: 84
Contract: Laboratory Research - No Contract
Project: 8219
Task: 821901
AD Number: AD0617314
Photo Enhancement: Not Needed
Abstract Text:
An investigation was made of the problem of providing an automatic control system for a large booster subject to severe mode interaction. This interaction is defined as a strong aerodynamic coupling between the rigid-body motion and one or more elastic modes of the vehicle and can appear as a flutter phenomenon between rigid and elastic degrees of freedom as opposed to 'classical' flutter between two or more elastic degrees of freedom. For the booster considered, the interaction resulted in a rigid-body mode static divergence for an aerodynamically, statically stable, rigid configuration in the uncontrolled or forward-loop-only system. It was shown that preliminary control system design must include the significant elastic modes when mode interaction is present. A rigid-body-only synthesis will not yield 'ball-park' values for the control element gains. The investigation revealed that the active control philosophy of using auxiliary control inputs to increase the frequencies of the elastic modes sufficient to reduce the mode of interaction in the forward-loop is a false notion. It is the free-free bending modes which interact with the rigid-body motion, and input forces cannot alter their mode shapes and frequencies. They can be altered only by mass and structural stiffness changes to the basic vehicle. The input forces result in changes to elastic mode coupled frequencies and damping ratios which do not affect the mode interaction phenomenon as defined in this report.
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Response of Elastic Structures to Deterministic and Random Excitation
Report Number: AFFDL TR 64-199
Author(s): R. L. Barnoski
Corporate Author: Measurement Analysis Corporation
Laboratory: Air Force Flight Dynamics Laboratory
Publication Date: 5/1/1965
Pages: 164
Contract: AF 33(615)-1418
Project: 1370
Task: 137005
AD Number: AD0619272
Photo Enhancement: Not Needed
Abstract Text:
The fundamental classical theory governing the response of linear distributed elastic structures to deterministic and to random excitation. A review is made of the basic dynamics theory for discrete and distributed systems when the excitation is deterministic. Integral expressions are derived for the mean square value and correlation functions for the response of an arbitrary linear elastic structure subjected to stationary random loading. The value and limitations of using classical theory as a tool for predicting structural vibrations in typical flight vehicles are explored. The theoretical results for distributed structures subjected g stationary random excitation are noted to yield complicated analytical expressions even for uniform beams. The direct extension of the shown theoretical results to include typical flight structures, although technically accurate, is not considered practical. The derivation procedures and results can be used as a basis for forming statistical parametric techniques for approximating the response behavior of distributed systems to random excitation. Several existing techniques reflecting compromises in theoretical rigor are discussed and subject areas for future study are noted.
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