The Lagrangian Multiplier Method of Finding Upper and Lower Limits to Critical Stresses of Clamped Plates

The Lagrangian Multiplier Method of Finding Upper and Lower Limits to Critical Stresses of Clamped Plates

Date: January 1, 1946
Creator: Hu, Pai C. & Budiansky, Bernard
Description: The theory of Lagrangian multipliers is applied to the problem of finding both upper and lower limits to the true compressive buckling stress of a clamped rectangular plate. The upper and lower limits thus bracket the truss, which cannot be exactly found by the differential-equation approach. The procedure for obtaining the upper limit, which is believed to be new, presents certain advantages over the classical Raleigh-Rite method of finding upper limits. The theory of the lower-limit procedure has been given by Trefftz but, in the present application, the method differs from that of Trefftz in a way that makes it inherently more quickly convergent. It is expected that in other buckling problems and in some vibration problems problems the Lagrangian multiplier method finding upper and lower limits may be advantageously applied to the calculation of buckling stresses and natural frequencies.
Contributing Partner: UNT Libraries Government Documents Department
A Theoretical Investigation of the Rolling Oscillations of an Airplane with Ailerons Free

A Theoretical Investigation of the Rolling Oscillations of an Airplane with Ailerons Free

Date: January 1, 1944
Creator: Cohen, Doris
Description: An analysis is made of the stability of an airplane with ailerons free, with particular attention to the motions when the ailerons have a tendency to float against the wind. The present analysis supersedes the aileron investigation contained in NACA Report No. 709. The equations of motion are first written to include yawing and sideslipping, and it is demonstrated that the principal effects of freeing the ailerons can be determined without regard to these motions. If the ailerons tend to float against the wind and have a high degree of aerodynamic balance, rolling oscillations, in addition to the normal lateral oscillations, are likely to occur. On the basis of the equations including only the rolling motion and the aileron deflection, formulas are derived for the stability and damping of the rolling oscillations in terms of the hinge moment derivatives and other characteristics of the ailerons and airplane. Charts are also presented showing the oscillatory regions and stability boundaries for a fictitious airplane of conventional proportions. The effects of friction in the control system are investigated and discussed. If the ailerons tend to trail with the wind, the condition for stable variation of stick force with aileron deflection is found to ...
Contributing Partner: UNT Libraries Government Documents Department
Spin Tunnel Investigation of a 1/30 Scale Model of the North American A-5A Airplane

Spin Tunnel Investigation of a 1/30 Scale Model of the North American A-5A Airplane

Date: June 1, 1964
Creator: Lee, Henry A.
Description: An investigation has been made in the Langley spin tunnel to determine the erect and inverted spin and recovery characteristics of a 1/30-scale dynamic model of the North American A-5A airplane. Tests were made for the basic flight design loading with the center of gravity at 30-percent mean aerodynamic chord and also for a forward position and a rearward position with the center of gravity at 26-percent and 40-percent mean aerodynamic chord, respectively. Tests were also made to determine the effect of full external wing tanks on both wings, and of an asymmetrical condition when only one full tank is carried.
Contributing Partner: UNT Libraries Government Documents Department
Spin-Tunnel Investigation of a 1/28-Scale Model of a Subsonic Attack Airplane

Spin-Tunnel Investigation of a 1/28-Scale Model of a Subsonic Attack Airplane

Date: July 1, 1964
Creator: Lee, Henry A. & Healy, Frederick M.
Description: An investigation has been made of a 1/28-scale model of the Grumman A-6A airplane in the Langley spin tunnel. The erect spin and recovery characteristics of the model were determined for the flight design gross weight loading and for a loading with full internal fuel and empty external wing fuel tanks. The effects of extending slats and deflecting flaps were investigated. Inverted-spin and recovery characteristics of the model were determined for the flight design gross weight loading. The size of the spin-recovery tail parachute necessary to insure satisfactory spin-recovery was determined, and the effect of firing wing-mounded rockets during spins was investigated.
Contributing Partner: UNT Libraries Government Documents Department
A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System

A Theoretical Investigation of Longitudinal Stability of Airplanes with Free Controls Including Effect of Friction in Control System

Date: January 1, 1944
Creator: Greenberg, Harry & Sternfield, Leonard
Description: The relation between the elevator hinge moment parameters and the control forces for changes in forward speed and in maneuvers is shown for several values of static stability and elevator mass balance. The stability of the short period oscillations is shown as a series of boundaries giving the limits of the stable regions in terms of the elevator hinge moment parameters. The effects of static stability, elevator moment of inertia, elevator mass unbalance, and airplane density are also considered. Dynamic instability is likely to occur if there is mass unbalance of the elevator control system combined with a small restoring tendency (high aerodynamic balance). This instability can be prevented by a rearrangement of the unbalancing weights which, however, involves an increase of the amount of weight necessary. It can also be prevented by the addition of viscous friction to the elevator control system provided the airplane center of gravity is not behind a certain critical position. For high values of the density parameter, which correspond to high altitudes of flight, the addition of moderate amounts of viscous friction may be destabilizing even when the airplane is statically stable. In this case, increasing the viscous friction makes the oscillation stable again. ...
Contributing Partner: UNT Libraries Government Documents Department
Model tests of a wing-duct system for auxiliary air supply

Model tests of a wing-duct system for auxiliary air supply

Date: January 1, 1941
Creator: Bierman, D. & Corson, B. W., Jr.
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Low-speed wind-tunnel tests of a 1/8-scale model of the bell d-188a vtol airplane

Low-speed wind-tunnel tests of a 1/8-scale model of the bell d-188a vtol airplane

Date: August 25, 1958
Creator: Mc Kinney, M. O. & Smith, C. C., Jr.
Description: None
Contributing Partner: UNT Libraries Government Documents Department
An investigation of supersonic store interference in the vicinity of a 22 deg swept wing fuselage configuration at Mach numbers of 1.61 and 2.01

An investigation of supersonic store interference in the vicinity of a 22 deg swept wing fuselage configuration at Mach numbers of 1.61 and 2.01

Date: February 24, 1958
Creator: Geier, D. J.
Description: Pressure tunnel investigation of supersonic store interference in vicinity of 22 deg swept wing fuselage configuration at mach numbers 1.61 and 2.01.
Contributing Partner: UNT Libraries Government Documents Department
Transonic aerodynamic and trim characteristics of 1/15-scale models of the convair mx-1964 airplane with indented fuselage

Transonic aerodynamic and trim characteristics of 1/15-scale models of the convair mx-1964 airplane with indented fuselage

Date: January 1, 1953
Creator: Allis, A. E.; Foss, W. E., Jr. & Swihart, J. M.
Description: None
Contributing Partner: UNT Libraries Government Documents Department
Preliminary investigation of reflections of  oblique waves from a porous wall

Preliminary investigation of reflections of oblique waves from a porous wall

Date: November 9, 1950
Creator: Davis, D. D., Jr. & Wood, G. P.
Description: None
Contributing Partner: UNT Libraries Government Documents Department
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