National Advisory Committee for Aeronautics (NACA) - 45 Matching Results

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Elastic properties in tension and shear of high strength nonferrous metals and stainless steel - effect of previous deformation and heat treatment

Description: A resume is given of an investigation of the influence of plastic deformation and of annealing temperature on the tensile and shear elastic properties of high strength nonferrous metals and stainless steels in the form of rods and tubes. The data were obtained from earlier technical reports and notes, and from unpublished work in this investigation. There are also included data obtained from published and unpublished work performed on an independent investigation. The rod materials, namely, nickel, monel, inconel, copper, 13:2 Cr-Ni steel, and 18:8 Cr-Ni steel, were tested in tension; 18:8 Cr-Ni steel tubes were tested in shear, and nickel, monel, aluminum-monel, and Inconel tubes were tested in both tension and shear. There are first described experiments on the relationship between hysteresis and creep, as obtained with repeated cyclic stressing of annealed stainless steel specimens over a constant load range. These tests, which preceded the measurements of elastic properties, assisted in devising the loading time schedule used in such measurements. From corrected stress-set curves are derived the five proof stresses used as indices of elastic or yield strength. From corrected stress-strain curves are derived the secant modulus and its variation with stress. The relationship between the forms of the stress-set and stress-strain curves and the values of the properties derived is discussed. Curves of variation of proof stress and modulus with prior extension, as obtained with single rod specimens, consist in wavelike basic curves with superposed oscillations due to differences of rest interval and extension spacing; the effects of these differences are studied. Oscillations of proof stress and modulus are generally opposite in manner. The use of a series of tubular specimens corresponding to different amounts of prior extension of cold reduction gave curves almost devoid of oscillation since the effects of variation of rest interval and extension spacing ...
Date: March 1, 1947
Creator: Mebs, R W & Mcadam, D J
Partner: UNT Libraries Government Documents Department

Tests on stiffened circular cylinders

Description: Compressive tests were made of two series of stiffened circular cylindrical shells under axial load. All the shells were 16 inches in diameter by 24 inches in length and were made of aluminum-alloy sheet curved to the proper radius and welded with one longitudinal weld. The ratios of diameter to thickness of shell wall in the two series of specimens were 258 and 572. Strains were measured with Huggenberger tensometers at a number of gage lines on the stiffeners and shell. The results of these tests indicate that a spacing of circumferential stiffeners equal to 0.67 times the radius is too great to strengthen the shell wall appreciably. The results are not inclusive enough to show the optimum in stiffeners. Plain cylinders without stiffeners developed ultimate strengths approximately half as great as the buckling strengths computed by the equation resulting from the classical theory and slightly greater than those computed by Donnell's large deflection theory.
Date: March 1, 1941
Creator: Holt, Marshall
Partner: UNT Libraries Government Documents Department

Shear Lag in a Plywood Sheet-Stringer Combination Used for the Chord Member of a Box Beam

Description: Theoretical and experimental investigations were made of the distribution of strains in a plywood sheet-stringer combination used as the chord member of a box beam acted upon by bending loads. The theoretical solution was obtained with the help of the principle of minimum potential energy and certain simplifying assumptions. Strain measurements were made on a build-up box beam by means of electrical-resistance strain gages connected with strain indicators. A very satisfactory agreement between the theoretical and experimental strains was obtained.
Date: March 1, 1948
Creator: Borsari, Palamede & Yu, Ai-Ting
Partner: UNT Libraries Government Documents Department

Ambient pressure determination at high altitudes by use of free-molecule theory

Description: From Introduction: "Several methods (references 1 and 2) based on gas-dynamic principles are available for reducing such measurements. The results obtained by these methods are subject to the limitation of the gas-dynamic theory which is that the mean free path of the molecules between impacts, is small with respect to the measuring device. Inasmuch as no information on the subject is to present known to be available, the purpose of the present paper is to present a method based on the concept of free-molecule theory for use in connection with this problem."
Date: March 1, 1949
Creator: Wiener, Bernard
Partner: UNT Libraries Government Documents Department

Preliminary Analysis of NACA Measurements of Atmospheric Turbulence Within a Thunderstorm - U.S. Weather Bureau Thunderstorm Project

Description: A general description of the field operations of the U.S. Weather Bureau thunderstorm project conducted in the vicinity of Orlando, Florida during the summer month of 1946 is given. The participation of NACA in this project is described and measurements of atmospheric turbulence taken by NACA are presented for one of the flights. The results indicate that some regions of thunderstorms may present no great hazard to flight, while exceptionally severe conditions of atmospheric turbulence may occur in other regions, or even in the same region, at about the same time. The results also indicate that these severe conditions of turbulence might lead to loss of control with the possible loss of the airplane.
Date: March 1, 1947
Creator: Tolefson, Harold B.
Partner: UNT Libraries Government Documents Department

Investigation of downwash and wake characteristics at a Mach number of 1.53 1: rectangular wing

Description: The results of an experimental investigation of the downwash and wake characteristics behind a rectangular plan-form wing of aspect ratio 3.5 are presented. The airfoil section was a 5-percent-thick, symmetrical double wedge. The tests were made at a Mach number of 1.53 and a Reynolds number of 1.25 million. A comparison between experimental and theoretical values of the downwash angles is made.
Date: March 1, 1949
Creator: Perkins, Edward W. & Canning, Thomas N.
Partner: UNT Libraries Government Documents Department

The Minimum Energy Loss Propeller

Description: Various cases are presented of the solution of the problem ot the most efficient propeller, more general cases being considered than the one by Betz in 1919: namely, that of a propeller under a limiting light load, The problem is solved directly and also with the aid of the Ritz method which became readily applicable after the author proposed a method for the solution of the propeller problem, in general, with the aid of trigonometric series. The design of a propeller with the aid of this method is given and an analysis is made of the effect of the fuselage and of the viscosity coefficient mu on the character of the solution of the variational problem.
Date: March 1, 1945
Creator: Poliakhov, N.
Partner: UNT Libraries Government Documents Department

Flow Pattern in a Converging-Diverging Nozzle

Description: The present report describes a new method for the prediction of the flow pattern of a gas in the two-dimensional and axially symmetrical case. It is assumed that the expansion of the gas is adiabatic and the flow stationary. The several assumptions necessary of the nozzle shape effect, in general, no essential limitation on the conventional nozzles. The method is applicable throughout the entire speed range; the velocity of sound itself plays no singular part. The principal weight is placed on the treatment of the flow near the throat of a converging-diverging nozzle. For slender nozzles formulas are derived for the calculation of the velocity components as function of the location.
Date: March 1, 1949
Creator: Oswatitsch, K. & Rothstein, W.
Partner: UNT Libraries Government Documents Department

The Characteristics Method Applied to Stationary Two-Dimensional and Rotationally Symmetrical Gas Flows

Description: By means of characteristics theory, formulas for the numerical treatment of stationary compressible supersonic flows for the two-dimensional and rotationally symmetrical cases have been obtained from their differential equations.
Date: March 1, 1949
Creator: Pfeiffer, F. & Meyer-Koenig, W.
Partner: UNT Libraries Government Documents Department

High-Speed Measurements on a Swept-Back Wing (Sweepback Angle phi = 35 Deg)

Description: In the following, high-speed measurements on a swept-back wing are reported. The curves of lift, moment, and drag have been determined up to Mach numbers of M = 0.87, and they are compared to a rectangular wing. Through measurements of the total-head loss behind the wing and through schlieren pictures, an insight into the formation of the compression shock at high Mach numbers has been obtained.
Date: March 1, 1947
Creator: Goethert, B.
Partner: UNT Libraries Government Documents Department

Ditching Tests of Two Models of the Army B-36 Airplane

Description: The ditching characteristics of the Army B-36 airplane were determined by testing 1/20- and 1/30-scale dynamic models in calm water in Langley tank no. 2 and at the outdoor catapult. The scope of the tests consisted of ditching the models at various conditions of simulated damage, landing attitudes, and speeds, with various flap settings using several degrees of restraint of the flap hinges. The ditching behavior was evaluated from recordings of deceleration, length of run, and motions of the models. The results showed that the airplane should be ditched at an attitude of about 9 deg with flaps full down. The probable ditching behavior will be a smooth run with a maximum longitudinal deceleration of 3g to 4g and a landing run of 4 to 5 fuselage lengths. Structural failure of the underside of the fuselage will not seriously affect the behavior of the airplane.
Date: March 1, 1948
Creator: Fisher, Lloyd J. & Cederborg, Gibson A.
Partner: UNT Libraries Government Documents Department