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The Influence of the Aerodynamic Span Effect on the Magnitude of the Torsional-Divergence Velocity and on the Shape of the Corresponding Deflection Mode

Description: "A procedure which takes into account the aerodynamic span effect is given for the determination of the torsional-divergence velocities of monoplanes. The explicit solutions obtained in several cases indicate that the aerodynamic span effect may increase the divergence velocities found by means of the section-force theory by as much as 17 to 40 percent. It is found that the magnitude of the effect increases with increasing degree of stiffness taper and decreases with increasing degree of chord taper" (p. 1).
Date: February 1944
Creator: Hildebrand, Francis B. & Reissner, Eric
Partner: UNT Libraries Government Documents Department

Methods of Measurement of High Air Velocities by the Hot-Wire Method

Description: Investigations of strengths of hot wires at high velocities were conducted with platinum, nickel, and tungsten at approximately 200 Degrees Celcius hot-wire temperature. The results appear to disqualify platinum for velocities approaching the sonic range; whereas nickel withstands sound velocity, and tungsten may be used for supersonic velocities under standard atmospheric conditions. Hot wires must be supported by rigid prolongs at high velocities to avoid wire breakage. Resting current measurements for constant temperature show agreement with King's relation.
Date: February 1943
Creator: Weske, John R.
Partner: UNT Libraries Government Documents Department

The Photoviscous Properties of Fluids

Description: Note presenting a method that has been developed to permit the extension of the methods of photoelasticity to include the measurement of velocity distribution in a moving fluid. The method is based on the fact that viscous shear in certain liquids gives rise to double refraction, which may be linearly related to the shear stresses.
Date: February 1942
Creator: Weller, R.; Middlehurst, D. J. & Steiner, R.
Partner: UNT Libraries Government Documents Department

Determination of control-surface characteristics from NACA plain-flap and tab data

Description: From Summary: "The data from previous NACA pressure-distribution investigations of plain flaps and tabs have been analyzed and are presented in this paper in a form readily applicable to the problems of control-surface design. The experimentally determined variation of aerodynamic parameters with flap chord and tab chord are given in chart form and comparisons are made with the theory. With the aid of these charts and the theoretical relationships for a thin airfoil, the aerodynamic characteristics for control surfaces of any plan form with plain flaps and tabs may be determined. A discussion of the basic equations of the thin-airfoil theory and the development of a number of additional equations that will be helpful in tail design are presented in the appendixes. The procedure for applying the data is described and a sample problem of tail design is included."
Date: February 1941
Creator: Ames, Milton B., Jr. & Sears, Richard I.
Partner: UNT Libraries Government Documents Department

A Hot-Wire Circuit With Very Small Time Lag

Description: A circuit for a hot-wire anemometer for the measurement of fluctuating flow is presented in the present report. The principal elements of the circuit are a Wheatstone bridge, one branch of which is the hot wire; and an electronic amplifier and a current regulator for the brief current which in combination maintain the bridge balance constant. Hence the hot wire is kept at practically constant resistance and temperature, and the time lag caused by thermal inertia of the wire is thereby reduced. Through the addition of a nonlinear amplifying stage the reading of the instrument has been rendered proportional to the velocity. A discussion of certain characteristics of the circuit and the results of related calibrating tests are given.
Date: February 1943
Creator: Weske, John R.
Partner: UNT Libraries Government Documents Department

An Investigation of Sheet-Stiffener Panels Subjected to Compression Loads With Particular Reference to Torsionally Weak Stiffeners

Description: "A total of 183 panel specimens of 24ST aluminum alloy with nominal thickness of 0.020, and 0.040 inch with extruded bulb-angle sections of 12 shapes spaced 4 and 5 inches as stiffeners were tested to obtain the buckling stress and the amplitude of the maximum wave when buckled. Bulb angles from 3 to 27 1/2 inches long were tested as pin-end columns. The experimental data are presented as stress-strain and column curves and in tabular form" (p. 1).
Date: February 1940
Creator: Dunn, Louis G.
Partner: UNT Libraries Government Documents Department

Measurement of the Forces Acting on Gliders in Towed Flight

Description: "The magnitude, the direction, and the fluctuations of tow forces exerted upon gliders by towing them aloft behind an automobile were measured under a variety of conditions covering a range from gentle to severe types of operation. For these tests, the glider towing force did not exceed 1.6 of the gross weight of the glider. V-G records obtained during the towed-flight period as well as during the subsequent return glide to earth showed accelerations in the range from 3 to -1 g. The results of preliminary airplane tow tests are also presented" (p. 1).
Date: February 1940
Creator: Klemperer, W. B.
Partner: UNT Libraries Government Documents Department

An Improved Continuous-Indicating Dew-Point Meter

Description: Note presenting the development of a continuous-indicating dew-point meter that automatically maintains a mirror surface at the dew point. The instrument was found to have an average accuracy of 1 degrees Fahrenheit over the range of 75 to -45 degrees. The accuracy of the instrument is uncertain at temperatures below 32 degrees Fahrenheit by the difference in vapor-solid and vapor-liquid equilibrium temperatures.
Date: February 1947
Creator: Friswold, Frank A.; Lewis, Ralph D. & Wheeler, R. Clyde, Jr.
Partner: UNT Libraries Government Documents Department

Two-Stage Supercharging

Description: "The arrangement of the parts and the installation and control problems of the two-stage mechanically driven superchargers for aircraft engines are discussed. Unless an entirely new form of supercharging is developed, there will be a definite need for a two-stage centrifugal supercharger. It is shown that the two-stage mechanically driven supercharger itself is a comparatively simple device; the complications arise from the addition of inter-coolers and controls" (p. 1).
Date: February 1941
Creator: Buck, Richard S.
Partner: UNT Libraries Government Documents Department

A Generalized Vortex Theory of the Screw Propeller and Its Application

Description: "The vortex theory as presented by the author in earlier papers has been extended to permit the solution of the following problems: (1) the investigation of the relation between thrusts and torque distribution and energy loss as given by the induction of helical vortex sheets and by the parasite drag; (2) the checking of the theorem of Betz of the rigidly behaving helical vortex sheet of minimum induced energy loss; (3) the extension of the theory of the screw propeller of minimum energy loss for the inclusion of parasite-drag distribution along the blades" (p. 1).
Date: February 1940
Creator: Reissner, Hans
Partner: UNT Libraries Government Documents Department

Fatigue Tests on 1/8-inch Aluminum Alloy Rivets

Description: Note presenting an investigation of the fatigue characteristics of riveted joints in aluminum alloy sheet. The purpose of this report is to summarize all the results of fatigue tests that have been made to date in the Aluminum Research Laboratories of lap joints with 1/8-inch aluminum alloy rivets.
Date: February 1945
Creator: Andrews, H. J. & Holt, M.
Partner: UNT Libraries Government Documents Department

Pressure Distributions for Representative Airfoils and Related Profiles

Description: Note presenting selected pressure-distribution diagrams for a number of conventional and special airfoils. The conventional airfoils include the NACA 22, 44, and 230 series airfoils and Clark Y family and the special airfoils consist of circular-arc sections of several thicknesses and a number of synthetic airfoils. The pressure distributions are in most cases given for several lift coefficients including that at the ideal angle of attack.
Date: February 1946
Creator: Theodorsen, Theodore & Naiman, Irven
Partner: UNT Libraries Government Documents Department

Determination of stress-strain relations from "offset" yield strength values

Description: Report presenting an investigation of the shape of stress-strain curve for a material, especially when the material is subjected to compression, which may cause materials to become unstable at stresses beyond the elastic range. The ratio of stresses to effective modulus is explored in equation form.
Date: February 1944
Creator: Hill, H. N.
Partner: UNT Libraries Government Documents Department

Exhaust-valve temperatures in a liquid-cooled aircraft-engine cylinder as affected by engine operating variables

Description: Report presenting an investigation of the operating temperatures of sodium-cooled exhaust valves in a liquid-cooled cylinder for a large variety of engine conditions by means of a thermocouple embedded in the valve head. The engine operating variables that affected the valve temperature most for a given percentage change in the operating variable included fuel-air ratio, indicated mean effective pressure, compression ratio, and spark advance. Results regarding temperature variations in constant engine conditions, effect of engine operating variables on exhaust-valve temperatures, and exhaust-valve temperatures at which preignition was encountered are provided.
Date: February 1947
Creator: Sutor, Alois T.; Corrington, Lester C. & Dudugjian, Carl
Partner: UNT Libraries Government Documents Department

A new method of studying the flow of the water along the bottom of a model of a flying-boat hull

Description: A new method of studying the flow of the water along the bottom of a model of a flying-boat hull is described. In this method, the model is fitted with a transparent bottom and is divided down the center line by a bulkhead. The flow is observed and photographed through one-half of the model by means of the diffused illumination from a battery of lamps contained in the other half of the model. Photographs of the flow, particularly of the changes that occur when the step ventilates, are shown. The results of the present investigation indicate that the method has considerable promise, chiefly in connection with motion-picture studies.
Date: February 1940
Creator: Ward, Kenneth E.
Partner: UNT Libraries Government Documents Department

In-line aircraft-engine bearing loads 3: main-bearing loads

Description: Report presenting the application of dimensional analysis to the computation of the main bearing of a V-type in-line aircraft engine. Two crankshafts have been considered, one designed for higher operating speed than the other. Two types of engines are considered: one for regular V-type engines and one for production V-type engines.
Date: February 1947
Creator: Shaw, Milton C. & Macks, E. Fred
Partner: UNT Libraries Government Documents Department

Reactions with steel of compounds containing chemical groups used in lubricant additives

Description: Report presenting an investigation of the chemical reactions between steel of a type used in aircraft-engine cylinder barrels and compounds containing reactive groups commonly found in lubricant additives. The products formed by reaction at temperatures from 400 to 650 degrees F were analyzed by reflection electron diffraction. Results regarding the diffraction patterns, a description of the products found, and correlation of the results with results form other investigations are provided.
Date: February 1947
Creator: Powell, Allen S.
Partner: UNT Libraries Government Documents Department

A portable calibrator for dynamic strain gages

Description: From Summary: "A portable device for calibrating dynamic strain gages is described. The device contains a motor-driven cam, which applies alternating tensile loads to a metal strip 5/8 inch wide and 6 1/4 inches long. The cam is designed to produce a nearly sinusoidal variation of strain with time. Dynamic strain gages with gage lengths up to 5 inches may be calibrated by mounting them on the strip and by changing the frequency and the amplitude of the tensile load. The frequency may be varied from 15 to 30 cycles per second and the strain amplitude from 0 to 10x10-4 in steps of 2x10-4."
Date: February 1943
Creator: McPherson, Albert E.
Partner: UNT Libraries Government Documents Department

The End-Plate Effect of a Horizontal-Tail Surface on Vertical Tail Surface

Description: Note presenting the end-plate effect of the horizontal-tail surface on the vertical-tail surface as theoretically studied by derivation of the flow corresponding to the condition of minimum induced drag and by solution of the usual lifting-line equations. The results obtained by the two methods were considerably different, indicated that the condition derived is not a close approximation to the actual condition.
Date: February 1941
Creator: Katzoff, S. & Mutterperl, William
Partner: UNT Libraries Government Documents Department

An investigation of the aerodynamic characteristics of a rotating axial-flow blade grid

Description: Report presenting the results of an experimental investigation of the aerodynamic characteristics of a rotating axial-flow blade grid with pressure-increasing effect. Several techniques of measurement were used, including pressure distribution measurements, pitot tubes, and hot wire wake surveys. Results regarding the lift and pressure drag of the blade sections, aerodynamic characteristics of the blade sections, profile drag, and static pressure are provided.
Date: February 1947
Creator: Weske, John R.
Partner: UNT Libraries Government Documents Department

Bearing strengths of 75S-T aluminum-alloy sheet and extruded angle

Description: Report presenting an investigation to determine the bearing yield and ultimate strengths of 75S-T alloy in sheet form in both with- and across-grain directions and extruded angle in the longitudinal direction. Ratios of bearing to tensile properties were also determined.
Date: February 1945
Creator: Wescoat, C. & Moore, R. L.
Partner: UNT Libraries Government Documents Department

Observations on the behavior of some noncircular aluminum alloy sections loaded to failure in torsion

Description: Report presenting an investigation of the strength and stiffness characteristics of noncircular aluminum alloy sections loaded to failure in torsion. Results regarding torque-twist and torque-stress curves and stress-distribution diagrams are provided.
Date: February 1947
Creator: Moore, R. L.
Partner: UNT Libraries Government Documents Department

Bearing strength of some sand-cast magnesium alloys

Description: Report presenting testing to determine the bearing strength characteristics of some magnesium-alloy sand castings and the relation between those and more commonly determined tensile properties. The primary sand-cast magnesium alloys of interest for aircraft design are AM403, AM260, and AM265. Results of all of the tension, compression, and shear tests are provided in tables.
Date: February 1947
Creator: Moore, R. L.
Partner: UNT Libraries Government Documents Department