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Bearing strengths of some wrought-aluminum alloys

Description: Although a number of investigations of the bearing strength of aluminum alloys have been made, the problem remains one of considerable interest to the aircraft industry. For this reason it has seemed advisable to make additional tests of the commonly used aircraft alloys in an effort to establish a better basis for the selection of allowable bearing values. Current design practice does not recognize the effect of edge distance upon bearing strengths, and for this reason edge distance was one of the principal variables considered in this investigation. The increasing emphasis being placed upon permanent set limitations makes it essential that more information on bearing yield phenomena be obtained. The object of this investigation was to determine bearing yield and ultimate strengths of the following aluminum alloy products: 17S-T, 24S-T, Alclad 24S-T, 24S-RT, 52S-0, 52S-1/2H, 52S-H, 53S-T, and 61S-T extrusions. Ratios of these bearing properties to tensile properties were also determined.
Date: August 1, 1943
Creator: Moore, R L & Wescoat, C

The Effect of Artificial Aging on the Tensile Properties of Alclad 24S-T and 24S-T Aluminum Alloy

Description: An experimental study was made to determine the effect of artificial aging on the tensile properties of alclad 24S-T and 24S-T aluminum-alloy sheet material. The results of the tests show that certain combinations of aging time and temperature cause a marked increase in the yield strength and a small increase in the ultimate strength; these increases are accompanied by a very large decrease in elongation. A curve is presented that shows the maximum yield strengths that can be obtained by aging this material at various combinations of time and temperature. The higher values of yield stress are obtained in material aged at relatively longer times and lower temperatures.
Date: August 1, 1943
Creator: Kotanchik, Joseph N.; Woods, Walter & Zender, George W.

The Effect of Mass Distribution on the Lateral Stability and Control Characteristics of an Airplane as Determined by Tests of a Model in the Free-Flight Tunnel

Description: The effects of mass distribution on lateral stability and control characteristics of an airplane have been determined by flight tests of a model in the NACA free-flight tunnel. In the investigation, the rolling and yawing movements of inertia were increased from normal values to values up to five times normal. For each moment-of-inertia condition, combinations of dihedral and vertical-tail area representing a variety of airplane configurations were tested. The results of the flight tests of the model were correlated with calculated stability and control characteristics and, in general, good agreement was obtained. The tests showed the following effects of increased rolling and yawing moments of inertia: no appreciable change in spiral stability; reductions in oscillatory stability that were serious at high values of dihedral; a reduction in the sensitivity of the model to gust disturbances; and a reduction in rolling acceleration provided by the ailerons, which caused a marked increase in time to reach a given angle of bank. The general flight behavior of the model became worse with increasing moments of inertia but, with combinations of small effective dihedral and large vertical-tail area, satisfactory flight characteristics were obtained at all moment-of-inertia conditions.
Date: August 1, 1943
Creator: Seacord, Charles L & Campbell, John P.

A method for determining the column curve from tests of columns with equal restraints against rotation on the ends

Description: The results are presented of a theoretical study for the determination of the column curve from tests of column specimens having ends equally restrained against rotation. The theory of this problem is studied and a curve is shown relating the fixity coefficient c to the critical load, the length of the column, and the magnitude of the elastic restraint. A method of using this curve for the determination of the column curve for columns with pin ends from tests of columns with elastically restrained ends is presented. The results of the method as applied to a series of tests on thin-strip columns of stainless steel are also given.
Date: August 1, 1943
Creator: Lundquist, Eugene E.; Rossman, Carl A. & Houbolt, John C