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Description of stress-strain curves by three parameters

Description: A simple formula is suggested for describing the stress-strain curve in terms of three parameters; namely, Young's modulus and two secant yield strengths. Dimensionless charts are derived from this formula for determining the stress-strain curve, the tangent modulus, and the reduced modulus of a material for which these three parameters are given. Comparison with the tensile and compressive data on aluminum-alloy, stainless-steel, and carbon-steel sheet in NACA Technical Note No. 840 indicates that the formula is adequate for most of these materials. The formula does not describe the behavior of alclad sheet, which shows a marked change in slope at low stress. It seems probable that more than three parameters will be necessary to represent such stress-strain curves adequately.
Date: July 1, 1943
Creator: Ramberg, Walter & Osgood, William R

Effect of rivet pitch upon the fatigue strength of single-row riveted joints of 0.025- to 0.025-inch 24S-T alclad

Description: S-N curves at the range ratio of 0.2 were experimentally obtained for each of the following values of rivet pitch P as used in a single-row lap joint of 0.025- to 0.025-inch 24S-T alclad with one-eight AN430 round-head rivets: p=0.5, 0.75, 1.0, 1.5. Families of constant rivet pitch curves, which define the fatigue life for specimens studied, were developed. Curves showing the variation of the effective stress concentration factor in fatigue with rivet pitch and maximum load per rivet were also established.
Date: July 1, 1943
Creator: Seliger, Victor

NACA procedure for flight tests of aileron characteristics of airplanes

Description: Report describes the standard procedure that NACA used for evaluating the aileron characteristics of airplanes. The variables measured in the testing are rolling velocity, aileron positions, aileron stick forces or tangential wheel force, indicated airspeed, altitude, free-air temperature, and rudder position. The step-by-step flight procedure is described and information regarding evaluation of the control data and general suggestions is included.
Date: July 1943
Creator: Johnson, Harold I.

Relation of preignition and knock to allowable engine temperatures

Description: From Summary: "The results are given of an investigation of some of the limitations that now prevent increases in the temperature level of engine cylinder heads, and a review of previous work in the field is included to supplement these results. Attention was given, in particular, to the effects of fuel knock and surface ignition on cylinder temperatures and the effects of cylinder temperatures on performance. Data were obtained from a Wright C9GC air-cooled cylinder and from a Lycoming O-1230 liquid-cooled cylinder."
Date: July 1943
Creator: Biermann, Arnold E. & Corrington, Lester C.

Round heat-treated chromium-molybdenum-steel tubing under combined loads

Description: The results of tests of round heat-treated chromium-molybdenum-steel tubing are presented. Tests were made on tubing under axial load, bending load, torsional load, combined bending and axial load, combined bending and torsional load, and combined axial, bending, and torsional load. Tensile and compressive tests were made to determine the properties of the material. Formulas are given for the evaluation of the maximum strength of this steel tubing under individual or combined loads. The solution of an example is included to show the procedure to be followed in designing a tubular cantilever member to carry combined loads.
Date: July 1, 1943
Creator: Osgood, William R

Some yawing tests of a 1/30-scale model of the hull of the XPB2M-1 flying boat

Description: Report discusses the results of yawing tests on a model of the complete hull of the XPB2M-1. The tests indicated that there was a tendency toward directional instability in the vicinity of the hump. The researchers concluded that at a certain range, the curves of yawing moment are discontinuous, and this has led to difficulty in preliminary test flights.
Date: July 1943
Creator: Locke, F. W. S., Jr

Theory of self-excited mechanical oscillations of hinged rotor blades

Description: From Summary: "Vibrations of rotary-wing aircraft may derive their energy from the rotation of the rotor rather than from the air forces. A theoretical analysis of these vibrations is described and methods for its application are explained herein." Information about self-excited speed range and shaft-critical speed are provided for any rotor with more than two blades.
Date: July 1943
Creator: Coleman, Robert P.

Wind-Tunnel Tests of the 1/9-Scale Model of the Curtiss XP-62 Airplane with Various Vertical Tail Arrangements

Description: The effect of various vertical tail arrangements upon the stability and control characteristics of an XP-62 fighter model was investigated. Rudder-free yaw characteristics with take-off power and flaps deflected were satisfactory after dorsal fin modifications. Directional stability was obtained with all modified vertical tails. Satisfactory rudder effectiveness resulted partly because the dual-rotation propellers produced no asymmetric yawing moments. Pedal forces in sideslips were undesirably large but may be easily reduced.
Date: July 1, 1943
Creator: Wallace, Arthur R. & Recant, I.G.