## You limited your search to:

**Partner:**UNT Libraries Government Documents Department

**Decade:**1930-1939

**Serial/Series Title:**NACA Technical Notes

**Collection:**Technical Report Archive and Image Library

### Local instability of columns with I-, Z-, channel, and rectangular-tube sections

**Date:**December 1, 1939

**Creator:**Stowell, Elbridge Z & Lundquist, Eugene E

**Description:**Charts are presented for the coefficients in the formulas for the critical compressive stress at which cross-sectional distortion begins in thin-wall columns of I-, Z-, channel, and rectangular-tube sections. The energy method of Timoshenko was used in the theoretical calculations required for the construction of the charts. The deflection equations were carefully selected to give good accuracy. The calculation of the critical compressive stress at stresses above the elastic range is briefly discussed in order to demonstrate the use of the formulas and the charts in engineering calculations. Two illustrative problems are included.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54537/

### Observations in flight of the region of stalled flow over the blades of an autogiro rotor

**Date:**December 1, 1939

**Creator:**Bailey, F J , Jr & Gustafon, F B

**Description:**The flow over the inner halves of the rotor blades on a Kellet YG-1B autogiro was investigated in flight by making camera records of the motion of silk streamers attached to the upper surfaces of the blades. These records were analyzed to determine the boundaries of the region within which the flow over the blade sections was stalled for various tip-speed ratios. For the sake of comparison, corresponding theoretical boundaries were obtained. Both the size of the stalled area and its rate of growth with increasing tip-speed ratio were found to be larger than the theory predicted, although experiment agreed with theory with regard to shape and general location of the stalled area. The stalled region may be an important factor in both the rotor lift-drag ratio and the blade flapping motion at the higher tip-speed ratios. The method of study used in this paper should be useful in further studies of the problem, including the reduction of the size of the region.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54525/

### Pressure-distribution measurements on a rectangular wing with a partial-span split flap in curved flight

**Date:**December 1, 1939

**Creator:**Rokus, Frank G

**Description:**Pressure-distribution tests were made on the 32-foot whirling arm of the Daniel Guggenheim Airship Institute of a rectangular wing of NACA 23012 section to determine the rolling and the yawing moment due to angular velocity in yaw. The model was tested at 0 and 5 degree pitch; 0, +/- 5, and +/- 10 degrees yaw; and with no flap and with split flaps 25, 50 and 75 percent of the wing span and deflected 60 degrees. The results are given in the form of span load distributions and as calculated moment coefficients. The experimental values of rolling- and yawing-moment coefficients were in fairly close agreement with theory.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54532/

### A recurrence formula for shear-lag problems

**Date:**December 1, 1939

**Creator:**Kuhn, Paul

**Description:**The analysis of the bending action in box beams with appreciable shear deformation of the flanges becomes very difficult in the general case of variable cross section and loading. This paper presents a convenient method of solving the problem by the familiar method of dividing the beam into a number of bays that can be assumed to have constant cross section and loading. Application of formerly derived shear-lag formulas leads to a general equation closely analogous in form to the well-known three-moment equation. A numerical example and two comparisons between calculation and experimental results are included.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54516/

### Stress concentration around an open circular hole in a plate subjected to bending normal to the plane of the plate

**Date:**December 1, 1939

**Creator:**Dumont, C

**Description:**An aluminum-alloy plate containing an open circular hole of diameter large compared with the thickness of the plate was subjected to bending forces normal to the plane of the plate. Deflection and strain measurements were taken for two different loads. Stress concentrations occurred at the edge of the hole and the maximum stresses were tangential to the hole at the ends of the transverse diameter. The maximum stress at the edge of the hole was 1.59 times the computed stress on the net section and 1.85 times the computed stress in a solid plate of the same dimensions subjected to the same bending forces. The maximum deflections were about 20 percent greater than the corresponding deflection for a solid plate of the same size subjected to the same bending forces. The smallest edge distance was equal to 2-1/2 times the diameter of the hole and the stress concentration on this side of the hole was the same as on the side where the edge distance was about 4-1/2 diameters. A theoretical analysis of the problem shows that, for an aluminum plate of infinite width, the stress concentration at the edge of the hole would be 1.87 times the stress in ...

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54521/

### Corrugated metal diaphragms for aircraft pressure-measuring instruments

**Date:**November 1, 1939

**Creator:**Goerke, V H & Wildhack, W A

**Description:**None

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc279681/

### Photoelastic analysis of three-dimensional stress systems using scattered light

**Date:**November 1, 1939

**Creator:**Weller, R & Bussey, J K

**Description:**A method has been developed for making photoelastic analyses of three-dimensional stress systems by utilizing the polarization phenomena associated with the scattering of light. By this method, the maximum shear and the directions of the three principal stresses at any point within a model can be determined, and the two principal stresses at a free-bounding surface can be separately evaluated. Polarized light is projected into the model through a slit so that it illuminates a plane section. The light is continuously analyzed along its path by scattering and the state of stress in the illuminated section is obtained. By means of a series of such sections, the entire stress field may be explored. The method was used to analyze the stress system of a simple beam in bending. The results were found to be in good agreement with those expected from elementary theory.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54514/

### Pressure-distribution investigation of an N.A.C.A. 0009 airfoil with a 50-percent-chord plain flap and three tabs

**Date:**November 1, 1939

**Creator:**Street, William G & Ames, Milton B

**Description:**Pressure-distribution tests of an N.A.C.A. 0009 airfoil with a 50-percent-chord plain flap and three plain tabs, having chords 10, 20, and 30 percent of the flap chord, were made in the N.A.C.A. 4- by 6- foot vertical tunnel. The tests supplied aerodynamic section data that may be applied to the design of horizontal and vertical tail surfaces. The results are presented as resultant-pressure diagrams for the airfoil with the flap and the 20-percent-chord tab. Plots are also given of increments of normal-force and hinge-moment coefficients for the airfoil, the flap, and the three tabs. The experimental results and values computed by analytical methods are in good agreement for small flap and tab deflections. The results of the tests indicated that the effectiveness of all three tab sizes in reducing flap hinge moments decreased with increasing flap deflection.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54501/

### Pressure-distribution measurements on a tapered wing with a partial-span split flap in curved flight

**Date:**November 1, 1939

**Creator:**Troller, TH & Rokus, F

**Description:**Pressure-distribution tests were made on the 32-foot whirling arm of the Daniel Guggenheim Airship Institute of a tapered wing to determine the rolling and the yawing moments due to an angular velocity in yaw. The model was tested at 0 degree and 5 degree pitch; 0 degree, 5 degree, and 10 degree yaw; and with split flaps covering 25, 50, 75, and 100 percent of the wing span and deflected 60 degrees. The results are given in the form of load distributions and as calculated moment coefficients. The experimental values of rolling- and yawing- moment coefficients were in fairly close agreement with theory.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54507/

### Tidewater and weather-exposure tests on metals used in aircraft

**Date:**November 1, 1939

**Creator:**Mutchler, Willard & Galvin, W G

**Description:**Tidewater and weather-exposure tests on various aluminum alloys, magnesium alloys, and stainless steels are now being conducted by the National Bureau of Standards. Exposures were begun in June 1938 and, according to present plans, are to continue over a 3-year period. The methods of exposure and the materials being investigated are described and the more important results obtained up to the conclusion of the first year's exposure are reported.

**Contributing Partner:**UNT Libraries Government Documents Department

**Permallink:**digital.library.unt.edu/ark:/67531/metadc54510/