"Results are given of drag tests of 4/9-scale model radial air-cooled engine nacelles made as a part of a general investigation of wing-nacelle-propeller interference. A small nacelle of the type commonly used with exposed engine cylinders was tested with various forms of cowling over the cylinders. The effects of cowling-ring position and of angle of ring chord to the thrust line were investigated. An N.A.C.A. cowled nacelle and a smooth body were also tested. The results are given at 50, 75, and 100 miles per hour for -5 degrees, 0 degrees, 5 degrees, 10 degrees, 15 degrees angle of pitch" (p. 1).

Note presenting a review of experiments on biaxial alternating stresses and simple combinations of static stress with alternating stress, which is shown to lead to a general criterion for the effect of static stress on the permissible amplitude of alternating stress. Tests were performed to determine the effect of static compression on alternating torsion, which is the one simple combination that had not been previously investigated. The results agree with the criterion.

Report presenting testing demonstrating that fatigue cracks initiate in preexisting slip bands on planes parallel to planes from tests on large-grained specimens of 1100 and 5052 aluminum alloys. The resolved shear stress on the planes in crystal where fatigue cracks had developed were compared to uncracked crystals. Results regarding the location fatigue cracks, number of stress cycles observed, and differences of the crystals observed in the two types of aluminum alloys are provided.

Note presenting a study of the impact behavior of normalized SAE X4130 steel after a variety of repeated stress treatments. Fatigue specimens of several types were used and the effects of surface finish, rest periods, stress amplitude, mean stress, stress concentration, and temperature during repeated stress received consideration.

Note presenting fatigue data for 76S-T61 aluminum alloy for several combinations of bending and torsion with both alternating and mean stresses. The literature on the effect of combined stress and of mean stress in fatigue is reviewed and the results of the present series are compared with those of various theories. Results regarding fatigue data, fatigue fractures, and static tests are provided.

Report presenting an experimental study of the changes in the stress-rupture life, ductility, hardness, and microstructure of S-816 and Inconel 550 specimens that had been exposed to varying amounts and conditions of thermal fatigue. Exposure to thermal-fatigue conditions was found to strengthen S-816 in stress rupture and to weaken Inconel 550.

"This report summarizes numerous theories relating to creep phenomena and the extent of current knowledge on the subject. Various possible mechanisms by which creep occurs both in single crystals and in polycrystals are described. An extensive bibliography of published works in this field is also included" (p. 1).

Note presenting a study to gain information as to the fundamental mechanism of fretting corrosion. The specific questions to be answered were whether chemical action played an important role in fretting of metal surfaces and whether any such action would improve the corrosion resistance of the metal investigated. The results indicated that the chemical action is of primary importance in fretting-corrosion effects and oxide formation does not give any protection to the metals but rather increases the rate of wear.

Report presenting experiments to study the start of fretting and cause of damage during the early stages of fretting of steel-steel combinations at a frequency 5 cycles per minute, an amplitude of 0.006 inch, a load of 150 grams, in air with relative humidity of less than 10 percent. Pure iron, glass, and iron oxide powder compacts were used in supplementary experiments.

Note presenting a summary of all phases of an investigation of fretting corrosion that has been conducted over a period of several years. Part I describes a test machine for measuring fretting damage under controlled experimental conditions. Part II presents data for mild steel fretted against itself, with a number of characteristics taken into consideration. Part III suggest a mechanism for the fretting process.

Report presenting testing in the variable density wind tunnel on two airship models known as the NPL Standardization Models, long and short. The resistance or shape coefficients were determined for each model through a range of Reynolds numbers. Further work is found to be necessary in the standardization of wind tunnels.

Report presenting a summary of the available information on lateral control. Some of the topics include the criterions used in lateral-control specifications, the factors involved in obtaining satisfactory lateral control, and the methods employed in making lateral-control investigations in flight and wind tunnels.