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Report
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Technical Note
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NASA Technical Note
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A Nonlinear Theory for Predicting the Effects of Unsteady Laminar, Turbulent, Or Transitional Boundary Layers on the Attenuation of Shock Waves in a Shock Tube with Experimental Comparison
The linearized attenuation theory of NACA Technical Note 3375 is modified in the following manner: (a) an unsteady compressible local skin-friction coefficient is employed rather than the equivalent steady-flow incompressible coefficient; (b) a nonlinear approach is used to permit application of the theory to large attenuations; and (c) transition effects are considered. Curves are presented for predicting attenuation for shock pressure ratios up to 20 and a range of shock-tube Reynolds numbers. Comparison of theory and experimental data for shock wave strengths between 1.5 and 10 over a wide range of Reynolds numbers shows good agreement with the nonlinear theory evaluated for a transition Reynolds nuniber of 2.5 million.
NASA Memorandum
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Wear and Sliding Friction Properties of Nickel Alloys Suited for Cages of High-temperature Rolling-contact Bearings
Wear and sliding friction properties of a number of nickel alloys operating against hardened SAE 52100 steel were studied. The alloys were cast beryllium nickel, heat-treated beryllium nickel, cast Inconel, Nimonic 80, Inconel X, Refractalloy 26, and Discaloy. Some of the allows studied may be useful as material for cages of rolling-contact bearings that operate at high speeds with temperatures above 600 degrees F in projected aircraft turbine engines or for bearings that operate in corrosive mediums. Desirable operating properties and the absence of extreme mass welding of all the materials could be associated with the development of the sliding surfaces of a naturally formed film of nickel oxide. On the basis of wear and friction properties, cast Inconel performed very well in these experiments and compares favorably with nodular iron. Nimonic 80 also showed promise as a possible cage material.
