An experimental investigation was conducted to study the effects of cumulative fatigue damage on endurance life. Stepwise-varying stress sequences were applied to rotating-cantilever-beam specimens. Typical curves of fatigue damage versus cycle ratio were deduced. The effect of scatter in the test results was evaluated.
An investigation was conducted to determine the effects of complex stress-time cycles on the fatigue properties of metals. The uniaxial stresses studied were complex in the sense that their stress-time patterns may be analyzed as composed of several harmonic components. Four theoretical design methods, and the results of an experimental investigation involving complex stresses are presented. Comparisons are made of the test results with the theory predictions.
The dependence of ion-chamber current on the density of the filling gas has been investigated, experimentally and analytically, to explore the use of an ion chamber as a high-pressure gas densitometer. A flat-plate ion chamber with a self-contained beta-particle source (Sr90-Y90) was used in experiments with methane, nitrogen, and carbon dioxide and for pressures up to 2000 psia and densities up to 9 lbm/ft3. Over an appreciable density range, the linearity of the current-density response was good with a static sensitivity of about 10−10 amp/(lbm/ft3) and a reproducibility of ±0.5 percent. Variables which could be used to increase the static sensitivity and the linear range were identified.
A new design method for V-belts has been developed. The new method involves a horsepower-life relationship which has been derived on the basis of the results of a vast experimental program of belt testing involving many hundreds of tests, together with an analysis of these data which introduces several new concepts of stress analysis for rubber-textile structures.
In this paper it is pointed out that the existing solutions for the deflections of thin plates under uniform lateral load and simply supported along all edges can be applied to the determination of the limiting temperature distributions in a fluid flowing in laminar motion in ducts of the same cross sections as those of the plates. The direct application of this solution is permissible only when (a) the axial temperature gradient is constant, with respect to both flow length and cross-section position. This implies uniform heating or cooling. (b) The cross section is a polygon. When the cross-section boundary contains curves, the constants of integration must be adjusted so that the boundary condition of nonslip flow is satisfied. Since the temperature and velocity distributions obtained by this analogy are expressed analytically, values of local heat transfer at any point in the cross-section boundary can be calculated. Examples are given for four cross sections, namely, rectangular, equilateral triangular, right-angled isosceles triangular, and semicircular. The heat-transfer distributions on the boundaries are calculated for square and equilateral triangular cross sections.
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