Volume 5, Issue 5, 01 May 1934
Index of content:
5(1934); http://dx.doi.org/10.1063/1.1745238View Description Hide Description
An analysis is made of the concept of oiliness and of the problems connected with the determination of the oiliness of oils. The major difficulty involves a separation of the effects of viscosity and oiliness since both effects enter into measurements made in practical devices and under practical conditions. On the basis of information obtained at the Bureau using several devices, a method is proposed for separating these two effects. This makes it possible therefore to investigate the effects of the pertinent variables on oiliness without the introduction of viscosity effects.
5(1934); http://dx.doi.org/10.1063/1.1745239View Description Hide Description
This paper describes apparatus developed to make creep tests on wires at high temperatures in a vacuum, and the results of a series of creep tests on wires of an alloy known as Konal at temperatures of from 800 to 1000°C. It is shown that Ludwik's logarithmic law connecting rate of deformation and stress holds for higher creep rates and stresses, although it certainly does not hold for the lower creep rates and stresses. In the range of temperatures tested, it is found that a linear relation best expresses the variation of the logarithm of the minimum creep rate with temperature. The method used is suggested as being readily adaptable to the making of short time creep tests, for obtaining comparative creep data in a relatively short time on materials used at high temperatures.
Concerning the Effect of Strain and Rate of Strain on Tensile Tests at Normal and Elevated Temperatures5(1934); http://dx.doi.org/10.1063/1.1745240View Description Hide Description
A few idealized cases of plastic flow have been analyzed in an attempt to show the influence of constant coefficients of work‐hardening and pure viscosity on tests made at normal and elevated temperatures. Although it is true that the assumed linear expression might approximately fit cases of very low stresses and small strains, of the order of a percent or less, it cannot be used to explain test results in which annealing and chemical changes occur, as they often do in practice. It is believed, however, that the cases discussed do bring certain fundamental considerations into sharper definition than in the past. They indicate that more emphasis should be placed by experimenters on the changes in yield stress (in the hardness) that occur in materials even without stress under exposure to time and high temperature.
5(1934); http://dx.doi.org/10.1063/1.1745241View Description Hide Description
Photoelastic tests are described in which the contact pressure distribution produced by laterally compressing a strip of Bakelite between rollers of the same material is approximately determined. Further, the shapes of the shear stress trajectories as predicted by the elastictheory for a cylinder compressed between two concentrated loads are compared with the shapes of the flow layers obtained by compression tests on mild steel cylinders. A fairly good agreement was obtained.