Volume 8, Issue 3, 01 March 1937
Index of content:
8(1937); http://dx.doi.org/10.1063/1.1710277View Description Hide Description
8(1937); http://dx.doi.org/10.1063/1.1710279View Description Hide Description
8(1937); http://dx.doi.org/10.1063/1.1710281View Description Hide Description
In the preceding article we reviewed the classical theories of the solid state, and sketched an outline of the modern wave mechanical theory. We saw that the valence electrons of a solid occupy an energy spectrum composed of zones of energy levels, and that the observed differences among various solids can be correlated largely with differences in the distribution and population of these zones. In this issue we shall first discuss in turn each of the five main types of solids, to see what explanation the zone theory offers for their distinguishing peculiarities. Following this, we shall review very briefly the progress of the theory in interpreting certain structure‐insensitive volume properties.
8(1937); http://dx.doi.org/10.1063/1.1710282View Description Hide Description
The stress‐strain relations for the cold working of the ductile metals are described for a group of cases assuming that the stresses under which they yield plastically depend only on the permanent parts of the strains, leaving out of the consideration the influence of the elasticity and of the speed of the plastic deformation. The behavior of the metals in the strain‐hardening range is expressed by means of a strain‐hardening function which connects the octahedral shearing stress with the octahedral unit shear. These variables are defined for strains of finite magnitude.
8(1937); http://dx.doi.org/10.1063/1.1710283View Description Hide Description
In order to observe the behavior of a material under various conditions of strain‐hardening, copper bars were tested in tension, in compression and in torsion. The results of the different tests were plotted on the same set of coordinates as a means of correlation. The shearing stress in the octahedral planes was used as ordinates and the corresponding octahedral shearing strain was used as abscissae. Good agreement was found between the curves for tension, compression, and torsion for small strains, but for very large strains (as obtained near the ultimate strength of annealedcopper) the curves tend to separate to a marked degree. Hardness readings were also taken to check the relation between hardness and strain.
8(1937); http://dx.doi.org/10.1063/1.1710284View Description Hide Description
Laminated material is often used as insulation in an electrical device in such a way that a large component of the dielectric field passes through it parallel to its laminations. In present test methods dielectric lossmeasurements are made on such material with the dielectric field passing through it perpendicular to its lamination. It is evident that the two conditions are different and the dielectric losses as measured by test are not the same as exist when in use. This paper presents a test method by which power factor, dielectric constant and dielectric loss factor of laminated insulating materials can be measured with the dielectric field parallel to the laminations. Results of measurements made with the dielectric field parallel to laminations of both unconditioned and conditioned specimens are compared, respectively, with results obtained with the field perpendicular to laminations.