Peculiarities of Microstructure Changing on Outer Surface of Carbon Steel Wire at Combined Deformational Processing by Drawing with Torsion

Drawing is the basic operation of wire manufacturing. At drawing a wire contacts with a die resulting in decrease of its diameter. During this interaction wire microstructure changes, especially on the contact area between a die and a wire. Specificity of microstructure changing on outer surface of carbon steel wire at drawing and its combination with torsion is presented in the paper. Using optical microscopy, it was found out that in the outer surface of carbon steel wire a narrow layer of highly deformed grains is formed. It is shown that thickness of this layer depends on the deformational processing intensity and is very specific depending on carbon content of the wire.

Velocity Gradients and the Evolution of Material Properties in a Narrow Layer near Surfaces of High Friction in Metal Forming Processes

Theoretical solutions for several rigid plastic models used to describe plastic flow in metal forming processes are singular in the vicinity of maximum friction surfaces. In particular, velocity gradients and the equivalent strain rate approach infinity near such surfaces. Such singular behavior can be excluded from consideration by choosing another friction law or material model. However, a different approach is proposed in the present paper. The starting point of this approach is that many experiments show that velocity gradients are very high in the vicinity of surfaces of high friction and that a narrow material layer is formed near such surfaces whose properties are very different from the properties in the bulk. Taking into account that the equivalent strain rate has a significant effect on the evolution of material properties, this experimental fact suggests that a theory based on the singular plastic solutions can be developed to describe the formation of the aforementioned material layer. In the present paper such a theory is proposed to describe the evolution of grain size. It is assumed that, in addition to the equivalent strain rate, the material spin has an effect of the evolution of grain size. It is then shown that the solutions for the material spin are singular as well. The interrelation between the present theory and strain gradient theories of plasticity is discussed. It is shown that it is necessary to account for the strain rate gradient to propose a more adequate theory to deal with the material flow near surfaces of high friction. Some experimental results on the formation of the narrow layer of ultra-fine grains in the vicinity of the fraction surface in extrusion are presented. An illustrative example to relate these experimental results and the new theory is given.

PHYSICALLY RELATED COORDINATE SYSTEM FOR COMPRESSIBLE FLOW

In this paper we apply the unified coordinate system developed by Hui and his co-workers to the steady compressible flow computation in such a way that the grid is generated physically and automatically. At the beginning of computation one only needs to build a narrow layer of grids near the left boundary. It is demonstrated that by continuously injecting layers of grid in the inflow boundary, the grid will gradually fill up the entire flow domain.

An experimental investigation of the flow of non-Newtonian fluids between rotating disks

The results of an experimental investigation on the flow of a non-Newtonian fluid between rotating, parallel disks are described in this paper. These results are qualitatively different from those exhibited by linearly viscous fluids in that a narrow layer of exceedingly high velocity gradients appears in the non-Newtonian fluid.

THE REPAIR OF POST-PARTUM NECROSIS OF THE ANTERIOR LOBE OF THE PITUITARY GLAND

ABSTRACT The healing of a post-partum necrosis of the anterior pituitary gland begins at about 4 days. The first change is the formation of a narrow layer of secondary atrophy at the inner edge of the live margin zone. There is then an invasion of macrophages which clear the debris from the other marginal zones and finally penetrate to a depth of 1 to 1.5 mm into the infarct. The remaining part of the central dead area becomes condensed and hyalinised in the course of the subsequent year or two. In the healed stage the remnants of parenchyma must certainly be functioning to their maximum capacity but they do not show any very striking histological changes to correspond to this. The cellular pattern of these remnants can not be correlated with variations in the clinical or pathological picture of prolonged hypopituitarism.

A “Vein” of Trondhjemite aplite: Granitization of Quartzite forming the sole of a Fold-thrust, Malin Head, Co. Donegal

A narrow layer of quartzite, emplaced within epidiorite by foldthrusting, is transformed to albite-trondhjemite aplite and contiguous zones of the epidiorite are enriched in biotite. By reference to six chemical analyses it is found that, with but small additions of potash these transformations can be accounted for by the combined processes of (a) mechanical mixing of the initial quartzite and epidiorite, and (b) metamorphic inter-diffusion between this mixture and the adjoining epidiorite.

VERTICAL EXTENT OF AURORAL ARCS AND BANDS

Measurements of the vertical extent of quiet arcs and bands from 181 auroral photographs, taken at Chesterfield (63.3 °N., 90.7 °W.), Coppermine (67.8 °N., 115.2 °W.), and Saskatoon (52.1 °N., 106.6 °W.), indicate that these forms are confined to a narrow layer of the atmosphere immediately above the 100-km. level. The most frequent thickness of this layer is between 20 and 40 km. Values in excess of 50 km. rarely occur. The percentage of auroral time that the luminosity is restricted to this layer is uncertain. The ratio of the number of arcs and bands to the total number of observed forms suggests a value exceeding 50%. When the occurrence of each form is weighted according to the angular field covered by it, a value as high as 60% is indicated.

Seleno-aluminium bridges

A seleno-aluminium bridge consists of a very thin and narrow layer of conducting selenium connecting two surfaces of aluminium which are separated by an insulator, such as glass or mica. The bridge may have a linear or a circular form. If the first, it is made thus: let P and Q be two strips of aluminium separated by a very thin plate of mica SS; the hole, as we look at the figure, forms a perfectly plane surface. If the plates P, Q are connected with a galvano­meter G and a battery B of a few cells, no current passes because of the insulation of the mica; but if we smear a thin layer of melted selenium over the surfaces of the plates, and, of course, over the mica, and then heat this layer in the well-known way until the selenium assumes the brownish grey modification which conducts a current, the narrow space of mica insulation is bridged over by a conductor, and the current of the battery passes. This bridge will have a certain conductivity in the dark, and that conductivity, as we shall see, will depend on the voltage of the battery. If light—even the feeble light of a distant candle—is allowed to fall on the face of the bridge, the conductivity is very much increased, and the galvanometer will show a much increased current.