Browsing by Author "Wright, WJ"
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- ItemExperiments in extrusion, Part 1 - review of the theories of extrusion.(Australian Atomic Energy Commission, 1964-09) Wright, WJThe theories of extrusion are examined; considerable limitations exist in the analysis of extrusion conditions using either the semi-empirical approach, which is based on the assumption of homogeneous straining, or the slip-line approach. More information is required on the basic extrusion parameters such as yield stress and friction coefficient and on the variation of extrusion conditions with tooling geometry.
- ItemExperiments in extrusion, Part 2 - the hot extrusion of beryllium.(Australian Atomic Energy Commission, 1964-12) Wright, WJ; Silver, JM; Spain, SWA technique for the hot extrusion of beryllium powder within a mild steel sheath has been developed. Limitations exist with this technique in the control of extruded dimensions, particularly on complex sections or where the sheath thickness is greater than about 0.020 inch. The use of pre-consolidated powder billets is recommended to reduce the danger of the sheath buckling or splitting during extrusion and to improve the surface finish and dimensions of the product. Pick-up of oxygen and nitrogen by the beryllium was observed where the beryllium was not completely sealed from the atmosphere during heating and extrusion. This factor affected the mechanical properties of the material, particularly hardness. The mechanical properties of the sections were determined as a function of extrusion conditions; these properties are sensitive to the choice of extrusion temperature, presumably reflecting a tendency for residual work hardening to increase at the lower extrusion temperatures.
- ItemExperiments in extrusion, Part 3 - the mechanics of extrusion of beryllium.(Australian Atomic Energy Commission, 1964-12) Wright, WJ; Silver, JM; Whatham, JFThe extrusion pressures determined for beryllium and mild steel over a wide range of reductions in area at temperatures between 750ºC and 1050ºC are significantly lower than those reported previously. This is attributed to better control of temperature in the work reported, the effects of container friction were assessed and the coefficient of friction between tooling and billets was estimated as 0.03 — 0.035 when using graphite lubricants. The flow of metal in extrusion through various dies was examined using gridded billets; the velocity profiles and extent of the plastic field were determined. The work was applied to a study of the shapes developed from plane interfaces in the billets during extrusion; the interface shape necessary in die original billet to produce a plane interface in the extruded section was determined and applied in the basic extrusion technique to improve the yield of product.
- ItemUranium resources and requirements(Australian Atomic Energy Commission, 1975-08) Silver, JM; Wright, WJThe amount of uranium available to support the world's nuclear power programs depends on the price which users are prepared to pay for its recovery. As the price is raised, it is attractive to recover uranium from lower grade deposits, thereby increasing the total quantity available. About 3.5 million tonnes of uranium is estimated to be available to the Western World in deposits which could be recovered for present day costs of less that $A30 per kilogram. This amount is believed to be sufficient to meet the nuclear power program until the turn of the century. There are good prospects for the discovery of further deposits (particularly in Africa, Canada, South America and Australia) which could extend these resources. If the Fast Breeder Reactor is introduced by about 1990, it could ultimately decrease the uranium from about 2020 onwards. The total amount of uranium required to support the Light Water Reactor power program until this happens would be about 7 million tonnes. On present evidence, this could be available from high grade deposits, together with some low grade deposits and by-product sources at costs less than $A60 per kilogram. If the Fast Breeder Reactor is not introduced as expected, the demand for uranium will continue to increase and it could be necessary to recover uranium from black shales or ultimately from sea water at costs ranging up to $A300 per kilogram. Australia has about 19% of the reasonably assured resources of uranium in the Western World recoverable at costs of less than $A20 per kilogram, or about 9% of the resources (reasonably assured and estimated additional) recoverable at costs of less than $A30 per kilogram. Australia's potential for further discoveries of uranium is good. Nevertheless, if Australia did not export any of these resources it would probably have only a marginal effect on the development of nuclear power; other resources would be exploited earlier and prices would rise, but not sufficiently to make the costs of nuclear power unattractive. On the other hand, this policy could deny to Australia real benefits in foreign exchange earnings, employment and national development.
- ItemThe vacuum hot pressing of beryllium(Australian Atomic Energy Commission, 1964-03) Clare, TE; Smith, PD; Wright, WJThe optimum conditions for vacuum hot pressing of Pechiney electrolytic beryllium powder have been established and compacts produced with densities exceeding 99 per cent, of theoretical density; these conditions depend markedly on the geometry of the compact and the oxide content of the powders being pressed, Effects of compact geometry, including low densities in long compacts, are associated with loss of pressure through die—wall friction, particularly where the length—to—diameter ratio of the compacts is greater than 0.5 . The presence of 2.3 per cent, beryllium oxide as a surface film on the particles reduced the final density attained to less than 97 per cent, of theoretical when pressing with 1500 lb/in2 at 1080ºC whereas this density could be attained in unoxidised powder with only 800 lb/in2 for similar conditions. The narrow size range of the oxidised powder may also have contributed to this difficulty in pressing.