الفهرس | Only 14 pages are availabe for public view |
Abstract The aim of the present investigation is to study some factors affecting Impact Extrusion proeess. These faetors are, the effect of slug thickness, reduction percent, shear factor, and the eftect ot lubrication on the product quality. The literat~ related to the process has been critically reviewed with special reference to lead. The theoretical solutions to the probl~ have been surveyed and three models using Upper-Bound- theorem (2-zone, 3-zone and 4-zone) are presented. The flow characteristics of lead and the friction conditions under study have been established experimentally using the ring compression test teehnique as a testing method. A sub-press especially designed and constructed ineorporating load cell together with the different sets of tools required for extrusion were used to perform the experimental work. Extrusion was carried out on a 250 KN b.,y’draulic press’ of maximum downward speed of 70 mm/see. The theoretical and experimental results and discussions in the present work led to the foll~wing conclusions: (1) In the range of reduction used in the present work (80-95%), the 4-zone model was found to - ii - describe closer to the detormational behaviour of impact extrusion than the 2-zone and 3-zone models during the steady state extrusion range. (2) During the non-steady state extrusion range, the 4-zone model failed to deecribe the defol’mational behaviour of impact extrusion while the 2-zone and 3-zone models were more descriptive in this aspect. (3) In the case of steady state extrusion, using any of the proposed models, the Upper-Bound solution (as an energy minimization technique) indicate that the shear pressure plays the main role in the determination of the total pressure. While in the case of non-steady state extrusion, the frictional pressure plays that role. (4) The use of lubricant prevents the pressure welding of the dead metal zone with the rest ot the extruded cup so that it can separate. In the dry condition, the dead metal zone welds to the deformed cup and therefore no separation (5) takes place. The deviation of the 2-zone and 3-sone models from the experimental results in the non-steady state extrusion is mainly attributed to th.tr shortage in considering the contribution of the dead metal zone.(6) Prevention of cavitation was achieved successfully through the application of the equation proposed by Avitzur concerning the design of extrusion tools. (7) Sound extrusion products can be obtained when the shear tactor is relatively high. Kateria1 t10w with lubricants of low shear tactor was tound to be random andLLncontroDab1e. (8) Decreasing the extrusion reduetion percent improves the product quality. |