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In the extrusion of sections with a multi-hole flat-faced die, the proper positioning of the die holes is of critical importance in avoiding the appearance of geometrical defects. In this paper, a methodology has been presented for radial positioning of the die holes in multi-hole extrusion process. A die with two non-symmetric T-shaped holes has been chosen as the computational example. A kinematically admissible velocity field at deformation zone has been obtained. The effects of dead metal zone formation have been considered in prediction of the velocity field. To measure the exit profile curvature a deviation function has been suggested. Using the proposed function, the velocity field has been used for prediction of the exit profile curvature and accordingly positioning of the die holes. It was found that a balanced metal flow at the exit of extrusion die could be achieved if the position of holes is near the centroid of the die area. In order to validate the results, finite element simulation has been used. The proposed methodology can be extended to dies with greater number of holes and more complex shapes. This methodology helps the die designer to have a better quality extrusion process.

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"DEFORM" three-dimensional finite element software is used to describe the behavior of plastic deformation of Ti-6Al-4V workpiece during blade preform extrusion process. Under different conditions of extrusion, numerical analysis of the process force parameter during extrusion process is presented. The relative effects of billet temperature, friction coefficient and die temperature on process force were investigated. To determine the process friction coefficient, the ring compression test of Ti-6Al-4V alloy with glass lubrication was performed. Also experimental tests were successfully done in order to manufacture blade preform. It was observed that billet temperature has much effect on force of Ti-6Al-4V alloy blade preform extrusion process. Die temperature has effect on the process force but its effect is not as much as the effect of the billet temperature. By increasing of the die temperature, the process force decreases. Experimental tests showed that the billet transfer process from the furnace to die has important effect on done or not done of the extrusion process because the billet transfer process from the furnace to die is cause of alters the billet initial temperature just before extrusion process. By reducing of the placing and transfer time of billet from the furnace to die, due to the vicinity of the billet and air, billet temperature have less reduction and therefore it becomes easier to shape. Also by increasing the friction coefficient, the force required for extrusion of Ti-6Al-4V alloy blades preform increased.

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In this study, severe plastic deformation of 7075 aluminum alloy was investigated using a new method, based on the combination of conventional upsetting and direct extrusion. In this process, which is called repetitive upsetting-extrusion, cylindrical samples were first subjected to upsetting and were subsequently subjected to extrusion at 250 °C with various processing cycles. Die design was carried out considering the possibility of conducting both upsetting and extrusion by using a single die and the maximum of four RUE cycles were successfully performed on the samples. Finite element method was used to simulate the deformation behavior of 7075 alloy during repetitive upsetting-extrusion processing and the strain distribution was obtained for the deformed samples. The finite element simulation results correlated fairly well with the microstructural observations. Based on the simulation results, the maximum effective strain was observed at the central region of the samples. The deformation behavior and the flow pattern were discussed based on the experimental and the simulation results. In addition, the effect of applied strain on mechanical properties of processed samples was studied. Tensile strength and elongation of deformed samples increased with extending the number of repetitive upsetting-extrusion cycles.