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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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Use of Forming limit diagrams (FLD) in process design of metal forming is a conventional method. Therefore many experimental and theoretical efforts have been carried out in order to investigate the FLDs. Many ways to obtain this FLDs and their effective parameters have been studied. But the stress state at these studies is planar which lead to an untrue model for several metal forming process such as incremental sheet forming. With this technique, the forming limit curve (FLC) appears in a different pattern, revealing an enhanced formability, compared to conventional forming techniques. Therefore, in this study, the effect of through thickness shear stress has been examined on the prediction of the forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak and Kuczynski (M–K) model with some modifications on the stress states for consideration of the through thickness shear stress effects. Also, the effective range of this stress has been investigated. The results showed that if the through thickness shear stress has a 10 per cent of yield stress value, this stress component has no effect on the FLD.

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Sheet Metals are widely used in different industries such as ship building. One important subject in these industries is to create the desired sheets through line heating process. In this paper, at first, the simulation of heat transfer between a gas torch and a plate during the line heating process is investigated. Impingement jet model is used to simulate the effect of a heat source (flame) and air cooling on the plate by using the commercial engineering software, FLUENT. Then, the computed temperature distribution by FLUENT is fed into the ANSYS FEM package for thermo Elasto-Plastic deformation analysis and the results are validated. Process execution needs heat paths and heat conditions. For this purpose heat paths of the cylindrical shape was obtained based on the Strain-Based Method. For thermal conditions a neural network was trained. In this regard, close to 63 different situations in different powers and torch speeds were run. Finally, to verify the thermal characteristics obtained for the cylindrical shape, paths and thermal conditions obtained was passed on a flat sheet metal by simulation and the result was compared with the desired shapes. It was shown that the Strain-Based Method in determining the thermal paths is very practical.

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In this study, special attention has been paid to modeling of the interface between the sheet metals in prediction of forming limit diagram (FLD) of two-layer sheets. In the present work, a two-layer sheet consists of 1.35 mm steel sheet and 0.45 mm copper sheet has been used. This two-layer sheet has been made by explosive welding method. To determine the FLD, numerical method has been used by applying ABAQUS finite element software. For this purpose, the so called Nakazima method has been simulated. The criteria used for determining the failure in steel and copper layers was GTN model. Also, in order to determine the failure in interface between the layers, the traction-separation law was used. For modeling the interface, cohesive elements were used. In order to verify the results, Nakazima tests were performed. The simulations and experimental works were done for both side directions of the sheets. The results indicate that the FLDs obtained by the numerical modeling are in good agreement with the experimental results.