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Minimization of the Exit – Curvature Profile in Extrusion Dies by Optimization of the Die Profile and Application of Die Land

Khalili Meybodi, Ali | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41684 (08)
  4. University: Sharif University of Technology
  5. Department: Mechanical Engineering
  6. Advisor(s): Assempour, Ahmad
  7. Abstract:
  8. One of the most practical deformation processes has been used to produce profiles with a diversity of shapes is forward extrusion. Minimizing the extrusion pressure along with reducing the curvature of the final product have always been the main concerns of the researchers in this area. To achieve the former, researchers have designed nonlinear dies and proposed various equations to determine proper die profile. To accomplish the latter, they have used bearing at the exit section of the extrusion die. The primary object of the current study is to design a proper bearing in order to eliminate the curvature of the final product in extrusion process. The effects of both bearing and die profile on final product distortion have been investigated. Three smooth curved (advanced-surface) dies with non-symmetric T-shaped sections and different off-centricities have been studied. For each die, the proper bearing has been designed and physical and numerical modeling have been performed to validate the design. In the first step, a formulation, based on Bezier curves, has been used to determine the exit velocity profile. Since the result of Bezier method is different from the actual velocity profile, the Chitkara corrective function has been modified and applied to improve the velocity field. Then, a deviation function has been developed to measure the curvature of the final product in terms of the exit velocity field. In the next step, the proper bearing for each die has been designed by using a proposed methodology and considering the obtained velocity field, the friction effects, and the geometry of the dies. In this methodology, bearing has been treated as an independent die which creates a certain amount of curvature in the output. If the direction of this curvature opposes the curvature of the product without application of bearing, straight profile is expected to exit the bearing. Finally, numerical and physical modeling have been performed on the die-bearing combination. According to the results, the curvature of the final product was eliminated to a great extent.
  9. Keywords:
  10. Direct Extrusion ; Nonlinear Die ; Bezier Curve ; Exit Curvature Profile ; Bearing

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