Simulation and modeling of flow-induced defect formation in meso-scaled plastic deformation

Pao Yue-kong Library Electronic Theses Database

Simulation and modeling of flow-induced defect formation in meso-scaled plastic deformation

 

Author: Wang, Jilai
Title: Simulation and modeling of flow-induced defect formation in meso-scaled plastic deformation
Degree: M.Sc.
Year: 2012
Subject: Metal-work
Deformations (Mechanics)
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: xiv, 124 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2526919
URI: http://theses.lib.polyu.edu.hk/handle/200/6665
Abstract: The requirements for manufacturing more complex components with superior mechanical properties greatly affected the developments of forging technology. The current and future needs of the aerospace industry, the increase in demand for stationary power systems, jet engines, and aircraft components, and the ever-increasing foreign technological competition require continuous upgrading of today’s technology. In recent years, the process design, analysis and control is increasingly important in the metal forming field due to increased competition, high quality product demands, lower margin profit, more consumer awareness and stringent standards in manufacturing industry. The traditional trial-and-error approach in manufacturing is no longer suitable for the current product developments. In order to obtain the desired geometry and mechanical properties, the process parameters must be investigated, well designed and properly controlled. In the current metal-forming industry, productivity, product quality and production economy are the fundamental considerations in process design. Product quality is the most critical issue in process design which means the process should be able to form the desired geometry accurately without any defects.
In this thesis, experiment about the cold extrusion process using prepared billet to investigate the defects formation mechanism and process. According to the experiment results the several folding defects are observed including the rarely observed inner folding. Subsequently, the FE-simulation is carried out to deeply study the folding formation mechanism and how to avoid these defects. Three design solutions namely four steps extrusion, backward extrusion, sliding insert, are proposed to prevent the folding defects formation based on the discovered defects formation mechanism with the help of CAE simulation. Die sets are designed and manufactured, and the first two design solutions are tested and verified by the experiments. The framework of sliding insert is proposed to obtain the desired component. Some state variables of simulation results are introduced to assess the design solution performance as systematic evaluation criterion. The integrated CAE simulation methodology is developed in this research which can effectively test and verify the performance of each design solution. To verify the developed methodology, a case study is presented to validate the performance and demonstrate the implementation procedure. The developed design and optimization methodology helps to evaluate the design at up-front design stage.

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