Multi-stage micro deep drawing process of micro cup with domed bottom and it's size effects

Pao Yue-kong Library Electronic Theses Database

Multi-stage micro deep drawing process of micro cup with domed bottom and it's size effects

 

Author: Li, Wenting
Title: Multi-stage micro deep drawing process of micro cup with domed bottom and it's size effects
Degree: M.Sc.
Year: 2015
Subject: Microtechnology.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Mechanical Engineering
Pages: x, 66 leaves : illustrations (some color) ; 30 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2817970
URI: http://theses.lib.polyu.edu.hk/handle/200/8053
Abstract: Recently microparts are increasingly needed in numerous industrial products found in many sectors, such as automotive, medical, telecommunication and so on. However, size effects are extremely important to influence on the manufacturing of microparts. In-depth understanding the deformation mechanism of microparts and designing methods to avoid defects during the manufacturing process will contribute to the development of industrial microparts. In this thesis, grain size effect on the multi-stage micro deep drawing process of micro cup with domed bottom is investigated deeply. A two-stage micro deep drawing system is designed to manufacture the micro cup with the domed bottom. Physical experiments are conducted by employing copper circle blanks of 0.2 mm thickness annealed at three different conditions, viz. 500, 600 and 750 °C with the holding time of 1, 2 and 3 hours respectively. Furthermore FEA simulation is used to study the effect of friction on the deformation load and verify the whole drawing process. The aim is to study the deformation defect, the grain size effect on deformation behavior and thickness variation of micro cups and the friction effect during the multi-stage micro deep drawing process. It reveals that blanking significantly affects the micro part’s deformation, earing and misalignment can be magnified, and the deformation load decreases with the increase of grain size in the multi-stage micro deep drawing process, while the grain size effect is not obvious in the second-stage micro deep drawing process. The friction coefficient effect on the deformation load is studied in FEA simulation as well. It can be observed that the deformation load increases with the increase of friction coefficient. Moreover, the micro part with larger grain size has more nonuniform thickness and severer thinning around the punch corner. Additionally, deformation load and thickness in simulation qualitatively agree with the values in the physical experiments.

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