LZ91鎂合金筆記型電腦蓋板之沖壓模具設計
Stamping Die Design for the Notebook Case with LZ91 Magnesium Alloy Sheets
Date Issued
2007
Date
2007
Author(s)
Liao, Chien-Chih
DOI
zh-TW
Abstract
Abstract
Due to its lightweight and high specific strength, magnesium alloys have been widely used for structural components. However, because of the hexagonal closed-packed (HCP) crystal structures, magnesium alloys show low ductility at room temperature, and require thermal activation to increase their formability. It is well known that ductility of magnesium alloys can be improved with addition of lithium which develops the formation of body centered-cubic (BCC) crystal structures. The BCC crystal structure gives rise to high formability at room temperature.
In the present study, the forming process was examined by the finite element simulations. According to finite element simulation analysis, two features in the notebook case were found to be relatively complex geometrically and were thus more difficult to form in the stamping forming. One of the complex features was caused by the small radius of the bottom, which would cause fracture and wrinkling during the stamping forming process. The process parameters resulting in the fracture defect were blank-holder force, blank size, and the location of draw-bead. However, this fracture defect could be easily removed by changing the punch comer radius, optimum blank size, and decreasing the blank-holder force. The other geometric complexity was caused by the dramatic change in the corner radius when the flange of hinge got too close to the edge of the notebook, which would easily cause the fracture defect around the flange of hinge during stamping forming process. Process parameters causing this defect includes the distance between the flange of hinge and the edge of the notebook, die corner radius, punch comer radius, friction coefficient, and lubricity. This fracture defect around the flange of hinge was eliminated through local trim of blank during the stamping forming process. As for the optimum position distance of local trim blank, it was determined based on the finite element simulation results.
To validate the finite element simulation results, an actual stamping process for producing notebook cases was performed. Three sets of tooling were machined to the profiles according to the finite element simulation results. The LZ91 sheets were then stamped into the shapes of notebook cases with the process parameters determined above. The experiment results have validated the finite element analysis for the process design for stamping LZ91 magnesium alloy sheets.
Subjects
鎂合金LZ91
有限元素法
筆記型電腦外殼
鉸鍊凸緣
沖壓模具設計
Magnesium Alloy LZ91
Finite Element Method
notebook case
flange of hinge
Die Design for Stamping
Type
thesis
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