1、Die design for stamping a notebook case with magnesium alloy sheetsHeng-KuangTsai, Chien-ChinLiao, Fuh-KuoChen,Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan, ROCAvailable online 8 December 2007.AbstractIn the present study, the stamping process for manufacturing a
2、notebook top cover case with LZ91 magnesiumlithium alloy sheet at room temperature was examined using both the experimental approach and the finite element analysis. A four-operation stamping process was developed to eliminate both the fracture and wrinkle defects occurred in the stamping process of
3、 the top cover case. In order to validate the finite element analysis, an actual four-operation stamping process was conducted with the use of 0.6 mm thick LZ91 sheet as the blank. A good agreement in the thickness distribution at various locations between the experimental data and the finite elemen
4、t results confirmed the accuracy and efficiency of the finite element analysis. The superior formability of LZ91 sheet at room temperature was also demonstrated in the present study by successful manufacturing of the notebook top cover case. The proposed four-operation process lends itself to an eff
5、icient approach to form the hinge in the notebook with less number of operational procedures than that required in the current practice. It also confirms that the notebook cover cases can be produced with LZ91 magnesium alloy sheet by the stamping process. It provides an alternative to the electroni
6、cs industry in the application of magnesium alloys.Keywords: Notebook case; LZ91 magnesiumlithium alloy sheet; Multi-operation stamping; FormabilityArticle Outline 1. Introduction 2. Mechanical properties of magnesium alloy sheets 3. The finite element model 4. Multi-operation stamping process desig
7、n o 4.1. Two-operation stamping process o 4.2. Four-operation stamping process 5. Experimental validation 6. Concluding remarks Acknowledgments References1. IntroductionDue to its lightweight and good performance in EMI resistance, magnesium alloy has been widely used for structural components in th
8、e electronics industry, such as cellular phones and notebook cases. Although the prevailing manufacturing process of magnesium alloy products has been die casting, the stamping of magnesium alloy sheet has drawn interests from industry because of its competitive productivity and performance in the e
9、ffective production of thin-walled structural components. As for stamping process, AZ31 magnesium alloy (aluminum 3%, zinc 1%) sheet has been commonly used for the forming process at the present time, even though it needs to be formed at elevated temperature due to its hexagonal closed-packed (HCP)
10、crystal structure ( Chen et al., 2003 and Chen and Huang, 2003 ). Recently, the magnesiumlithium (LZ) alloy has also been successfully developed to improve the formability of magnesium alloy at room temperature. The ductility of magnesium alloy can be improved with the addition of lithium that devel
11、ops the formation of body centered-cubic (BCC) crystal structure ( Takuda et al., 1999a , Takuda et al., 1999b and Drozd et al., 2004 ).In the present study, the stamping process of a notebook top cover case with the use of LZ sheet was examined. The forming of the two hinges in the top cover of a n
12、otebook, as shown in Fig. 1(a and b), is the most difficult operation in the stamping process due to the small distance between the flanges and the small corner radii at the flanges, as displayed in Fig. 1(c). This geometric complexity was caused by a dramatic change in the corner radius when the fl
13、ange of hinge gets too close to the edge of the notebook, which would easily cause fracture defect around the flange of hinge and require a multi-operation stamping process to overcome this problem. In the present study, the formability of LZ magnesium alloy sheets was investigated and an optimum mu
14、lti-operation stamping process was developed to reduce the number of operational procedures using both the experimental approach and the finite element analysis.Full-size image (22K)Fig. 1. Flange of hinges at notebook top cover case. (a) Hinge, (b) top cover case and (c) flanges of hinge.View Withi
15、n Article2. Mechanical properties of magnesium alloy sheetsThe tensile tests were performed for magnesiumlithium alloy sheets of LZ61 (lithium 6%, zinc 1%), LZ91, and LZ101 at room temperature to compare their mechanical properties to those of AZ31 sheets at elevated temperatures. Fig. 2(a) shows th
16、e stressstrain relations of LZ sheets at room temperature and those of AZ31 sheets at both room temperature and 200 C. It is noted that the stressstrain curve tends to be lower as the content of lithium increases. It is also observed from Fig. 2(a) that the curves of LZ91 sheet at room temperature and AZ31 sheet at 200 C are close to each other. LZ101 sheet at room temperature exhibits eve
