1、 1 Die design for stamping a notebook case with magnesium alloy sheets Content Summary In the present study， the stamping processfor manufacturing anotebook top cover case with LZ91 magnesiumlithium alloy sheet at roomtemperature was examined using both the experimental approach and the finite eleme
2、nt analysis. A four-operation stamping process was developed to eliminate both the fracture and wrinkle defects occurred in the stamping process of the top cover case. In order to validate the finite element analysis， an actua four-operation stamping process was conducted with the use of 0.6mm thick
3、 LZ91 sheetas the blank. A good agreement in the thickness distribution at various locations between the experimental data and the finite element results confirmed confirmed the accuracy and efficiency of the ementanalysis.The super or for mability of LZ91 sheet at room temperature was also demonstr
4、ated in the present study by successful manufacturing of the notebook topcover case. The proposed four operation process lend sit selftoan efficient 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
5、 the notebook cover cases can be produced with LZ91 magnesium alloy sheet by the stamping process. It provides an alternative to the electronics industry in the application of magnesium alloys. Keywords: Notebook case； LZ91 magnesiumlithium alloy sheet； stamping； Multi-operation； Formability 2 1. In
6、troduction Due to It slight weight and good performance in EMI resistance, magnesium alloy has been widely used for structural components in the electronics industry, such as cellular phones and notebook cases. Although the prevailing manufacturing process of magnesium alloy products has been die ca
7、sting， the st- amping of magnesium all sheet has drawn interests from industry because of its competitive productivity and performance in the effective production of thin-walled structural components.As for stamping process， AZ31 magne siumalloy (aluminum 3%, zinc 1%) sheet has been commonly used fo
8、r the for ming process at the present time,even though it needs to be formed at elevated temperature due to its hexagonal closed packed (HCP) crystal structure Recently,the magnesiumlithium(LZ)alloy has also been successfully deve- loped to improve the formability of magnesium alloy at room temperat
9、ure. The ductility of magnesium alloy can be improved with the addition of lit hium that develops the formation of body centered-cubic (BCC) crystal structure (Takuda et al., 1999a,b； Drozd et al,2004). In the present study, the stamping process of a notebook top cover case with the use of LZ sheet
10、was examined. The forming of the two hinges in the top cover of a notebook, 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 geometri complexity
11、was caused by a dramatic change in the corner radius when the flange of get stooclo set the notebook,which would easily cause fracture defect around the flange of hinge and requirea multi-operation stamping process to overcome this problem. In the present study, the formability of LZ magnesium alloy
12、 sheets was invest- igated and an optimum multi-operation stamping process was developed to reduce the number of operation all proced using both the experiment approach and the finite element analysis. 3 Fig.1Flange of hinges at notebook top cover case. (a) Hinge, (b) top cover case and (c) flanges
13、of hinge. 2. Mechanical properties of magnesium content of lithium increases. It is also observ 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 exhibit seven better ductility than LZ91 and AZ31 do at 20
14、0,C. Since the cost of lithium is very expensive, LZ91 sheet, instead of LZ101 sheet, can be considered as a suitable LZ magnesium alloy sheet to render favorable formability at room temperature. For this reason ,the present study adopted LZ91 sheet as the blank for the notebook top cover case and a
15、ttempted to examine the formability of LZ91 at room temperature. In order to determine if the fracture would occur in the finite element analysis, the forming limit diagram for the 0.6mm thick LZ91 sheet was also established as shown in Fig. 2(b).alloy sheets The tensile test swereper formed for mag
16、nesiumlithiumalloy 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 the 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.
