笔记本顶盖的镁合金板材冲压模具设计外文翻译-模具设计(编辑修改稿)

笔记本顶盖的镁合金板材冲压模具设计外文翻译-模具设计(编辑修改稿)内容摘要：

of operational procedures using both the experimental approach and the finite element analysis. Fig. 1. Flange of hinges at notebook top cover case. (a) Hinge, (b) top cover case and (c) flanges of hinge. View thumbnail images 2. Mechanical properties of magnesium alloy sheets The tensile tests were performed for magnesium–lithium alloy sheets of LZ61 (lithium 6%, zinc 1%), LZ91, and LZ101 at room temperature to pare their mechanical properties to those of AZ31 sheets at elevated temperatures. Fig. 2(a) shows the stress–strain relations of LZ sheets at room temperature and those of AZ31 sheets at both room temperature and 200 176。 C. It is noted that the stress–strain 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 200 176。 C are close to each other. LZ101 sheet at room temperature exhibits even better ductility than LZ91 and AZ31 do at 200 176。 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 attempted 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 mm thick LZ91 sheet was also established as shown in Fig. 2(b). 9 Fig. 2. Mechanical properties of magnesium alloy. (a) The stress–strain relations of magnesium alloy。 (b) forming limit diagram (FLD) of LZ91 sheet. View thumbnail images 3. The finite element model The tooling geometries were constructed by a CAD software, PRO/E, and were converted into the finite element mesh, as shown in Fig. 3(a), using the software DELTAMESH. The tooling was treated as rigid bodies, and the fournode shell element was adopted to construct the mesh for blank. The material properties and forming limit diagrams obtained from the experiments were used in the finite element simulations. The other simulation parameters used in the initial run were: punch velocity of 5 mm/s, blankholder force of 3 kN, and Coulomb friction coefficient of . The finite element software PAM_STAMP was employed to perform the analysis, and the simulations were performed on a desktop PC. 10 Fig. 3. The finite element simulations. (a) Finite element mesh and (b) fracture at the corners. View thumbnail images A finite element model was first constructed to examine the oneoperation forming process of the hinge. Due to symmetry, only one half of the top cover case was simulated, as shown in Fig. 3(a). The simulation result, as shown in Fig. 3(b), indicates that fracture occurs at the corners of flanges, and the minimum thickness is less than mm. It implies that the fracture problem is very serious and may not be solved just by enlarging the corner radii at the flanges. The finite element simulations were performed to study the parameters that affect the occurrence of fracture. Several approaches were proposed to avoid the fracture as well. 4. Multioperation stamping process design In order to avoid the occurrence of fracture, a multioperation stamping process is required. In the current industrial practice, it usually takes at least ten operational procedures to form the top cover case using the magnesium alloy sheet. In the present study, attempts were made to reduce the number of operational procedures. Several approaches were proposed to avoid the fracture, and the fouroperation stamping process had demonstrated itself as a feasible solution to the fracture problem. To limit the length of this paper, only the twooperation and the fouroperation stamping processes were depicted in the following. . Twooperation stamping process T。