筆記本上蓋外殼的鎂合金薄板沖壓模具設(shè)計外文文獻(xiàn)翻譯、中英文翻譯

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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 magnesium–lithium alloy sheet at roomtemperature 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 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 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 demonstrated 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 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 magnesium–lithium alloy sheet；stamping； Multi-operation；Formability 1. Introduction 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 casting，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 for 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 magnesium–lithium(LZ)alloy has also been successfully deve- loped to improve the formability of magnesium alloy at room temperature. 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 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 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 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. Fig.1–Flange of hinges at notebook top cover case. (a) Hinge, (b) top cover case and (c) flanges 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 200,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 0.6mm thick LZ91 sheet was also established as shown in Fig. 2(b).alloy sheets The tensile test swereper formed for magnesium–lithiumalloy 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 stress–strain relations of LZ sheets at room temperature and those of AZ31 sheets at both room temperature and 200?C. It is noted that the stress–strain curve tends to be lower. Fig. 2 – Mechanical properties of magnesium alloy. (a) The stress–strain relations of magnesium alloy; (b) forming limit diagram (FLD) of LZ91 sheet. 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 four-node shell element was adopted to construct the mesh for blank. The material lproper ties and forming limitd iagram sobtained from the experiments were used in the finite element simulations. The other simulation parameters used in the initial run were: punch velocity of 5mm/s, blank-holder force of 3kN, and Coulomb friction coefficient of 0.1. The finite element software PAM STAMP was employed to perform the analysis, and the simulations were performed on a desktop PC. 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 showninFig.3(a).The simulation result, as show ninFig.3(b),indicates that fracture occurs at the corners of flanges, and the minimum thickness is less than 0.35mm. 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 simulation swere performed to study the parameters .That affect the occurrence off racture. Several approaches were proposed to avoid the fracture as well. Fig. 3 – The finite element simulations. (a) Finite element mesh and (b) fracture at the corners. 4. Multi-operation stamping process design In order to avoid the occurrence of fracture, a multi-operation stamping process is required. In the current industrial practice, itusually take satle ast tenoperational procedures to form the top cover case using the magnesium alloy sheet. In thepresent study, attempts were made to reduce the number of operational procedures. Several approaches were proposed to avoid the fracture, and the four-operation stamping process had demonstrated itself as a feasible solution to the fracture problem. To limit the length of this paper, only the two operation and the four-operation stamping processes were depicted in the following. 4.1 Two-operation stamping process The first operation in the two-operation stamp in process was side wall forming as shown in Fig.4(a),and the second one was the forming off lange of hing epresented in Fig.4(b),the height of the flange of hinge being 5mm .Fig.4(c)shows the thickness distribution obtained from the finite element simulation. The minimum thickness of the deformed sheet was 0.41mm and the strains were all above the forming limit diagram. It means the fractured effect could be avoided. Inaddition, the height of the flange conformed to the target goal to be achieved. How- ever, this process produced a critical defect of wrinkling, as shown in Fig. 4(d), on the flange of hinge, which induces a problem in the subsequent trimming operation. Hence, even though the two-operation stamping process solved the fracture problem at the corner of the bottom and the flange of hinge, a better forming process is still expected to solve the wrinkling of flange of hinge. Fig. 4 – Two-operation stamping process. (a) Formation of sidewalls, (b) formation of hinges, (c) thickness distribution and (d) wrinkle. 4.2. Four-operation stamping process The four-operation forming process proposed in the present study starts with the forming of three side wall sand the flange of the hinge with a generous corner radius, as shown in Fig.5(a).Since the side wall close to the flange was open and the corner radius was larger than the desired ones, the flange was successfully formed without fracture. Such process success-fully avoided the difficulty of forming two geometric features simultaneously, but increased the material flow of the blank sheet. The next step was to trim the blank outside the side walls, and to calibrate the corner radius of 4mm to the desired value of 2.5mm. The hinge was thus formed, as shown in Fig. 5(b). The third step was to fold the open side, so that the sidewall could be completed around its periphery, as shown in Fig. 5(c). The effect of trimming the extra sheet outside the sidewalls in the second step on the third step was studied. When the extra sheet was not trimmed, the thickness at the corner was 0.381mm, as shown in Fig. 5(d). The thickness of Table Comparison of thickness measured ABCD Experiment 0.42mm 0.44mm 0.49mm 0.53mm Simulation 0.423mm 0.448mm 0.508mm 0.532mm Error 0.71% 1.79% 3.54% 0.38% the corner increased to 0.473mm, as shown in Fig. 5(e), if the trimming was implemented in the second step. The excessive material producedby the folding process in the third step was then trimmed off according to the parts design. The last step was the striking process that is applied to calibrate all the corner radii to the designed values. The minimum thickness at the corner of the final product was 0.42mm,and all the strains were above the forming limit diagram. It is to be noted that Fig. 5(a–c) only shows the formation of one hinge. The same design concept was then extended to the stamping process of the complete top cover case. 5. Experimental validation In order to validate the finiteel ement analysis,an actualfour operation stamping process was conducted with the use of 0.6mm thick LZ91 sheet as the blank. The blank dimension and the tooling geometries were designed according to the finite element simulation results. A sound product without fracture and wrinkle was then manufactured, as shown in Fig. 6(a). To further validate the finite element analysis quantitatively, the thickness at the corners around the hinge of the sound product, as shown in Fig. 6(b), were measured and compared with those obtained from the finite element simulations, as listed in Table 1. It is seen in Table 1 that the experimental data and the finite element results were consistent. The four-operation process design based on the finite element analysis was then confirmed by the experimental data. Fig. 6 – The sound product. (a) Without fracture and wrinkle and (b) locations of thickness measured. Concluding remarks The press forming of magnesium alloy sheets was studied in the present study using the experimental approach and the finite element analysis. The formability of both AZ31 and LZ sheets was examined first. The research results in dicated th a the LZ91 sheet has favorable formability at room temperature, which is similar to that of AZ31 sheet at the forming temper- ature of 200C.The superior formability of LZ91 sheet at room tempera Ture 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 efficient approach to form the hinge in the notebook with fewer operational procedures than that required in the current practice. It also confirms that the notebook cover cases can be produced with LZ91 magne siumalloy LZ91sheet by the stamping process. It provides an alternative to the electronics industry in the application of magnesium alloys. Acknowledg ments The authors would like to thank the National Science Council of the Republic of China for financially supporting this research under the Project No. NSC-95-2622-E-002-019-CC3, which made this research possible. They would also like to thank ESI, France for the help in running the PAM STAMP program. References [1] Chen. F.K.Huang.T.B.Chang. C.K.2003. Deep drawing of square cups with magnesium alloy AZ31 sheets. Int. J. Mach. Tools [2] Manuf. 43.1553–1559.Drozd.Z..Trojanova′ .Z, Ku′ dela.S.2004. Deformation of behavior of Mg–Li–Al alloy. J. Mater. Compd. 378. 192–195. [3]Takuda.H.Yoshii.T. Hatta, N.1999a. Finite-element analysis of the formability of a based alloy AZ31 sheet. J. [4] Mater. Process. Technol. 89/90. 135–140.Takuda.H. Kikuchi.S. [5]Tsukada.T.Kubota.K.Hatta.N.1999b.Effect of strain rate on deformation behavior of a Mg–8.5 Li–1Zn alloy sheet at room temperature. Mater. Sci. Eng. 271, 251–256. 筆記本上蓋外殼的鎂合金薄板沖壓模具設(shè)計 內(nèi)容提要 在本研究中，在室溫下分別用實驗方法和有限元分析對筆記本上蓋的lz91鎂合金薄板沖壓工藝制造情況進行檢查。四操作沖壓工藝的開發(fā)消除了上蓋沖壓過程中的斷裂和褶皺缺陷。為了驗證有限元分析，以0.6毫米厚的LZ91薄板作為毛坯，執(zhí)行了一個實際的四操作沖壓工藝過程。在實驗數(shù)據(jù)和有限元結(jié)果之間，恰當(dāng)?shù)胤喜煌瑔卧械暮穸确植?，證實了有限元分析的精確性和有效性。本研究還通過成功地制造筆記本上蓋外殼論證了室溫下LZ91薄板的最優(yōu)可模鍛性。本文提出的四操作過程有助于產(chǎn)生一種有效的方法，實現(xiàn)用比目前實際要求還要少的操作程序來設(shè)計筆記本鉸鏈，也證實了筆記本外殼可以用LZ91鎂合金薄板的沖壓工藝來制造，提供了一個鎂合金在電子工業(yè)應(yīng)用中的選擇方法。 關(guān)鍵字：筆記本外殼；LZ91鎂合金薄板；多操作沖壓；可模鍛性 1. 緒論 鎂合金由于具有重量輕和在電磁干擾阻力下有良好性能的優(yōu)點，已被廣泛用于電子行業(yè)的結(jié)構(gòu)部件，如手機和筆記本電腦外殼。雖然在主要的鎂合金制造過程中產(chǎn)品是進行壓鑄的，但是由于鎂合金薄板的沖壓強競爭性的生產(chǎn)力和在有效生產(chǎn)薄壁結(jié)構(gòu)單元時的性能，在工業(yè)領(lǐng)域里人們已對其產(chǎn)生興趣。在沖壓過程中，盡管由于它封閉的六角晶體結(jié)構(gòu)以至它的形成需要高溫，AZ31鎂合金（鋁3％，鋅1％）薄板在當(dāng)前形成過程中已被廣泛應(yīng)用。 最近，鎂鋰（LZ）合金已研制成功，它可以改善室溫下鎂合金的可模鍛性。鎂合金的韌性可以通過增加鋰成分得到改善，來發(fā)展以立方體為中心的晶體結(jié)構(gòu)的坯體的形成。 在本研究中，檢驗了LZ薄板在筆記本電腦上蓋外殼的沖壓過程中的應(yīng)用。筆記本上蓋外殼的兩個鉸鏈的形成顯示在圖1的a和b中，由于邊緣和邊緣的小角落半徑之間微小的距離，鉸鏈的形成成了沖壓過程中最困難的運行部分，這些影響在圖1的c中已表示出來。這種幾何的復(fù)雜性是當(dāng)鉸鏈的邊緣與筆記本的邊緣太接近時，由角落半徑的變化引起的，這將很容易造成鉸鏈周圍的破裂，此時需要一個多操作沖壓過程來克服這個問題。 在本研究中， 研究了LZ鎂合金薄板的可模鍛性，并用實驗方法和有限元分析兩種方法開發(fā)了最優(yōu)多操作沖壓過程，來減少運行程序的數(shù)量。 圖1 筆記本上蓋外殼鉸鏈的邊緣 （a）鉸鏈 （b）上蓋外殼 （c）鉸鏈邊緣 2. 鎂合金薄板的力學(xué)性質(zhì) 對室溫下LZ61（鋰6％，鋅1％）、LZ91、LZ101鎂合金薄板與高溫下AZ31薄板在拉伸實驗中的力學(xué)性質(zhì)做比較。圖2（a）表明了LZ薄板在室溫下與AZ31薄板在室溫和200攝氏度時的應(yīng)力變化關(guān)系。據(jù)圖可知，應(yīng)力變化曲線隨著鋰的增加而降低。同時可從圖2觀察到，室溫下LZ91薄板和200攝氏度下AZ31薄板的力學(xué)性質(zhì)是很接近的，顯示了室溫下LZ101比室溫下LZ91和200攝氏度下AZ31更好的延展性。由于鋰的成本非常昂貴，可選LZ91作為合適的LZ鎂合金薄板，而不選用LZ101，來反應(yīng)室溫下良好的可模鍛性。基于此，本研究采用LZ91薄板作為筆記本上蓋外殼的毛坯，并研究其在室溫下的可模鍛性。 為了判定在有限元分析中是否會發(fā)生破裂，0.6毫米的LZ91薄板形成極限圖在圖2（b）中已給出。 圖2 鎂合金的力學(xué)性質(zhì) （a）鎂合金的應(yīng)力應(yīng)變關(guān)系（b）LZ91薄板的形成極限圖 3. 有限元模型 模具的幾何結(jié)構(gòu)是由CAD、PRO/E軟件構(gòu)造的，并用DELTAMESH軟件修正為有限元網(wǎng)格，如圖3（a）所示。模具可視為剛體，四節(jié)點外殼組成部分用來構(gòu)建毛坯網(wǎng)格。從實驗中獲得的材料性能和成形極限圖被用來做有限元模擬。其他用于初始運行的模擬參數(shù)有：沖床速度為5毫米/秒，壓邊力為3KN， 干摩擦系數(shù)為0.1 。有限元軟件PAM-STAMP用來進行分析，模擬在臺式電腦上完成。 有限元模型的構(gòu)造首先用來研究鉸鏈的單操作成形過程。考慮大批上蓋外殼的對稱性，我們只對其一半進行模擬，如圖3（a）所示。圖3（b）所顯示的模擬結(jié)果表明破裂發(fā)生在最小厚度小于0.35毫米的邊緣的拐角處。這意味著破裂問題是非常嚴(yán)重的，可能無法通過擴大邊緣的拐角半徑得到解決。進行有限元模擬來研究影響發(fā)生破裂的參數(shù)，并提出了幾種避免破裂的方法。 圖3 有限元模擬 （a）有限元網(wǎng)格 （b）拐角處的破裂 4. 多操作沖壓過程設(shè)計 為了避免發(fā)生破裂，多操作沖壓過程是必需的。在目前的工業(yè)實踐中，使用鎂合金薄板形成上蓋外殼通常需要至少十個運行程序。在本研究中，我們試圖減少運行程序數(shù)目，并提出了幾種方法來避免破裂，證明了四操作沖壓過程在破裂問題中是一個可行的解決辦法。由于文章長度的限制，接下來只對兩操作和四操作沖壓過程進行描述。 4.1 兩操作沖壓過程 兩操作沖壓過程中的第一個運行程序是形成側(cè)壁，如圖4（a）所示，第二個運行程序是形成高度為5毫米的鉸鏈邊緣，如圖4（b）所示。圖4（c）顯示了從有限元模擬中得到的厚度分布，變形薄板的最小厚度為0.41毫米，而且應(yīng)力都高于成形極限，這意味著破裂是可以避免的。此外，邊緣的高度符合要實現(xiàn)的目標(biāo)。然而，如圖4（d）所示，這一進程產(chǎn)生了一個關(guān)鍵的缺陷——在鉸鏈邊緣處發(fā)生起皺，這將導(dǎo)致在后面去毛刺過程中產(chǎn)生問題。因此，盡管兩操作沖壓過程解決了底部和鉸鏈邊緣拐角處的破裂問題，仍期望有更好的形成過程來解決鉸鏈邊緣的起皺問題。 圖4 兩操作沖壓過程 （a）側(cè)壁的形成（b）鉸鏈的形成（c）厚度分布（d）起皺 4.2 四操作沖壓過程 四操作形成過程在本研究中的提出，如圖5（a）所示，是始于三個側(cè)壁和具有大的拐角半徑的鉸鏈邊緣的形成。由于邊緣附近的側(cè)壁是打開的，而且拐角半徑比設(shè)計的要大，可成功形成邊緣，而且無破裂現(xiàn)象。這樣的過程成功地避免了同時形成兩個幾何特征的困難，但增加了毛坯薄板的材料流通量。下一步工作是對側(cè)壁界外的毛坯進行修剪，并把4毫米的拐角半徑修正到要求的2.5毫米。鉸鏈就這樣形成了，如圖5（b）所示。第三步是把打開的一面折起來，這樣側(cè)壁就可以完成其周邊區(qū)域了，如圖5（c）所示。研究了第二步中修剪側(cè)壁界外的毛坯對第三步的影響。當(dāng)多余的薄板沒有被修剪時，拐角的厚度是0.381毫米，如圖5（d）所示，而當(dāng)?shù)诙街行藜艄ぷ鲗嵤┖蠊战呛穸仍黾拥?.473毫米，如圖5（e ）所示。第三步中由折疊過程產(chǎn)生的多余的材料在接下來的零件設(shè)計中會被作修剪處理。最后一步是最重要的一步，要對所有拐角半徑與設(shè)計值進行校準(zhǔn)。最終產(chǎn)品的拐角最小厚度是0.42毫米，并且所有的應(yīng)力都高于形成極限。這是應(yīng)當(dāng)指出的是，圖5（a-c）只顯示一個鉸鏈的形成。同樣的設(shè)計概念可延伸到完整的上蓋外殼的沖壓過程中去。 圖5沖壓過程 （a）第一步操作（b）第二步操作（c）第三步操作（d）未修剪（e）已修剪 5 實驗確認(rèn) 為了證實有限元分析，以0.6毫米厚的LZ91薄板作為毛坯，進行了一個實際的四操作沖壓過程。毛坯的尺寸和模具的幾何形狀是根據(jù)有限元模擬的結(jié)果設(shè)計的。一個無破裂無皺紋的完美的產(chǎn)品便制造出來了，如圖6（a）所示。為了進一步定量驗證有限元分析，如圖6（b），對完美產(chǎn)品的鉸鏈附近的拐角的厚度進行測量，并與有限元模擬中得到的數(shù)據(jù)進行比較，結(jié)果列在表1中。 從表1可以看出，實驗數(shù)據(jù)和有限元結(jié)果是一致的。四操作過程是以有限元分析為基礎(chǔ)設(shè)計的，并由實驗數(shù)據(jù)進行驗證。 圖6 完美產(chǎn)品（a）無破裂無起皺（b）厚度測量點 總 結(jié) 本研究使用實驗方法和有限元分析兩種方法對鎂合金薄板的沖壓進行了研究。首先對AZ31和LZ薄板的可模鍛性進行檢驗。研究結(jié)果表明，LZ91薄板在室溫下有良好的可模鍛性，同樣，AZ31薄板在200攝氏度的形成溫度下也有該性質(zhì)。本研究還通過成功地制造筆記本上蓋外殼證實了LZ91薄板在室溫下的良好的可模鍛性。本文提出的四操作過程證實了它自身是一種有效的方法，可以運用比現(xiàn)在實際要求少的運行程序來制造筆記本的鉸鏈。它也證實，筆記本外殼可通過對LZ91鎂合金薄板進行沖壓制造而成。這為鎂合金在電子工業(yè)中的應(yīng)用提供了選擇方案。 References [1]Chen. F.K.Huang.T.B.Chang. C.K.2003. Deep drawing of square cups with magnesium alloy AZ31 sheets. Int. J. Mach. Tools [2]Manuf. 43.1553–1559.Drozd.Z..Trojanova′ .Z, Ku′ dela.S.2004. Deformation of behaviorof Mg–Li–Al alloy. J. Mater. Compd. 378. 192–195. [3]Takuda.H.Yoshii.T. Hatta, N.1999a. Finite-element analysis of the formability of a based alloy AZ31 sheet. J. [4]Mater. Process. Technol. 89/90. 135–140.Takuda.H. Kikuchi.S. [5]Tsukada.T.Kubota.K.Hatta.N.1999b.Effect of strain rate on deformation behavior of a Mg–8.5 Li–1Zn alloy sheet at room temperature. Mater. Sci. Eng. 271, 251–256. 18