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机械类毕业论文中英文对照文献翻译
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【机械类毕业论文中英文对照文献翻译】AZ31和
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【机械类毕业论文中英文对照文献翻译】AZ31和 AZ61镁合金的等温板料成形【PDF英文6页word中文翻译3460字8页】【有出处】,机械类毕业论文中英文对照文献翻译,PDF英文6页,word中文翻译3460字8页,有出处,【机械类毕业论文中英文对照文献翻译】AZ31和,AZ61镁合金的等温板料成形【PDF英文6页,word中文翻译3460字8页】【有出处】,机械类
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AZ31和 AZ61镁合金的等温板料成形李士永 陈韵珲 王建怡机械工业出版社 2001/1/18摘要在工业上已经有关于镁合金板料成形的报道，但这些报道很有可能是研究AZ31 和AZ61镁合金板料在不同的高温下成形的第一份正式的报道。结果表明，制造出厚度为0.5mm、1.3mm、1.7mm和2mm的挤压制品是可行的。当前成形出厚度为0.5mm的板料被看为是工业上取得的技术成就。可采用两种模具，凸模和凹模，凹模的设置似乎利用受压的气体将板料压入凹模型腔。这种技术从来没有在镁合金领域应用过，并且在工业制造上有很大的潜力。由于这种伸展性能已经在气压成形中体现出来，所以冲压成形应该可以实现，许多冲压实验已经证明了这一点。如2002年注册的B.V科学。关键词：AZ31；冲压；等温板料成形1.简介镁合金是用于结构成形的最轻的合金，在以前，将镁合金作为机构材料的不多，这是因为商业需求和执照方法的限制。现在，镁合金压铸成形在自动化领域变得流行起来，包括在笔记本电脑和蜂状电话领域。然而，这种加工方法并不适合于制造薄壁的镁合金结构，因为这样会造成大量的废料。大家都知道，由于镁晶体机构是密排六方，所以镁在室温下的成形能力较差，然而镁合金的加工性能可以随着加工温度的提高得到明显的改善，如加工温度提高的300以上。在这份报道中研究的是AZ31 和 AZ61在不同的高温下的板料成形，为的是能够实现从挤压板料中获得产品。可采用两种方法，冲压成形和气压成形，如图1所示。气压成形模的设计是利用受压的气体讲板料压入凹模型腔。这种方法有利于减少工件和冲模之间的摩擦力，所以材料的伸展性能能更好的展现出来。首先研究制品在不同部位上的应力分布，其实是描绘和构建出材料的流线结构。在另一方面，利用凸模冲压的方法不仅材料的延伸性能不好，而且应力分布不均匀，所以材料的失效形式和气压成形完全不同。图 1 (a)气压成形矩形模；（b）矩形凸凹模；（c）圆柱形凸凹模2. 材料和实验过程板料成形所采用的合金是AZ31和AZ61镁合金，AZ31和AZ61的第一个数字分别表示各自的含铝量为3%和6%，最后一个数字表示含锌量为1%。板料成形的材料是通过将203 mm762 mm的胚料通过开口为0.5, 1.3, 1.7和2mm的模具挤压而成。AZ31的工作温度为250，AZ61的工作温度为280。实验的基本工具是压力机，该压力机有一个熔炉可以提供一个等温的条件。对于气压成形，只需一个，宽40mm，长120mm，深度为20mm的模具，但是可以通过插入一个挤压垫成形厚度为8mm, 12mm和16mm的板料。将已经成形好的板料放置在模具上，具有压边圈的盖板下放并夹紧工件，然后室腔被密封，使受压的气体将板料压到凹模底部。在成形过程中，根据材料的形状不同所需要输入的气压也不同。有些板料标有明显的格子，以使可以通过测量格子的变形程度来确定该处的应力状态。对于冲压成形加工，矩形状的板料所用的模具也是矩形的，和气压成形的一样，但是凸模与凹模之间有2mm的间隙。对于圆形状的板料也是一样，模具直径为20mm，凸凹模之间有2mm的间隙。3.结果和分析3.1.气压成形1.7mm厚的AZ31镁合金（模具为矩形）3.1.1.气体增压速率的成形性能为了研究板料在不同的综合条件下（如成形厚度，温度，压力和加压时间）的成形能力，通过气压成形技术得到许多样品。在410成形的两个厚度为8mm样品的pt图如图2所示。和其他变形大的工件相比，这种变形小的工件只需要在较高压力下保压90s。对于进一步拉深深度为12mm的板料在同一温度下的pt曲线如图3所示。对于这个深度，成形温度在310以下也能成形，但是由于材料具有很大的流动应力，所以所需的压力更大，保压时间更长。对于成形深度为16mm的工件，进行里两组成形实验，一组成功了，一组失败了，这是由于所加的压力和保压时间都不同，如图4所示。如图5所示，尝试拉深深度为20mm，由于拉深深度从来没有高于16mm过，所以这注定要失败。以上两种失败的样品的照片如图6所示，失效的是从模具入口的的长边中间开始的。对于这些成形工艺，气压随着时间的延长而增加，因为成形的板料是球壳表面的一部分，瞬时的外形和厚度构成一个时间函数，然后应用这个方程式计算屈服应力值Ie=pr/2t。p表示气压，r表示弯曲半径，t表示厚度。这个公式可以大致的计算出以上实验的增压速率。一种先进的压力分析和精准的建模可以绘制出一个理想的pt曲线。图 2 图 3图 4 图 5图 2 410下成形出8mm深的矩形盒p-t图图 3 410和310下成形深度为12mm深的矩形盒子的成功案例的p-t图图 4 410下两组输入不同的压力-时间成形深度为16mm的板料，一个成功，一个失败 图 5 410下成形矩形盒（20mm深）的p-t关系图 6气压成形拉深1.7mm的板料16mm和20mm的失败案例3.1.2.材料的应力分析和流动轨迹在7种气压成形件中，有些工件有明显的网格，以便测量其应力分布，最初，网格都是相同的直径为2.5mm的圆，将其在成形之前印在板料表面。可以从变形的网格中看出：最大拉伸应力位于上部弯曲长边的中间位置。（图7）如果板料承受不利的增压速率和温度，失效就会从这里开始。从第一个实验测量的应力表明，大家认为的长边中间在平面应力状态下所得到的pt曲线不一定完全正确。值得注意的是，在压边圈下的材料并没有被完全固定好，而是有滑动的趋势，如图8所示。在高温下，板料被软化，盖板上的压边圈使板料向内缩进，在压力的作用下形成一个槽。最初槽里面和外面的界限是平行的，但是内边界的一部分向里面移动，这表明，压边圈上的材料即使在夹紧的情况下仍然被拉伸了。这种机制在成功应用气压成形技术中很重要。图 7放大成形工件不同部位变形的格子，（上图）12mm深，测量凹进去的那部分尺寸；（下图）16mm深，格子位于凸起的那部分，e1表示最大表面应力，e2表示与之垂直的方向。图 8气压成形中材料的流线3.2. 气压成形0.5mm厚的AZ31镁合金（矩形形状）完成了成形厚度为1.7mm厚的板料，更具挑战的是成形0.5mm厚的板料。他的实现可以被认为是工业上的一次技术成就。实验了三个工件，其中型腔的深度分别为12mm，16mm,20mm。工作温度在可行的范围（310410）内接近330。开始的增压速率设定在5 kgf/cm2 (490 kN/m2)，考虑到板料的厚度相对于原材料会减小三分之二。图像显示出来所采用成形工艺的增压速率是可行的。（图9）对于型腔是12mm和16mm，气体成形工艺是可行的。只是和先前的工艺相比，需要更多的时间。对于型腔是20mm的实验，成形工艺没有取得成功。板料从周边轨迹处开始失效。由于夹紧使加压气体密封是材料凹陷，所以失效开始的地方很薄。这种失效的形式和厚度为1.7mm的不同，他的失效出现在冲模的入口可以知道的是当弯曲更薄的板料时其冲模所受的压力更大。图 9 330下从0.5mm厚的板料成形不同深度的矩形盒的p-t关系图（a）12mm;(b)16mm（c）20mm3.3. 冲压成形厚度为1.3mm厚的矩形状AZ31镁合金对于冲压成形厚度为1.3mm厚的AZ31镁合金这类范畴中，在室温下对九个工件进行了测试（3295件、4353件）。正如所预测的那样，在室温下冲压成形并没有取得成功，在435的高温下，3个样品都能成形。在中低温度下，除了那五个工件外，只有一个可以完成成形。这就表明，当温度不是唯一的决定因数时，其他的因数，如润滑、冲压速度、和凸凹摸之间的间隙值对成形也有影响。这类失效的位置主要出现在转角处（图10）。在转角处冲模给板料施加一个集中的应力。这正式气体成形所能避免的。图 10 典型冲压失效的模型样品3.4.矩形冲头冲压成形2mm厚的AZ61镁合金普遍认为，AZ61镁合金比AZ31更难成形，这是以为前者的含铝量比后者多，两个2mm厚的板料在295下拉深16mm，只有一个成功了。它的加工温度比实际所需的温度相对要低一些。结果进一步说明了还有除了温度之外的影响因数。3.5.圆柱型冲头冲压成形2mm厚的AZ61镁合金用圆柱形冲头冲压成形深度为16mm深的18个工件中，在温度范围内达到屈服的如下所示： Temperature range (8C)No. of testYield24841150420435324504608549749822 成功和失败的结果从温度中就可以很清楚的知道，但是有一个转变区域温度不是唯一的决定因数，润滑作用，材料的预处理，凸凹模之间的间隙值等等都有可能成为影响因数。4. 结论AZ31和AZ61镁合金板料成形在较高温度下可以通过冲压成形和气压成形两种方法。温度是决定成形是否成功的主要因数，也有第二影响因数，如润滑，材料的预处理，冲压速度，凸凹模间隙等等。气压成形技术从未应用于镁合金，但是很有运用的潜力，运用这项技术，控制气压是最重要的技术。成形深度较浅的工件所需要的气压的量和气压速率都比成形深度较大的工件要小，气压成形失效的模具主要出现在模具入口的中间相对较薄处，而冲压成形的失效主要是出现在冲压的边缘部分。文献1 N.A. El-Mahallawy, M.A. Taha, E. Pokora, F. Klein, On the influenceof process variables on the thermal conditions and properties of highpressure die-cast magnesium alloys, J. Mater. Process. Technol. 73(1998) 125138.2 A. Mwembela, E.B. Konopleva, H.J. McQueen, Microstructuraldevelopment in Mg alloy AZ31 during hot working, Scripta Mater.37 (11) (1997) 17891795.3 H. Takuda, T. Yoshii, N. Hatta, Finite-element analysis of theformability of a magnesium-based alloy AZ31 sheet, J. Mater. Process.Technol. 8990 (1999) 135140.4 H. Takuda, H. Fujimoto, N. Hatta, Modelling on flow stress ofMgAlZn alloys at elevated temperatures, J. Mater. Process. Technol.8081 (1998) 513516.Isothermal sheet formability of magnesiumalloy AZ31 and AZ61Shyong Leea,*, Yung-Hung Chena, Jian-Yih WangbaDepartment of Mechanical Engineering, National Central University, Chung-li, Taiwan, ROCbChung-Shan Institute of Science and Technology, Lung-tan, Taiwan, ROCReceived 18 February 2001AbstractThere have been reports on the forming of magnesium alloy sheet in industry, but this paper is probably the first formal paper for studyingthe sheet formability of AZ31 and AZ61 at various elevated temperatures. The results indicate that it is feasible to form products fromextruded sheets of 0.5, 1.3, 1.7 and 2 mm thickness. Presently, the forming of a sheet of 0.5 mm thickness is considered to be a technicalachievement by industry. There were two kinds of tooling employed, punch and punchless. The punchless die setting used pressurized gas topress the sheet into a female die cavity. This technique applied to Mg-alloy is unprecedented and shows potential for industrial utilization. Asthe stretch ability was demonstrated in gas forming, punchdie pressing should be achievable, numerous punching tests being performed toconfirm this. # 2002 Elsevier Science B.V. All rights reserved.Keywords: AZ31; Punchdie pressing; Isothermal sheet forming1. IntroductionMagnesium alloy is the lightest metal that can beemployed for structural use. In the past, the demand forthis alloy as a structural material was not high because of itsless availability commercially as well as limited manufac-turing methods. In recent years, the die casting of magne-sium alloy has been prevailing in the making of parts in theautomotive industry 1,2 and such items as the covers ofnotebook computers as well as cellular phones. However,this process is not ideal in making thin-walled magnesiumstructures because an excessive amount of waste materialcanresult.Apotentialsolutionwouldbetoresorttothesheetformingprocess. Itiscommonlyrecognizedthat magnesiumpossesses poor formability at room temperature because ofits hexagonal close-packed structure 3,4. Fortunately, theworkability of Mg-alloy can be effectively improved byincreasing the working temperature, e.g., increasing above300 8C 2. In this paper, the sheet formability of AZ31 andAZ61 at various elevated temperatures is studied to assessthe feasibility of forming products from extruded sheets.There are two kinds of tooling employed, punch and punch-less as described in Fig. 1. The punchless die setting usespressurized gas to press the sheet into a female die cavity.This method has the advantage of eliminating frictionbetween the workpiece and the punch tool, so that thematerials stretch ability can be more genuinely exhibited.The strain distribution on various locations of the formedproduct will be studied. Further, the material flow path willbe traced and constructed. On the other hand, the punchdiemethod involves much less stretching effect, but also anuneven load distribution, so that its failure mode may bequite different from that in the gas-forming process.2. Materials and experimental procedureThe alloys employed in the sheet forming work are AZ31andAZ61, inwhichthemagnesium alloys contains 3and6%of aluminum, respectively, as indicated in the first numericaldigit in the designation: the last digit represents the zinccontent, which is 1% in the above cases. The material forsheetformingworkwasobtainedbyextrudingabilletof8 in.(203 mm) diameter ? 30 in. (762 mm) length through a diewith 0.5, 1.3, 1.7 and 2 mm openings at 250 8C (for AZ31)and280 8C (for AZ61).The basic tool for the experiment is apress machine equipped with a furnace offering desiredisothermal conditions. For thegasforming (punchless) work,only one die is needed, which is in rectangular shape of40 mm width and 120 mm length. The depth of the die is20 mm,butcouldbeadjustedto8,12and16 mmbyinsertingJournal of Materials Processing Technology 124 (2002) 1924*Corresponding author.E-mail address: .tw (S. Lee).0924-0136/02/$ see front matter # 2002 Elsevier Science B.V. All rights reserved.PII: S0924-0136(02)00038-9dummy blocks. The pre-formed flat sheet was positionedon the die; the cover plate with a peripheral rail was placedon to clamp the sheet; and then the chamber was sealed toenable pressurized gas to mold the sheet towards the contourof the die. The input gas pressure needed to be adjustedconstantlyinaccordancewiththevaryingsheetconfigurationduring the whole forming process. Some of the sheets weremarked with a grid so that local strain state could bedetermined by measuring the deformation of the grid. Forpunchdie pressing, the rectangular shape sheet used thesame die as that for gas forming but the die setting had a2 mm clearance between the punch and the die. A circular-shape pressing was also performed, where the die diameterwas 20 mm and there was a 2 mm clearance.3. Results and discussion3.1. Gas-forming of 1.7 mm thick AZ31(rectangular shape)3.1.1. Formability as a function of the gaspressurization rateSeveral specimens were formed by the gas-pressing tech-nique to study the formability of the sheet at various com-binations of forming depth and temperatures, as well aspressuretime (pt) input. Two pieces were formed success-fully at 410 8C with 8 mm depth following the pt profilesdepicted in Fig. 2. For this shallow forming, only 90 s wereneeded utilizing a higher pt profile as compared with otherdeepercases.Furtherformingto12 mmdepthwas performedat the same temperature with the pt profile shown in Fig. 3.This depth, formed at a lower temperature, 310 8C, was alsoFig. 1. Schematic diagram of the tools for isothermal sheet forming: (a) gas forming with a rectangular die; (b) rectangular punch and die; (c) circular punchand die.Fig. 2. Pressuretime profile leading to the successful forming of arectangular-shaped box of 8 mm depth at 410 8C.20S. Lee et al./Journal of Materials Processing Technology 124 (2002) 1924completed successfully, but it took a higher pressure and alonger time because the material had a larger flow stress. Forthe 16 mm case, two blow formings were done with onesuccess and one failure, due to the different pt inputsemployed as depicted in Fig. 4. The full depth, 20 mm,was tried with a pt profile (Fig. 5) that was even higherthan that for the two 16 mm cases, so it was doomed to fail.The above two unsuccessful specimens were photographedand are shown in Fig. 6. It is seen that failure started at themiddle of the long side on the die entrance. For all theseformingjobs,thegaspressureincreasedasthetimeincreased,which should be needed for maintaining the flow stress in thematerial at a constant level. Considering the forming sheet asa part of spherical shell surface having an instantaneousconfiguration and thickness as a function of time; then usingthe equation for calculating the flow stress, i.e. s pr=2t,where p is the gas pressure, r the curvature radius and t thethickness, can partially justify the above experimental pres-surization rate. An advanced stress analysis with accuratemodeling may suggest a more ideal pt curve.3.1.2. Strain distribution and the materials flow locusAmong the seven gas-formed pieces, some were markedwith grids in order to measure the strain distribution. Origin-ally, the grid was an array of identical circles of 2.5 mmdiameter, printed on the sheet surface prior to the formingwork. It can be seen from the deformed grids that themaximum tensile strains are located at the middle of the longside on the upper curved spot (Fig. 7). Failure would start atthis position if the sheet suffered an unfavorable pressuriza-tion rate and temperature. This measured strains are the firstexperimentaldisclosureindicatingthatthecommonlyFig. 3. Pressuretime profile leading to the successful forming of arectangular-shaped box of 12 mm depth at 410 and 310 8C.Fig. 4. Two different pt inputs for 16 mm depth gas forming at 410 8Cresulted in one success and one failure.Fig. 5. Pressuretime profile for the attempt to form a rectangular-shapedbox of 20 mm depth at 410 8C.Fig. 6. Failed gas forming of a 1.7 mm thick sheet for the cases of 16 and20 mm depths.S. Lee et al./Journal of Materials Processing Technology 124 (2002) 192421Fig. 7. Enlarged view of the deformed grids at various locations in the forming of a part to: (upper) 12 mm depth, measuring the grids on the concave (upper) side;(lower) 16 mm depth, the grids being on the convex side (lower). e1denotes the greatest local surface strain whilst e2is that in the perpendicular direction.Fig. 8. Flow paths of the material under peripheral sealing in the gas-forming process.assumed plane-strain state in the middle of the long side forderiving a pt curve may not be absolutely correct. It wasnoteworthy that the material under the peripheral sealing railwas not firmly held, but actually had the tendency to slide asshown in Fig. 8. At high temperatures the peripheral rail onthe cover plate indented the softened sheet and created agroove under pressing load. The outer and inner boundariesof the groove were originally parallel, however, some parts ofthe inner boundary was displaced inwards, indicating thatthe material under the peripheral sealing rail was still beingstretched evenunder the clampingload. This mechanismmaybe important in achieving successful gas forming.3.2. The gas-forming of 0.5 mm thick AZ31(rectangular shape)After completion of the gas forming with sheets of1.7 mm thickness, a more challenging task was that for0.5 mm thickness, where success would be considered atechnical achievement from the industrial point of view.Three pieces were tried with cavity depths of 12, 16 and20 mm. The working temperature was chosen to be 330 8Cbased on the previous feasibility with 310 and 410 8C.The initial pressurization rate was set to be 5 kgf/cm2(490 kN/m2) considering that the thickness is to bedecreased by more than two-thirds relative to that for thepreviously worked cases. Plots showing the pressurizationrate employed for the forming work are provided (Fig. 9).For the 12 and 16 mm cases, the gas forming work wassuccessful, only that much more time was consumed com-pared to the previous counterparts. For the 20 mm case,the forming was not successful, and failure started from theposition under the peripheral rail, which is thinner in thebeginning because of the indentation of the material due toclamping for sealing the pressurized gas. This failure modeis not the same as its 1.7 mm thick counterpart, in whichfailure occurred at the die entrance. It can be proposed thatthe stress is much higher at the die entrance when bendingthicker sheet.3.3. The rectangular punchdie forming of1.3 mm thick AZ31For the punchdie press work to ?16 mm depth on AZ31of 1.3 mm thickness in this category, nine pieces were testedat room temperature at 329 8C (five pieces) and at 435 8C(three pieces). The room temperature work was not asuccess, as was expected. At high temperature, 435 8C,all of the three specimens were formed successfully. Atintermediate temperature, only one out of the five workingpieces was formed successfully. This indicates that otherparameters such as lubrication, punch speed and clearancecan exhibit an influence when the temperature factor is notdominating. The failures in this category occurred mostly atthe corners (Fig. 10) where the punch exerted a concentrat-ing pulling force to drag the sheet down: this is just what thegas forming method can avoid.3.4. The rectangular punchdie forming of2 mm thick AZ61It is commonly stated that AZ61 is less formable thanAZ31 because of its greater aluminum content in the Mg-alloy. Two pieces of 2 mm thickness were punch-pressed to?16 mm deep at 295 8C; one was successful and one failed.The working temperature was relatively lower than thatwhich was expected to be needed. The results strengthenthe observation above that there are some influential factorsother than temperature.Fig. 9. Pressuretime profiles for the forming of rectangular-shaped boxesof depth: (a) 12 mm, (b) 16 mm and (c) 20 mm at 330 8C from 0.5 mmthick sheets.S. Lee et al./Journal of Materials Processing Technology 124 (2002) 1924233.5. The circular punchdie forming of 2 mm thick AZ61The circular punching of 16 mm depth of up to 18 pieceswas performed. The yield as a function of temperature islisted in the following:That the success and failure results are dictated by thetemperature seems quite clear. However, there is a transitionzone in which the temperature is not the only decisivefacto
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