止動件沖裁模具設計【沖壓模具】【落料沖孔復合模】【說明書+CAD+UG】

止動件沖裁模具設計【沖壓模具】【落料沖孔復合?！俊菊f明書+CAD+UG】,沖壓模具,落料沖孔復合模,說明書+CAD+UG,止動件沖裁模具設計【沖壓模具】【落料沖孔復合?！俊菊f明書+CAD+UG】,止動件沖裁,模具設計,沖壓,模具,沖孔,復合,說明書,仿單,cad,ug 畢 業(yè) 設 計 說 明 書 止動件沖裁模具設計 完成時間 2016 年 11 月 22 日至 2017 年 4 月 22 日 目 錄 引言 ………………………………………………………………………………1 第1章 零件的工藝性分析………………………………………………………2 1.1 零件材料分析………………………………………………………………2 1.2 零件結構分析………………………………………………………………2 1.3 零件精度分析………………………………………………………………2 第2章沖裁方案的選定 …………………………………………………………3 第3章零件相應尺寸的計算 ……………………………………………………4 3.1 刃口尺寸的計算……………………………………………………………4 3.2 排樣方法的比較與選澤……………………………………………………4 3.3 沖壓力與壓力中心計算……………………………………………………5 第4章沖裁設備的選擇 …………………………………………………………7 第5章模具的零件設計以及模架選擇 …………………………………………8 5.1 該零件各板的選用 …………………………………………………………8 5.2 其它模具零件結構尺寸 ……………………………………………………9 5.3模架的選擇 …………………………………………………………………13 第6章 模具總裝圖 ……………………………………………………………14 結束語……………………………………………………………………………15 參考文獻…………………………………………………………………………16 引 言 工業(yè)是一個國家發(fā)展必不可少的部分，而模具更是基礎工業(yè)，而今社會在不停的進步，經(jīng)濟飛速發(fā)展，各式各樣的制品在不斷被生產(chǎn)，許多商品都靠著模具的多樣性。國民經(jīng)濟的發(fā)展與模具產(chǎn)業(yè)的發(fā)展也是想呼應的。 現(xiàn)如今模具應用也是越來越大眾化，生活中隨處可見模具制造的東西，我們也是越來越離不開這一技術，給我們的日常生活帶來了很多方便。我國這些模具制品扮演了越來越重要的角色，這是我國發(fā)展所必不可少的。 同樣在制造業(yè)中模具具有著重要地位，最近幾年模具制造能力在不斷提高，我們所能接觸到的模具也在不斷變得復雜。模具加工越來越高級化，對日常生活帶來了更多的影響，對我國當代經(jīng)濟的發(fā)展帶來了許多的便利。當然我國模具發(fā)展同樣存在著不足，這使得模具發(fā)展延慢了。三年的學習，我對模具的認識也有了深刻的理解。我這次設計的是一個止動件，通過對沖壓件進行分析，加上自己的理解，利用UG、CAD等軟件制圖，當然也有朋友同學的幫忙。這個設計是三年的一次大總結，當然我自身知識的不夠完善，總會有不足之處，也需要老師提點。 第1章 零件的工藝性分析 做的零件是圖1.1的落料沖孔件，材料是Q235鋼，零件厚度2mm，需要大批量進行生產(chǎn)。這個止動件的工藝性分析內(nèi)容如下： 圖1.1 1. 1零件材料分析 Q235是常見的普通碳素結構鋼，很方便沖裁成形的。 1.2零件結構分析 該零件比較簡單，結構對稱，沒有尖角。有兩個對稱的孔，所以，該零件的結構滿足沖裁的要求。 1.3模具精度分析 零件上尺寸未標注了公差要求，內(nèi)有2孔，其孔邊距，精度為11級。而其他尺寸屬于是自由尺寸，精度等級為IT14。所以可以正常的去沖裁。查表得到，mm，，，。 兩孔心距離。 所以該件適合沖裁。 第2章沖裁方案的選定 該零件為一落料沖孔件，可以使用如下三種方案： 方案一：先進行落料，后沖孔。采用兩套單工序模制造。 方案二：落料和沖孔復合沖壓，采用復合模制造。 方案三：沖孔和落料連續(xù)沖壓，采用級進模制造。 解析：與其他兩方案對比方案一的模具結構相對比較簡單，但卻需要兩套不一樣的模具和方案，顯得稍微難做，在這種大批量生產(chǎn)情況下不適合。方案二則是只需要設計一套較精準的模具，生產(chǎn)效率也算不錯，也很容易保證零件精度。而且要做的零件形狀較為簡單，制造起來不會太困難。方案三各方面都還算好，但輸在零件精度上，不太合適。 再因為孔邊距尺寸 mm有公差要求，所以選用了方案二。 第3章零件相應尺寸的計算 3.1 刃口尺寸的計算 根據(jù)這個零件形狀的特點，可以如下計算。 （1）查詢得到落料件尺寸的基本計算公式為 尺寸，可以得到凹模制造公差，，最大間隙，凸模制造公差。然后將所求值代入，經(jīng)過校驗，該不等式是成立的，所以該公式可使用。 即 （2）沖孔的計算公式如下 尺寸，查表得凸模制造公差，凹模制造公差。經(jīng)過計算，滿足不等式≤，由于這個尺寸是單邊磨損尺寸，所以可以減少一半時間，得到下列式子 （3）再算中心距： 尺寸 3.2 排樣方法的比較與選澤 通過查表，確定搭邊值： 兩個工件間的搭邊： 而工件邊緣搭邊： 得到步距為：32.2mm 條料寬度 確定后排樣圖3.2所示圖3.2 可以算到一個步距內(nèi)的材料利用率η為： 3.3 沖壓力與壓力中心計算 ⑴沖壓力 落料力 沖孔力 卸料力 推件力 算式中 n=6 是因有兩個孔。 總沖壓力： ⑵壓力中心 如圖3.3.2所示：以兩邊分別貼住XY軸。 由于工件X方向?qū)ΨQ，故壓力中心 計算時，忽略邊緣4-R2圓角。 綜上所述，該壓力中心位置為 圖3.3.2 第4章沖裁設備的選擇 根據(jù)這個總沖壓力 F總=328.346KN，結合沖床工作臺面尺寸，模具閉合高度及現(xiàn)有設備，我決定選用J23-63開式雙柱可傾沖床，并要在工作臺面上備制墊塊。其主要工藝參數(shù)如下： 公稱壓力：63KN 滑塊行程：130mm 行程次數(shù)：50次/分 最大閉合高度：360mm 連桿調(diào)節(jié)長度：80mm 工作臺尺寸（長×寬）：480mm×710mm 第5章模具的零件設計以及模架選擇 5.1 該零件各板的選用 （1）落料凹模板尺寸： 凹模板的厚度： 凹模邊的壁厚： 實取 凹模板的邊長： 通過查詢：凹模板寬 可以確定凹模板外形為：。結合實際，我添加了一塊墊板，實取為： ，如圖5.1。 圖5.1.1 （2）凸凹模長度：，如圖5.1.2 注：h1代表凸凹模固定板厚度 h2代表彈性卸料板厚度 h代表增加長度 圖5.1.2 （3）沖孔凸模尺寸： 經(jīng)計算凸模長度：，如圖5.1.3 注：h1代表凸模固定板厚 h2-空心墊板厚 h3-凹模板厚 圖5.1.3 5.2其它模具零件結構尺寸 再根據(jù)這個倒裝復合模形式特點：確定凹模板尺寸并查詢表，可以確定其它模具模板的尺寸 (1) 模具的上墊板，取，經(jīng)計算得到以下圖5.2.1。 圖5.2.1 (2) 凸模固定板，取，制出如下圖5.2.2。 圖5.2.2 (3) 空心墊板，取，如下圖5.2.3。 圖5.2.3 (4) 卸料板，取，如下圖5.2.4。 圖5.2.4 (5) 凸凹模固定板，取，如圖5.2.5。 圖5.2.5 (6) 下墊板，取，如下圖5.2.6. 圖5.2.6 5.3模架的選擇 根據(jù)模具零件結構尺寸，選取后側導柱標準模架一副，如圖5.3。 圖5.3 第6章 模具總裝圖 通過一系列零件組裝后，剖視出如下圖6.1。 圖6.1 結束語 三年的大學生活就快結束了，這是一個結束，同樣也是開始，是三年的一次總結，內(nèi)心有的是感慨，同時也有些許興奮，離別的傷感總是有的，但總要自己去面對。而在這段時間中我的畢業(yè)設計也是快要做完了，在這里我要感謝那些給過我?guī)椭睦蠋熗瑢W們，他們在我迷茫時給了我很多的指導,也給了許多的鼓勵。在與他們的交流中，我也是在不停的成長，不斷的變得懂事?！澳昴隁q歲花相似，歲歲年年人不同”，時光就是這樣，一去就再不會回頭。最重要的也是活在當下，永遠懷著一腔熱血面對每一天的生活。 至此再次感謝高老師對我畢業(yè)設計的指導。 參考文獻 [1]翁其金，沖壓工藝與模具設計，北京：機械工業(yè)出版社，2003. [2]王孝培，沖模手冊，北京：機械工業(yè)出版社，2000. [3]模具實用技術叢書編委會，沖壓模具設計應用實例，北京：機械工業(yè)出版社，2000. [4]梅伶，模具課程設計指導，北京：機械工業(yè)出版社，2000. [5]湯酞則，冷沖壓工藝與模具設計，長沙：湖南大學出版社，2007. [6]鐘毓斌，沖壓工藝與模具設計，北京：機械工業(yè)出版社，2009. [7]劉建超，張寶忠，沖壓模具設計與制造，北京：高等教育出版社2004. [8]陳黎明，李淑寶，沖壓工藝與模具設計，北京：電子工業(yè)出版社2012. [9]沖模設計手冊編寫組，沖模設計手冊，模具手冊之四，北京：機械工業(yè)出版社，1998. [10]李文超，UG模具設計與制造，北京：化學工業(yè)出版社，2008. 15 編號 無錫太湖學院 畢業(yè)設計（論文） 相關資料 題目： 軸承保持架沖壓模具設計 機電 系 機械工程及自動化專業(yè) 學 號： 　　　 0923181　　　 學生姓名： 呂金勇 指導教師： 　 黃敏（職稱：副教授） 2013年5月25日 無錫太湖學院 畢業(yè)設計（論文） 開題報告 題目： 軸承保持架沖壓模具設計 機電 系 機械工程及自動化 專業(yè) 學 號： 0923181 學生姓名： 呂金勇 指導教師： 黃敏 （職稱：副教授） 2012年11月25日 課題來源 自擬。 科學依據(jù)（包括課題的科學意義；國內(nèi)外研究概況、水平和發(fā)展趨勢；應用前景等） （1）課題科學意義 隨著與國際接軌的腳步日益放慢,市場競爭的日益加劇,人們對模具的各種要求也不斷的加大.可以說模具制造技術是用來衡量一個國家工業(yè)發(fā)展水平的重要標志。則現(xiàn)階段的工業(yè)生產(chǎn)中，模具是一種非常重要的工藝裝備。其在各個行業(yè)中也演繹著非常重要的角色，其運用于汽車、機械、航天、航空、輕工、電子、電器、儀表等行業(yè)。在我國的模具行業(yè)中有50%的是沖壓模具，足以看出沖壓模具之重要。所以現(xiàn)階段對于沖壓模具的研究也是非常有必要的。 軸承保持架沖壓模具的研究狀況及其發(fā)展前景 隨著計算機技術的發(fā)展和普及，沖壓模具也基本實現(xiàn)了計算機化，其中使用最多的是cad軟件。抽高壓模具的計算機化也是日益發(fā)展趨勢下不可避免的。近些年來各種多軸數(shù)控機床，激光切割機床數(shù)控雕刻機床等等紛紛面世，這些設備在提高模具的數(shù)量，規(guī)模和制造能力上的作用是不可估量的。還有其中快速成形技術和快速模具技術這兩種先進的制造技術也越來越廣泛的應用于模具行業(yè)。 中國的模具行業(yè)每年都保持著25%的增長率，其行業(yè)的生產(chǎn)能力也僅次于美國日本，位列世界第三。其行業(yè)生產(chǎn)能力約占世界總量的10%。 然而, 與國際先進水平相比, 中國的模具行業(yè)的差距不僅表現(xiàn)在精度差距大、 交貨周期長等方面, 模具壽命也只有國際先進水平的 50% 左右。大型、精密、技術含量高的轎車覆蓋件沖壓模具和精密沖裁模具是現(xiàn)階段最需要解決的問題。綜上由于市場需求模具的現(xiàn)階段發(fā)展快速，應用廣其前景也是也是非?？春玫摹? 研究內(nèi)容 ①了解沖壓加工的工作原理，國內(nèi)外的研究發(fā)展現(xiàn)狀； ②完成軸承保持架沖壓模具的總體方案設計； ③完成有關零部件的選型計算、結構強度校核及液壓系統(tǒng)設計； ④熟練掌握有關計算機繪圖軟件，并繪制裝配圖和零件圖紙，折合A0紙不少于3張； ⑤完成設計說明書的撰寫，并翻譯外文資料1篇。 擬采取的研究方法、技術路線、實驗方案及可行性分析 沖壓是一種利用壓力加工的方法，就是壓力機上裝上模具對材料施加壓力。使材料分離或者變形形成合格的所需產(chǎn)品。 沖壓模具材料的確定是一開始必須要確認的，其次是沖壓模具的結構設計分沖壓工藝的確定和模具結構的設計兩個方面，則需從這兩個方面入手。最后是對模具的壓力計算還有軟件模擬。 研究計劃及預期成果 研究計劃： 2012年11月17日-2013年1月13日：按照任務書要求查閱論文相關參考資料，填寫畢業(yè)設計開題報告書,學習并翻譯一篇與畢業(yè)設計相關的英文材料。 2013年1月11日-2013年3月5日：指導員實訓。 2013年3月8日-2013年3月14日：查閱與設計有關的參考資料不少于10篇，其中外文不少于5篇,翻譯機械方面的外文資料。 2013年3月15日-2013年3月21日：軸承保持架工藝分析。 2013年3月22日-2013年4月11日：初步繪制裝配圖和修改完成。 2013年4月12日-2013年4月25日：對凹凸模尺寸計算，繪制凹凸模及各零件。 2013年4月26日-2013年5月21日：繪制上下模及其各零件，完成設計說明書（論文）、摘要和小結，修改設計說明書開題報告格式，整理所有資料，打印后上交，準備答辯。 預期成果。 特色或創(chuàng)新之處 ① 沖模的使用便于生產(chǎn)自動化，操作簡單，生產(chǎn)率提高。 ② 減少制作軸承保持架的材料。 已具備的條件和尚需解決的問題 ① 已找到大量相關資料文獻，對軸承保持架零件有相關認識。 ② 沖壓工藝的加工工序 指導教師意見 指導教師簽名： 年 月 日 教研室（學科組、研究所）意見 教研室主任簽名： 年 月 日 系意見 主管領導簽名： 年 月 日 英文原文 Stress Analysis of Stamping Dies J. Mater. Shaping Technoi. (1990) 8:17-22 9 1990 Springer-Verlag New York Inc. R . S . R a o Abstract: Experimental and computational procedures for studying deflections, flit, andalignment characteristics of a sequence of stamping dies, housed in a transfer press, are pre-sented. Die loads are actually measured at all the 12 die stations using new load monitors and used as input to the computational procedure. A typical stamping die is analyzed using a computational code, MSC/NASTRAN, based on finite element method. The analysis is then extended to the other dies, especially the ones where the loads are high. Stresses and deflections are evaluated in the dies for the symmetric and asymmetric loading conditions. Based on our independent die analysis, stresses and deflections are found to be reasonably well within the tolerable limits. However, this situation could change when the stamping dies are eventually integrated with the press as a total system which is the ultimate goal of this broad research program. INTRODUCTION Sheet metal parts require a series of operations such as shearing , drawing , stretching , bending , and squeezing. All these operations are carried out at once while the double slide mechanism descends to work on the parts in the die stations, housed in a transfer press [1]. Material is fed to the press as blanks from a stock feeder. In operation the stock is moved from one station to the next by a mechanism synchronized with the motion of the slide. Each die is a separate unit which may be independently adjusted from the main slide. An automotive part stamped from a hot rolled steel blank in 12 steps without any intermediate anneals is shown in Figure 1. Transfer presses are mainly used to produce different types of automotive and aircraft parts and home appliances. The economic use of transfer presses depends upon quantity production as their usual production rate is 500 to 1500 parts per hour [2]. Although production is rapid in this way, close tolerances are often difficult to achieve. Moreover, the presses produce a set of conditions for off-center loads owing to the different operations being performed simultaneously in several dies during each stroke. Thus, the forming load applied at one station can affect the alignment and general accuracy of the operation being performed at adjacent stations. Another practical problem is the significant amount of set-up time involved to bring all the dies into proper operation. Hence, the broad goal of this research is to study the structural characteristics of press and dies combination as a total system. In this paper, experimental and computational procedures for investigating die problems are presented. The analysis of structural characteristics of the transfer press was pursued separately [3]. A transfer press consisting of 12 die stations was chosen for analysis. Typical die problems are excessive deflections, tilt, and misalignment of the upperand lower die halves. Inadequate cushioning and offcenter loading may cause tilt and misalignment of the dies. Tilt and excessive deflections may also be caused by the lack of stiffness of the die bolster and the die itself. Part quality can be greatly affected by these die problems. There are a lot of other parameters such as the die design, friction and lubrication along the die work interface, speed, etc. that play a great role in producing consistently good parts. Realistically, the analysis should be carded out by incorporating the die design and the deforming characteristics of the work material such as the elastic-plastic work hardening properties. In this preliminary study, the large plastic deformation of the workpiece was not considered for the reasons mentioned below. Large deformation modeling of a sheet stretching process was carded out using the computational code based on an elastic-plastic work hardening model of the deformation process [4]. Laboratory experiments were conducted on various commercial materials using a hemispherical punch. The coefficient of friction along the punch-sheet interface was actually measured in the experiment and used as a prescribed boundary to the numerical model. Although a good solution was obtained, it was realized that the numerical analysis was very sensitive to the frictional conditions along the interface. In the most recent work, a new friction model based on the micromechanics of the asperity contact was developed [5]. In the present problem, there are several operations such as deep drawing, several reduction drawing operations, and coining, which are performed using complex die geometries. The resources and the duration of time were not adequate to study these nonlinear problems. Hence,the preliminary study was limited to die problems basedon linear stress analysis. A detailed die analysis was carried out by using MSC /NASTRAN code based on finite ele mentmethod. Die loads were.measured at all the stations using new load monitors. Such measured data were used in the numerical model to evaluate stresses and deflections in the dies for normal operating conditions and for asymmetric loading conditions. Asymmetric loading conditions were created in the analysis by tilting the dies. In real practice, it is customary to pursue trial-and-error procedures such as placing shims under the die or by adjusting the cushion pressure to correct the die alignment problems. Such time consuming tasks can be reduced or even eliminated using the computational and experimental procedures presented here. DIE GEOMETRY AND MATERIALS The design of metal stamping dies is an inexact process. There are considerable trial-and-error adjustments during die tryout that are often required to finish the fabrication of a die that will produce acceptable parts. It involves not only the proper selection of die materials, but also dimensions. In order to withstand the pressure, a die must have proper cross-sectional area and clearances. Sharp comers, radii, fillets, and sudden changes in the cross section can have deleterious effects on the die life. In this work, the analysis was done on the existing set of dies. The dies were made of high carbon, high chromium tool steel. The hardness of this tool steel material is in the range of Rockwell C 57 to 60. Resistance to wear and galling was greatly improved by coating the dies with titanium nitride and titanium carbide. The dies were supported by several other steel holders made of alloy steels such as SAE 4140. The geometry of a typical stamping die is axisymmetric but it varies slightly from die to die depending on the operation. Detailed information about geometry andmaterials of a reduction drawing die (station number 4) was gathered from blueprints. It was reproducedin three-dimensional geometry using a preprocessor, PATRAN. One quadrant of the die is shown in Figure2. The data including geometry and elastic properties of the die material were fed to the numerical model. The work material used was hot rolled aluminumkilled steel, SAE 1008 A-K Steel and the blank thickness was about 4.5 ram. Stampings used in unexposed places or as parts of some deisgn where fine finish is not essential are usually made from hot rolled steel. The automotive part produced in this die set is a cover for a torque converter. A principal advantage of aluminum-killed steel is its minimum strain aging. EXPERIMENTAL PROCEDURES As mentioned earlier, this research involved monitoting of die loads which were to be used in the numerical model to staldy the structural characteristicsof dies. The other advantage is to avoid overloadingthe dies in practice. Off-center loading can be detected and also set-up time can be reduced. Thus, any changes in the thickness of stock, dulling of the die,unbalanced loads, or overloadings can be detected using die load monitors. Strain gage based fiat load cells made of high grade tool steel material were fabricated and supplied by IDC Corporation. Four identical load cells were embedded in a thick rectangular plate as shown in Figure 3. They were calibrated both in the laboratory and in the plant.The plate was placed on the top of the die. The knockout pin slips through the hole in the plate. Six such plates were placed on each of six dies. In this way,24 readings can be obtained at a given time. Then they were shifted to the other six dies for complete data. All the 12 die loads are presented in Table 1. COMPUTATIONAL PROCEDURES Linear static analysis using finite element method wasused to study the effect of symmetric and asymmetric loading for this problem. A finite element model of die station 4 was created using the graphical preprocessor, PATRAN, and the analysis was carried outusing the code MSC/NASTRA N . The code has a wide T a b l e I. Die Loads Die Station Load Number (kN) 1 356 2 641 3 214 4 356 5 854 6 712 7 285 8 32O 9 2349 10 1139 11 214 12 2100 spectrum of capabilities, of which linear static analysis is discussed here. The NASTRAN code initially generates a structural matrix and then the stiffness and the mass matrices from the data in the input file. The theoretical formulations of a static structural problem by the displacement method can be obtained from the references [6]. The unknowns are displacements and are solved for the appropriate boundary conditions. Strains are obtained from displacements. Then they are converted into stresses by using elastic stress-strain relationships of the die material. The solution procedure began with the creation of die geometry using the graphical preprocessor, PATRAN. The solution domain was divided into appropriate hyper-patches. This was followed by the generation of nodes, which were then connected by elements. Solid HEXA elements with eight nodes were used for this problem. The nodes and elements were distributed in such a way that a finer mesh was created at the critical region of the die-sheet metal interface and a coarser mesh elsewhere. The model was then optimized by deleting the unwanted nodes. The element connectivities were checked. By taking advantage of the symmetry, only one quarter of the die was analyzed. In the asymmetric case, half of the die was considered for analysis. Although, in practice, the load is applied at the top of the die, for the purpose of proper representation of the boundary conditions to the computational code, reaction forces were considered for analysis. The displacement and force boundary conditions are shown for the two cases inFigure 4. As mentioned earlier, sheet metal was not modeled in this preliminary research. As shown in Figure 4(a),the nodes on the top surface of the die were constrained (stationary surface) and the measured load of 356 kN was equally distributed on the contact nodes at the workpiece die interface. Similar boundary conditions for the punch are shown in Figure 4(b). It is noticeable that fewer nodes are in contact with the sheet metal due to the die tilt for the asymmetric loading case as shown in Figure 4(c). In real practice, the pressure actually varies along the die contact surface. Since the actual distribution was not known, uniform distribution was considered in the present analysis. DISCUSSION OF RESULTS As described in the earlier section, the numerical analysis of die Station 4 (both the die and punch) was performed using the code MSC/NASTRAN . Two cases were considered, namely: (a) symmetric loading and (b) asymmetric loading Fig. 4. Boundary conditions. (A) Symmetric case (onequadrant of the die). (B) Symmetric case (one quadrant ofnthe punch). (C) Asymmetric case (half of the die). Symmetric Loading Numerical analysis of the die was carried out for a measured load o f 356 kN as distributed equally in Figure 4(a). The major displacements in the loading direction are shown in Figure 5(a). These displacement contours can be shown in various colors to represent different magnitudes. The m aximum displacement value is 0.01 m m for a uniformly distributed load of 356 kN. The corresponding critical stress is very small, 8.4 MPa in the y direction and 30 MPa in the x direction. The calculated displacements and stresses at the surrounding elements and nodes were of the same order, but they decreased in magnitude at the nodes away from this critical region. Thus, the die was considered very rigid under this loading condition. Symmetric loading was applied to the punch and the numerical analysis was carried out separately. The displacement values in the protruding region of the punch were high compared to the die. The maximum displacement was 0.08 m m . It should be noted that the displacement values in this critical range of the punch were of the same order ranging from 0.05 mm to 0.08 ram. Although the load acting on the punch (bottom half) was the same as the die (upper half), that is, 356 kN, the values of displacements and stresses were higher in the punch because of the differences in the geometry. This is especially true for the protruding part of the punch. The corresponding maxim u m stress was 232 MPa. This part of the punch is still in the elastic range as the yield strength of tool steel is approximately 1034 MPa. The critical stress value might be varied for different load distributions. Since the actual distribution of the load was not known,the load was distributed equally on all nodes. As the die (upper half) is operating in a region which is extremely safe, a change in the load distribution may not produce any high critical stresses in the die. Although higher loads are applied at other die stations(see Table 1), it is concluded that the critical stresses are not going to be significantly higher due to the appropriate changes in the die geometries. Asymmetric Loading For the purpose of analysis, an asymmetric loading situation was created by tilting the die. Thus, only 15 nodes were in contact with the workpiece compared to 40 nodes for the symmetric loading case. As shown in Figure 4(c), a 356 kN load was uniformly distributed over the 15 nodes that were in contact with the workpiece. Although the pressure was high, because of the geometry at the location where the load was acting, the critical values of displacement and stress were found to be similar to the symmetric case. The predicted displacement and stress values were not significantly higher than the values predicted for the symmetric case. Fig. 5. Displacement contours in the loading direction. (A) Symmetric case (one quadrant of the die). (B) Symmetric case (one quadrant of the punch). (C)Asymmetric case (half of the die). CONCLUSIONS In this preliminary study, we have demonstrated the capabilities of the computational procedure, based on finite element method, to evaluate the stresses and deflections within the stamping dies for the measured loads. The dies were found to be within the tolerable elastic limits for both symmetric and asymmetric loading conditions. Thus the computational procedure can be used to study the tilt and alignment characteristics of stamping dies. In general, the die load monitors are very useful not only for analysis but also for on-line tonnage control. Future research involves the integration of the structural analysis of stamping dies with that of the transfer press as a total system. ACKNOWLEDGMENTS Professor J.G. Eisley, W.J. Anderson, and Mr. D.Londhe are thanked for their comments on this paper. REFERENCES 1. R.S. Rao and A. Bhattacharya, "Transfer Process De-flection, Parallelism, and Alignment Characteristics,"Technical Report, January 1988, Department of Mechanical Engineering and Applied Mechanics, the University of Michigan, Ann Arbor. 2. Editors of American Machinist, "Metalforming: Modem Machines, Methods, and Tooling for Engineers and Operating Personnel," McGraw-Hill, Inc., 1982, pp. 47-50. 3. W.J. Anderson, J.G. Eisley, and M.A. Tessmer,"Transfer Press Deflection, Parallelism, and Alignment Characteristics," Technical Report, January 1988, Department of Aerospace Engineering, the University of Michigan, Ann Arbor. 4. B.B. Yoon, R.S. Rao, and N. Kikuchi, "Sheet Stretching: A Theoretical Experimental Comparison," International Journal of Mechanical Sciences, Vol. 31, No.8, pp. 579-590, 1989. 5. B.B. Yoon, R.S. Rao, and N. Kikuchi, "Experimental and Numerical Comparisons of Sheet Stretching Using a New Friction Model," ASME Journal of Engineering Materials and Technology, in press. 6. MSX/NASTRAN, McNeal Schwendler Corporation.22 9 J. Materials Shaping Technology, Vol. 8, No. 1, 1990 中文譯文 沖壓模具的受力分析 R.S.Rao J.Mater.Shaping Tec