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南昌航空大學科技學院學士學位論文
紡機搖架后支架零件沖壓模具設計與制造
學生姓名：朱學晶 班級：0681053
指導老師：羅海泉
摘要：模具是現代工業(yè)生產中應用廣泛的優(yōu)質、高效、低耗、適應性很強的生產技術或稱成型工具、成型工裝產品，是技術含量高、附加值高、使用廣泛的新技術產品，是價值很高的社會財富。
本課題的主要任務是紡機搖架后支架的沖壓工藝和模具設計。因為是紡機上的重要部件，精度要求比較高。采取的工藝方案是先落料—沖孔復合沖壓，然后再彎曲，采用復合模生產。設計的過程是：首先進行工藝方案的論證和各種參數的計算，確定模具各主要部件的結構和尺寸，進行刃口尺寸的計算和相關件的強度校核；查閱相關書籍，選取模具的標準零件；然后根據計算的參數繪制模具裝配圖和非標零件圖，再撰寫說明書。
關鍵詞：復合沖壓，復合模，彎曲，模具設計
指導老師簽名:
Textile Machinery Parts cradle after the stent design and manufacture of stamping dies
Student Name:Zhu Xuejing Class:0681053
Supervisor:Luo HaiQuan
Abscract:Mold is a modern industrial production of a wide range of high-quality, high-efficiency, low consumption and strong adaptability of the production technology, or molding tools, Prototyping Tool products, high technological content and high added value, the wider use of new technology products, is the high value of social wealth. The main task of the issue is Textile Machinery Swing stamping process and die design. As the important components, textile needs high precision. The program is the first of blanking-punching composite punch, then bending modulus composite production. The design process: First, the program for the verification process and the various parameters, Die identify the major components of the structure and size, Cutting Edge for the calculation of the size and intensity of the relevant pieces of the check; Access to the relevant books, To Die standard components; Then calculated the entries drawn die assembly and non-standard components map, Further written statement.
Keyword: Stamping compound，Compound，Die Bending，Mold Design
Signature of Supervisor:
畢業(yè)設計（論文）任務書
I、畢業(yè)設計(論文)題目：
后支架零件沖壓模具設計
II、畢 業(yè)設計(論文)使用的原始資料(數據)及設計技術要求：
設計原始資料：1．零件圖；
2．零件材料牌號及厚度：Q235，δ2.0；
設計技術要求：1．年生產綱領：80000件；
2. 要求外文資料翻譯忠實原文；
3. 要求編制的沖壓工藝規(guī)程合理；
4. 要求設計的沖壓模具滿足加工要求；
5. 要求圖紙設計規(guī)范，符合制圖標準；
6. 要求畢業(yè)論文敘述條理清楚，設計計算正確，論文格式規(guī)范。
III、畢 業(yè)設計(論文)工作內容及完成時間：
1．繪制零件圖，收集、查閱有關資料，外文翻譯(6000實詞以上)，撰寫開題報告；
3.1 －3.19 3周
2．對零件進行沖裁/彎曲工藝分析，確定工藝方案； 3.22－3.26 1周
3．計算、確定沖壓力模具工作部分尺寸及公差，選取模具結構
3.29－4.9 2周
4．設計模具裝配圖，拆繪主要零件圖； 4.12－5.21 6周
5．撰寫畢業(yè)論文、畢業(yè)設計審查、畢業(yè)答辯。 5.24 －7.2 6周
Ⅳ 、主 要參考資料：
[1]．姜奎華主編. 沖壓工藝與模具設計. 北京：機械工業(yè)出版社，2003.6
[2]．解汝升. 沖壓模具設計與制造技術. 北京：中國標準出版社，1997
[3]．許發(fā)樾主編. 實用模具設計與制造手冊. 北京：機械工業(yè)出版社，2001.2
[4]．廖念釗等主編. 互換性與技術測量. 北京：中國計量出版社，2001
[5]. Wilson，F.W.Die design handbook MaGraw Hill 1990.6
航空工程 系 機械設計制造及其自動化 專業(yè)類 0681053 班
學生（簽名）： 朱學晶
日期： 自 2010 年 3 月 1 日至 2010 年 7 月 2 日
指導教師（簽名）： 羅海泉
助理指導教師(并指出所負責的部分)：
航空工程 系（室）主任（簽名）： 姚坤弟
附注:任務書應該附在已完成的畢業(yè)設計說明書首頁。
畢業(yè)設計（論文）開題報告
題目 后支架零件沖壓模具設計
專 業(yè) 名 稱 機械設計制造及其自動化
班 級 學 號 068105340
學 生 姓 名 朱學晶
指 導 教 師 羅海泉
填 表 日 期 2010 年 3 月 5 日
一、 選題的依據及意義：
后支架零件是紡機的沖壓零件之一。沖壓工藝及模具設計是汽車、家電等產品生產中常用的制造工藝及方法。
本課題可鍛煉綜合運用所學知識，獨立進行沖壓工藝分析及模具設計制造的能力。
本課題的任務是：設計后支架零件沖壓模具。通過畢業(yè)設計，熟悉常用沖壓材料的使用性能（沖壓、力學），能正確選擇模具材料并提出合適的熱處理工藝，掌握沖壓模具設計的基本程序和方法。主要內容包括：沖壓工藝分析與參數計算；沖壓工藝方案確定與優(yōu)選；關鍵工序成形的數值仿真驗證。凸模、凹模、定位、導向、連接、卸料等工作零件的設計；模具裝配圖與零件圖設計；等等。
二、 國內外研究概況及發(fā)展趨勢（含文獻綜述）：
我國模具工業(yè)的發(fā)展動向
目前，我國經濟仍處于高速發(fā)展階段，國際上經濟全球化發(fā)展趨勢日趨明顯，這為我國模具工業(yè)高速發(fā)展提供了良好的條件和機遇。一方面，國內模具市場將繼續(xù)高速發(fā)展，另一方面，模具制造也逐漸向我國轉移以及跨國集團到我國進行模具采購趨向也十分明顯。因此，放眼未來，國際、國內的模具市場總體發(fā)展趨勢前景看好，預計中國模具將在良好的市場環(huán)境下得到高速發(fā)展，我國不但會成為模具大國，而且一定逐步向模具制造強國的行列邁進。“十一五”期間，中國模具工業(yè)水平不僅在量和質的方面有很大提高，而且行業(yè)結構、產品水平、開發(fā)創(chuàng)新能力、企業(yè)的體制與機制以及技術進步的方面也會取得較大發(fā)展。
模具產品的設計不同于普通產品,它的主要特點是:(1) 設計過程復雜,信息含量大。 (2) 設計因素眾多,專業(yè)分工細致。 (3) 計算、分析過程煩瑣。 (4) 制造資源要求高。
在現代工業(yè)生產中，60%~90%的工業(yè)產品需要使用模具，模具工業(yè)已經成為工業(yè)發(fā)展的基礎。發(fā)達國家將制造業(yè)紛紛轉移到我國，使我國的模具工業(yè)面臨空前的發(fā)展機遇。我國加入WTO，給經濟發(fā)展帶來前所未有的機遇和挑戰(zhàn)。時代在發(fā)展，科技日新月異。計算機前的操作逐步代替現場操作；以高精度加工代替人的手工勞動；模具的設計、制造高度標準化；單件生產方式向流水線式生產方式發(fā)展等等。高新技術的應用是模具技術發(fā)展發(fā)動力。我們必須向世界最先進的模具技術學習，并用最短的時間掌握這些技術，盡早地應用于模具設計與制造中。
三、 研究內容及實驗方案
畢業(yè)設計的總體思路
1）工藝分析
由工件圖可知，該工件的形狀，尺寸，精度和材料等均符合沖壓工藝性要求，沖壓的主要工序有：落料、彎曲、沖裁等，工藝比較復雜，生產批量大，適宜用復合模沖制。
2）排樣圖設計
由所給零件圖畫出零件展開圖，合理安排工位。零件厚度為1mm，壓邊有多個凹槽，因而要注意其尺寸質量問題及控制等。
3）沖壓工藝參數計算與壓力機選擇
①坯料的展開長度及料寬計算②進距計算③沖材間隙值的確定④凸凹模刃口尺寸的確定⑤沖壓力及壓力中心的計算
4）模具結構的設計
①凹模設計
②凸模設計
5）模具裝配圖與零件圖的設計
6）沖壓成形模具結構與成形參數的數值仿真分析
7）撰寫畢業(yè)設計說明書
8）答辯
(3) 初步擬定的設計方案
1) 零件沖壓工藝的初步方案
零件沖壓工藝按沖孔、落料后再彎曲成型。
2) 模具結構設計的初步方案
模具結構設計：第一，搜集必要的資料，分析制件的工藝。第二，模具形式的選擇。第三，模具的總體設計。第四，選擇壓力機。
四、 目標、主要特色及工作進度
(1)、2010年3月1日－3月19日，繪制零件圖，收集、查閱有關資料，外文資料翻譯(6000字符)，撰寫開題報告。
(2)、2010年3月22日－3月26日，對零件進行沖裁/彎曲工藝分析，確定工藝方案。
(3)、2010年3月29日－4月9日，計算、確定沖壓力模具工作部分尺寸及公差，選取模具結構。
(4)、2010年4月12日－5月 21日，設計沖孔落料復合模具或級進模一套，繪制裝配圖，拆繪主要零件圖。
(5)、2010年5月22日－5月23日，任選模具一個主要工作零件，進行機加工藝規(guī)程設計。
(6)、2010年5月24日－7月2日，撰寫畢業(yè)論文、畢業(yè)設計審查、畢業(yè)答辯。
五、參考文獻
[1] 李光耀，淺談現代模具設計與制造[J].太原理工大學學報，2001，32(1)：51-53.
[2] 張曉陸，CAE技術在注塑模具設計及制造中的應用[J].江蘇春蘭機械制造有限公司年報，2004，25（6）：68-73.
[3] 周永泰，模具設計和加工技術的發(fā)展方向[J].中國模具工業(yè)協會學報，2000，23（3）：45-50.
[4] 董占峰，王成端，綠色模具設計概論[M].綿陽：西南科技大學出版社，2003.
[5] 江昌勇，模具設計中的可靠性問題[J].常州工學院延陵學院學報,2001，10（2）：30-36.
[6] 楊慶東，現代模具制造的高速加工技術[M].北京：機械工業(yè)出版社，2004.
[7] 白釗, 林慶文, 賀艷苓，有限元分析在沖壓模具設計中的應用[J].中國模具工業(yè)協會學報，2004，12（1）：62-65.
[8] 左智勇，試論沖壓工藝與模具之關系[J]鄭州日產汽車有限公司制造部報刊，2002，12-16.
[9] 曲慶文,邵淑玲，模具設計中的摩擦學問題研究[M]。山東理工大學出版社，2001.
[10] 張培耘,戴勇,華?？?袁國定，國內模具工業(yè)技術現狀與發(fā)展趨勢[M].江蘇理工大學機械工程學院出版社，2003.
[11]馮炳亮,韓泰榮,殷振海,蔣文森,模具設計與制造簡明手冊:上?？茖W技術出版社.
[12]潘慶修,模具制造工藝教程:電子工業(yè)出版社.
[13]趙昌盛,使用模具材料應用手冊.
[14]K.Stoeckhert/G..Mennig,模具制造手冊?；瘜W工業(yè)出版社。
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第 26 頁 共 27 頁
e pos 模具工業(yè)現狀Process simulation in stamping – recent
applications for product and process design
Abstract
Process simulation for product and process design is currently being practiced in industry. However, a number of input variables have a significant effect on the accuracy and reliability of computer predictions. A study was conducted to evaluate the capability of FE-simulations for predicting part characteristics and process conditions in forming complex-shaped, industrial parts.
In industrial applications, there are two objectives for conducting FE-simulations of the stamping process; (1) to optimize the product design by analyzing formability at the product design stage and (2) to reduce the tryout time and cost in process design by predicting the deformation process in advance during the die design stage. For each of these objectives, two kinds of FE-simulations are applied. Pam-Stamp, an incremental dynamic-explicit FEM code released by Engineering Systems Int'l, matches the second objective well because it can deal with most of the practical stamping parameters. FAST_FORM3D, a one-step FEM code released by Forming Technologies, matches the first objective because it only requires the part geometry and not the complex process information.
In a previous study, these two FE codes were applied to complex-shaped parts used in manufacturing automobiles and construction machinery. Their capabilities in predicting formability issues in stamping were evaluated. This paper reviews the results of this study and summarizes the recommended procedures for obtaining accurate and reliable results from FE simulations.
In another study, the effect of controlling the blank holder force (BHF) during the deep drawing of hemispherical, dome-bottomed cups was investigated. The standard automotive aluminum-killed, drawing-quality (AKDQ) steel was used as well as high performance materials such as high strength steel, bake hard steel, and aluminum 6111. It was determined that varying the BHF as a function of stroke improved the strain distributions in the domed cups.
Keywords: Stamping; Process ;stimulation; Process design
1. Introduction
The design process of complex shaped sheet metal stampings such as automotive panels, consists of many stages of decision making and is a very expensive and time consuming process. Currently in industry, many engineering decisions are made based on the knowledge of experienced personnel and these decisions are typically validated during the soft tooling and prototyping stage and during hard die tryouts. Very often the soft and hard tools must be reworked or even redesigned and remanufactured to provide parts with acceptable levels of quality.
The best case scenario would consist of the process outlined in Fig. 1. In this design process, the experienced product designer would have immediate feedback using a specially design software called one-step FEM to estimate the formability of their design. This would allow the product designer to make necessary changes up front as opposed to down the line after expensive tooling has been manufactured. One-step FEM is particularly suited for product analysis since it does not require binder, addendum, or even most process conditions. Typically this information is not available during the product design phase. One-step FEM is also easy to use and computationally fast, which allows the designer to play “what if” without much time investment.
Fig. 1. Proposed design process for sheet metal stampings.
Once the product has been designed and validated, the development project would enter the “time zero” phase and be passed onto the die designer. The die designer would validate his/her design with an incremental FEM code and make necessary design changes and perhaps even optimize the process parameters to ensure not just minimum acceptability of part quality, but maximum achievable quality. This increases product quality but also increase process robustness. Incremental FEM is particularly suited for die design analysis since it does require binder, addendum, and process conditions which are either known during die design or desired to be known.
The validated die design would then be manufactured directly into the hard production tooling and be validated with physical tryouts during which the prototype parts would be made. Tryout time should be decreased due to the earlier numerical validations. Redesign and remanufacturing of the tooling due to unforeseen forming problems should be a thing of the past. The decrease in tryout time and elimination of redesign/remanufacturing should more than make up for the time used to numerically validate the part, die, and process.
Optimization of the stamping process is also of great importance to producers of sheet stampings. By modestly increasing one's investment in presses, equipment, and tooling used in sheet forming, one may increase one's control over the stamping process tremendously. It has been well documented that blank holder force is one of the most sensitive process parameters in sheet forming and therefore can be used to precisely control the deformation process.
By controlling the blank holder force as a function of press stroke AND position around the binder periphery, one can improve the strain distribution of the panel providing increased panel strength and stiffness, reduced springback and residual stresses, increased product quality and process robustness. An inexpensive, but industrial quality system is currently being developed at the ERC/NSM using a combination of hydraulics and nitrogen and is shown in Fig. 2. Using BHF control can also allow engineers to design more aggressive panels to take advantage the increased formability window provided by BHF control.
Fig. 2. Blank holder force control system and tooling being developed at the ERC/NSM labs.
Three separate studies were undertaken to study the various stages of the design process. The next section describes a study of the product design phase in which the one-step FEM code FAST_FORM3D (Forming Technologies) was validated with a laboratory and industrial part and used to predict optimal blank shapes. Section 4 summarizes a study of the die design stage in which an actual industrial panel was used to validate the incremental FEM code Pam-Stamp (Engineering Systems Int'l). Section 5 covers a laboratory study of the effect of blank holder force control on the strain distributions in deep drawn, hemispherical, dome-bottomed cups.
2. Product simulation – applications
The objective of this investigation was to validate FAST_FORM3D, to determine FAST_FORM3D's blank shape prediction capability, and to determine how one-step FEM can be implemented into the product design process. Forming Technologies has provided their one-step FEM code FAST_FORM3D and training to the ERC/NSM for the purpose of benchmarking and research. FAST_FORM3D does not simulate the deformation history. Instead it projects the final part geometry onto a flat plane or developable surface and repositions the nodes and elements until a minimum energy state is reached. This process is computationally faster than incremental simulations like Pam-Stamp, but also makes more assumptions. FAST_FORM3D can evaluate formability and estimate optimal blank geometries and is a strong tool for product designers due to its speed and ease of use particularly during the stage when the die geometry is not available.
In order to validate FAST_FORM3D, we compared its blank shape prediction with analytical blank shape prediction methods. The part geometry used was a 5?in. deep 12?in. by 15?in. rectangular pan with a 1?in. flange as shown in Fig. 3. Table 1 lists the process conditions used. Romanovski's empirical blank shape method and the slip line field method was used to predict blank shapes for this part which are shown in Fig. 4.
Fig. 3. Rectangular pan geometry used for FAST_FORM3D validation.
Table 1. Process parameters used for FAST_FORM3D rectangular pan validation
Fig. 4. Blank shape design for rectangular pans using hand calculations.
(a) Romanovski's empirical method; (b) slip line field analytical method.
Fig. 5(a) shows the predicted blank geometries from the Romanovski method, slip line field method, and FAST_FORM3D. The blank shapes agree in the corner area, but differ greatly in the side regions. Fig. 5(b)–(c) show the draw-in pattern after the drawing process of the rectangular pan as simulated by Pam-Stamp for each of the predicted blank shapes. The draw-in patterns for all three rectangular pans matched in the corners regions quite well. The slip line field method, though, did not achieve the objective 1?in. flange in the side region, while the Romanovski and FAST_FORM3D methods achieved the 1?in. flange in the side regions relatively well. Further, only the FAST_FORM3D blank agrees in the corner/side transition regions. Moreover, the FAST_FORM3D blank has a better strain distribution and lower peak strain than Romanovski as can be seen in Fig. 6.
Fig. 5. Various blank shape predictions and Pam-Stamp simulation results for the rectangular pan.
(a) Three predicted blank shapes; (b) deformed slip line field blank; (c) deformed Romanovski blank; (d) deformed FAST_FORM3D blank.
Fig. 6. Comparison of strain distribution of various blank shapes using Pam-Stamp for the rectangular pan.
(a) Deformed Romanovski blank; (b) deformed FAST_FORM3D blank.
To continue this validation study, an industrial part from the Komatsu Ltd. was chosen and is shown in Fig. 7(a). We predicted an optimal blank geometry with FAST_FORM3D and compared it with the experimentally developed blank shape as shown in Fig. 7(b). As seen, the blanks are similar but have some differences.
Fig. 7. FAST_FORM3D simulation results for instrument cover validation.
(a) FAST_FORM3D's formability evaluation; (b) comparison of predicted and experimental blank geometries.
Next we simulated the stamping of the FAST_FORM3D blank and the experimental blank using Pam-Stamp. We compared both predicted geometries to the nominal CAD geometry (Fig. 8) and found that the FAST_FORM3D geometry was much more accurate. A nice feature of FAST_FORM3D is that it can show a “failure” contour plot of the part with respect to a failure limit curve which is shown in Fig. 7(a). In conclusion, FAST_FORM3D was successful at predicting optimal blank shapes for a laboratory and industrial parts. This indicates that FAST_FORM3D can be successfully used to assess formability issues of product designs. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.
Fig. 8. Comparison of FAST_FORM3D and experimental blank shapes for the instrument cover.
(a) Experimentally developed blank shape and the nominal CAD geometry; (b) FAST_FORM3D optimal blank shape and the nominal CAD geometry.
3. Die and process simulation – applications
In order to study the die design process closely, a cooperative study was conducted by Komatsu Ltd. of Japan and the ERC/NSM. A production panel with forming problems was chosen by Komatsu. This panel was the excavator's cabin, left-hand inner panel shown in Fig. 9. The geometry was simplified into an experimental laboratory die, while maintaining the main features of the panel. Experiments were conducted at Komatsu using the process conditions shown in Table 2. A forming limit diagram (FLD) was developed for the drawing-quality steel using dome tests and a vision strain measurement system and is shown in Fig. 10. Three blank holder forces (10, 30, and 50?ton) were used in the experiments to determine its effect. Incremental simulations of each experimental condition was conducted at the ERC/NSM using Pam-Stamp.
Fig. 9. Actual product – cabin inner panel.
Table 2. Process conditions for the cabin inner investigation
Fig. 10. Forming limit diagram for the drawing-quality steel used in the cabin inner investigation.
At 10?ton, wrinkling occurred in the experimental parts as shown in Fig. 11. At 30?ton, the wrinkling was eliminated as shown in Fig. 12. These experimental observations were predicted with Pam-stamp simulations as shown in Fig. 13. The 30?ton panel was measured to determine the material draw-in pattern. These measurements are compared with the predicted material draw-in in Fig. 14. Agreement was very good, with a maximum error of only 10?mm. A slight neck was observed in the 30?ton panel as shown in Fig. 13. At 50?ton, an obvious fracture occurred in the panel.
Fig. 11. Wrinkling in laboratory cabin inner panel, BHF=10?ton.
Fig. 12. Deformation stages of the laboratory cabin inner and necking, BHF=30?ton.
(a) Experimental blank; (b) experimental panel, 60% formed; (c) experimental panel, fully formed; (d) experimental panel, necking detail.
Fig. 13. Predication and elimination of wrinkling in the laboratory cabin inner.
(a) Predicted geometry, BHF=10?ton; (b) predicted geometry, BHF=30?ton.
Fig. 14. Comparison of predicted and measured material draw-in for lab cabin inner, BHF=30?ton.
Strains were measured with the vision strain measurement system for each panel, and the results are shown in Fig. 15. The predicted strains from FEM simulations for each panel are shown in Fig. 16. The predictions and measurements agree well regarding the strain distributions, but differ slightly on the effect of BHF. Although the trends are represented, the BHF tends to effect the strains in a more localized manner in the simulations when compared to the measurements. Nevertheless, these strain prediction show that Pam-Stamp correctly predicted the necking and fracture which occurs at 30 and 50?ton. The effect of friction on strain distribution was also investigated with simulations and is shown in Fig. 17.
Fig. 15. Experimental strain measurements for the laboratory cabin inner.
(a) measured strain, BHF=10?ton (panel wrinkled); (b) measured strain, BHF=30?ton (panel necked); (c) measured strain, BHF =50?ton (panel fractured).
Fig. 16. FEM strain predictions for the laboratory cabin inner.
(a) Predicted strain, BHF=10?ton; (b) predicted strain, BHF=30?ton; (c) predicted strain, BHF=50?ton.
Fig. 17. Predicted effect of friction for the laboratory cabin inner, BHF=30?ton.
(a) Predicted strain, μ=0.06; (b) predicted strain, μ=0.10.
A summary of the results of the comparisons is included in Table 3. This table shows that the simulations predicted the experimental observations at least as well as the strain measurement system at each of the experimental conditions. This indicates that Pam-Stamp can be used to assess formability issues associated with the die design.
Table 3. Summary results of cabin inner study
4. Blank holder force control – applications
The objective of this investigation was to determine the drawability of various, high performance materials using a hemispherical, dome-bottomed, deep drawn cup (see Fig. 18) and to investigate various time variable blank holder force profiles. The materials that were investigated included AKDQ steel, high strength steel, bake hard steel, and aluminum 6111 (see Table 4). Tensile tests were performed on these materials to determine flow stress and anisotropy characteristics for analysis and for input into the simulations (see Fig. 19 and Table 5).
Fig. 18. Dome cup tooling geometry.
Table 4. Material used for the dome cup study
Fig. 19. Results of tensile tests of aluminum 6111, AKDQ, high strength, and bake hard steels.
(a) Fractured tensile specimens; (b) Stress/strain curves.
Table 5. Tensile test data for aluminum 6111, AKDQ, high strength, and bake hard steels
It is interesting to note that the flow stress curves for bake hard steel and AKDQ steel were very similar except for a 5% reduction in elongation for bake hard. Although, the elongations for high strength steel and aluminum 6111 were similar, the n-value for aluminum 6111 was twice as large. Also, the r-value for AKDQ was much bigger than 1, while bake hard was nearly 1, and aluminum 6111 was much less than 1.
The time variable BHF profiles used in this investigation included constant, linearly decreasing, and pulsating (see Fig. 20). The experimental conditions for AKDQ steel were simulated using the incremental code Pam-Stamp. Examples of wrinkled, fractured, and good laboratory cups are shown in Fig. 21 as well as an image of a simulated wrinkled cup.
Fig. 20. BHF time-profiles used for the dome cup study.
(a) Constant BHF; (b) ramp BHF; (c) pulsating BHF.
Fig. 21. Experimental and simulated dome cups.
(a) Experimental good cup; (b) experimental fractured cup; (c) experimental wrinkled cup; (d) simulated wrinkled cup.
Limits of drawability were experimentally investigated using constant BHF. The results of this study are shown in Table 6. This table indicates that AKDQ had the largest drawability window while aluminum had the smallest and bake hard and high strength steels were in the middle. The strain distributions for constant, ramp, and pulsating BHF are compared experimentally in Fig. 22 and are compared with simulations in Fig. 23 for AKDQ. In both simulations and experiments, it was found that the ramp BHF trajectory improved the strain distribution the best. Not only were peak strains reduced by up to 5% thereby reducing the possibility of fracture, but low strain regions were increased. This improvement in strain distribution can increase product stiffness and strength, decrease springback and residual stresses, increase product quality and process robustness.
Table 6. Limits of drawability for dome cup with constant BHF
Fig. 22. Experimental effect of time variable BHF on engineering strain in an AKDQ steel dome cup.
Fig. 23. Simulated effect of time variable BHF on true strain in an AKDQ steel dome cup.
Pulsating BHF, at the frequency range investigated, was not found to have an effect on strain distribution. This was likely due to the fact the frequency of pulsation that was tested was only 1?Hz. It is known from previous experiments of other researchers that proper frequencies range from 5 to 25?Hz [3]. A comparison of load-stroke curves from simulation and experiments are shown in Fig. 24 for AKDQ. Good agreement was found for the case where μ=0.08. This indicates that FEM simulations can be used to assess the formability improvements that can be obtained by using BHF control techniques.
Fig. 24. Comparison of experimental and simulated load-stroke curves for an AKDQ steel dome cup.
5 Conclusions and future work
In this paper, we evaluated an improved design process for complex stampings which involved eliminating the soft tooling phase and incorporated the validation of product and process using one-step and incremental FEM simulations. Also, process improvements were proposed consisting of the implementation of blank holder force control to increase product quality and process robustness.
Three separate investigations were summarized which analyzed various stages in the design process. First, the product design phase was investigated with a laboratory and industrial validation of the one-step FEM code FAST_FORM3D and its ability to assess formability issues involved in product design. FAST_FORM3D was successful at predicting optimal blank shapes for a rectangular pan and an industrial instrument cover. In the case of the instrument cover, many hours of trial and error experimentation could have been eliminated by using FAST_FORM3D and a better blank shape could have been developed.
Second, the die design