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南京航空航天大學(xué)金城學(xué)院 畢業(yè)設(shè)計（論文） 開題報告 題 目 客車門鎖鎖舌沖模設(shè)計 系 部 機(jī)電系 專 業(yè) 機(jī)械制造及其自動化 學(xué)生姓名 邵躍龍 學(xué)號 2007011828 指導(dǎo)教師 冷晟 職稱 教授 畢設(shè) 地點 南京航空航天大學(xué)金城學(xué)院 2011 年 4 月 2 日 填 寫 要 求 1開題報告只需填寫 “文獻(xiàn)綜述 ”、“ 研究或解決的問題和擬 采用的方法 ”兩部分內(nèi)容，其他信息由系統(tǒng)自動生成，不需要手 工填寫 。 2為了與網(wǎng)上任務(wù)書兼容及最終打印格式一致，開 題報告 采用固定格式，如有不適請調(diào)整內(nèi)容以適應(yīng)表格大小 并保持整 體美觀 ，切勿輕易改變格式 。 3任務(wù)書須用 A4 紙，小 4 號字， 黑色宋體，行距 1.5 倍 。 4使用此開題報告模板填寫完畢，可直接粘接復(fù)制相應(yīng)的 內(nèi)容到畢業(yè)設(shè)計網(wǎng)絡(luò)系統(tǒng) 。 1. 結(jié)合畢業(yè)設(shè)計（論文）課題任務(wù)情況，根據(jù)所查閱的文獻(xiàn)資料，撰寫 1500 2000 字左右的文獻(xiàn)綜述： 級進(jìn)模的概述 級進(jìn)模，也叫連續(xù)模（據(jù)說連續(xù)模在標(biāo)準(zhǔn)術(shù)語將取消）由多個工位組成，各 工 位完成不同的加工，各工位順序 關(guān)聯(lián)，在沖床的一次行程中完成一系列的不同 的沖 壓加工。一次行程完成以后，由沖床送料機(jī)按照一個固定的步距將材料向前 移動， 這樣在一副模具上就可以完成多個工序，一般有沖孔，落料，折彎，切邊， 拉伸等 等。 級進(jìn)模發(fā)展與應(yīng)用 現(xiàn)代沖壓技術(shù)的迅速發(fā)展，使形狀復(fù)雜的沖壓件，特別是一些按傳統(tǒng)沖壓工 藝 要多副沖模分序沖制的中小型復(fù)雜的沖壓件，越來越多地采用多工位級進(jìn)模成 形， 以提高沖件質(zhì)量和效率，降低沖件生產(chǎn)成本。但設(shè)計與制造這類多工位級進(jìn) 模難度 大，技術(shù)要求高，而排樣圖設(shè)計則首當(dāng)其中。只有設(shè)計出合理的排 樣圖才 有可能順 利完成這類級進(jìn)模設(shè)計與制造。級進(jìn)模沖件的排樣設(shè)計是級進(jìn)模結(jié)構(gòu)設(shè) 計的基礎(chǔ)及 其重要組成部分，影響到級進(jìn)模結(jié)構(gòu)選型及制模工藝性，制模周期與 模具費、沖件 質(zhì)量及材料利用率以及沖件生產(chǎn)成本，是一項綜合性技術(shù)很強(qiáng)的設(shè) 計工作。 級進(jìn)模的特點 對沖壓生產(chǎn)而言，單工位模具結(jié)構(gòu)單一，生產(chǎn)效率低，而且鈑金零件不能過 于 復(fù)雜，否則就需要多副單工位模具才能 實現(xiàn)。如果采用級進(jìn)模進(jìn)行沖壓生產(chǎn) ,就可以 改變這些缺點。級進(jìn)模的特點是生產(chǎn)效率高，生產(chǎn)周期短，占用的操作人 員少，非 常適合大批量生產(chǎn)。 參考文獻(xiàn) 1 郝濱海 . 沖壓模具簡明設(shè)計手冊 . 北京：化學(xué)工業(yè)出版社 ,2005.1 2 李遠(yuǎn)瞻 . 夾簧級進(jìn)模設(shè)計 . 模具工業(yè) ,2005,(10) 3 高錦張 . 塑性成形工藝與模具設(shè)計 . 北京：機(jī)械工業(yè)出版社 ,2006.5 4 郭平喜 . 多工位級進(jìn)模設(shè)計 .科技交流， 2000，（ 11） 5 李志剛 . 模具大典 . 江西科學(xué)技術(shù)出版社 ,2003.1 6 成紅 ,李學(xué)鋒 .多工位精密級進(jìn)模排樣設(shè)計的研究 .模具工業(yè) ,2000,(4) 7 梁炳文 . 實用板金沖壓圖集 .第 2 集 . 北京：機(jī)械工業(yè)出版社 ,1999.8 8 楊玉英 . 實用沖壓工藝及模具設(shè)計手冊 . 北京：機(jī)械工業(yè)出版社 ,2004.7 9 高鴻庭 劉建超 . 冷沖模設(shè)計及制造 . 北京：機(jī)械工業(yè)出版社 ,2003.1 10 王新華 . 沖模設(shè)計與制造實用計算手冊 . 北京：機(jī)械工業(yè)出版社 ,2003.7 11 Sang B. Park. An expert system of progressive die design for electron gun grid parts. Journal of Materials Processing Technology 88 (1999) 216 221 12 S.E. Clift, P. Hartley, E.N. Sturgess, G.W. Rowe, Fracture prediction in plastic deformation processes, Int. J. Mech. Sci. 32 1 畢業(yè)設(shè)計任務(wù)要研究或解決的問題和擬采用的方法： （ 1） 畢業(yè)設(shè)計任務(wù)要研究或解決的問題 研究 基于 多工位級進(jìn)模問題 ，要求 1)閱讀 多工位級進(jìn)模 相關(guān)的論文和書籍，系統(tǒng)地了解 多工位級進(jìn)模 相關(guān)知識和原 理的目的。 2)掌握 模版的 基本原理和常用解決方面 。 3)掌握 鑲塊設(shè)計的基本原理及常用解決方法 4)通過多工位級進(jìn)模的設(shè)計及運用解決實際問題 (2）預(yù)期成果： 通過研究和分析各種 多工位級進(jìn)模 模型 ，掌握 其 基本 原理和實現(xiàn)步驟 。 （ 3） 擬采用的 研 究 方法 1，完成產(chǎn)品的計算與排樣 2，鑲塊設(shè)計（設(shè)計沖裁的凸凹模，折彎設(shè)計） 3，模版設(shè)計，包括卸料板 ,固定板，凹模版，上模座，下模座等 4，刀口設(shè)計 5，其他零件設(shè)計 指導(dǎo)教師意見（對課題的深度、廣度及工作量的意見和對畢業(yè)設(shè)計（論文）結(jié)果的預(yù)測） ： 指導(dǎo)教師簽字 ： 年 月 日 上級 審查意見： 負(fù)責(zé)人 簽字： 年 月 日 編號 南京航空航天大學(xué)金城學(xué)院 畢 業(yè) 設(shè) 計 題 目 客車門鎖鎖舌沖模設(shè)計 學(xué)生姓名 邵躍龍 學(xué) 號 2007011828 系 部 機(jī)電工程系 專 業(yè) 機(jī)械工程及自動化 班 級 20070118 指導(dǎo)教師 冷晟 副教授 二一一年六月 南京航空航天大學(xué)金城學(xué)院 本科畢業(yè)設(shè)計（論文）誠信承諾書 本人鄭重聲明：所呈交的畢業(yè)設(shè)計（論文） （題目：客車門鎖鎖 舌沖模設(shè)計）是本人在導(dǎo)師的指導(dǎo)下獨立進(jìn)行研究所取得的成果。 盡本人所知，除了畢業(yè)設(shè)計（論文）中特別加以標(biāo)注引用的內(nèi)容外， 本畢業(yè)設(shè)計（論文）不包含任何其他個人或集體已經(jīng)發(fā)表或撰寫的 成果作品。 作者簽名： 2011 年 06 月 9 日 （學(xué)號）：2007011828 畢業(yè)設(shè)計（論文）報告紙 6 i 客車門鎖鎖舌沖模設(shè)計 摘 要 本設(shè)計進(jìn)行了壓彎，切斷連續(xù)模的設(shè)計。論文簡要的概述了沖壓模具目前的發(fā)展?fàn)顩r和 趨勢。對產(chǎn)品進(jìn)行了詳細(xì)的工藝分析和工藝方案的確定。按照沖壓模具設(shè)計的一般步驟，計 算并設(shè)計了本套模具上的主要零部件，采用了少廢料排樣與標(biāo)準(zhǔn)模架，選用了合適的沖壓設(shè) 備。設(shè)計中對工件零件和壓力機(jī)規(guī)格進(jìn)行了必要的校核計算。通過對門鎖套件沖裁工藝性的 正確分析，設(shè)計了一副多工位級進(jìn)沖裁模。 詳細(xì)的敘述了模具的整個設(shè)計過程包括零件工藝性分析、沖裁工藝方案的確定、模具結(jié) 構(gòu)形式的確定、模具總體結(jié)構(gòu)的設(shè)計、主要參數(shù)設(shè)計計算等，并繪制了模具裝配圖和非標(biāo)準(zhǔn) 件零件圖。 關(guān)鍵詞：零件分析 ，裝配圖，模具設(shè)計。 畢業(yè)設(shè)計（論文）報告紙 6 ii Abstract This design of bending, cutting off consecutive modulus design. This paper briefly outlined the Stamping Die current development status and trends. The product of a detailed analysis and the identification process. Stamping die design in accordance with the general steps to calculate and design the sets on the main mold parts such as ：Punch and die. Punch and die, punch and so an. Die-standard model planes, to choose a suitable stamping equipment. Design wok on the part and specifications will press for the necessary checking calculation. The mold used for a small scrap layout, automatic centering device.Boards of locks blanking of the correct process analysis, design of a compound is loaded Die. Through the door lock blanking process of the correct package analysis,design a pair of multi-position Progressive Die A detailed description of the mold of the entire design process, including parts of analysis, blanking the identification process, the mold structure forms of identification, the overall structure of the mold design, the main design parameters, and mapping out mold assembly and non-standard pieces Fig. Keywords：Part analysis；Assembly；Mold Design. 畢業(yè)設(shè)計（論文）報告紙 6 - 3 - 目 錄 摘 要 ........................................................................i Abstract......................................................................ii 第一章 沖裁件工藝分析 ......................................................- 1 - 第二章 模具工藝設(shè)計 .......................................................- 1 - 2.1 沖裁工藝方案確定 .....................................................- 1 - 2.2 模具結(jié)構(gòu)形式的確定 ...................................................- 1 - 2.3 模具總體設(shè)計 .........................................................- 1 - 第三章 模具設(shè)計計算 .......................................................- 4 - 3.1 排樣 .................................................................- 4 - 3.2 計算條料寬度 .........................................................- 4 - 3.3 送料步距 .............................................................- 5 - 3.4 材料的利用率 .........................................................- 6 - 3.5 沖壓力的計算 .........................................................- 7 - 3.5.1 沖裁力的計算 .....................................................- 7 - 3.5.2 卸料力、頂件力的計算 .............................................- 7 - 3.6 模具壓力中心的確定 ...................................................- 8 - 3.7 模具刃口尺寸的計算 ...................................................- 9 - 3.7.1 沖裁間隙分析 .....................................................- 9 - 3.7.2 沖孔刃口尺寸設(shè)計 ................................................- 11 - 3.7.3 落料刃口尺寸設(shè)計 ................................................- 12 - 第四章 主要零部件設(shè)計 .....................................................- 15 - 4.1 工作零件的結(jié)構(gòu)設(shè)計 ..................................................- 15 - 4.1.1 凸模 ............................................................- 15 - 畢業(yè)設(shè)計（論文）報告紙 6 - 4 - 4.1.2 落料凹模板 ......................................................- 16 - 4.1.3 凹模鑲塊的設(shè)計 ..................................................- 17 - 4.2 卸料部件的設(shè)計 ......................................................- 17 - 4.2.1 卸料板的設(shè)計 ....................................................- 17 - 4.2.2 卸料螺釘?shù)倪x用 ..................................................- 17 - 4.3 模架及其他零部件的選用 ..............................................- 17 - 第五章 較核模具閉合高度及壓力機(jī)有關(guān)參數(shù) ..................................- 19 - 5.1 較核模具閉合高度 ....................................................- 19 - 5.2 沖壓設(shè)備的選定 ......................................................- 19 - 總 結(jié) .....................................................................- 20 - 致 謝 .....................................................................- 21 - 參考文獻(xiàn) ..................................................................- 22 -
本科畢業(yè)設(shè)計（論文）答辯記錄表
系 （部） 機(jī)電工程系 答辯地點： 15A-2
學(xué)生姓名
邵躍龍
學(xué)號
2007011828
題 目
客車門鎖鎖舌沖模設(shè)計
答辯記錄（教師提問與學(xué)生回答情況）
1、正裝與倒裝比較？
答：正裝式級進(jìn)模適用于沖制材質(zhì)較軟或板料較薄的平直度要求較高的沖裁件，還可以沖制孔邊距較小的沖裁件。而倒裝式級進(jìn)模不宜沖制孔邊距較小的沖裁件，但倒裝式級進(jìn)模結(jié)構(gòu)簡單，又可以直接利用壓力機(jī)的打桿裝置進(jìn)行推件卸件可靠，便于操作，并為機(jī)械化出件提供了有利條件，所以應(yīng)用十分廣泛。
2、沖模時，條料如何定位？
答：條料開始送進(jìn)模具時候，第一個工步將由擋料塊進(jìn)行定位來沖中間的導(dǎo)正孔，當(dāng)?shù)谝粋€工步完成后繼續(xù)送進(jìn)時，擋料塊將彈下去，由彈簧頂針頂進(jìn)第一工步即當(dāng)前第二工步的導(dǎo)正孔里進(jìn)行定位，隨后依次每送進(jìn)一個工步都由彈簧頂針進(jìn)行導(dǎo)正定位。
3、凹模鑲塊采用什么材質(zhì)？
答：Cr12MoV模具鋼。
答辯組 組長簽名： 年 月 日
第 26 頁 共 27 頁
e pos 模具工業(yè)現(xiàn)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