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河南機(jī)電高等?？茖W(xué)校
畢業(yè)設(shè)計(jì)論文
論文題目：落料拉深復(fù)合模
系 部： 材料工程系
專 業(yè)： 模具設(shè)計(jì)與制造
班 級(jí)： 模具034班
學(xué)生姓名： 陶中清
學(xué) 號(hào)： 0312419
指導(dǎo)教師： 于智宏
2006年 5 月 31 日
畢業(yè)設(shè)計(jì)（論文）成績
畢業(yè)設(shè)計(jì)成績
指導(dǎo)老師認(rèn)定成績
小組答辯成績
答辯成績
指導(dǎo)老師簽字
答辯委員會(huì)簽字
答辯委員會(huì)主任簽字
插圖清單
1零件圖 ……………………………………………1
2螺釘與螺釘或與銷釘間距離圖…………...……….7
3上模座圖…………………………………………...10
4下模座圖 ………………………………………10
5模柄圖 ………………………… ………………… 12
表格清單
1. 排樣及相關(guān)計(jì)算……………………………….........2
2. 模具工作部分尺寸計(jì)算 …………………………4
3. 主要零件材料的選擇……………………………...14
4. 凸凹模的加工方案的確定………………………...15
目錄
摘要 …………………………………………………… Ⅰ
緒論 ………………………………………………….Ⅱ
第一章 工藝性分析 ………………………………………………1
1.1 零件的工藝性分析……………………………………… 1
1.2工藝方案的確定 ………………………………………………2
第二章主要設(shè)計(jì)計(jì)算 …………………………………………………2
2.1毛坯直徑的確定 ………………………………………………3
2.2排樣及相關(guān)計(jì)算 …………………………………………… 3
2.3成型次數(shù)的確定 ……………………………………………3
2.4沖壓設(shè)備的初選及壓力中心的確定………………………… 3
2.4.1沖壓設(shè)備的初選 ……………………………………… 3
2.4.2壓力中心的計(jì)算 …………………………………………3
第三章 工作部分尺寸的計(jì)算 ………………………………………4
3.1工作部分尺寸的計(jì)算 …………………………………………4
3.2 模具總體的校核 …………………………………………… 4
3.2.1模具的類型選擇 ………………………………………… 4
3.3定位方式的選擇 ……………………………………………4
3.4卸料，出件方式的選擇 …………………………………… 4
第四章 主要零件的設(shè)計(jì) …………………………………5
4.1拉深凸模的設(shè)計(jì) …………………………………………… 5
4.2落料凹模的設(shè)計(jì) ……………………………………… 5
4.2.1 凹模的外形的尺寸的確定 …………………………… 5
4.2.2 凹模的壁厚（刃口到邊緣的距離 ……………… 6
4.2.3 凹模圓角半徑確定 …………………………………… 6
4.2.4 凹模定位固定時(shí)螺釘與螺釘或與銷釘之間的距離 …………………………………………………………………… 6
4.3凸、凹模的設(shè)計(jì) ………………………………………… 7
第五章 模架及其他零部件的選擇 …………………………… 8
5.1 模架的設(shè)計(jì) …………………………………………… 8
5.2 導(dǎo)向裝置的設(shè)計(jì) …………………………………………8
5.3 模座的設(shè)計(jì) ………………………………………………9
5.4 卸料板的設(shè)計(jì) ……………………………………………11
5.5 凸，凹模固定板的厚度 …………………………………11
5.6 彈性元件的設(shè)計(jì) …………………………………………11
5.7 模柄的設(shè)計(jì) ……………………………………………11
5.8 擋料銷的選擇 …………………………………………… 12
第六章 沖壓設(shè)備的選擇 …………………………………… 12
6.1沖壓設(shè)備參數(shù)的確定 …………………………………… 12
第七章 主要工作零件材料的選擇極其加工………………… 13
7.1材料的選擇 ……………………………………………… 13
7.2工作零件加工方案的確定 ……………………………… 14
7.2.1凸，凹模的加工工藝路線的確定 ………………………… 14
7.3 其他零件加工方法的確定 ……………………………… 15
7.3.1導(dǎo)向零件的加工方法 …………………………………… 15
7.3.2 固定板與卸料板的加工方法 ………………………………15
7.4模具的裝配 ………………………………………………… 15
7.4.1 裝配注意事項(xiàng) …………………………………………15
致 謝 ………………………………………………………… Ⅰ
參考文獻(xiàn) …………………………………………………………… Ⅰ
緒論
冷模設(shè)計(jì)是在冷沖模設(shè)計(jì)理論教學(xué)之進(jìn)行的實(shí)踐性教學(xué)環(huán)節(jié).其目的是在與鞏固所學(xué)知識(shí)、熟悉有關(guān)資料、樹立正確設(shè)計(jì)思想、掌握設(shè)計(jì)方法、培養(yǎng)實(shí)際工作能力.通過沖模結(jié)構(gòu)設(shè)計(jì),使我們?cè)跊_壓工藝分析、沖壓工藝方案確論證、沖壓工藝計(jì)算、沖模零件結(jié)構(gòu)設(shè)計(jì),編寫技術(shù)文件和查閱技術(shù)文獻(xiàn)等方面受到一次綜合訓(xùn)練.
設(shè)計(jì)內(nèi)容包括沖壓工藝分析、工藝方案的制定、排樣圖的設(shè)計(jì)、總沖壓力及壓力中心的計(jì)算、彈性元件的選用,凸凹模的設(shè)計(jì)及其他沖模零件的結(jié)構(gòu)設(shè)計(jì)和工作零件圖，編寫設(shè)計(jì)說明書,填寫機(jī)加工工藝卡和工作零件機(jī)械加工工藝過程卡.
模具是工業(yè)產(chǎn)品生產(chǎn)用的工藝裝備，主要應(yīng)用與制造業(yè)和加工業(yè)．模具屬于精密機(jī)械產(chǎn)品，主要由機(jī)械零件和機(jī)構(gòu)組成，如成型工作零件、導(dǎo)向零件、支撐零件、定位零件等；送料機(jī)構(gòu)、推料機(jī)構(gòu)、抽芯機(jī)構(gòu)等。為提高模具的質(zhì)量，性能精度和生產(chǎn)效率，縮短制造周期，其零部件多由標(biāo)準(zhǔn)件組成，所以模具應(yīng)屬于標(biāo)準(zhǔn)化程度較高的產(chǎn)品。
現(xiàn)代產(chǎn)品生產(chǎn)中，模具由于其加工效率高，互換性好，節(jié)約原材料所以得到很廣泛的應(yīng)用。
現(xiàn)代工業(yè)產(chǎn)品零件廣泛應(yīng)用與沖壓，成型鍛造，壓鑄成型，擠壓成型等其他加工方法和成型模具相配套，經(jīng)單工序和多工序使材料或胚料成型加工成符合產(chǎn)品要求的零件。
高精度、高效率、長壽命的沖模，可成型加工幾十萬件，快換沖模，疊層沖?；虺尚湍＞?，低熔點(diǎn)合金成型模具等，在現(xiàn)代加工業(yè)中具有重要的經(jīng)濟(jì)價(jià)值，稱這類模具為通用，經(jīng)濟(jì)模具。
電子、計(jì)算機(jī)、現(xiàn)代通信器材與設(shè)備、電器、儀器和儀表等工業(yè)產(chǎn)品的元器件或零部件，越來越趨于微型化，精密化，其零件結(jié)構(gòu)設(shè)計(jì)中的槽、縫、孔、尺寸要求在０.３mm以下，批量生產(chǎn)用的模具要求很高。
隨著現(xiàn)代工業(yè)和科學(xué)技術(shù)的發(fā)展，模具的應(yīng)用越來越廣泛，其適應(yīng)性也越來越強(qiáng)，以成為工業(yè)國家制造水平的標(biāo)志和基礎(chǔ)工業(yè)體系 。
沖壓中材料的性能是成型過程中一個(gè)重要的因素，沖壓生產(chǎn)中的材料有板料，帶料和型材。板料可根據(jù)排樣裁剪成條料、板、帶料的厚度偏差對(duì)彎曲件拉深件的成型情況影響較大，型材的徑向偏差影響坯料在模具中的定位。
材料的力學(xué)性能與沖壓成型性能有密切的關(guān)系，深長率是材料的朔性指標(biāo)。材料產(chǎn)生的均勻變形或穩(wěn)定的變形的能力。屈強(qiáng)比愈小，表示材料允許的朔性區(qū)愈大，在拉深工序中材料的屈強(qiáng)比較小時(shí)，所需要的壓邊力和摩擦力相應(yīng)較小，從而降低拉深了筒壁傳力區(qū)的載荷，同時(shí)隨著拉深強(qiáng)度的提高增加了筒壁的抗拉能力有利與提高成型極限。
目前，我國的沖壓技術(shù)與工業(yè)發(fā)達(dá)國家相比還比較落后，主要原因?yàn)槲覈鴽_壓基礎(chǔ)理論及成型工藝，模具標(biāo)準(zhǔn)化，模具設(shè)計(jì)，模具制造工藝及設(shè)備等方面與發(fā)達(dá)國家尚有相當(dāng)大的距離，導(dǎo)致我國在模具壽命、效率、加工精度、生產(chǎn)周期等方面還與發(fā)達(dá)國家的模具相比差距相當(dāng)大。
隨著工業(yè)產(chǎn)品質(zhì)量的不斷提高，沖壓產(chǎn)品生產(chǎn)正呈現(xiàn)多品種、少批量、復(fù)雜、大型、精密、更新?lián)Q代速度快等特點(diǎn)，沖壓模具正向高效精密，長壽命，大型化方向發(fā)展。為適應(yīng)市場(chǎng)變化，隨著計(jì)算機(jī)技術(shù)的發(fā)展和制造技術(shù)的迅速發(fā)展，沖壓模具設(shè)計(jì)與制造正在有手工設(shè)計(jì)依靠人工經(jīng)驗(yàn)和機(jī)械加工技術(shù)向以計(jì)算機(jī)輔助設(shè)計(jì)、數(shù)控切削加工、數(shù)控電加工為核心的計(jì)算機(jī)輔助設(shè)計(jì)與制造技術(shù)轉(zhuǎn)變。
模具應(yīng)用廣泛，現(xiàn)代制造業(yè)中的產(chǎn)品構(gòu)件成形加工，幾乎都需要使用模具來完成。因此，凡制造業(yè)發(fā)達(dá)的國家，模具市場(chǎng)均極為廣闊；凡模具發(fā)達(dá)國家，制造業(yè)也必定很發(fā)達(dá)和繁榮，也必定擁有國內(nèi)、國外兩個(gè)市場(chǎng)。所以，模具產(chǎn)業(yè)是國家高新技術(shù)產(chǎn)業(yè)的重要組成部分，是重要的、寶貴的技術(shù)資源。優(yōu)化模具系統(tǒng)結(jié)構(gòu)設(shè)計(jì)和型件的CAD/CAE/CAM，并使之趨于智能化，提高型件成形加工工藝和模具標(biāo)準(zhǔn)化水平，提高模具制造精度與質(zhì)量，降低型件表面研磨、拋光作業(yè)量和制造周期；研究、應(yīng)用針對(duì)各種類模具型件所采用的高性能、易切削的專用材料，以提高模具使用性能；為適應(yīng)市場(chǎng)多樣化和新產(chǎn)品試制，應(yīng)用快速原型制造技術(shù)和快速制模技術(shù)，以快速制造成型沖模、塑料注射?；驂鸿T模等，應(yīng)當(dāng)是未來5~20年的模具生產(chǎn)技術(shù)的發(fā)展趨勢(shì)。
致謝
在畢業(yè)設(shè)計(jì)的制作過程中遇到很多困難，在解決問題和分析問題的過程中，指導(dǎo)老師扮演著向標(biāo)的作用，為我排憂解難。畢業(yè)設(shè)計(jì)是煩瑣的，疲勞戰(zhàn)和持久戰(zhàn)使我們筋疲力盡，這時(shí)精神食糧是重要的，在這過程中同學(xué)之間相互鼓勵(lì)著，互相幫忙著，老師不斷的講解著加之小有所成的成就感，使我們煩躁的心情如加干泉。
再此要感謝我的輔導(dǎo)老師和同學(xué)他們給了我大量的幫助，能使我的畢業(yè)設(shè)計(jì)順利完成。
在實(shí)習(xí)期間公司領(lǐng)導(dǎo)給了很大的幫助，在資料和物資上也給予了很大的支持，使我能在實(shí)習(xí)期間能夠理論聯(lián)系實(shí)踐，達(dá)到事半功倍的效果。
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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