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各位評(píng)委老師大家好倒裝復(fù)合模設(shè)計(jì) 姓名：周志勇 班級(jí)：農(nóng)機(jī)1001班 指導(dǎo)老師：樊十全前言隨著我國機(jī)械工業(yè)技術(shù)的迅速發(fā)展制造技術(shù)已成為當(dāng)代科隨著我國機(jī)械工業(yè)技術(shù)的迅速發(fā)展制造技術(shù)已成為當(dāng)代科學(xué)技術(shù)發(fā)展最為重要的領(lǐng)域之一，是產(chǎn)品更新，生產(chǎn)發(fā)展，學(xué)技術(shù)發(fā)展最為重要的領(lǐng)域之一，是產(chǎn)品更新，生產(chǎn)發(fā)展，市場(chǎng)競(jìng)爭的重要的手段。從一定意義上講，機(jī)械制造技術(shù)市場(chǎng)競(jìng)爭的重要的手段。從一定意義上講，機(jī)械制造技術(shù)的發(fā)展水平?jīng)Q定著其它產(chǎn)業(yè)的發(fā)展水平。而模具成為加工的發(fā)展水平?jīng)Q定著其它產(chǎn)業(yè)的發(fā)展水平。而模具成為加工的重要手段，所以對(duì)這一方向的設(shè)計(jì)發(fā)展將嚴(yán)重影響我國的重要手段，所以對(duì)這一方向的設(shè)計(jì)發(fā)展將嚴(yán)重影響我國機(jī)械制造及加工水平。機(jī)械制造及加工水平。在本次設(shè)計(jì)中我們所設(shè)計(jì)的是一種倒裝式復(fù)合模，采用落在本次設(shè)計(jì)中我們所設(shè)計(jì)的是一種倒裝式復(fù)合模，采用落料沖孔方式。凹模、凸模、凹凸模的設(shè)計(jì)及機(jī)床的選擇。料沖孔方式。凹模、凸模、凹凸模的設(shè)計(jì)及機(jī)床的選擇。在設(shè)計(jì)說明書當(dāng)中都有詳細(xì)的設(shè)計(jì)說明。在設(shè)計(jì)說明書當(dāng)中都有詳細(xì)的設(shè)計(jì)說明。本書在自己的努力和樊老師及同學(xué)的幫助下，通過查閱大本書在自己的努力和樊老師及同學(xué)的幫助下，通過查閱大量的相關(guān)資料。使得這次課程設(shè)計(jì)得到圓滿的成功。在此量的相關(guān)資料。使得這次課程設(shè)計(jì)得到圓滿的成功。在此對(duì)他們表示衷心的感謝。由于我的水平有限，在設(shè)計(jì)當(dāng)中對(duì)他們表示衷心的感謝。由于我的水平有限，在設(shè)計(jì)當(dāng)中難免有不足之處，還請(qǐng)各位老師多多的海涵和指導(dǎo)。難免有不足之處，還請(qǐng)各位老師多多的海涵和指導(dǎo)。圖為所要加工的零件簡圖，采用落料圖為所要加工的零件簡圖，采用落料沖沖孔復(fù)合沖壓，采用復(fù)合模生產(chǎn)。孔復(fù)合沖壓，采用復(fù)合模生產(chǎn)。1、零件分析零件材料為零件材料為Q235Q235，厚度為，厚度為1mm1mm。本道工序需沖壓。本道工序需沖壓4 4個(gè)個(gè)4.2和一個(gè)和一個(gè)12的孔。的孔。Q235為普通碳素結(jié)構(gòu)鋼，具有較好的沖裁成形性為普通碳素結(jié)構(gòu)鋼，具有較好的沖裁成形性能。能。零件為大批量生產(chǎn)，所以需采用結(jié)構(gòu)簡單，操作零件為大批量生產(chǎn)，所以需采用結(jié)構(gòu)簡單，操作方便的模具進(jìn)行沖壓。方便的模具進(jìn)行沖壓。2、沖裁工藝方案的確定由于該零件是落料沖孔件，結(jié)構(gòu)簡單。有三種方案可選擇，由于該零件是落料沖孔件，結(jié)構(gòu)簡單。有三種方案可選擇，方案一：先落料，后沖孔。采用兩套單工序模生產(chǎn)。方案一：先落料，后沖孔。采用兩套單工序模生產(chǎn)。方案二：落料方案二：落料沖孔復(fù)合沖壓，采用復(fù)合模生產(chǎn)。沖孔復(fù)合沖壓，采用復(fù)合模生產(chǎn)。方案三：沖孔方案三：沖孔落料連續(xù)沖壓，采用級(jí)進(jìn)模生產(chǎn)。落料連續(xù)沖壓，采用級(jí)進(jìn)模生產(chǎn)。方案一模具結(jié)構(gòu)簡單，但需兩道工序、兩副模具，生產(chǎn)效率低，方案一模具結(jié)構(gòu)簡單，但需兩道工序、兩副模具，生產(chǎn)效率低，零件精度較差，在生產(chǎn)批量較大的情況下不適用。方案二只需一副模零件精度較差，在生產(chǎn)批量較大的情況下不適用。方案二只需一副模具，沖壓件的形位精度和尺寸精度易保證，且生產(chǎn)效率高。盡管模具具，沖壓件的形位精度和尺寸精度易保證，且生產(chǎn)效率高。盡管模具結(jié)構(gòu)較方案一復(fù)雜，但由于零件的幾何形狀較簡單，模具制造并不困結(jié)構(gòu)較方案一復(fù)雜，但由于零件的幾何形狀較簡單，模具制造并不困難。方案三也只需一副模具，生產(chǎn)效率也很高，但與方案二比生產(chǎn)的難。方案三也只需一副模具，生產(chǎn)效率也很高，但與方案二比生產(chǎn)的零件精度稍差。欲保證沖壓件的形位精度，需在模具上設(shè)置導(dǎo)正銷導(dǎo)零件精度稍差。欲保證沖壓件的形位精度，需在模具上設(shè)置導(dǎo)正銷導(dǎo)正，模具制造、裝配較復(fù)合模略復(fù)雜。正，模具制造、裝配較復(fù)合模略復(fù)雜。所以，比較三個(gè)方案欲采用方案二生產(chǎn)?，F(xiàn)對(duì)復(fù)合模中凸凹模壁所以，比較三個(gè)方案欲采用方案二生產(chǎn)?，F(xiàn)對(duì)復(fù)合模中凸凹模壁厚進(jìn)行校核，當(dāng)材料厚度為厚進(jìn)行校核，當(dāng)材料厚度為1mm1mm時(shí)，可查得凸凹模最小壁厚為時(shí)，可查得凸凹模最小壁厚為4.9mm4.9mm，現(xiàn)零件上的最小孔邊距為現(xiàn)零件上的最小孔邊距為2.7mm2.7mm，所以可以采用復(fù)合模生產(chǎn)，即采用，所以可以采用復(fù)合模生產(chǎn)，即采用方案二。方案二。3、排樣計(jì)算分析零件形狀，應(yīng)采用單直排的排樣方式分析零件形狀，應(yīng)采用單直排的排樣方式裁成寬裁成寬54.4mm、長、長4000mm的條料，則一張板材能出的零件總個(gè)數(shù)的條料，則一張板材能出的零件總個(gè)數(shù)為為材料利用率計(jì)算：一張板料上的材料利用率材料利用率計(jì)算：一張板料上的材料利用率n=NF/BL100%=2555（5026）/40001000=83%4、凸模的設(shè)計(jì)由于沖孔截面為圓形，所以選擇臺(tái)階式結(jié)構(gòu)。由于沖孔截面為圓形，所以選擇臺(tái)階式結(jié)構(gòu)。凸模的長度計(jì)算：凸模的長度計(jì)算：L=hL=h1 1+h+h2 2+h3+t+h=15+10+10+1+15=51mm+h3+t+h=15+10+10+1+15=51mm（采用固定（采用固定卸料板時(shí)），卸料板時(shí)），h h1 1-凸模固定板厚度，凸模固定板厚度，h h2 2-卸料板厚度，卸料板厚度，h h3 3-導(dǎo)料板厚度，導(dǎo)料板厚度，t-t-材料厚度，材料厚度，h h附加長度。附加長度。凸模的強(qiáng)度校核。在一般的情況下，凸模的強(qiáng)度時(shí)足夠凸模的強(qiáng)度校核。在一般的情況下，凸模的強(qiáng)度時(shí)足夠的的。5、裝配圖6、凹模的設(shè)計(jì)凹模的高度和壁厚計(jì)算公式，凹模高度凹模的高度和壁厚計(jì)算公式，凹模高度H=kb=0.22H=kb=0.2250mm=11mm50mm=11mm，k k值值的取值可查表得到。的取值可查表得到。凹模壁厚凹模壁厚C=C=（1.5-21.5-2）H=1.8H=1.811=20mm11=20mm凹模長度凹模長度L=L=（50+250+22020）mm=90mmmm=90mm凹模的寬度凹模的寬度B=B=（26+226+22020）=66mm(=66mm(取取70mm)70mm)6、卸料裝置中彈性元件的計(jì)算.橡膠的自由高度橡膠的自由高度H H0 0=（3.5-43.5-4）H HI I,H HI I=H=H工作工作+H+H修磨修磨=t+1+(5-10)H=t+1+(5-10)HI I =1+1+7=9mm,=1+1+7=9mm,則則H H0 0=36mm=36mm確定橡膠的截面積確定橡膠的截面積A:A=FX/P=5700N/0.6Mpa=9500mmmm2 2暫定一邊長為暫定一邊長為100mm100mm，另一邊長，另一邊長b b為為:100:100b-55b-5530=A,30=A,可求得可求得A=112mm A=112mm 8.沖壓力計(jì)算沖壓力計(jì)算可知沖裁力基本計(jì)算公式為可知沖裁力基本計(jì)算公式為:F=KLT:F=KLTi i零件周長零件周長L=50L=502+362+362 2172mm172mm。此零件的周長為此零件的周長為172mm172mm，材料厚度，材料厚度1mm1mm，Q235Q235鋼的抗剪強(qiáng)度取鋼的抗剪強(qiáng)度取350MPa350MPa，則沖裁該零件所需沖裁力為則沖裁該零件所需沖裁力為F=1.3F=1.31721721 1350350=80KN=80KN卸料力卸料力F Fx x=K=KX XF=0.05F=0.0580KN=4KN80KN=4KN推件力推件力F FT T=NK=NKT TF=3F=30.0550.05580KN=13.2KN80KN=13.2KN沖壓力沖壓力F F總總=F+F=F+FX X+F+FT T=97.2KN=97.2KN9、沖壓設(shè)備的選用根據(jù)沖壓力的大小，選取開式雙柱可傾壓力機(jī)JH2335，其主要技術(shù)參數(shù)如下：公稱壓力：350kN 滑塊行程：80mm 最大閉合高度：280 mm閉合高度調(diào)節(jié)量：60 mm滑塊中心線到床身距離：205mm工作臺(tái)尺寸：380 mm610 mm工作臺(tái)孔尺寸：200 mm290 mm模柄孔尺寸：50 mm70 mm墊板厚度：40 mm1 1、橡膠的高徑比在、橡膠的高徑比在0.5-1.50.5-1.5之間，所以之間，所以H H0 0/D=36/56=0.65/D=36/56=0.65，在合理范圍內(nèi)，在合理范圍內(nèi)2 2、橡膠的裝模高度為：、橡膠的裝模高度為：0.850.8536=31mm36=31mm。10、標(biāo)準(zhǔn)模架的選用標(biāo)準(zhǔn)模架的選用依據(jù)為凹模的外形尺寸，所以應(yīng)首先計(jì)算凹模周界的標(biāo)準(zhǔn)模架的選用依據(jù)為凹模的外形尺寸，所以應(yīng)首先計(jì)算凹模周界的大小。由凹模高度和壁厚的計(jì)算公式得，凹模高度，凹模壁厚大小。由凹模高度和壁厚的計(jì)算公式得，凹模高度，凹模壁厚20mm凹?？傞L取凹?？傞L取100mm，寬度為，寬度為70mm?？刹榈媚＜芤?guī)格為上模座可查得模架規(guī)格為上模座112mm100mm40mm，下模座，下模座112mm100mm40mm，導(dǎo)柱，導(dǎo)柱36mm150mm，導(dǎo)套，導(dǎo)套38mm85mm33mm。結(jié)束語 經(jīng)過這次畢業(yè)設(shè)計(jì)，學(xué)會(huì)了很多東西。深深的感受到知識(shí)的連串性是那么的重要。讓我深刻地體會(huì)到，要想成為一名合格的設(shè)計(jì)人員，必須具備良好的素質(zhì)、嚴(yán)謹(jǐn)?shù)墓ぷ髯黠L(fēng)。無論做什么事情，只要只要自己足夠堅(jiān)強(qiáng)，有足夠的毅力與決心，有足夠挑戰(zhàn)困難的勇氣，就沒有什么辦不到的。同時(shí)也要感謝老師的大力支持和不斷鼓勵(lì)。謝謝觀看第 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