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1、Application of a feasible formability diagram for the effective design in stamping processes of automotive panelsDae-Cheol Ko a, Seung-Hoon Cha b, Sang-Kon Lee c, Chan-Joo Lee b, Byung-Min Kim d,*a ILIC, Pusan National U

2、niversity, 30 Jangjeon-Dong, Kumjeong-Gu, Busan 609-735, South Korea b Precision Manufacturing Systems Division, Pusan National University, 30 Jangjeon-Dong, Kumjeong-Gu, Busan 609-735, South Korea c PNU-IFAM, Joint Rese

3、arch Center, Pusan National University, 30 Jangjeon-Dong, Kumjeong-Gu, Busan 609-735, South Korea d School of Mechanical Engineering, Pusan National University, 30 Jangjeon-Dong, Kumjeong-Gu, Busan 609-735, South Koreaa

4、r t i c l e i n f oArticle history:Received 4 May 2009Accepted 11 September 2009Available online 16 September 2009Keywords:Stamping processFeasible formability diagramFE-simulationDesign of experimentArtificial neural ne

5、tworkAutomotive panela b s t r a c tThe objective of this study is to propose a method of process design that uses a feasible formability dia-gram, which denotes the safe region without fracture and wrinkle, for the effe

6、ctive and rapid design ofstamping processes. To determine the feasible formability diagram, FE-analyses have been performedfor combinations of process variables that correspond to the orthogonal array of design of experi

7、ments.Subsequently, the characteristic values for fracture and wrinkle have been estimated from the results ofFE-analyses on the basis of the forming limit diagram. The characteristic values for all combinationswithin a

8、whole range of process variables have been predicted through the training of an artificial neuralnetwork. The feasible formability diagram has been finally determined for all combinations of processvariables. The stampin

9、g processes of automotive panels to support suspension module, such as the turretsuspension and the wheel house, have been taken as examples to verify the effectiveness of processdesign through feasible formability diagr

10、am. A comparison of the FE-simulation results with the exper-imental results reveals that the design of stamping processes through feasible formability diagram is effi-cient and suitable for actual processes.? 2009 Elsev

11、ier Ltd. All rights reserved.1. IntroductionIn metal forming technologies, the stamping process for sheet metal is one of the significant manufacturing processes in the pro- duction of sheet metal components. Stamping te

12、chnology has been extensively applied in the automotive industry. The formability of stamping products is generally influenced by various process vari- ables such as the shape of the die, material properties, the shape o

13、f the initial blank, the blank holding force, the layout of the draw bead, lubrication. It is very important to design stamping processes that can produce sound products without defects, such as fracture and wrinkle. The

14、 design of stamping processes has been mainly performed by either a trial-and-error approach, which is both time- and cost-intensive, or Finite Element analysis (FE-analysis) combined with optimal design procedure, which

15、 poses some prob- lems in actual industrial applications [1–7]. Since the formability and product quality in stamping processes depend on the initial blank shape, the optimal design of blanks has been investigated by man

16、y researchers. Lee and Huh [8] suggested an inverse finite element approach for the prediction of the blank shape. Guo et al. [1] conducted the optimal design of blanks onthe basis of the variation in the thickness of th

17、e sheet material. A method for the design of optimal blank shape that uses the initial nodal velocity was proposed by Son and Shim [9]. Yeh et al. [10] suggested a forward-inverse prediction scheme to determine the optim

18、al blank shape. Although the methods mentioned above are excellent, there still remain problems when the methods are ap- plied for the optimal design of blanks in actual industrial problems with various process variables

19、. In recent years, much research has focused on the combination of FE-analysis and optimization technology to optimize stamping processes. Katayama et al. [11] optimized the die shape to improve forming defects, such as

20、fracture and wrinkle, in a two-stage deep- drawing process. Jansson et al. [12] optimized the draw-in of an automotive part by adjusting the draw bead restraining force through response surface methodology and a space-ma

21、pping tech- nique. Kayabasi and Ekici [6] proposed an optimization method to improve the formability of automotive side panels. The optimal values of process variables were calculated by the method. Wei et al. [7] propos

22、ed a method to optimize process variables and to predict performance with regard to tolerance in the stamping of deck-lid outer panels. A Pareto-based multi-objective genetic algo- rithm was proposed by Liu and Yang [13]

23、. Their proposed algo- rithm was applied for the optimization of process variables, such as the blank holding force and the draw bead restraining force.0261-3069/$ - see front matter ? 2009 Elsevier Ltd. All rights reser

24、ved.doi:10.1016/j.matdes.2009.09.022* Corresponding author. Tel.: +82 51 510 3697.E-mail address: bmkim@pusan.ac.kr (B.-M. Kim).Materials and Design 31 (2010) 1262–1275Contents lists available at ScienceDirectMaterials a

25、nd Designjournal homepage: www.elsevier.com/locate/matdeserror is within a specified tolerance assumed to be 10?3 in this study. The formula for the error is given below:E ¼ AT ? AD AT? ?2 ð1Þwhere E is th

26、e shape error and AT and AD are the areas of the target and deformed contours, respectively. As mentioned above, the optimal shape of blank is dependent on the process variables. To determine the feasible shape of blank,

27、 the contour of the initial blank obtained from Eq. (1) is offset by a uniform distance along the normal direction of the contour. The lower and upper bounds on the offset distance of the blank are the blank shape to bec

28、ome the target contour after stamping and the blank shape to be enlarged up to the end of the stamping die face, respectively. The offset shape of blank, as shown in Fig. 1b, is determined as follows:^ xd ¼ ^ xi 

29、54; db N ð2Þwhere ^ xd is the coordinate vector of the nodal point located at the outline of the offset blank, ^ xi is the coordinate vector of the nodalpoint located at the outline of the initial blank, d is t

30、he amount of offset, and b N is the unit normal vector in the direction of movement. The other process variables, viz., the blank holding force and the draw bead, play an important role in the control of defects. The bla

31、nk holding force is designed to be within the range of capacities of presses in actual industry. A circular draw bead is employed in order to supply an additional restraining force to the blank. Various shapes of draw be

32、ad are considered with different parameters, such as the height and shoulder radius of the draw bead, as shown in Fig. 2.Fig. 2. Geometric parameters of the draw bead.Fig. 3. Definition of characteristic values on the ba

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