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1、F.-K. Chen, J.-H. Liu / Journal of Materials Processing Technology 55 (1995) 40S-416413JournalELSEVIERMaterials Processing TechnologyJournal of Materials Processing Technology 55 (1995) 408-416:Analysis of die designs for the stamping of an automobile rear floor panelFuh-Kuo Chen Corresponding autho
2、r., Jia-Hong LiuDepartment of Mechanical Engineering, National Taiwan University, Taipei, Taiwan, ROC Received 10 October 1994Industrial summaryThe stamping process of manufacturing a one-piece rear floor panel of a passenger car has been investigated in the present study. An analysis of the origina
3、l die design, in which a split defect occurred at the drawn-cup wall, was performed using circle-grid analysis as well as the 3-D finite-element method. The split defect is due to the large area of sheet metal under the blank-holder that limits the flow of the metal towards the cup area. An optimum
4、die design，which consists of a separate die face and a wedge mechanism mounted in the lower die frame, was proposed to provide additional metal for the cup area and to eliminate the split defect without adding an extra operation. This optimum die design was validated by the results of circle-grid an
5、alysis performed for the first and second draw operations and also by the good-quality panels produced.Keywords: Stamping dies; Rear floor panel; Splits; Circle-grid analysis.0924-0136/96/S 15.00 1996 Elsevier Science S.A. All rights reserved SSDI 0924-01 36(95)02038-N1. IntroductionSplits are among
6、st the major defects occurring commonly in the stamping process. A lot of research effort has been made to investigate the causes of and solutions to the split problem during the last few decades 1-4, the methods used including forming-limit analysis and the finite-element method. Since Keeler and B
7、ackofen 5 first introduced the concept of forming-limit diagrams (FLDs) in 1963, they have been used widely in the analysis of sheet metal forming in press shops. The FLDs indicate the strains which lead to failure and thus provide a useful tool to determine if the forming process is likely to be pr
8、one to splitting, whilst the finite-element method can calculate the strain distributions in the stamped parts accurately and thus predict if the split defect is likely to occur.In general, the solution to problems of splitting is to provide more metal to the critical area before the major drawing p
9、rocess starts. This can be achieved either by decreasing the blank-holder pressure or improving the lubrication conditions, but the most straight-forward method is to add an extra operation solely for the purpose of feeding more metal into the critical area.However, the extra operation increases the
10、 production cost by adding one more set of dies and additional man-power; and hence in reality, it should be avoided.In the present study，an optimum die design in which a separate die face and a wedge mechanism mounted in the lower die frame is proposed to eliminate the occurrence of a split-defect
11、in the stamping process for a one- piece floor panel of a passenger car. The special die face and wedge mechanism were designed to provide additional metal for the critical area where the split defect occurred, without adding an extra operation. Both circle- grid analysis and 3-D finite-element simu
12、lations were performed to analyze this split defect.2. Problem descriptionThe common design for a rear floor panel of a passenger car is usually a two-piece type, namely, welding two stamped pieces together, as shown in Fig. 1. The two- piece type design is chosen mainly due to the difficulty encoun
13、tered in stamping a one-piece rear floor panel, in which a split tends to take place at the wall of the deeply drawn cup used for storing the spare tire, as shown in Fig. 2. The occurrence of the split is attributed to the substantial distance between the cup wall and one side of the blank-holder, a
14、s shown by line A-B in Fig. 3, thatrestricts the metal under the blank-holder from flowing into the cup area. Whilst in the two-piece design this distance is much shorter and sufficient metal can flow easily into the cup to prevent the edge of the cup from splitting，due to cost-effective considerati
15、ons, a one-piece rear floor panel is always desired, so that the split problem must therefore be overcome.The original procedure in the press shop for the production of the one-piece rear floor panel consists of four operations: first draw, second draw, trimming, and flanging. The first-draw operati
16、on was designed only to produce a cup shape, as shown in Fig. 3. As for the ribs around the cup, these were formed in the second-draw operation. Like most stamping processes, the main deformation of the rear floor panel is completed in the first- draw operation. The conventional draw process allows the punch to pull more metal into the die cavity from the blank-holder. To facilitate metal-flow, no draw bea
