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Xxxxx大学毕业设计（论文）
The mechan-ical properties in the tensile direction are indicated in Table 1.
D.H. Park et al. / Journal of Materials Processing Technology 113 (2001) 662—665 Table 1
Mechanical property in the tensile direction
Direction Yield strength(MPa) Tensile strength(MPa) Elongation(%) 0° 210 311 46 45° 226 323 43 90° 222 307 45
2.2. Experimental equipment
Deep drawing tests were carried out using a punch with a diameter of 56 mm and a die with a diameter of 60 mm.Fig. 1 presents the dimensions of the tools used in the first drawing process. The clearance and the corner radii of the punch and die are listed in Table 2. The forming sequence for the product consists of three processes which are: (a) first drawing; (b) redrawing; (c) elliptical drawing. The corner radii of the punch (Rp) and die (Rd) were different for each process. The initial blank-holder force was determined as the minimum force that could prevent the wrinkling of the blanks and was kept constant during the test for each blank.Elliptical deep drawing tests were performed at various corner radii in a 300 t mechanical press. The corner radii of the punch and die in first drawing were the three types mentioned in Table 3. Fig. 1. Dimensions of the tools (mm) used in the first drawing process.
Table 2
Corner radius and clearance （t= 1.6 mm）
Process Corner radius (mm) Clearance (mm)
First drawing Rp =15, Rd = 10 2 (1.25 t) Redrawing Rp =12, Rd = 8 2 (1.25 t)
Elliptical drawing Rp =8, Rd = 5 Long side: 1.50,short side: 1.39
Table 3
Test conditions in first drawing Type Rp (mm) Rd (mm) A3 6.4 16 B3 9.6 16 C3 12.8 16
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D.H. Park et al. / Journal of Materials Processing Technology 113 (2001) 662—665
2.3. Blank shape and measurement The final product is of an elliptical shape that consists of a circular arc at the long side and a straight line at the short side. The blank shape designed by trial-and-error was simply fabricated with an equivalent surface area to the final product, and then a size of final blank was determined through many experiments [11—13]. Fig. 2 presents the blank shape designed by trial-and-error. Figs. 3 and 4 present experimental results for each process of elliptical deep drawing. Measurement of the thickness distribution of the product has been made a point micrometer measuring from the center of the product to the edge of flange at the interval of 3 mm, and the thickness of the product is measured in two parts of both the long and short sides.
Fig. 2. Blank shape designed by trial-and-error.
Fig. 3. Experimental result for each process.
Fig. 4. An elliptical deep drawing
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Xxxxx大学毕业设计（论文）
3. Results and discussion
The material used in computation is electro-galvanized steel for which the stress-strain characteristic is expressed as MPa: (1) The process variables used in simulation are as follows: (1)sheet thickness, t =1.6 mm; (2) diameter of die, 60 mm; (3)diameter of punch, 56 mm; (4) blank-holder force, 9800 N;5) Young's modulus, MPa; (6) Poisson's ratio,0.3; (7) Coulomb coefficient of friction, 0.04 The coefficient of friction among the sheet, punch, die and blank holder was taken as 0.04 due to the wet friction of using drawing oil. It was assumed that the friction coeffi-cient would remain constant during the operation. The finite element mesh system is constructed with 445 nodal points and 404 elements. By the geometric symmetry, a quarter of a sheet blank is considered. Fig. 5 shows the deformed mesh configurations at a stroke of 46 mm. The formability and productivity of sheet metal forming process can improve the proposed corner radii of the punch and die. In order to show the change of the deformed shape, the corresponding boundary contours of the deformed mesh with respect to punch height are shown in Fig. 6. In case of Rp =6.4 mm and Rd = 16 mm, the computed results are in better agreement with the experimental results at a stroke of 46 mm. Fig. 7 shows the comparison of the boundary shape contour between the computed and experimental results in the case of Rp =9.6 mm and Rd = 16 mm, whilst Fig. 8 shows the comparison of the boundary shape contour between the computed and experimental results in the case of Rp =12.8 mm and Rd = 16 mm.In the case of Rp = 6.4 mm and Rd = 16 mm, the thick-ness distribution along the rolling direction (the long side) and transverse direction (the short side) at a stroke of 46 mm is shown in Fig. 9. The thickness from the long side is smaller than that from the short side near the punch shoulder, which is in better agreement with experiment. The thickness distribution of the flange region presents a difference between the experimental and computed results. Fig. 10 shows the comparison of the experimental results and the finite element method in the case of Rp = 9.6 mm and Rd =16 mm, whilst Fig. 11 shows the comparison of the experimental results and the finite element method in case of Rp =12.8 mm and Rd = 16 mm.
The thickness distribution of the entire region has a good agreement between the experimental and computed results.An optimum design procedure of process parameters has been carried out for the optimum process of sheet metal forming. Optimum design conditions of the corner radii are sought in deep drawing processes for a better quality of product. Fig. 5. Thickness distribution of the first drawing product.
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D.H. Park et al. / Journal of Materials Processing Technology 113 (2001) 662—665
Fig. 6. Comparison of the boundary shape contour between the computed and experimental results (type A3). Fig. 7. Comparison of the boundary shape contour between the computed and experimental results (type B3). Fig. 8. Comparison of the boundary shape contour between the computed and experimental results (type C3
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D.H. Park et al. / Journal of Materials Processing Technology 113 (2001) 662—665