*3.3.1. Simulation of stamping-forging processing for the center hole edge of clutch hub*

Stamping-Forging Processing of Sheet Metal Parts 41

a) Scheme of punch and die of upsetting b) Size of upsetting-extruding punch

The result of finite element simulation is shown in Fig. 14. It can be observed that there is no folding at the bottom and the right-angle shape is formed perfectly. The load for the upsetting-extruding punch predicted by FEM is given in Fig. 15, of which the maximum is

**Figure 13.** Scheme of punch and die when upsetting

**Figure 14.** Result of upsetting-extruding

about 526.7 kN.

Stamping-forging processing for the center hole edge of car clutch hub was presented in this section. The schematic of clutch hub is shown in Fig. 12. As we can see in view B, the center hole edge is 3.5 mm in height and 1 mm in thickness, while in other position of part the thickness is 2.5 mm. There is a bevel of 45° to the center hole and a right angle shape around the hole. According to the features of the component, SFP technology should be employed. So, drawing, piercing, and spinning processes were used to obtain its structure of hollow shape, and then flanging and upsetting were used to obtain the required part.

**Figure 12.** Schematic of clutch hub

As shown in Fig. 13, the shape of upper-punch and die cavity is in accord with the component, while the upsetting-punch (shown in Fig. 13b) is with ladder shape. Two steps were applied to implement the procedure: in the first step, the flanging-punch moved down to complete flanging process while other dies stayed where they were, and then it moved up; in the second step, the center hole edge was thickened and the right angle of it was formed with the upsetting-punch moving up. Since the thickness of the inner wall is not thinned by flanging, machining was needed to obtain the diameter 38 mm as well as the angle 45°.

The FEM software MSC.Marc can be used to simulate the forming process by taking half of the part because of the axisymmetric shape. Four-node quadrangles were available, and the mesh adaptive function was activated considering the large deformation in the process of forming. The initial thickness of the blank was 2.5±0.1 mm, and the stress-strain curve was obtained by tensile test. As we described before, the flanging-punch moved down and returned for the first 400 steps to finish flanging, and then in the last 200 steps of simulation, the upsetting-extruding punch moved up to complete upsetting process. The friction coefficient was set as 0.1.

a) Scheme of punch and die of upsetting b) Size of upsetting-extruding punch

*3.3.1. Simulation of stamping-forging processing for the center hole edge of clutch hub* 

shape, and then flanging and upsetting were used to obtain the required part.

Stamping-forging processing for the center hole edge of car clutch hub was presented in this section. The schematic of clutch hub is shown in Fig. 12. As we can see in view B, the center hole edge is 3.5 mm in height and 1 mm in thickness, while in other position of part the thickness is 2.5 mm. There is a bevel of 45° to the center hole and a right angle shape around the hole. According to the features of the component, SFP technology should be employed. So, drawing, piercing, and spinning processes were used to obtain its structure of hollow

As shown in Fig. 13, the shape of upper-punch and die cavity is in accord with the component, while the upsetting-punch (shown in Fig. 13b) is with ladder shape. Two steps were applied to implement the procedure: in the first step, the flanging-punch moved down to complete flanging process while other dies stayed where they were, and then it moved up; in the second step, the center hole edge was thickened and the right angle of it was formed with the upsetting-punch moving up. Since the thickness of the inner wall is not thinned by flanging, machining was needed to obtain the diameter 38 mm as well as the

The FEM software MSC.Marc can be used to simulate the forming process by taking half of the part because of the axisymmetric shape. Four-node quadrangles were available, and the mesh adaptive function was activated considering the large deformation in the process of forming. The initial thickness of the blank was 2.5±0.1 mm, and the stress-strain curve was obtained by tensile test. As we described before, the flanging-punch moved down and returned for the first 400 steps to finish flanging, and then in the last 200 steps of simulation, the upsetting-extruding punch moved up to complete upsetting process. The friction

b) Section view of clutch hub c) Detail view B

**3.3. Application** 

a) 3-D schematic of clutch hub

angle 45°.

coefficient was set as 0.1.

**Figure 12.** Schematic of clutch hub

**Figure 13.** Scheme of punch and die when upsetting

The result of finite element simulation is shown in Fig. 14. It can be observed that there is no folding at the bottom and the right-angle shape is formed perfectly. The load for the upsetting-extruding punch predicted by FEM is given in Fig. 15, of which the maximum is about 526.7 kN.

**Figure 14.** Result of upsetting-extruding

Stamping-Forging Processing of Sheet Metal Parts 43

a) Blanking b) Forward drawing c) Powerful backward drawing

Parameter Density/kg/mm3 Young's modulus

**Table 1.** Mechanical properties of the material

**Figure 17.** Scheme of stamping-forging processing of double-cup-shape part

clearance 3.5 mm was obtained. The formed part is shown in Fig. 20.

The mechanical properties of the material are shown in Table 1. The experiment was conducted at a dual-action deep drawing hydraulic press (see Fig. 18), and the sheet metal material was 08AL steel with initial thickness of 2 mm. The nominal pressure of inner slider is 3000 kN and the outer is 2000 kN. The velocity and maximum effective stroke of the inner and outer slider are 10 mm/s and 500 mm, respectively. The nominal pressure of ejector of the hydraulic machine is 1000 kN, while the ejection stroke is 160 mm, and the velocity is 30

/N/mm2

Value 7.8×10-6 2.07×105 0.28 1.713×102

The partial view of backward drawing and upsetting die is shown in Fig. 19. Δ is clearance which influences the flow of material in powerful backward drawing between punch-die and the die. If the gap is too much, wrinkling and folding defect may happen more easily. Instead, the resistance force will be increased, which leads to thinning or even rupture of the inner wall in backward drawing process. According to the thickness of the sheet metal is 2 mm, experiments on the gap were conducted more than once until the most satisfied

Poisson ratio

Yield stress /N/mm2

d) Piercing and flanging e) Thickening by upsetting

mm/s.

**Figure 15.** Forming load curve (from step 400 to step 600)
