The thickness of the wheel disc manufactured by using the spinning process can be accurately predicted by using Simufact.forming software[8]. Considering the great effect of the residual stress in the wheel disc arising from the spinning process on the strength of the wheel, this software is also used to obtain the residual stress.
The wheel disc is made of the special steel plate (SW400) for wheel with original thickness of 11 mm. The hardening characteristic curve of SW400 is obtained through test (Fig. 1), and the key mechanical parameters affecting the forming results including density, elastic modulus, Poisson’s ratio, yield stress are shown in Table 1. According to the actual processing experience of the relevant enterprises, the spinning process parameters of the disc are: the feed rate of the rollers (2 mm/r), and the rotating speed of the mandrel (450r/min). And the friction coefficient between the rollers and the workpiece is appropriately set to be 0.13.
Table 1
Material parameters of SW400
Density (kg/m3)

Elastic modulus (MPa)

Poisson's ratio

Yield stress (MPa)

7800

2.0 × 105

0.3

400

The machining residual stress needs to be considered in the design stage since its great effect on the strength of the wheel[4]. In this paper, the residual stress of the disc arising from the spinning process after unloading and rebounding is simulated, and the stress distribution is shown in Fig. 2.
To validate the effectiveness of the method, the measurement of the residual stress is performed. In this paper, the holedrilling method is used since its convenience and low cost. In this method, the small blind hole is with the diameter of 1.5 mm and the depth of 2.0 mm[9]. The installation of strain gauge is shown in Fig. 3. Considering the disc shape and the feasibility of the residual stress test, three measure points on the outer surface of the disc are selected. The distance between measure points is great, and the angle between the radii where the measure points is located is about 90° (Fig. 4 (a)). This distribution may avoid the interaction of the stress fields at different measure points. The axial distance from the three measure points (Fig. 4 (b)) to the installation surface is 41.5 mm, 53.5 mm and 74.0 mm, respectively.
For each of the three selected measure points, the strain values along the directions of 0°, 45°, 90° and temperature compensation sheets are measured respectively. The results are shown in Table 2.
Table 2
Measure point

0° direction

45° direction

90° direction

Compensation

ε0°

ε45°

ε90°

Point 1

20.54

28.94

140.59

0.85

19.96

28.09

139.74

Point 2

22.80

8.06

186.29

0.52

23.32

7.54

185.77

Point 3

103.89

28.52

120.83

3.22

100.67

25.30

117.61

Since the stress distribution obtained by the spinning simulation is nonuniform (Fig. 2 ), 7 positions are selected on the same circumference where each measure point is located. The average value of stresses at 7 positions is recognized as the residual stress of the point. Table 3 indicates the comparison of the residual stress measured from the test with ones from the simulation. We may see that the deviations of the residual stress at the three measure points are from − 1.53–11.26%. So the simulation results are in good agreement with the test ones. Therefore, the residual stress in the wheel disc after spinning may be predicted appropriately, and in the design stage of disc, the residual stress may be introduced to obtain the reliable optimization results.
Table 3
Test results of measure points
Measure point

σ1
(MPa)

σ2
(MPa)

θ
(°)

Simulation results (MPa)

Test results
(MPa)

Deviation

Point 1

172.14

61.12

0.36

151.15

151.15

1.53%

Point 2

208.33

28.95

0.31

195.47

195.47

0.63%

Point 3

218.49

100.32

0.73

189.43

189.43

11.26%
