PSI - Issue 19

T. Kato et al. / Procedia Structural Integrity 19 (2019) 238–248 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

242

5

100 150 200 250

0 50

Brake energy / wheel (kW)

0 20 40 60 80 100

Time (s)

Fig. 5. Time history of the braking energy.

3. Finite element analysis results 3.1. Stress distribution and variation with different wheel size

Examples of contact pressure distribution at the tread surface of the wheel model in each wheel size with the rail model during rolling contact loadings are shown in Figure 6. The contact pressure distributions in the tread center position are shown in this figure. The contact pressure distributions and the maximum contact pressures are almost the same between the three different wheel sizes. The maximum contact pressures obtained by the finite element analyses are lower than those calculated based on the Hertzian theory in Table 1. In addition, the maximum contact pressures by the Hertzian theory are not the same between the three wheel sizes, which indicates that J33 wheel has a lower maximum contact pressure. The differences of results between the finite element analysis and the Hertzian theory are considered to be caused by the difference of tread surface profile or plastic deformation in the finite element analyses. Figure 7 shows the shear stress  r  (r: radial direction,  : circumferential direction) distribution at the cross section of the wheel rim during the third rolling cycle. This figure shows the result in a case where the contact position is the tread center of the B38 wheel. The stress  r  is the highest at the subsurface, which is same as the result of the previous study. At this subsurface location, the variation of  r  is almost fully reversed and each of the normal stress components varies under a compressive field with rolling contact as shown in Figure 8. This indicates that a multiaxial fatigue strength evaluation method should be applied to evaluate the criteria of RCF crack initiations at the subsurface.

Contact pressure (MPa)

Front rim side

Flange side

Front rim side

Flange side

Front rim side

Flange side

c

a

b

Max. 1391 MPa

Max. 1390 MPa

Max. 1407 MPa

Wheel rolling direction

Wheel rolling direction

Wheel rolling direction

Fig. 6. Contact pressure distributions of the wheel model; (a) J33 wheel; (b) H36 wheel; (c) B38 wheel.