PSI - Issue 8

Francesca Curà et al. / Procedia Structural Integrity 8 (2018) 204–211 Author name / StructuralIntegrity Procedia 00 (2017) 000 – 000

207

4

Table 2 resumes the parameters involved in FE models (Model m1, m2, ...., m6; first column). As for theoretical calculations, also for numerical models torque levels (second column) and micro geometries (maximum and minimum curvatures) for shaft (third and fourth columns) and for hub (fifth and sixth columns) have been taken into account. In total, six models have been run for the aligned conditions. Similar FE models have been developed for misaligned conditions between haft and hub, referring to the case of a 10’misalignment angle (corresponding to the maximum angle that can be considered in actual applications to be then reproduced during the experimental activity).

Fig. 2. Numerical model of the spline coupling: shaft (left) and hub (right).

Table 2. FE models parameters. Model Torque [Nm]

ρ 1max [mm

ρ

ρ

ρ

-1 ]

1min [mm

-1 ]

2max [mm

-1 ]

2min [mm

-1 ]

m 1 m 2 m 3 m4 m5 m6

500 500 500 700 700 700

1/11.3 1/10.5 1/10.7 1/10.9 1/10.7 1/10.9

1/3000 1/3000 1/3000 1/3000 1/4000 1/4000

0 0 0 0 0 0

-1/14.051 -1/14.051 -1/14.051 -1/14.051 -1/14.051 -1/14.051

3 Results and discussion The main parameters needed for this research are related to contact pressure and slidings, in order to design an isodamage specimen. So, all results are focused on this aim. Figures 3 and 4 show respectively the trend of both maximum and mean contact pressures and of the contact area by varying the microgeometries of the shaft, obtained by analitycal and FE calculations. In particular, maximum and mean contact pressure and contact area are represented as a function of the maximum curvature ρ 1max (related to the involute radius) and the crowned radius, or better the minimum curvature ρ 1min , acts as a curves parameter. It may be noted that, as expected, the entity of microgeometries strongly influences the contact parameters. In particular, the variation of the involute curvature radius makes possible to tune the actual value of the maximum pressure together with the contact area. As expected, all curves are shifted by the increasing of the torque level in the direction of a corresponding damage increasing; this represents a local phenomenon. The effect of the torque entity has also to be taken into account concerning the sliding values that globally influence the actual behaviour of the spline coupling. From the fretting wear point of view, a key parameter is the contact ellipse shape, well represented by the a/b ratio between the two half-axis. Values of a/b for each combination of maximum and minimum curvatures are reported in