PSI - Issue 66

5

Andrea Zanichelli et al. / Procedia Structural Integrity 66 (2024) 471–477 Author name / Structural Integrity Procedia 00 (2025) 000–000

475

10 7

Group 1 Group 2 Group 3 Group 4

10 6

N f,cal [cycles]

2x

CONSERVATIVE

10 5

10 5

10 6

10 7

N f,exp [cycles]

Fig. 1. Calculated vs experimental fatigue life for each test considered.

12

10 7

(a)

(b)

10

10 6

N f [cycles]

8

GROUP No. 2

Experimental

6 CRACK NUCLEATION ORIENTATION [°] 0 60 GROUP No. 2 Analytical

Analytical

10 5

0

60

120

180

120

180

PAD RADIUS, R [mm]

PAD RADIUS, R [mm]

Fig. 2. (a) Fatigue life and (b) crack nucleation orientation computed as a function of different pad radii. The experimental fatigue lives for the Group No. 2 are also plotted.

Related to the contact geometry, in addition to the contact type, the radius of the pad affects the results, as is reported in Figures 2(a) and (b) in terms of fatigue life and crack nucleation orientation, respectively. In particular, both the fatigue life and the crack nucleation orientation computed by the present methodology decrease as the pad radius increases. Note that this trend is also confirmed experimentally as can be inferred from Figure 2(a), where the experimental fatigue lives are also plotted for the tests belonging to the Group No. 2. As far as the fretting loads are concerned, different values and ratios obviously affect the stress state and, accordingly, the fatigue life. On the other hand, no significant effect on the crack nucleation orientation is found as a function of the fretting loads, with the exception of the amplitude of the axial load. In particular, as , B a  increases, the crack nucleation orientation decreases. As far as the material properties are concerned, the fatigue properties are surely some of the most significant input parameters in this kind of problems, as well as in any other fatigue problem. Moreover, the effect of the friction coefficient on the fatigue life is shown in Figure 3 (a), in which a friction coefficient of 0.5 is adopted. It can be observed that a decrease of the value of the friction coefficient results in an increase of the fatigue lives, thus obtaining fewer conservative estimations. On the other hand, the crack orientation is almost independent of the value of the coefficient of friction: in the present case, it decreases of only 1.1° with respect to the reference condition.