PSI - Issue 39

Andrea Zanichelli et al. / Procedia Structural Integrity 39 (2022) 632–637 Author name / Structural Integrity Procedia 00 (2021) 000–000

635

4

load amplitude were considered. Moreover, for the medium level of tangential load amplitude, three different values of bulk load were examined. The fretting loads are listed in Table 2 for each loading configuration, together with the theoretical semi-widths of both the contact zone a and the stick zone c .

Table 2. Fretting loading condition for each test. Loading configuration No. P [N/mm]

Q a [N/mm]

B σ [MPa]

a [mm]

c [mm]

1 2 3 4 5

800 800 800 800 800

240 320 400 320 320

0 0 0

1.331 1.331 1.331 1.331 1.331

0.888 0.678 0.362 0.678 0.678

25 50

All the tests were stopped at 10 6 loading cycles in order to analyse the experimental crack paths. The cracks were generally observed to nucleate within the contact zone close to the contact trailing edge, with an angle exp θ (defined from the line perpendicular to the material surface, with positive values inward the contact zone) ranging from 7° to 56°. The crack orientations observed during the experimental campaign are shown in Figure 1 for each loading configuration tested. Note that such angles were measured at a depth equal to 56.5 microns.

0.05 0.04 0.03 0.02 0.01 0.00 NORMALISED VERTICAL COORDINATE, z / a ESTIMATED IN A ESTIMATED IN B 41.5° EXPERIMENTAL

(c)

(b)

(a)

ESTIMATED IN A ESTIMATED IN B EXPERIMENTAL

ESTIMATED IN A ESTIMATED IN B EXPERIMENTAL

37°

32.5°

37.5°

24.8°

7.3°

CONFIGURATIONNo. 2

CONFIGURATIONNo. 3

CONFIGURATIONNo. 1

0.96 0.98 1.00 1.02 NORMALISEDHORIZONTAL COORDINATE, x / a

0.96 0.98 1.00 1.02 NORMALISEDHORIZONTAL COORDINATE, x / a

0.96 0.98 1.00 1.02 NORMALISEDHORIZONTAL COORDINATE, x / a

0.05 0.04 0.03 0.02 0.01 0.00 NORMALISED VERTICAL COORDINATE, z / a 54.4° ESTIMATED IN A ESTIMATED IN B EXPERIMENTAL

(e)

(d)

ESTIMATED IN A ESTIMATED IN B EXPERIMENTAL

55.6°

32.8°

17.3° CONFIGURATIONNo. 4

CONFIGURATIONNo. 5

0.96 0.98 1.00 1.02 NORMALISEDHORIZONTAL COORDINATE, x / a

0.96 0.98 1.00 1.02 NORMALISEDHORIZONTAL COORDINATE, x / a

Fig. 1. Experimental and theoretical crack path orientations for loading configurations (a) No. 1, (b) No. 2, (c) No. 3, (d) No. 4, and (e) No. 5.