Crack Paths 2009

Table 1. R C Flife NF

po=2000 MPa po=2200 M P a po=2400 M P a

SpecimenA 7 6 1 4 8 1 4 5 1 8 5 2 3 6 4 8 1 5

SpecimenB 8 8 5 9 2 6 5 1 1 1 1 1 3 8 1 4 8 1

SpecimenC 8 1 6 6 6 7 5 0 1 8 5 2 4 2 8 1 4 8

All specimens also showed a similar damage evolution on the rolling surface during

the test, which can be synthesised in the phases described in the following.

Phase a: early appearance of micro-pitting phenomena with dimension of the order of

a few tens of microns. An example is reported in fig.1.

Phase b: joining of some micro-pits giving origin to larger pits, as shown in the same

fig.1, reaching a maximumdimension of the order of 1-2 mm.

Phase c: increasing of the pits number, but not of their maximumdimension.

Phase d: sudden occurrence of macro-spalling, with consequent test interruption. The

failure covers almost the whole axial length of the ring, extending for an

analogue distance in the circumferential direction, as shown in fig.2.

100 µ m

10 m m

a

large pit

micro-pits

Figure 1. Example of pitting phenomena on the rolling surface

10 m m

10 m m

Figure 2. Example of spalling

785