PSI - Issue 59

Olha Maksymiv et al. / Procedia Structural Integrity 59 (2024) 378–384 Olha Maksymiv et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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(aqueous or oil) in which tests are carried out or the components work under high contact loads. The crack is initiated under the surface in the oil working environment and on the surface – in an aqueous environment. Figure 5 shows crack nucleation after contact fatigue tests in oil and water (Kyryliv et al. (2016)). In the oil working environment, the crack initiated under the rolling surface propagated parallel or angularly to it, and only then appeared on the surface. Tangential stresses, which reach maximal values at a certain depth from the surface, are considered to be responsible for the failure. The role of the working environment is partially taken into account, being limited only to its disjoining action. In the aqueous working environment, the crack initiated on the rolling surface and propagated into depth angularly to it. Normal stresses are considered to be responsible for the failure.

a

b

Fig. 5. Crack nucleation in the alloy steel with the surface NCS after contact fatigue tests (a) in oil and (b) in water.

Such an influence is also explained by the action of decomposition elements (carbon, hydrogen, oxygen) of the working environment in the zone of contact loads (Fig. 6).

Fig. 6. Distribution of (a) hydrogen, (b) carbon and (c) oxygen on the rolling pass in the zone of contact load action after tests in industrial oil (I) and in tap water (II) of the specimens with NCS after MPT in different TF: grey – air; white – 10% aqueous solution of emulsol; dark grey – industrial oil; dashed line – the concentration of the element in the initial state.