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Low sliding conditions are typical for the centre of raceway rolling bearings online contacts. Using the detailed SKF model, it is possible to simulate the passage of an indentation geometry through a heavily loaded lubricated contact and calculate the generated deformed geometry inside the contact and the generated pressure ripples. shows the initial “model” indentation imposed on the upper contact surface and the centre-line profile of the isolated deformed indentation and the generated pressure ripple at the centre of the contact calculated under pure rolling conditions. 

Increasing slightly the sliding in either direction will considerably alter the results. Fig. 5 shows that the film thickness deformed shape exhibits a collapse in film thickness in the frontal part of the dent. Slightly higher pressures, however, are found in the back (trailing edge) of the dent. This suggests that when there is a good lubricating film, the indentations are likely to fail first fag bearings on the trailing edge of the dent, since the pressures are higher and not from metal-to-metal contact in the leading edge of the dent. However, if the lubrication is poor, wear and possibly surface distress can be expected at the leading edge of the dent. 

This result is in full agreement with the experimental results carried out at the SKF Engin­eering & Research Centre laboratory using full ball-bearing tests with artificially made indentations on the raceway. Here, a zone of surface distress (microspalls) can be observed in the trailing edge of the dent while substantial wear occurs at the leading edge, possibly caused by the local film collapse.

Moderate sliding conditions can be present in gear contacts. Using the detailed SKF model with non-Newtonian fluid behaviour (increasing sliding does not increase friction), it is possible to simulate the passage of an indentation in the lubricated contact with these sliding conditions. Fig. 7 shows the isolated pressure ripples, film thickness and subsurface normalized von Mises stresses calculated for a heavily loaded contact with two different moderate sliding bearings conditions lower smooth surface travelling faster than upper dented surface and lower smooth surface travelling slower than upper dented surface). It can be seen that for this moderate sliding condition, inverting the sign of the sliding inverts the location of the maximum pressure ripple, and thus the location of the first possible failure. This perhaps explains some apparently contradictory experimental results reported in the literature.

High sliding conditions are not present in the central part of bearing raceways; however, they may be present in gear contacts. Using the detailed SKF model with a realistic behaviour of the lubricant as a non-Newtonian fluid (increasing sliding does not increase friction) it is possible to simulate the passage of an indentation in the lubricated contact with these sliding koyo bearings conditions as it moves inside the contact.shows the isolated pressure and film thickness ripples as a function of time for one high sliding condition the smooth lower surface moving faster than the upper dented surface).