Antifriction bearings – main research
The life theory of solid lubricated antifriction bearings is based on the friction energy converted in the contact area. All energetic wear calculations assume proportionality between the friction energy converted in the tribological contact and the generated wear volume. In previous work, a friction energy model was developed which enables estimating the service life of solid lubricant layers under the assumption of a continuous cut of the layer.
To prove the theoretically determined life statements, there are two test benches at pmd consisting of four bearings.
In contrast to experiments with real bearings, which usually take several weeks to complete, the end of the service life of a solid lubricant layer in VCA can already be achieved within a day under similar conditions as in the bearing. Since at least five attempts are necessary for statistically significant results, the renunciation of experiments with bearings means a considerable acceleration in the layer development for solid lubricant ball bearings.
Previous research at pmd could prove that the rolling wear model experiment on the modified four-ball apparatus (VKA) is suitable to examine the quality of a solid lubricant layer in a way which is accelerated and similar to that of a bearing.
In the case of a conventional lubrication, the dominant wear mechanism is the weariness of the substrate. There is an adhesive wear of the solid lubricant in the pairings with solid lubricant. That is, a continuous erosion of the layer.
It was found that the friction energy is proportional to the wear of the solid lubricant layer and, inversely, proportional to the service life.
The following may be concluded:
In order to make statements about the life of solid lubricated ball bearings, the friction energy converted in the rolling contact should be adequately calculated.
Friction force and I
Since the surface pressure and the relative velocities in a curved Hertzian contact both change in and across the rolling direction, Holland created the friction energy model by means of which the converted friction energy may be calculated in the rolling contact.
By integration, we obtain explicit values of the friction energy converted in the rolling contact.
Probability networks are an important tool for the graphical analysis and presentation of the sampling results. Furthermore, it can be visually evaluated whether a sample comes from a parent population with a given distribution.
Numerous empirical studies showed that the Weibull distribution is very suitable for static description of lifetimes of technical products.