EHD rolling contacts under highest surface speeds

• Applicant: Professor Dr.-Ing. Christian Brecher
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 578674743

In many high-speed applications such as spindle bearings in machine tool main spindles, lubricant film formation and friction in the EHD rolling contacts limit the permissible process parameters. However, due to a lack of empirical data and the increasingly non-linear behavior of the lubricating film, the existing calculation models do not currently allow a reliable calculation of the friction under the very high surface speeds of 100 m/s and more that occur in these applications. The aim of the research project is to provide a calculation model for rolling contacts in spindle bearings under the highest surface speeds, which is based on experimentally determined friction coefficient data from tribometer tests. The calculation model is based on a known approach that is characterized by a discretized view of the rolling contact, which relates the local pressures and surface speeds of the contact partners to empirically determined friction coefficient data. The friction coefficient data required for the modeling are determined on a tribometer test rig tested by the applicant at varying pressures and speeds. Various contact geometries (point and line contact), material pairings (steel-steel, steel-ceramic) and lubricant viscosities (ISO-VG 32, 46, 68, 220) are tested. Furthermore, drilling components that are superimposed on the ideal rolling motion are also mapped. In preliminary tests on a first prototype, promising friction coefficient measurements have already been carried out, which show similar friction coefficient curves to those known from the literature. To validate the model and the measurement methodology, the measurement and test results are compared with test data from other authors at lower speeds under otherwise similar operating conditions. In a planned second funding period, the developed model will be integrated into a higher-level model for the holistic calculation of overall bearing friction. This overall model can then be validated using the test bench technology for spindle bearings available to the applicant. The measured friction values will be made available to the research community, which will support the further development of other existing models.

• DFG Programme: Research Grants