Improved prediction of rolling bearing kinematics due to accurate consideration of hydraulic forces

• Applicant: Professor Dr.-Ing. Oliver Koch
• Subject Area: Engineering Design, Machine Elements, Product Development
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 542942635

For the design of rolling bearings, the fatigue life according to ISO281 or ISO/TS16281 is used in most cases. In practical application, the operating life in terms of classical fatigue is usually exceeded under ideal conditions. Depending on the operating conditions, however, rolling bearing failures can occur with damage patterns whose cause is not classical fatigue. For example, in the field of wind power plants, premature failures of rolling bearings of highspeed generator output shafts, planetary gear bearings or rotor shaft bearings occur because of damage such as smearing, which can be attributed to insufficient bearing load. At low loads, slippage of the rolling elements occurs, i.e., increased sliding movements. Particularly when the rolling elements re-enter the load zone or in the event of a sudden increase in load, the rolling elements accelerate very rapidly. In the case of high mass inertias, such as those found in wind turbines, this means large frictional forces and consequently high energy inputs. A possibility for predicting slippage-related operating conditions at low bearing loads exists in the form of manufacturer-dependent minimum load formulas. However, their fundamentals are mainly based on empirical evidence and only partly based on the physical phenomena involved. Moreover, the above-mentioned formulae are conservatively fine-tuned for static operating conditions regarding the risk of damage. This leads to uncertainties and unused potentials. For example, applying bearing preload as a countermeasure leads to energy loss. In addition, interactions between operating parameters such as bearing load and speed cannot be reliably evaluated in this process. Thus, unscheduled bearing failures under dynamic load can be the result. To avoid these, there is an urgent need for a method to determine the influence of hydraulic forces on rolling bearing kinematics in Multi-Body Simulation (MBS) to subsequently make damage predictions in minimum load conditions. The main goal of the project is to develop and validate a method to predict the kinematic of each bearing component taking into consideration contact and hydraulic forces. To reach this goal suitable equations from complex, time-dependent CFD models will be derived, which describe the distribution of the hydraulic loads to the individual bearing elements and can thus be considered in the form of forces and moments in existing MBS-models for rolling bearings.

• DFG Programme: Research Grants
• International Connection: Italy
• Partner Organisation: Autonome Provinz Bozen - Südtirol
• Cooperation Partner: Professor Dr.-Ing. Franco Concli, Ph.D.