Geometrical Optimization of the EHL Roller Face/Rib Contact for Energy Efficiency in Tapered Roller Bearings

In the context of targeted improvements in energy efficiency, secondary rolling bearing contacts are gaining relevance. As such, the elastohydrodynamically lubricated (EHL) roller face/rib contact of tapered roller bearings significantly affects power losses. Consequently, this contribution aimed at numerical optimization of the pairing’s macro-geometric parameters. The latter were sampled by a statistical design of experiments (DoE) and the tribological behavior was predicted by means of EHL contact simulations. For each of the geometric pairings considered, a database was generated. Key target variables such as pressure, lubricant gap and friction were approximated by a meta-model of optimal prognosis (MOP) and optimization was carried out using an evolutionary algorithm (EA). It was shown that the tribological behavior was mainly determined by the basic geometric pairing and the radii while eccentricity was of subordinate role. Furthermore, there was a trade-off between high load carrying capacity and low frictional losses. Thereby, spherical or toroidal geometries on the roller end face featuring a large radius paired with a tapered rib geometry were found to be advantageous in terms of low friction. For larger lubricant film heights and load carrying capacity, spherical or toroidal roller on toroidal rib geometries with medium radii were favorable.

CONSTRUCTION MODIFICATION OF RADIAL THRUST ROLLER BEARINGS

Analytical relationships have been developed for the design of modified tapered roller bearings based on standard bearings of the 7000 type. The modification consists in replacing the rolling elements in the form of tapered rollers with a straight generatrix by concave rollers with an arc generatrix, which are in contact with the convex raceways of the rings. By calculation, the advantage of modified roller bearings in terms of service life in comparison with standard roller bearings of similar overall dimensions is shown.

Defect detection in freight railcar tapered-roller bearings using vibration techniques

Currently, there are two types of defect detection systems used to monitor the health of freight railcar bearings in service: wayside hot-box detection systems and trackside acoustic detection systems. These systems have proven to be inefficient in accurately determining bearing health, especially in the early stages of defect development. To that end, a prototype onboard bearing condition monitoring system has been developed and validated through extensive laboratory testing and a designated field test in 2015 at the Transportation Technology Center, Inc. in Pueblo, CO. The devised system can accurately and reliably characterize the health of bearings based on developed vibration thresholds and can identify defective tapered-roller bearing components with defect areas smaller than 12.9 cm2 while in service.

Constructing fast and representative analytical models of wind turbine main bearings

This paper considers the modelling of wind turbine main bearings using analytical models. The validity of simplified analytical representations used in existing work is explored by comparing main-bearing force reactions with those obtained from higher-fidelity 3D finite-element models. Results indicate that there is good agreement between the analytical and 3D models in the case of a non-moment-reacting support (such as for double-row spherical roller bearings), but the same does not hold in the moment-reacting case (such as for double-row tapered roller bearings). Therefore, a new analytical model is developed in which moment reactions at the main bearing are captured through the addition of torsional springs. This latter model is shown to significantly improve the agreement between analytical and 3D models in the moment-reacting case. The new analytical model is then used to investigate load characteristics, in terms of forces and moments, for this type of main bearing across different operating points and wind conditions.

A semi-analytical approach for rapid detection of roller-flange contacts in roller element bearings

For axially loaded cylindrical and tapered roller bearings, the dynamic behaviour of individual rollers, wear and friction losses are strongly influenced by roller-flange contact forces. For a realistic modelling of normal and friction forces of the roller-flange contact, it is essential to determine location and theoretical penetration of this contact. The rapid contact detection is particularly significant for rolling element bearing dynamic modelling in multibody systems. In this paper a semi-analytical algorithm for contact detection is introduced and compared to state of the art methods. The new approach adopts piecewise functions of spheres, cones and tori for modelling of roller end and flange geometry. The location of the contact and its theoretical penetration is calculated using analytical and combined analytical-numerical schemes. The semi-analytical approach proves to be significantly faster and numerically more stable than current contact detection algorithms without compromising precision.