Experimental Analysis of Rolling Torque and Thermal Inlet Shear Heating in Tapered Roller Bearings

Abstract

The investigation in this article focuses on the rolling resistance torque and thermal inlet shear factor in tapered roller bearings (TRBs) through systematic experiments using a modular test setup. TRBs typically operate under Elastohydrodynamic Lubrication (EHL) conditions. At sufficiently high speeds, the majority of rolling friction is due to a significant shift of the pressure centre in the EHL contact. While at lower speeds, sliding friction in the roller-rib contact becomes dominant, which operates under mixed lubrication conditions. Limited literature exists on the impact of inlet shear heating on effective lubricant temperature (Tin_c) and rolling friction in TRBs. To fill this gap, experimental measurements of the total frictional torque under axial loading at different speeds and oil temperatures are performed. With existing models for different friction contributions described in the literature, the rolling resistance due to EHL has been determined for various operating conditions. The effects of dimension-less speed (U), material (G), and load (W) parameters have also been investigated. Under fully flooded conditions, it was observed that the influence of material (G) and load (W) parameters on rolling friction is minor, while the impact of velocity (U) is significant. In the context of rolling resistance, the heating due to shear of the lubricant in the inlet zone plays a significant role. For higher rotational velocities, the estimated rotational torque reduction resulting from inlet shear heating was found to be approximately 6–8%.

Electrical Impedance Spectroscopy for Precise Film Thickness Assessment in Line Contacts

“…In this study, an electrical impedance measurement device from flucon fluid control GmbH [49] was integrated into an in-house-developed vertical-shaft roller bearing test rig, for which the details can be found [4]. The test bearing was a purely axially loaded cylindrical roller thrust bearing (details in Table 1), such that all contacts could be assumed to be equal and representable by the same electrical model.…”

“…However, in most rolling bearings, micro-slip inherently occurs in the finite-line EHL contacts, making proper evaluation of the correction factor difficult [55]. In the recent work of the authors, a detailed friction-based experimental procedure for thermal shear factor was applied [4]. The same method has been used throughout this work.…”

“…A detailed explana Figure 12a shows the increase in bearing temperature and behaviour of frictional torque in two zones, whereas Figure 12b shows the frictional torque compositions (details in Appendix A) as well as the shear inlet effect as a function of speed. A detailed explanation can be found in [4]. The measured global bearing impedance (𝑍 ) and phase angle were used to calculate the average oil film thickness and breakdown ratio using Equations ( 5)-( 9) of Maruyama et al [42][43][44].…”

“…For very high entrainment speeds, shear heating takes place at the rolling contact inlet in the recirculation zone of excess lubricant being repelled. This raises the oil temperature, affecting the oil viscosity and resulting in a thinner lubricant film [4] and an increased risk for mixed lubrication.…”

“…affecting the oil viscosity and resulting in a thinner lubricant film [4] and an increased risk for mixed lubrication.…”