1st ICAI 2020

International Conference on Automotive Industry 2020

Mladá Boleslav, Czech Republic

(20 kHz – 100 kHz). (Lineham, 2008). Resonant frequencies are excited by rolling elements passing and interacting with irregular structure of the race. The identification of problems is then by comparison of historical data of the magnitude with a baseline measured during initial set-up. Drawback of this method is indirect measurement of lubrication state. Data itself, do not bring much evidence about the lubrication regime itself. Prof. Lindner et al. from Coburgh University of Applied Sciences described in (Lindner, 2010) an alternative method for bearing lubrication monitoring. It uses phenomenon of Surface Acoustic Waves (SAW), which is outlined in (Worden, 2001), to detect state of the lubricant in the bearing – e.g. amount of lubricant or it changes with time. The method was later patented by company BestSens AG, patent No. EP 2616791 B1, and developed into a stand-alone system for lubrication monitoring of rolling bearings traded as device BeMoS. However, there were not found any publications describing the application of the method for monitoring actual state of lubrication film e.g. in which lubrication regime, described by Stribeck’s curve, the bearing operates. 1.2 Scope A scope of academic doctoral research, further presented in this article, was to challenge limitation of the bearing lubrication monitoring method provided by BestSens AG. The goal was to describe and validate a method of signal analysis allowing to monitor the state of lubrication film and simultaneously leverage the available device. 2. Methods Conducted literature research revealed that no other suitable methods are available for assessment of lubrication film in rolling bearings. Therefore, an approach of verification and validation of the new described method, based on comparison of data from experiment with predictions obtained by mathematical models had to be used. Mathematical models were also used to design parameters of experiment (speed, load and lubricant viscosity) which would allow observation of transition between bearing lubrication regimes from boundary, through mixed to fully developed elastohydrodynamic film (EHL) and thus enable validation of the method. 2.1 Modelling of Lubrication Film in Bearing Developed mathematical model consists of two coupled components. One is a model of radial roller bearing which is used for calculation of load distribution over individual rolling elements. The other model is a detailed model of EHL line contact, which provides estimation of lubrication film thickness between selected roller and race. The assessment of results frommodels and prediction of lubrication regimes for real bearing is performed by Tallian’s Lambda ratio which relates the thickness of EHL film and Ra parameter of surface roughness profile to predict actual operating regime. For sake of clarity, this article describes only a state- of-art of both models. For full description reader is kindly referred to publication (Chmelar, 2019a) or in case of the lubrication film model to original reference (Venner, 1991).

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