Dynamic bearing behaviour

Research in Action: Developing a tool to predict complex dynamic bearing behaviour

Sharad Jain,

Romax has always been involved in research, whether internally through our Innovation and Research team, externally through partnerships with commercial, research or industry bodies, or by collaborating in academic research projects. Indeed, my own PhD program at the University of Cambridge was funded by Romax. The subject of my research was high speed bearing behaviours, which can lead to failures in applications from wind turbines to aerospace main engine bearings, and which are becoming more prevalent within the electric vehicle industry, where bearings are operating under increasingly high speeds. Combined with low load, these conditions can lead to a dynamic phenomenon known as bearing skidding. In certain circumstances, bearing skidding can generate excessive frictional heat and high surface shear stress, and subsequently cause efficiency issues or premature bearing failure. We recognised that there was a need for simulation methods to predict dynamic behaviour of ball bearings operating under a wide range of conditions.

However, prediction of skidding phenomenon in rolling-element bearings has a lot of challenges. It requires consideration of a number of parameters such as internal load distribution in a bearing, properties and rheology of lubricating oil, heat generation and temperature rise of lubricant and bearing, any fluctuations in the load acting on a bearing and operating speed, and influence of internal clearances on internal load distribution.

To continue our research efforts in this area, we have conducted subsequent projects on the experimental measurements of heat generation and thermal losses in high-speed bearings, in collaboration with Aachen University. In addition, we have researched analytical and numerical methods to predict the skidding characteristics of high-speed bearings operating under transient conditions, faster solvers to analyse multi-physical interactions in bearings, and tribology to model the complex friction behaviour in lubricating oil-films.

As part of our research, we developed a new type of simulation technology to understand dynamic bearing behaviour and avoid these new, non-conventional failure modes. Our analysis approach considers all the multi-physics interactions between rolling elements, cage, raceways and lubricating oil. All these multi-physics interactions are solved at each time step, which traditionally makes this type of analysis computationally expensive. In addition to the complexity of the model, the mathematical nature of the skidding problem has both stiff and non-stiff elements. When rolling elements skid, the mathematical formulation becomes non-stiff. When rolling elements don’t skid, i.e., operate in micro-slip regime, then the mathematical formulation becomes stiff. Therefore, most conventional numerical solvers struggle to solve this problem and take a large number of time steps, making the analysis very slow. We have developed a novel solver scheme that handles this stiff/non-stiff problem efficiently and as a result performs the skidding analysis much faster than the generic multi-body tools.

Often, significant research such as this feeds into our software development. That happened with this project – the knowledge we’d gained from this research, together with the simulation methods we had developed, have now been released in the new Romax Bearing Dynamics tool.

Romax Bearing Dynamics is a web-enabled application which uses transient time-domain multibody dynamic roller bearing simulation to predict the occurrence of skidding in electric-vehicle bearings in a matter of minutes. The model considers structural, thermal and fluid domains, including the influence of centrifugal and gyroscopic effects on rolling-element dynamics, heat generated by the lubricant, and rheology and traction behaviour of the lubricating oil. The effect of design parameters and operating conditions can be quantified, providing understanding of the mechanisms of skidding and pinpointing potential design improvements.

The application is cloud-accessed, which means it harnesses the power of flexible computing (rather than relying on local resources), can be run anywhere (even on a smartphone), and can continue unattended. Of course, the application is linked to the Romax Nexus master design model on your workstation, to enable collaboration across the whole organisation and supply chain. Romax Bearing Dynamics helps design engineers and bearing analysts to avoid damaging failures by designing more reliable bearings and selecting better lubricants, through unique insight of the underlying skidding mechanism and bearing dynamic behaviour.

To find out more about our new Bearing Dynamics application, join our webinar:

Bearing Dynamics – a validated tool for predicting skidding and other phenomena

Sharad Jain joined Romax in 2007 after graduating from Indian Institute of Technology Roorkee, India in Mechanical Engineering. He also has a PhD in engineering from University of Cambridge, UK. During his PhD, Sharad worked on dynamics of high-speed bearings and planetary gearboxes. Sharad has 12 years of experience in mathematical modelling and dynamics and vibration of rotating machines. His areas of interest include bearing dynamics, contact mechanics, automatic discretisation of continuous structures for dynamic analysis, and dynamics of electro-mechanical drivetrains.