Current Projects
Film Thickness in Grease Lubricated Ball Bearings (PhD Candidate: Pramod Shetty)
The thickness of the Elasto-Hydrodynamic film in grease lubricated bearings deviates significantly from that in oil lubricated bearings. Here, we use an “electrical capacitance method” to measure the thickness of these films that separate balls from rings in running bearings and are typically 0.5 micrometers thick. We correlate the thickness of these films to the physical properties of the grease.
Remaining Grease Life (PhD Candidate: Femke Hogenberk)
Currently, the remaining useful life of grease in a bearing cannot be accurately predicted. The aim of this project is to develop a model which combines concepts and theories in fluid mechanics, thermodynamics and rheology with experiments to predict the remaining grease life in bearings operating at low and medium temperatures. Thermodynamic characterization of grease lubrication mechanisms such as “grease bleed” is studied via the evolution of yield stress, bleed rate and oil content of the grease.
Grease Base Oil Efficiency (PhD Candidate: Lieke van Ginkel)
In grease lubricated bearings, grease life dominates bearing performance. Oil separation (bleed) from grease plays a major role in grease lubrication. To extend grease life—and thus, bearing life—control of the bleed rate as well as an efficient base oil is very important (minimum oil for maximum lubrication). Therefore, it is crucial to study the impact of oil chemistry on bleed and investigate what makes an efficient base oil.
Film Thickness in Grease Lubricated Roller Bearings (PhD Candidate: Min Gao)
This research focuses on understanding the lubrication mechanism in a grease lubricated roller bearing. In the contact region, film thickness model for a cylindrical roller bearing (CRB) as a function of grease properties and operating conditions is developed. Outside the contact region, the replenishment mechanism in a CRB is investigated.
Thermal Degradation of Greases (MSc Student: Jorn Dokter)
Understanding grease degradation mechanisms is paramount in the grease/lubricants industry. Within the operating temperature range of most bearings, both mechanical and thermal degradation occur concurrently. This work focuses on thermal degradation of grease under various conditions. The process of grease churning in a bearing, usually during the first few hours of operating a freshly lubricated bearing, has been identified to involve significant thermal degradation. Here, the thermal contribution to overall churning degradation is also studied. Degradation thermodynamics—in which entropy generation is correlated with a degradation measure—is employed to generate an experimentally verified characteristic degradation model.
Completed Projects
- Thermo-mechanical aging of grease during churning
- Development of an evaporation model
- Development of a wear model or grease lubricated bearings
- On rheology film-build-up and water in grease lubricated bearings
- Lubrication of railway switches
- On the mechanical aging of lubricating greases
- Grease bleed model