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PhD candidate On the Thermodynamics of a Complex Fluid and its Application to Rolling BearingsPosted by: University of Twente
Posted date: 2020-Mar-04
The Tribology Group, Faculty of Engineering Technology of the University of Twente has an opening for a PhD candidate in the research area of Grease Lubrication. This project operates at the interface of fluid dynamics, rheology, complex fluids and tribology. The expected outcome of this 4-year project will be a model that can predict the remaining functional life of lubricating grease in rolling bearings. This requires a thorough understanding of the flow and rheology, phase separation and degradation of the micro-structure of lubricating greases in rolling bearings. The project is sponsored and executed in close collaboration with SKF, a leading global bearing manufacturer.
Lubricating grease is a visco-elastic material, consisting of a thickener matrix (usually a soap, 5-15%), base oil (mineral or synthetic) and additives (anti-corrosion, anti-wear, 1-5%). At small strains, lubricating grease is apparently solid. This quantity makes grease easy to use: it does not easily leak out of a bearing and acts as a seal, preventing contamination to enter the bearing. The apparent stiffness is ascribed to the thickener matrix that forms a network filled with oil. At larger shear rates the viscous properties dominate. At very high shear rates the viscosity approaches that of the base oil. The oil is slowly released from the grease (“grease bleed”) into the tribological contacts (ball-ring contacts) providing a feed mechanisms for the lubricant film (with thickness up to typically 0.2 microns). When the bearing is rotating the grease will be “worked” in the bearing by shear and over-rolling. This results in a degradation of the thickener network. Grease may leak from the bearing, the bleed rate will change and the positioning of the grease inside the bearing will change. In the case of higher temperatures, such as in electric motors, oxidation may take place. At some point in time, the grease is deteriorated such that it no longer lubricates the bearing and the bearing will fail. In this project a model should be developed for the remaining life of grease in a bearing as a function of the operating conditions and time. The project starts with a fundamental study on the degradation mechanisms and the development of a model that can be used to predict the degradation as a function of shear, temperature and time (energy/entropy). Subsequently, this needs to be applied to a bearing where the shear rates vary throughout the internal bearing design.
Information and application
Please upload your application before 22 March 2020 with the following documents via the ‘Apply now’ button below:
Since only three documents can be up loaded, please combine the documents if needed. For information, please contact Prof.dr.ir. Piet M. Lugt (p.m.lugtutwente.nl or piet.lugtskf.com)
The start of the project is a.s.a.p. We also invite applications from candidates, who expect to graduate soon.
Conditions of Employment
The University of Twente. We stand for life sciences and technology. High tech and human touch. Education and research that matter. New technology which leads change, innovation and progress in society. The University of Twente is the only campus university of the Netherlands; divided over five faculties we provide more than fifty educational programmes. We have a strong focus on personal development and talented researchers are given scope for carrying out groundbreaking research.
We are an equal opportunity employer and value diversity at our company. We do not discriminate on the basis of race, religion, color, national origin, gender, sexual orientation, age, marital status or disability status. Because of our diversity values we do particularly support women to apply.