Numerical study of grain shape in granular lubrication

Conventional liquid lubricants fail to perform adequately in extreme environments, i.e. at high temperatures and loads. As an example, modern turbine engines require bearings which can operate at up to 800 °C under loads of several Mpa at relative velocities of up to 50 m/s. Dry particulate lubricants are promising candidates for such applications [1]. The required functionalities of particulate lubricants are their load carrying capability, accommodation of the velocity difference and separation of the first bodies. Of course, a small coefficient of friction (COF) is energetically favorable. A distinction has to be made between powder and granular lubricants. Powder lubricants typically consist of soft and cohesive particles which deform under load while granular lubricants consist of hard, cohesionless particles. The present work focuses on granular lubricants.