A numerical approach for the determination of graphite deformation behaviour by using microtribological pressure tests

Abstract

Most tribological systems use oil or grease to keep up the desired operation conditions, whereas unlubricated systems are relatively rare. Beside these three possibilities, tribological systems can also be lubricated by solid materials such as graphite. Especially in high temperatures environments, graphite has high potential to increase the lifetime of rolling bearings. For such applications, new coating and lubrication concepts for roller bearings are engineered. This process requires a detailed understanding of the system behaviour on micro and macro scale.This contribution investigates the influence of the surface topography and the material behaviour of graphite as coating in pressure tests. Numerical simulations in combination with microtribometer experiments allow to analyse the deformation behaviour of the graphite coating. A numerical parameter study is conducted to remodel microtribometer pressure experiments. The results of the experiments show that a graphite coating of thickness 3.6 μm compresses about 30% under a load of 402 mN in microtribometer experiments. The combination of experiments and simulations allows to determine a yield stress for a perfect elastic-plastic material model for further usage in finite element simulations.