RELATION OF KINEMATICS AND CONTACT FORCES IN THREE-BODY SYSTEMS WITH A LIMITED NUMBER OF PARTICLES

Abstract

In many tribological systems, an intermediate layer of a limited number of abrasive particles exist. Thereby, the resulting wear and friction phenomena are desirable in many manufacturing processes, such as lapping or polishing, whereas in machine elements, they are unwanted due to reducing lifetime or performance.

For a better understanding of the contact phenomena and the interaction of tribological systems with an intermediate layer of a limited number of particles, fundamental investigations are carried out on a tribometer test rig. For this purpose, two test scenarios are investigated, a) the kinematics and contact forces of single geometrically defined particles such as dodecahedron, icosahedron and hexahedron, and b) the contact forces and surface roughness of a layer of silicon carbide particles of different sizes.

The measured ratio of tangential to normal force can be used as an indicator of the dominating kinematics of the particles and of the generated surface roughness, respectively. The higher the force ratio, the higher the tendency to slide for a given particle type and paring of particle and counter body.

For one geometrically defined particle the short-time Fourier transform additionally helps to distinguish the state of motion since the excited frequencies during rolling are reduced.  For a layer of silicon carbide particles, the velocity and particle size have the strongest influence on the overall motion and the surface roughness produced. Larger particles tend to slide and create more scratches, while smaller particles tend to roll and create indentations in the counter body. Furthermore, for the same particle size, an increase in velocity causes a transition from sliding to rolling, resulting in an increased surface roughness.