Test Device for Precise Investigations of Transport Phenomena in the Boundary Layer

Abstract

The boundary layer dynamics are significantly responsible for the friction behavior of a tribo contact. A test bench to investigate the processes in the boundary layer was introduced in [1]. The so-called Wear Debris Investigator (WDI) of the Institute of Dynamics and Vibrations (IDS) forms a friction gap between a rotating and a fixed disc. For a measurement, artificial wear particles are added into the friction gap. The rotating disc of the friction contact consists of a transparent material. This allows the boundary layer to be observed in situ using a high-resolution camera. The obtained image data is used, i. a., to make statements about the formation and destruction processes of contact patches. With the measurement data of an implemented force and torque sensor, correlations between the boundary layer dynamics and the occurring friction forces can be made. This requires a high-precision measurement setup. A large number of measurements at the WDI revealed that precision and force measurement are not sufficient for all dynamic phenomena. For this reason, an innovative measuring system has been developed within the framework of this paper, which allows accurate statements to be made about the interactions of the third body with the first bodies. One major advantage of the new measuring device is that there are almost no drift effects observed during the measurement of the normal forces and friction moments. System-related normal force fluctuations are countered by a force adjustment with three adjustable elasticities, whereby the fluctuations are almost eliminated. This design allows to precisely adjust the normal forces in a wide range. Even measurements with smallest load ranges are provided by the innovative test design. First measurements using the new measuring device are presented in this paper.