Abstract
KEYWORDS – friction, testing, tribometer
ABSTRACT
The boundary layer between the brake pad and disk is a crucial component of technical brake systems. To better comprehend the behavior of the boundary layer dynamics, it is necessary to perform friction tests under specific reproducible conditions. It is also necessary to analyze the wear behavior of the friction partners and to analyze simultaneously the noise, which can be generated by the boundary layer, the topography, and wear behavior of the friction partners. An automated measurement device based on the pin-on-disk principle, which fulfills these requirements, has been developed and is the focus of this paper.
The Automated Universal Tribotester (AUT) is an instrument capable of analyzing friction in combination with noise, topography, and the wear behavior of brake components. Thus, correlations between the individual variables can be identified. Using this device, measurements can be made automatically, without the need to dismount the disk or the pad specimen.
The AUT has a modular design allowing for fast adaptions to future boundary conditions (see. Figure 2). It currently consists of a rotary drive with a drive power of up to 10 kW, capable of reaching rotation speeds up to 2000 rpm (corresponding to vehicle speeds of approximately 160 km/h), and two linear stages for positioning the reduced-scale brake pad test specimen and loading the normal force against a non-scaled industrial rotor. The normal load can be applied up to 300 N (corresponding to approximately 45 bar brake line pressure) using a spring load unit. Additionally, the normal load can be modulated by a voice coil. The forces are measured by a 3-axes piezoelectric sensor directly at the test specimen. Topography measurement devices in the form of laser distance sensors and a digital camera with 18MP resolution are used to analyze the surfaces of the brake components. The AUT is also equipped with an acoustic unit for detecting NVH-phenomena. The process control and data acquisition of the complete assembly are fully-automated.
In this paper, the measurement device is introduced, its design is presented in greater detail, and results of selected sample measurements are shown.