Mr. Sven Brandt, TU Braunschweig, GERMANY

Mr. Malte Sandgaard, TU Braunschweig, GERMANY

Dr.-Ing. Sebastian Gramstat, Audi AG, GERMANY

Mr. Frank Stebner, Volkswagen AG, GERMANY

Mr. Conrad Weigmann, Volkswagen AG, GERMANY

Prof. Dr.-Ing. Arno Kwade, Institute of Particle Technology, GERMANY

Prof. Dr.-Ing. Georg-Peter Ostermeyer, TU Braunschweig, GERMANY

Prof. Dr.-Ing. Carsten Schilde, Institute of Particle Technology, GERMANY

The increasing degree of electrification as well as the optimization of particle based exhaust emissions, which is already being driven forward due to legislation, will direct the focus of fine dust considerations in automotive technology to non-exhaust emissions. In contrast to exhaust emissions, there are currently only a few vehicle-related limit values or uniform standards in measurement technology and the measurement procedure. The area of non-exhaust emissions includes tire abrasion, the turbulence of organic and inorganic road particles, and brake wear. Since, in addition to the material component, the particle size also has a significant influence on the health hazard of the material, particulate emissions from brakes are often directly related to health effects.

In comparison to previous measurements, which have mostly been carried out in enclosed and clinical environments, the dynamics of the fine dust emitted from the brake will be investigated using a fully automated tribometer and used as a possibility to validate a DEM simulation. Besides the pure measurement of the emitted particle size distributions during the brake application, conclusions on the agglomeration behaviour of the emission particles in the environment shall be drawn. The aim is to predict the environmental impact and the potential danger of the particles to humans due to the particle size released into the environment. The pin-disc contact between brake pad and brake disc serves as the emission source. A coupled CFD-DEM simulation environment was set up to simulate particle dynamics. Based on a rotating brake disc model, the flow-relevant components of the test bench environment were implemented into the simulation setup. The area around the actual brake contact as well as the environment at the tribometer should be considered. For the metrological validation of the simulation, a swarm of calibrated low-cost sensors as well as a scattered light based particle size measuring device will be set up around the tribometer.

Prof. Dr.-Ing. Georg-Peter Ostermeyer, TU Braunschweig, GERMANY

Mr. Chengyuan Fang, Institute of Dynamics and Vibration of TU Braunschweig, GERMANY

Mr. Guido Lehne-Wandrey, Institute of Dynamics and Vibration of TU Braunschweig, GERMANY

Mr. Malte Sandgaard, Institute of Dynamics and Vibration of TU Braunschweig, GERMANY

Mr. Alexander Vogel, Institute of Dynamics and Vibration of TU Braunschweig, GERMANY

Mr. Jacek Kijanski, Institute of Dynamics and Vibration of TU Braunschweig, GERMANY

Mr. Thomas Hillner, wenglor sensoric GmbH, GERMANY

Mr. Fabian Repetz, wenglor sensoric GmbH, GERMANY

Friction tests under controlled conditions are crucial for the understanding of the boundary layer dynamics in technical brake systems. The dynamics of the friction interface characterize the braking performance. In order to evaluate and monitor the dynamics of the friction interface, detailed insights into the friction behavior is obtained by high precision tribotesters under laboratory conditions. Especially in the low sliding speed range, specialized machines such as the Variable Velocity Tribotester (VVT) make it possible to mimic real world phenomena under controlled conditions, e.g. creep groan or COF in low temperatures.

This paper presents the wenglor sensoric 3D sensor ShapeDrive MLAS201 for measuring the pad surface between friction applications at VVT. With this device, quasi in-situ measurements with high speed and precision of the pad’s surface are attained. The 3D sensor consists of a light engine which projects several patterns onto the pad surface and a high resolution camera which can record these patterns again. The topography and intensity information of the pad surface would be stored in a point cloud file with high precision of 12 megapixels. Such information can be used to analyze the surface properties such as roughness and height. With further algorithms it is also possible to observe the change of the entire topography and in further way to determine the wear volume and analyze the contact situations.

Prof. Dr.-Ing. Georg-Peter Ostermeyer, TU Braunschweig, GERMANY

Mr. Alexander Vogel, TU Braunschweig, GERMANY

Mr. Jacek Kijanski, TU Braunschweig, GERMANY

Mr. Malte Sandgaard, TU Braunschweig, GERMANY

Mr. Guido Lehne-Wandrey, TU Braunschweig, GERMANY

Friction tests under controlled conditions are crucial for the understanding of the boundary layer dynamics in technical brake systems. The dynamics of the friction interface characterize the braking performance, which has to be evaluated and monitored in the early stages and throughout the development process of new friction materials. For this purpose, detailed insights into the friction behavior is obtained by high precision tribotesters under laboratory conditions. Especially in the low sliding speed range, specialized machines such as the Variable Velocity Tribotester (VVT) make it possible to mimic real world phenomena under controlled conditions, e.g. creep groan or COF in low temperatures.

The VVT is modularly designed with two linear stages to move the test specimen and a highly capable servor motor for the rotation of the brake disc. A rotational disk speed of up to 400 rpm is reached with a resolution of 25 bit and a 1:10 gearbox. The normal load can reach up to 300 N (approx. 45 bar brake line pressure) by utilizing a leaf spring load unit. A 3-axis piezoelectric force sensor directly at the test specimen measures the applied and resulting forces.

In addition to the friction testing, it is possible to automatically move the specimen to a high precision 3D laser scanning device with stripe light projection and to record height information and pictures of the friction surface. For measurements below room temperature, the VVT is located in an insulated chamber and equipped with two cooling aggregates.