A Cellular Automaton Approach to Numerically Simulate the Contact Situation in Disc Brakes

Abstract

Since brake wear is an important contributor to the concentration of airborne particles in urban atmospheres, it is important to increase our understanding of the origin of these particles. The contact situation between the pad and disc is complicated. Metal fibres in the pad (or other hard materials) form stable contact plateaus, which carry the main part of the load. A flow of wear particles in the boundary layer between the pad and disc partially stack up against these plateaus (and increase their area), and some will escape from the contact and become airborne. The purpose of this article is to investigate the possibility to numerically simulate the contact situation in the boundary layer between the pad and disc and the amount of wear that leaves the contact using a cellular automaton approach. To do so, the contact pressure, pad temperature and wear are determined in that order. Based on these results, the creation, growth and destruction of contact plateaus are simulated using a cellular automaton model. Finally, the amount of wear that leaves the contact is determined. The simulated behaviour of the contact situation correlates qualitatively with experimental observations found in the literature.

A comparison of measured and simulated friction, wear, and particle emission of disc brakes

“…A first step towards a CA approach to simulate friction, wear, and particle emission (airborne wear) of disc brakes has been previously presented by Wahlström et al [12], [13]. The point of this approach is to determine how much of the wear volume becomes stuck in the contact due to the build-up of secondary contact plateaus (or contact patches) and how much leaves the contact and has the possibility of becoming airborne.…”

“…The wear depth at a calculation point on the pad surface can be computed as: (12) and the wear depth at a calculation point on the disc can be computed by numerical integration of the following equation: (13) if the change in pressure distribution is assumed to be negligible during a small rotation ∆θ. The specific wear can be determined by evaluating the mass losses of the test specimens in PoD tests.…”

“…With this in mind, Wahlström et al [12], [13] developed a CA approach that can be used to simulate braking times in the order of seconds and lengths in the order of centimetres. This approach uses literature findings regarding the microscopic and macroscopic scale as input parameters.…”

A Factorial Design to Numerically Study the Effects of Brake Pad Properties on Friction and Wear Emissions

“…Müller and Ostermeyer [7] developed a cellular automaton (CA) approach to simulate the plateau dynamics on a mesoscopic length scale. Inspired by this idea, Wahlström et al [8][9][10] have developed a CA approach on a mesoscopic length scale that can be used to simulate macroscopic wear, friction, and wear emissions for a number of brake events. A comparison with tests conducted with an inertia dynamometer bench shows a promising qualitative correlation between the simulated and experimentally measured friction and wear behaviour.…”

Survey on Modelling and Techniques for Friction Estimation in Automotive Brakes

“…In other words, it is a suitable approach to obtain insight into the pad-disc interface. The authors of [57] propose a simulating tool based on 2D cellular automata that can be used to determine the concentration of airborne wear particles generated from disc brakes. To achieve this goal, a model able to describe the physical behaviour of the contact situation in disc brakes is sought.…”