Research and/or Engineering Questions/Objective
Nature of braking friction is extremely complex and a deeper understanding of the physical mechanisms that govern the energy dissipation at the interface of friction pair is an important tool to create an even deeper knowledge of tribological behavior of friction material. Friction brakes need to transform kinetic energy into heat: a complete knowledge of thermal effects during this process in every brake component is an essential part of brake design.
As referred to brake pads, the analysis of dyno testing data highlighted experimental evidences related to thermo-mechanical effects, such as the different wear resistance capabilities of material classes (NAO and Low Steel). In fact as it's known, tribological characteristics are not constant under all testing conditions and they strongly depend on temperature being the direct consequence of kinetic energy dissipation. The aim of this work is to explain the relation between wear and energy for different type of friction materials.
Methodology and results
We developed a group of dyno-testing procedures which investigate the relation between wear rate and energetic / dynamical parameters through different ways to dose kinetic energy and power density. Testing parameters are defined at the pad to disc interface, in order to produce results unconstrained from a specific brake design. Different friction mix concepts show characteristic wear behaviors that can be described by mathematical functions. Wear of mixes with LS characteristics are sensible only to the amount of kinetic energy dissipated while NAO-like mixes show a more complex dependence on velocity, deceleration and pressure.
A tribological characterization of brake materials from an energy point of view has been started using innovative dyno-testing investigation techniques. It has been pointed out that there's a complex relation between compositions and tribological characteristics. Thanks to this testing procedure wear can be mapped using a representative two dimensional surface defined by energetic variables in a 3-D space.
Niccolò Patron, Guila Garello, Luca Martinotto, Peitro Buonfico - ITT Italia S.R.L