Development of a Physics-Based Computational Model for Predicting Thermal Behaviour During High-Speed Braking

Abstract

Brake pad fade is a phenomenon in which the braking torque created by a disc-brake system loses strength as temperatures rise. Empirical testing is costly, and accurate models are needed to predict performance under extreme “panic stop” conditions, which is important in road safety for determining the minimum stopping distance. Braking performance is also limited by the tire-road grip limit, which defines the maximum braking force before skid occurs. This study uses physics principles to mathematically model and simulate the thermomechanical and energy-dissipation behavior of an automotive disc-brake system during a stop where maximum braking force is applied, helping determine the prevalence of brake pad fade between different pad materials and disc geometries. Temperature-dependent friction data is used to differentiate between three distinct pad materials, and a primary computational conjugate heat transfer (CHT) simulation combined with secondary material data differentiates between two pad geometries. An iterative forward-Euler differential equation was modelled and simulated in the study, containing temperature updates, heat partitioning, and friction changes over time. Subsequently, the braking torque was calculated using classical vehicle mechanics as friction changed over time. Ultimately, asbestos composite binder pad material 42-773 experienced the least fade. Asbestos resin composite material 2-61 fell below the tire-grip limit first, while iron-based cermet material FMC-11 experienced the most fade. For all pad materials, vented disc geometries experienced less fade than solid disc geometries, though marginally. Significant fade effects occurred primarily at elevated initial temperatures, demonstrating the importance of energy dissipation, temperature-dependent material properties, and thermal behavior in computational models of braking performance.

Keywords: Disc-Brake; CHT; Thermal Modelling