Inertia Dynamometer Test Procedure for Corrosion and Contamination Effects on Friction Couple Behavior
Cyclic corrosion and media contamination effects during inertia dynamometer testing on torque output, coefficient of friction, surface condition, for passenger cars and light duty trucks up to 4540 kg of Gross Vehicle Weight Rating.
Rationale: The need to assess the behavior of the friction couple closer to actual driving conditions including the effects of prolonged environmental exposure increases the need to expand the testing programs using laboratory testing. Shorter development cycles along with the need to provide robust foundation brakes on global platforms for the intended life cycle of the product, require potential failure modes under varied climatic conditions and environmental contamination Current inertia dynamometer tests published by Standard Development Organizations assess the friction behavior, wear, noise, vibration, and harshness under dry and non-contamination conditions without the effect of prolonged environmental exposure. There are several corporate laboratory tests which combine inertia dynamometer tests with cyclic corrosion cycles. In some cases, the cyclic corrosion is combined with exposure to contamination media (water, mud, slurries, etc.). Nevertheless, these procedures remain proprietary or rely on moving the brake fixture (or brake components) between the inertia dynamometer, which disturb the friction couple during the test, and creates logistical challenges to the testing facility. The objective of this Recommended Practice (RP) is to combine inertia dynamometer test cycles with cyclic corrosion and media contamination (while keeping the brake assembly undisturbed on the dynamometer) to assess multiple effects like: a) torque output, b) friction coefficient behavior, c) surface conditions (on the friction material and the mating disc or drum), and d) structural integrity, among others. This RP does not include acceptance criteria, it provides measurements that, when combined with other tests, provide a comprehensive assessment on the robustness and stability of the friction couple, the foundation brake, and the braking system to various driving environments.