Abstract
Brake durabilities on public roads are one of the main activities for the development and validation of OEMs vehicles, in terms of brake noise research and parts wear in the vehicle testing field. Many routes have been defined worldwide; some of them turned into brakes NVH verification standards. Chinese, European and American markets are clear examples, with both city traffic and mountain road patterns. The scope of this paper is to describe a complete correlation of the worldwide public road brake durability standards, in order to get global ratios defining the equivalence between each test.
The complete study will include Shanghai City Traffic (China), Los Angeles City Traffic (USA), and Barcelona City Traffic and Mojácar (Spain) for the European market. For each location a standard route profile has been defined and local drivers (skilled on NVH evaluations) have been selected for the mileage accumulation. In this way, local driving pattern has been assessed on each site and kept into account for the comparison.
Parameters included in this study are the ones affecting brake noise issues (objective characterization, mainly focused on squeal noise frequency ranges, noise loudness, occurrence, etc.), but also parts wear due to the harshness of the durability itself (pads, discs, tires and wheel dust). Furthermore, many other factors have been considered, with the purpose of fully characterizing each route and its local driving pattern: number of brake applications, vehicle speed ranges, deceleration, brakes temperature, brakes load factor (from braking energy and power profile) and lateral acceleration among others.
This study, which contains a wide variation of route profiles, has its limitation on the total mileage accumulated on each location, as well as the number of standards performed. An extension on both parameters would provide a deeper and more complete analysis.
This project offers a fully controlled comparison in all aspects of a brake durability. To ensure the validity and trust of results, exactly the same vehicle specifications have been used on each location. In addition, the brake components (calipers, discs and pads) have been selected from the same production batch. Specifically for linings, a previous study of compressibility was made and the ones with lower dispersion were selected, in order to reduce the uncertainty on wear or brakes noise results.
From the outputs of the comparison made, it has been clearly demonstrated the differences in terms of route severity of each standard; not only between city traffic and mountain road profiles, but also among the same types of profile. Same kind of conclusion has been obtained from noise evidences, where a rank of squeal occurrence and events has been achieved among all the durability patterns.
KEYWORDS durability, comparison, brake noise, severity, squeal