BRAKE WEAR TESTING: CORRELATION BETWEEN VEHICLE AND DYNAMOMETER TESTING (PART 2 OUT OF 3)

This research focuses on reducing the mileage of open-road brake tests by simulating brake patterns on dynamometers, writes Fabio Squadrani, Senior Manager, Braking Systems in Applus IDIADA.

- Fabio Squadrani

Modern braking systems development is moving towards the reduction of long tests on open roads. However, one of the most critical items when reducing the mileage in open roads is brake wear. This work answers a simple question about how to simulate brake patterns in dynamometers to reduce the mileage of brake tests to be performed on vehicles. In the first part of this article, a set of data coming from a brake durability test was analysed. Particularly this is needed to define the target wear value for the brake dynamometer procedure.

➤ Brake Dynamometer Testing

The fixture is mounted on the Applus IDIADA PC2 (Passenger Car 2) dynamometer. This dynamometer is a full-scale dyno, which can replicate the exact vehicle performance, at its corresponding inertia. The specifications of the dyno is as follows:

➤ Route classification and selection To reproduce the routes on the dyno the first important element is the selection of a representative route. First of all, a standard Mojacar route is made of the following main sections:

a. Bedding routes

b. Country road routes (usually called Lubrin Routes)

c. Highway routes.

To select representative routes for wear correlation purposes, both bedding routes and highway routes are not considered. The first ones because they are considered as not representative of the study. The motorway routes, instead, are assumed not to be contributing to the wear generation.

In addition to this, the following snubs are also eliminated:

Snubs at low speed (<3 km/h)

Snubs in the noise search area

Snubs where the difference between initial and final speed

is less than 3km/h

In this way, the average mileage for each route in the dyno is calculated to be 125 km.

Under this criterion, the mileage of the test is modified as follows:

No impact on the average wear is assumed.