Abstract
KEYWORDS – brake testing, test fixtures, test setup, passenger car, commercial vehicle, performance, NVH, durability, environmental conditions, climate control
ABSTRACT
Decades of inertia dynamometer testing in multiple regions have led to a myriad of fixture design philosophies and methodologies, with substantial effects on the test results. In addition, in the current landscape of the automotive manufacturing industry, vehicles are designed in one location, manufactured at another location(s), and sold all over the world with significant differences in environmental conditions during their life cycles. Efforts to reproduce vehicle-level conditions and environmental factors in the laboratory setting lead to redundancy, conflicting results, or high-variability in test results of the same test program.
This first half of the paper deals with test fixtures. Initially, it presents the taxonomy of the most common fixture designs and configurations. As the fixture and its design are critical to the test at hand, a global survey was conducted among multiple testing facilities around the world. The survey helped to document variations, uses and types of different fixtures, as well as allowed for direct feedback from the industry.
The second half of the paper deals with environmental conditions. It describes the influence of humidity on friction behaviour and its relationship to the friction material formulation and the manufacturing process. The impact of humidity on friction materials behaviour is squared with our test performed for three different friction materials applied on the same brake under a multitude of different environmental conditions.
This paper supports and expands the investigations and evaluations conducted by the ISO Task Force on Test Variability, which has found brake hardware condition, cooling air setup and amount, temperature measurement, dynamometer control programming, and calculations of friction coefficient, as sources of test-to-test and dyno-to-dyno variability (1, 2). Also, reference the VDA 307 – EKB 3010 standard (3) for items to verify when setting up properly a squeal noise testing.