High Precision Measurements of Topography for Brake Components 2014-01-2522
There are few principal excitation mechanisms that brake system NVH simulations are based on, especially the high frequency squeal simulations. These mechanisms can be described by some simple mechanical models that exhibit excitation or self-excitation effects induced by friction [1, 2]. These models use very simple friction laws of Coulomb type, described by a friction coefficient that is either a constant or simple functions of some state variables, taking into account a Stribeck characteristic.
Measurements from the AK-Master or SAE J2521, however, show that the friction coefficient is not a simple function of some state variables, describing a steady state behavior of friction. In the past several years, material dependent descriptions of the frictional brake interface have started attracting attention . These aspects are greatly influenced by the tribological effects at the frictional interface, which can be characterized by typical wear patterns.
To get a better understanding of the friction mechanisms between the brake pad and the disk, the topography of the disk must be measured using in-situ nondestructive methods, which must be very fast because of the size of the data set and also highly accurate to attain, for example, the wear properties of ceramic disks.
In this work, a fast contactless method to measure the topography and the wear of the brake disk will be presented. Here a laser triangulation sensor mounted on a linear stage, scans radially the surface of the disk, which is connected on a high precision electric motor. In this way the total topography of the disk can be measured, a single profile in radial direction as well as a single profile in tangential direction along the disk. Using the radial profiles statements can be made about roughness parameters, and the tangential profiles can be used to determine axial run out and waviness of the disk.