Elastic Constants

ETEK Technology measures elastic constants using non-destructive ultrasound.  The complexities of this technology are explained in this knowledgebase to help you understand how ETEK technology can help in the development of material formulations and quality control during the manufacture of a material.  ETEK technology is used widely in the automotive industry for friction material formulations.

Brake noise, a major source of warranty costs, is a complex problem involving a myriad of design and processing variables that include friction material properties, rotor design, caliper design, and vehicle suspension. The mechanical properties of friction materials are thought to play an important role in braking system noise performance1-4.  These mechanical properties can be measured by ETEK technology to aid the development of friction material formulations.

Although brake noise is minimized through proper design and appropriate friction material formulation, the realization of noise-free brakes requires that the manufacturer maintain these properties in production. Process variations can significantly alter friction material properties. This can adversely influence noise performance. Better measurement tools applied at the point of manufacture are important.

Non-Destructive Ultrasonic Measurements on Brake Pads

IMS, Inc. received a NSF grant to investigate the production applications of our ETEK technology in the automotive industry through the Small Business Innovative Research (SBIR) program.  Over 300 brake pads of 7 different configurations from 5 different manufacturers were non-destructively measured.  Data and results from this program along with how ETEK technology can be applied to manufacturing facilities is available here.

Non-Linear Aspects of Friction Material Elastic Constants

Friction materials properties show significant load-dependence, meaning the behavior of a material and its NVH performance can differ significantly depending on the situations.  ETEK technology can quantify this often overlooked non-linearity in friction materials.

Other Resources:

Silence is Golden: Eliminating NVH

A presentation promoting the measurement of elastic constants in brake pad friction materials.

Elastic Constant Measurement on Composites
H. M. Ledbetter and D. T. Read

A good background on composite elastic constant measurement.