Journal Article
Model Approach for a Load and Frequency Dependent Stiffness in Friction Materials
2011-09-18
2011-01-2352
It is widely known that friction materials show a load and frequency dependent stiffness. The load dependency can be explained with a geometrical nonlinear material structure, like the existence of porosities that are compressed by increasing the load. The frequency dependency is principally due to the viscoelastic characteristics of the polymer matrix that binds the different components together. Today there are commonly three different measurement systems used to investigate the material stiffness in compression: Ultrasound, which measures in a MHz-range, piezoelectric actuator to measure in a kHz-range, and hydropulser used for low frequency and quasi-static conditions [1]. Comparing the results from different authors it can be observed, that the stiffness does not change dramatically in the frequency range of each system, but between systems. There is a great discrepancy in the observed results, and it is said, due to the material's frequency dependence.