Brake insulators often offer optimal solutions to squeal noise. In the process of engineering solutions to reduce the brake noise, a system-level finite element complex eigenvalue analysis is often used and has gained popularity in recent years. Models of insulators have also been proposed for system-level evaluation, however many challenges remain in efficiently implementing an insulator model, owing to complexities of the insulator component model. The complexities arise from the visco-elastic behavior (primarily the frequency and temperature dependence), and the thin polymer/steel multi-layer nature of the construction - typical in an insulator.
As a first part of a joint investigation, this paper explores the nature of frequency and temperature dependence in insulator models and reduces the cumbersome multi-layer model into a simpler form that can be more easily implemented in a typical brake system stability analysis. Using optimization, the original multi-layer, multi-frequency and multi-temperature set of models is reduced to an equivalent set of single-layer, (relatively) frequency-independent models. It is argued that this type of insulator model can be more easily extended to capture the multiple mechanisms involved, allowing the system-level stability analysis to more fully account for the effects of insulator damping. The proposed insulator model is verified through modal testing, during which it is observed that a pad-with-insulator model necessitates inclusion of the damping contributed by the brake pad assembly, particularly if an under-layer exists. A later paper will discuss the results from the full brake system stability analysis.