Vehicle Brake Noise Shims: A Tutorial For Continuous Product Improvements

Commercial, electronics, aerospace, and automotive industries use a wide variety of methods to attenuate - damp - unwanted noises and vibrations. A well-established passive method for controlling structure-borne noise is based on viscoelastic materials that are specially selected for the application. In these cases, the materials are based on organic polymers that exhibit elastic and viscous properties. In the simplest cases, the damping material may be composed of a viscoelastic adhesive applied to one side of a suitable substrate.

Expected performance for these layered assemblies of polymer-based coatings and supporting substrates is based on two factors: (1) the composition, quality, and durability of each coating; and (2) the composition, quality, and durability of each material-to-material interface.

This is the second of two papers about this type of material for noise and vibration control. The objective is to provide readers with an overview of issues affecting design/development of products for controlling vehicle brake noise. Taking the format of a tutorial, it is intended for anyone involved in their design, manufacture, or use. It provides basic information and numerous references that will support evaluating potential failure modes and their effects in relation to choices of materials and provides an appendix with generic root causes.

Summary

Unwanted performance variations in materials for noise and vibration control can be minimized. The viscoelastic damping materials discussed in this paper are multi-layered combinations of various chemical coatings and supporting substrates. In designing and producing these products, there are many opportunities to affect the physical and chemical properties of the interfaces and coatings, for better or worse.

Initially, this requires a detailed understanding of the application-specific requirements for the engineering component made from these materials. Based on these requirements, appropriate selections of raw materials - polymers, additives, metal substrate, paints, adhesives, etc. - can be decided as part of the design/development of new products. The product design phase must consider manufacturing processes capable of converting the raw materials into products with consistency.

The format of the paper is a tutorial intended for anyone involved in the design, manufacture, or use of material for vehicle brake noise control. It provides basic information that will support evaluating potential failure modes and their effects in relation to choices of materials and provides an appendix with generic root causes. It can be used as the basis for preparing a detailed Product Design/Development Potential Failure Mode and Effects Analysis (FMEA).

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