Why brake lining overheating will cause weak braking ability?

Why brake lining overheating will cause weak braking ability?

Because overheating will cause thermal attenuation of brake lining friction material, resulting in a decrease in brake disc friction. Thermal decay refers to a phenomenon that friction coefficient decreases when the initial braking speed is large, the pressure increases, and the braking frequency causes the temperature of friction pairs to rise. Thermal attenuation will directly affect the safety of vehicles and machinery, serious thermal attenuation will even cause brake failure, resulting in accidents. The reasons for thermal decay are more complex, so let's briefly introduce them. Thermal decay is particularly pronounced in polymer-based friction materials because they use resins as binders. Phenolic resin at high temperature will occur thermal decomposition, decomposition of phenol and other liquids, these liquids adhere to the friction plate surface to form a layer of lubricating film, on the other hand, at high temperature, the resin will also decompose carbon dioxide and other gases, the oxide film on the metal surface of the dual parts and easy to absorb gas, finally in the friction plate between the formation of a layer of air cushion film. The oxide film here is also one aspect of the friction performance decline, at high temperatures, the metal surface is easy to oxidize, forming a layer of oxide film, this layer of oxide film strength is low, hard and brittle, easy to crack under the action of friction, peeling off from the surface into abrasive particles, not only reducing the friction plate action area, but also further damage the surface. In some metal friction materials, there may be low melting point metal melting precipitation, the formation of lubricating film on the surface of the friction plate, reduce friction performance, such as tin melting point is only 231℃, brake pads overheating, which tin may melt precipitation.