Why does the brake pads overheated cause the brake ability weakened?

answer:

Because overheating will cause the brake pads friction material heat attenuation, resulting in a decrease in the friction of the brake disc.

Thermal attenuation refers to a phenomenon that decreases the friction coefficient when the rising speed of the braking is high, the pressure is increased, and the frequent brake has caused the friction sub -temperature to increase. The heat attenuation will directly affect the safety of vehicles and mechanical driving. Severe heat attenuation can even cause brake failure and cause accidents. The reasons for the heat attenuation are more complicated, let's briefly introduce it.

The heat attenuation is particularly obvious in the polymer friction material. This is because this friction material will use resin as a binder. The phenolic resin will cause heat decomposition at high temperature to decompose liquids such as phenol. These liquids are attached to the surface of the friction sheet to form a layer of lubricant. On the other hand, at high temperature, the resin will decompose carbon dioxide and other gases. The oxidation film is easy to adsorb gas, and eventually forms a layer of gas cushion membrane between the friction tablets. The oxide film here is also a decline in friction performance. Under high temperature, the metal surface is easy to oxidize, forming a layer of oxide film. This layer of oxide film is low, hard and crispy, and it is easy to crack under the action of friction. It becomes abrasive, which not only reduces the area of ​​the friction tablet, but also further damages the surface. In some metal friction materials, there may also be a low melting point metal melting out, forming a lubricant on the surface of the friction tablet to reduce the friction performance. For example, the melting point of the tin is only 231 ° C. When the brake pads are overheated, the tin may melt into it. Elected.

The reason for the heat decline of friction materials is relatively complicated, and the above is just a rough introduction. Remember to change the brake pads in time.

references:

[1] The research and analysis of the mechanism of the heat recession of Zhu Pan. Zhu Pan.

[2] Huang Zhigang. Solution of the problem of thermal recession of polymer friction materials [d]. Hunan University, 2008.

By Frost Bai

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