How do Drum Brake Linings maintain stable friction performance under high temperature and wear conditions?

Drum Brake Linings are one of the key components in the automotive braking system. Their main function is to slow down or stop the vehicle through friction with the brake drum. In actual use, especially under frequent braking, long downhill or heavy load conditions, brake linings will face the dual challenges of high temperature environment and continuous wear. Therefore, how to maintain stable friction performance under these extreme conditions has become a core issue for improving braking safety and service life.

1. Working principle and performance requirements of drum brake linings
The drum brake system relies on the brake shoe to push the lining outward, close to the rotating brake drum surface, and slow down the vehicle through friction. Since the braking process is accompanied by energy conversion (kinetic energy is converted into heat energy), the brake lining must have the following key properties:
Good friction coefficient stability: maintain constant friction at different temperatures and speeds;
Excellent high temperature resistance: prevent material carbonization or failure due to high temperature;
Excellent wear resistance: reduce material loss and extend service life;
Low noise and low dust emission: improve driving comfort and meet environmental protection standards.
2. Effect of high temperature on friction performance and countermeasures
During continuous or high-intensity braking, the temperature of the contact area between the brake drum and the lining can exceed 300°C, or even reach more than 500°C. This high temperature can cause the following problems:
The material undergoes thermal decay and the friction coefficient decreases;
The resin binder decomposes, affecting the structural integrity;
The surface is oxidized or carbonized, reducing the friction efficiency.
To deal with the above problems, modern drum brake linings usually adopt the following technical means:
Select high-temperature resistant binders and fillers: such as phenolic resin modified systems, ceramic fibers, etc., to enhance the thermal stability of the material.
Add friction modifiers: such as metal sulfides, graphite, etc., which can still maintain a certain friction coefficient at high temperatures.
Optimize the formula design: balance the ratio of hard particles and soft lubricating components in the friction material to ensure that the friction performance does not fluctuate drastically with temperature.

3. Wear control and material life improvement measures
Wear is one of the main factors affecting the service life of brake linings. Wear not only causes material loss, but also may change the state of the friction surface, thereby affecting the braking effect. In order to slow down wear and improve durability, the following measures are often taken in engineering:
Introducing high-strength reinforcing fibers: such as steel fibers, aramid fibers, etc., to improve the shear and fatigue resistance of the material.
Optimizing particle size ratio: Reasonably matching coarse and fine particles to form a dense and uniform friction layer and reduce surface peeling.
Using surface treatment technology: such as sandblasting, coating, etc., to improve the compatibility of linings and brake drums and reduce the initial wear rate.
Simulation testing and material iteration: With the help of bench tests and computer simulations, the wear trend of materials under complex working conditions is predicted, thereby guiding the optimization design of materials.

The friction stability of drum brake linings under high temperature and wear conditions is directly related to the safety and reliability of the vehicle's braking system. Through material formulation optimization, structural design improvements and the application of advanced processes, its performance can be effectively maintained under extreme working conditions.