The thermal cracking of brake pads refers to the phenomenon of cracks appearing in the brake pads during the braking process due to high temperatures and thermal stresses. Thermal cracks in brake pads typically occur during high-speed braking or continuous braking, especially in prolonged high-temperature environments. These cracks generally appear on the friction surface of the brake pads and may extend along the grain or layering direction of the pads.

The formation of thermal cracks in brake pads can be attributed to several factors:

1. Uneven thermal expansion: Under high temperatures, brake pads expand due to heat, but the non-uniformity of the material and structure may lead to inconsistent expansion in different parts, resulting in internal stress and eventual formation of thermal cracks.
2. Excessive temperatures: Prolonged or frequent high-temperature braking can cause the brake pads to exceed their design temperature range, leading to decreased strength and toughness of the brake pad material and making it more prone to thermal cracking.
3. Issues with brake pad materials: Poor-quality materials or prolonged usage of brake pads can cause material deterioration or fatigue, making them more susceptible to thermal cracking.

The presence of thermal cracks in brake pads has a significant impact on the performance and safety of the brake system. Thermal cracks can reduce the strength and rigidity of the brake pads, thereby diminishing their braking efficiency and stability. In severe cases, thermal cracks may lead to delamination or fracture of the brake pad layers, further affecting the normal operation of the brake system, increasing braking distance, and potentially causing brake failure, leading to serious accidents.

Therefore, regular inspection of the condition of brake pads to ensure the absence of thermal cracks and timely replacement of heavily worn pads are important measures to ensure the proper functioning of the brake system and driving safety.