Brake Pad Friction Coefficient and Material
Brake pads, also known as brake linings, are friction materials whose main function is to create friction with the surface of the brake disc when braking the car, thus achieving braking force. Therefore, it is an important part of the brake pad structure. The friction factor is a coefficient of friction effectiveness of brake pads and is an important indicator of brake pad quality. If a force is applied to a horizontal plane to move a 100kg object, the force is equal to its own weight, i.e. the coefficient of friction between the object and the ground is 1, what is the coefficient of friction of a brake pad?
The coefficient of friction of brake pads is the coefficient of friction of brake pads, which has a high coefficient of friction. The higher the braking friction, the more sensitive the braking is, and the car can get better braking effect by reducing the force of stepping on the pressure. Brake performance is affected by a brake pad having a coefficient of friction that is either too high or too low.
If the coefficient of friction is too large, the brake will produce tyre holding phenomenon, or too sensitive, comfort and heat resistance will be poor; if the coefficient of friction is too low, there will be a brake failure, which is not good, and it will cause a serious threat to driving safety. The friction coefficient of brake pads is 0.3-0.4 under normal circumstances.
Let's talk about the friction material of brake pads:
Generally speaking, the friction materials of brake pads include four main aspects: basic materials, filling materials, wear-increasing agents and reinforcing fibres. The proportion of these materials varies from product to product, depending on the different applications and friction coefficients. In addition, the friction materials used for different classes of vehicles and for disc brake pads differ from those used for drum brake pads. For brake friction pads, the formulation of the friction material is more important. The relative proportions of the individual components are affected by the braking effect, resistance to wear, temperature resistance and other properties of the brake pad.
The common friction materials available on the market today can be classified into four types according to the basic material. Asbestos, semi-metallic, low-metallic, and NAO ceramic formulations (i.e., non-asbestos organic). Next, we will look specifically at the different materials of brake pads.
1. Asbestos formulation: has been banned for environmental protection reasons.
2. Semi-metallic blends: "Semi-metallic" blends use 30-50% "iron alloy" as the reinforcing fibre and combine it with an important blend. It has the advantage of better heat dissipation and better heat attenuation. However, due to the high hardness, it is easy to generate noise.
3. Low-metal mixture brake pads: "Low-metal" mixture brake pads are mainly made of less than 10% iron and non-ferrous metals as reinforcing fibres. It is characterised by moderate hardness, comfortable braking, high braking sensitivity and low braking noise.
4. Ceramic formula: ceramic formula is the current direction of brake pad friction material formula research and development. Earlier developed asbestos materials, mainly glass fibre, aramid fibre and other fibres (carbon, ceramic, etc.) as reinforcing materials. And ceramic formulations have good braking comfort, low braking noise, long service life, cleaner and more environmentally friendly. However, due to the properties of the material itself, the braking force is relatively low, generally used for Japanese and Korean models. It is not suitable to use pure ceramic formula for heavy-body vehicles such as European and American vehicles.
