Why can anti-skid chains prevent skidding? What is the principle? Regardless of the difference between tracks and wheels, the first thing you need to know is the relationship between stress area and pressure.
1. Relationship between tire area and pressure
The larger the stress area is, the smaller the pressure is; The smaller the force area, the greater the pressure. The ratio of the pressure on the object to the force area is called pressure, which can be understood as the greater the pressure, the greater the pressure
2. Friction of tire
The friction force of the tire is determined by the roughness of the contact surface and the positive pressure. Only when the friction force is strong enough can the tire not slip, but the positive pressure is constant, that is, the curb weight of the car body will not change. The total mass is determined by the number and weight of the drivers and passengers, and the difference will not be large.
Then the core factors that determine the tire's grip are the roughness of the contact surface and the size of the contact area, but the contact area mainly refers to the width of the common tire crown. The wider the tire, the greater the deformation, and the higher the grip at high speed; Generally speaking, a wider tire has a higher skid limit on snow and ice, and a narrower tire is more likely to skid, but the difference is not great for snow chains such as 9mm snow chains.
3.Reduce the stress area
The determinants of pressure are force area and positive pressure, which are the same as the determinants of friction (can be understood in this way); When the positive pressure cannot be changed, the pressure can only be increased by reducing the contact area. Increasing the contact area will reduce the pressure, but for rubber tires, the traction can be improved through deformation; The automatic truck chain or track is made of metal material, so the contact surface can be reduced without considering this factor. In fact, increasing the contact area can only improve the grip of the rubber tire, but it cannot improve the friction force. A large contact area is equal to "the roughness of the contact surface is reduced". If the contact surface becomes smooth, the friction force will be reduced.
If the track is a smooth steel plate, it means that the contact area with the ground is too large. If the pressure is reduced and the friction is low, it will slip. On the contrary, if most of the tracks are concave, leaving only some protruding metal edges to contact the ground, it means that the contact area is reduced and the roughness of the contact surface is increased to improve the friction. This is why the crawler basically does not skid. Of course, there are also factors that make tanks or excavators very heavy.
The anti-skid chain is imitating the track. The ordinary metal anti-skid chain is almost the track. However, the weight of the car body is too small, and the pressure of the metal anti-skid chain is still low. It can not crush the ice layer on the snow that is compacted into ice, or the friction at the release position is too small, and it will continue to skid.
