Is the contact area of the brake pad related to the friction coefficient? (一)
Why is the larger the contact area between the disc brake pad and the brake disc, the better the effect?
Increasing the area of the brake pad does not change the coefficient of friction. It mainly has the following functions:
In the case of the same required braking pressure, the contact area between the brake pad and the brake disc increases, the heat generated per unit area of the friction pad decreases, and the temperature is relatively low, which is beneficial to reduce wear and prolong the life of the friction pad;
When the required braking torque is the same, the area of the brake disc becomes larger, that is, the diameter becomes larger, which is equivalent to the larger resistance arm, the required frictional resistance is correspondingly reduced, and the required braking pressure is also reduced. Similar to above, better for reduced wear and longer life.
Conversely, if the limit heat generated per unit area of the brake pad is a constant value, the area of the brake pad increases, and the total heat that the entire contact area can withstand can increase, so it can withstand greater braking power (of course Need to increase the brake pressure), that is, the braking effect is better (provided that the tires and the ground do not slip).
Isn't the magnitude of sliding friction only related to the roughness and pressure of the contact surface?
This is because P=F/A=mg/A, f=uPA=uN
So if F is not mg, the bigger the area the better
sliding friction.
Once the external force is greater than the maximum value of static friction, then the phenomenon of sliding friction occurs. This is the relative sliding of two objects. There is a formula for sliding friction: f=μkN.
Among them, μk is called the coefficient of sliding friction, which is often set as a constant in exercises, but in fact it is related to the relative sliding speed, N is the normal pressure between two objects, from the whole formula, the sliding friction For two given surfaces, the contact surface area is irrelevant.
The coefficient of friction of the brake pads is not that the bigger the better the performance.
