The friction force in the clutch works just like the blocks in the frication section of brake, except that the spring presses on the clutch plate instead of weight pressing the block into the ground.

The relationship between static and dynamic friction coefficients of the rigid blocks with smooth surfaces has been studied preliminarily by means of a dynamic test of rigid blocks in this paper.

In computing the reliability extent of blocks, the influences of a variety of factors are taken into account such as occurrences, cohesion coefficient and friction coefficient of the structural plane.