The isolation function of the wafer is manifested in the reduction of loosening, which has two aspects: non-rotary loosening and rotary loosening.
Non-rotational loosening
Non-rotational loosening is that in the threaded connection, the bolt and nut may be loosened without relative rotation, so that the axial force is reduced. The preloading force is the result of the joint action of the elastic elongation of the bolt and the elastic compression of the connected part. When the elastic elongation of the bolt decreases or the elastic compression of the connected part decreases, the axial preloading force of the bolt will decrease, resulting in loosening.
The reasons that affect the elastic elongation of bolts and elastic compression of connected parts are as follows: wear of connected parts, plastic collapse and creep compression; Bolt and nut bearing surface embedded; Frontal creep elongation of bolt; Thermal expansion of bolts, etc.
In order to reduce such non-rotational loosening, the washer can play a role, in the connection system with a thick wafer, it is equivalent to increasing the length of the bolt and the thickness of the connected part, so that the elastic deformation of the bolt and the connected part is increased, the decline of the axial preload is controlled, and the non-rotational loosening is reduced, which is the isolation role of the washer.
Rotary loosening
Rotary loosening is the loosening of the internal and external threads in the threaded connection when the relative rotation occurs in the direction of loosening, the important reason for this loosening is that there is sliding on the supporting surface of the connection, that is, the sliding momentum of the connected part is larger than the critical sliding momentum. This critical sliding momentum is the maximum sliding momentum between the connected parts without causing the sliding of the supporting surface, which includes two aspects: the head displacement caused by the friction of the supporting surface; The displacement of the bolt head caused by tilt in the internal thread of the bolt.
The factors related to the critical sliding momentum of the connector are the thickness of the connection, the length of the bolt, the axial preload force, the friction coefficient of the support surface when the side slide, etc.
Adding the thick washer to the connection system can increase the critical sliding momentum of the connected part, so as to reduce or avoid rotating loosening, that is to say, the washer plays an isolating role in increasing the thickness of the connected part and reducing the risk of sliding of the supporting surface.
