The above is the main reason for the loosening of the bolt connection, and there are also looseness caused by other reasons, such as manufacturing precision, installation and maintenance level, harmful gas and impurities. To prevent loosening, the following measures can be taken.
In order to prevent the initial looseness caused by the elastic slack, the mechanical equipment adopting the bolt connection should be re-tightened after a certain time or period of operation to eliminate the looseness caused by the elastic relaxation and restore the initial pre-tightening force. For the reliability of the work of the joint, regular torque check should be carried out during use. In order to reduce the initial looseness, the surface roughness and unevenness of each part of the bolt and the connected part should be relatively increased, and the shape error should be reduced.
In order to prevent the reduction of friction coefficient and the loss of tightening torque, the impact and vibration of the joint should be minimized. In particular, the peak value of the vibration force should be controlled. Even if the various vibrations existing cannot be eliminated, the amplitude and vibration force should be kept. Low level.
In order to prevent the change of the tightening torque caused by the fluctuation of the friction coefficient, the number of bolt removals and the appearance of scratches and damage should be reduced.
For important joints with strict anti-loose requirements, fine thread can be used, which is more effective and self-locking. In addition, it is more effective to prevent the pre-tightening force under the possible conditions or to use the highest pre-tightening force allowed by the bolt strength.
In addition to the conventional anti-loose method, some special mechanical anti-loose methods, such as the combination of long screws and thick washers or sleeves, can be used to prevent anti-vibration loosening. It is also possible to use the screw with the bottom of the bolt head. It is also more effective; in addition, the new type of gasket used in the form of a convex and concave pair can be used together with the spring washer to not only provide anti-vibration and anti-loose effect.
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