The first is to prevent screw friction from loosening. This is a widely used anti-loosening method. This method generates a positive pressure between the thread pairs that does not change with the external force to generate a frictional force that can prevent the thread pairs from rotating relative to each other. This positive pressure can be achieved by pressing the thread pair axially or simultaneously in two directions. Such as the use of elastic washers, double nuts, self-locking nuts and nylon insert welding nuts. This kind of anti-loosening method is more convenient for the disassembly of the nut, but in the case of impact, vibration and variable load, the pre-tightening force of the bolt will decrease due to slack at the beginning. As the number of vibrations increases, the lost pre-tightening force gradually increases. , Z will eventually cause the nut to loosen and the threaded connection to fail.
The second method is to prevent the screws from loosening mechanically. The relative rotation of the thread pair is directly restricted by the stopper. For example, split pins, tandem steel wires and stop washers are used. Since the stopper has no pre-tightening force, the anti-loosening stopper can only work when the nut is loosened to the stop position. Therefore, this method does not actually prevent loosening but prevents falling off.
The third method is screw riveting to prevent loosening. After tightening, using methods such as punching, welding, bonding, etc., the thread pair loses the characteristics of the movement pair and the connection becomes an undetachable connection. The disadvantage of this method is that the bolt can only be used once, and the disassembly is very difficult, and the bolt pair must be destroyed before disassembly.
The fourth way is to prevent loosening of the screw structure. It uses the structure of the thread pair itself, that is, the anti-loosening method of Down's thread. The first three types of anti-loosening methods mainly rely on the force of a third party to prevent loosening, which mainly refers to frictional force. The quality of the anti-loosening effect depends on the size of the third party's force. The anti-loose structure does not rely on the power of a third party, but only on its own structure. The structural anti-loosening method, namely the Down's thread anti-loosening method, is also the current advanced and effective anti-loosening method, but it is not known to most people.
