Weld nuts are commonly used fasteners in life and industry. The biggest problem and hidden danger in use are loosening and slipping. How to prevent welding nuts and other fasteners from loosening during use? loose points:
The first is screw friction to prevent loosening. This is the most widely used anti-loosening method. This method generates a positive pressure between the thread pairs that does not change with the external force, so as to generate a friction 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 in both directions at the same time. Such as the use of elastic washers, double nuts, self-locking nuts and nylon insert welding nuts. This anti-loosening method is more convenient for the disassembly of the nut, but in the case of shock, vibration and variable load, the preload force of the bolt will decrease due to relaxation at the beginning, and as the number of vibrations increases, the lost preload force increases slowly. , which will eventually lead to the loosening of the nut and the failure of the threaded connection.
The second way is to mechanically prevent the screw from loosening. The relative rotation of the thread pair is directly restricted by the stopper. Such as the use of split pins, serial wires and stop washers. 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 it from falling off.
The third way is screw riveting to prevent loosening. After tightening, punching, welding, bonding and other methods are used to make the threaded pair lose the characteristics of the kinematic pair and the connection becomes an inseparable 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 it can be disassembled.
The fourth way is to prevent the screw structure from loosening. It is to use 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 third-party force to prevent loosening, mainly referring to frictional force, and the quality of the anti-loosening effect depends on the magnitude of the third-party force. The structural anti-loosening does not rely on the force of a third party, but only on its own structure. The structural anti-loosening method is the Down's thread anti-loosening method, which is also the most advanced and effective anti-loosening method at present, but it is not known to most people.
