1, the nut and bolt are self-locked by friction. However, under dynamic load, the reliability of this self-locking will decrease. On some important occasions, we will take some anti-loosening measures to ensure the reliability of nut locking. Locking nut is one of the anti-loosening measures.
2. The locking effect of the locking nut mainly depends on the interaction between the meshing thread of the nut and the bolt. There are many ways to improve the interaction force between meshing threads, such as improving nut thread structure, roughening nylon nut, thread surface treatment and so on.
Extended data:
The maximum loosening torque of the lock nut is influenced by many factors:
1. For the study of the low-cycle fatigue performance of the lock nut, the pitch diameter of the thread, the helix angle and the bevel angle of the tooth profile remain unchanged, and only the maximum elastic restoring force FNmax and the equivalent friction angle ρe of the threaded part will change to some extent after repeated use.
2. It is necessary to analyze the variation law of the maximum loosening torque of the lock nut under cyclic load from these two aspects. Material strain hardening, the phenomenon of "cyclic strain hardening" or "cyclic strain softening" will appear when the material is subjected to cyclic load, that is, under the condition of constant amplitude cyclic strain, the stress amplitude will increase or decrease with the increase of the number of cycles.
3. After several cycles, the stress amplitude enters a cyclic stable state. The low-cycle fatigue of lock nut is carried out under the condition of constant strain, and the strain hardening or softening of threaded parts will affect the maximum screw-out torque. The alloy steel used to manufacture the lock nut belongs to cyclic strain hardening material, and the hardening of the material will increase the elastic restoring force FN and screw-out torque of the threaded part.
References:
Baidu encyclopedia-lock nut