How to choose the preload of bolts?

1. Bolt material and strength grade
Bolts of different materials and strength grades can withstand different preloads, which need to be determined based on their performance parameters.
2. Working load of the connection
The preload should be sufficient to ensure that the connection will not loosen or slip under the working load. Generally speaking, the preload should reach a certain proportion of the working load, usually 1.5-2 times.
3. Importance and reliability requirements of the connection
For critical and important connections, a higher preload is required to ensure absolute reliability.
4. Material and stiffness of the connected parts
Softer or less stiff connected parts may not be able to withstand excessive preload to avoid deformation or damage.
5. Thread friction coefficient
The friction coefficient will affect the conversion and transmission of the preload, and its impact on the selection of the preload needs to be considered.
6. Installation conditions and tools
The tools and conditions that can be provided during actual installation will also limit the size of the preload.
7. Fatigue life requirements
If there are high requirements for the fatigue life of the connection, it is necessary to select a suitable preload to reduce the stress amplitude of the bolt.
8. Industry standards and experience data
Reference to relevant industry standards and engineering experience data, which can provide recommended values ​​for preload in common connection situations.
Usually, the appropriate bolt preload can be selected through calculation, reference standards and experience, and comprehensive judgment based on actual conditions.