Bolt connections, as a common type of mechanical connection, are widely used in many fields such as construction, bridges, mechanical equipment, automobiles, and ships. However, in the process of actual use, bolt connections often face the problem of loosening, which not only affects the normal operation of equipment but may also lead to serious safety accidents. Therefore, how to effectively prevent bolt loosening is a topic that must be paid attention to in engineering practice.



One, The main reasons for bolt loosening



1. Vibration and impact: During the operation of mechanical equipment, continuous vibration and impact will cause the bolt connections to gradually lose pre-tension, resulting in loosening.

2. Temperature change: The differences in thermal expansion coefficients of different materials will cause relative displacement of the connecting parts during the temperature change process, thereby affecting the stability of the connection.

3. Incorrect installation: Such as insufficient tightening torque, not using washers, asymmetric tightening, and other factors will lead to hidden dangers in the initial stage of bolt connections.

4. Fatigue damage: Bolts subjected to alternating loads for a long time will produce fatigue cracks, reducing their locking performance.



Two, Effective measures to prevent bolt loosening



1. Reasonable selection of fasteners

Select thread fasteners with anti-loosening functions, such as self-locking nuts, spring washers, nylon insert nuts, etc., which can effectively enhance the stability of the connection. In addition, selecting appropriate materials and strength grades according to the working conditions of the connection parts is also an important premise for preventing loosening.



2. Control the tightening torque

Use torque wrenches or tensioning tools to precisely control the tightening torque according to design requirements, ensuring that bolts obtain sufficient pre-tension. The greater the pre-tension, the higher the friction between the connection surfaces, and the less likely it is to loosen.



3. Adopt multi-point symmetrical tightening method

For flange connections or multi-bolt structural connections, the principle of 'diagonal, phased, and symmetrical tightening' should be followed to ensure that each bolt is subjected to uniform force, and to improve the overall stability of the connection.



4. Use anti-loosening glue or coating agent

In some high-vibration or high-precision applications, thread locking adhesive (such as anaerobic adhesive) can be applied to the thread surface to enhance the friction and sealing between threads through curing, effectively preventing loosening.



5. Regular inspection and maintenance

Establish a regular inspection system, especially in the early stage of equipment use and during operation, to promptly find and retighten bolts that may loosen. Equipment operating in harsh environments such as high temperature and vibration should strengthen regular inspections even more.



6. Mechanical anti-loosening measures

If using mechanical structures such as open-ended set screws, locking washers, and locking plates, physically lock bolts or nuts to prevent them from rotating autonomously due to vibration and other reasons.



Three, Conclusion



In summary, although bolt connections are structurally simple, they are of great importance in practical applications. The key to preventing bolt loosening lies in the combination of scientific design, standardized installation, and regular maintenance. Only by paying attention to the safety of bolt connections from the source and taking effective anti-loosening measures can the stability and safety of equipment operation be guaranteed, and economic losses and safety hazards caused by connection failure can be reduced. Summarizing experience in engineering practice and optimizing connection plans is the fundamental way to improve equipment reliability.