The main reasons for the failure of locking nuts to prevent loosening include the following:
Insufficient or excessive preload: Insufficient preload may cause the threaded connection to be unable to withstand the workload and easily loosen; while excessive preload may cause damage or deformation of the thread, which will also cause loosening.
Vibration and shock: Vibration and shock to the equipment during operation can cause threaded connections to loosen.
Corrosion: Chemical substances or moisture in the environment can cause corrosion at the threaded connection, reduce friction, and cause loosening.
Thread quality problems: Imprecise thread processing or defects (such as thread damage, chips or burrs) can cause loose connections.
Temperature changes: Changes in temperature can cause materials to expand or contract, affecting the tightening state of threaded connections.
Insufficient lubrication: Lack of proper lubrication can lead to increased friction, which can cause threaded connections to loosen.
Manufacturing problems: Improper raw material selection or insufficient production processes (such as imprecise thread cutting or inadequate heat treatment) can affect the performance of locking nuts.
Improper use: Improper operation during installation and use (such as excessive force or insufficient tightening force) can cause the nut to be damaged or loose.
Environmental factors: Corrosion, humidity changes, extreme temperatures, etc. can cause irreversible damage to fasteners.
Specific manifestations and effects of locking nut anti-loosening failure include:
Loosening: Loosening of threaded connections is usually manifested as relative sliding between bolts and nuts, resulting in a decrease in clamping force and inability to serve reliably.
Plastic deformation of materials: In the early loosening stage, plastic deformation of materials is one of the main reasons, such as uneven contact surfaces and material yielding caused by excessive local stress.
Preload attenuation: During the loosening process, the axial clamping force of the threaded connection continues to decrease, resulting in loose connections.
Vibration and noise: Loosening can cause parts to loosen, make abnormal noises, fall off and be damaged, and even endanger personal safety.
Performance degradation: Loose bolts cannot offset the effects of axial tensile force and radial shear force, resulting in fatigue of connected parts, and eventually plastic deformation and loosening. Measures to prevent locking nut anti-loosening failure include: Select high-quality materials and strict quality control: Use high-quality materials and strictly control the production process to avoid failure caused by material or process problems. Standard operation: Ensure that the installation and use process are operated in accordance with the specifications to avoid excessive force or insufficient tightening force. Environmental adaptability design: Fully consider environmental factors during the design stage and select suitable materials and treatment methods, such as anti-corrosion treatment or avoid extreme climate areas. Regular inspection and maintenance: Regularly inspect and maintain the status of fasteners to detect and solve potential problems in a timely manner.
