What are the preload control methods of metal fasteners and their influence mechanisms on the overall performance of the connection structure?
Publish Time: 2024-08-15
Metal fasteners play a key role in various connection structures, and the control of preload is an important factor to ensure their performance.
There are various methods to control preload. The most common one is the torque method, which is to apply a certain torque through a torque wrench to achieve the expected preload. However, this method is affected by factors such as the friction coefficient, and its accuracy is limited. Another method is the stretching method, which directly stretches the fastener to accurately control the elongation to achieve accurate preload. There is also the angle method, which controls the preload by measuring the rotation angle of the nut or bolt.
The preload has a significant impact on the overall performance of the connection structure. Appropriate preload can increase the stiffness of the connection structure, reduce the relative sliding and loosening between the connection parts, and improve the stability and reliability of the structure. For example, in a mechanical transmission system, insufficient preload of the fastening bolts may cause loose fit between components, generate vibration and noise, and affect transmission accuracy and efficiency. On the contrary, if the preload is too large, it may cause excessive deformation or even breakage of the fastener. At the same time, it may also cause the connector to be subjected to excessive pressure, causing local yielding and fatigue cracks, and reducing the service life of the structure.
In some connections that require sealing, such as the head connection of a pressure vessel, insufficient preload will lead to seal failure, while excessive preload may damage the sealing element. In addition, uneven preload distribution will lead to uneven stress distribution inside the connection structure, which is easy to cause failure in the stress concentration area. In order to achieve the best connection performance, it is necessary to select a suitable preload control method according to the specific connection structure and working conditions, and determine the optimal preload range through precise calculation and experimental verification.
In short, preload control of metal fasteners is a complex and critical task. A deep understanding of its control method and the mechanism of influence on the performance of the connection structure is of great significance to ensure the safe and reliable operation of engineering structures.
