What Are The Consequences Of Inappropriate Preload For Threaded Fasteners?
The preloading force of the threaded fastener connection is the force acting on the threaded fastener connection before it is subjected to the working load. Proper preload is an important prerequisite to enhance the reliability and tightness of the fastener connection. If the pre-tightening force does not reach the specified requirements, there will be gaps or relative slippage between the connected parts after loading, resulting in the loosening of fasteners, or even making the whole machine unable to work normally. If the preload is too large, it will cause artificial parts damage. For example, if the pre-tightening force at the O-ring seal is too large, it will crush the O-ring and make the seal fail.
Improper preload of threaded fasteners will bring bad consequences. As a professional fastener manufacturer, Xinchi Fastener Company will introduce the following three situations for you.
Static failure of threaded fastener joints
If the threaded fasteners are screwed too tightly, that is, the pre-tightening force is too large, it will cause artificial parts damage. The bolt may be broken, the coupling may be crushed, seized, twisted, or broken, or the thread tooth may be cut and fall out.
Slippage and separation of connected parts, Or the loosening of fasteners
For the ordinary bolt connection bearing transverse load, the preloading force generates positive pressure between the connected parts, which relies on friction to resist external load, so the preloading force determines its bearing capacity. If the pretightening force is insufficient, the connected part will slip, resulting in dislocation, skew, and wrinkle, and the bolt may be cut. For the bolt connection subjected to axial load, the preload makes the joint surface produce compression force, and the remaining preload after the external load is the compression force when the joint surface is working. If the preload is insufficient, it will lead to the loosening of the joint surface, and even lead to the serious consequences of the separation of the two connected parts. At the same time, insufficient preload will also cause strong transverse vibration, resulting in nut loosening and other phenomena.
Bolt fatigue failure
Improper preload will cause the bolt to fail due to fatigue in most cases. Although reducing the preload can reduce the average value of the total cyclic load on the bolt, it increases the load amplitude, so the overall effect is mostly to reduce the fatigue life of the bolt, resulting in fatigue failure.
Therefore, the range of preload must be determined in the assembly process. Xinchi fastener Company suggests that a scientific and reasonable range of pretightening torque should be determined according to the comprehensive consideration of the importance, force, motion, structural characteristics, thread specifications, and grades, materials of the connected parts, and the purpose of connection. During assembly, the torque requirements stipulated by the process should be strictly observed. Only in this way can we really improve the reliability of the threaded connection and the fatigue strength of the connection.
Xinchi Fastener Company is a trustworthy fastener company, especially in furniture nuts. And we are the designated fastener supplier to“STAPLE”. As a trusted fastener supplier, Xinchi Fastener Company can offer a wide range of high-quality fasteners, including tee nuts, screws, bolts, rivets, washers, etc. If you want to know more about fasteners or want to wholesale fasteners, please feel free to contact us. And then our experienced and expert service team will reply to you as soon as possible.