What are the causes of high strength bolt cracking

Stainless steel bolts, high-strength bolts and general bolts will occasionally appear cracking. Today, we will talk about the cracking causes of high-strength bolts? The looseness of threaded fasteners is not due to the fatigue strength of bolts
The threaded fastener can only be loosened 100 times in transverse oscillation test and 1 million times in fatigue strength test. In other words, the threaded fastener is loose when one tenth of its fatigue strength is applied. We only use one thousandth of its large capacity, so the loosening of threaded fasteners is not due to the fatigue strength of bolts.
The real reason for the damage of threaded fasteners is looseness
After the screw fastener is loose, a huge kinetic energy MV2 occurs. This huge kinetic energy directly acts on the fastener and the equipment, resulting in the fastener damage. After the fastener is damaged, the equipment can not work in the normal state, which further leads to the equipment damage.

For fasteners under axial force, the thread is damaged and the bolt is broken.
For fasteners subjected to radial force, the bolt is sheared and the bolt hole is made into ellipse.
The key to solve the problem is to select a thread locking method with excellent anti loosing effect
At present, the most advanced and the best anti loosing method is the large screw thread fastener locking method.
The large hairpin thread has the characteristics of left-handed and right-handed threads. It can cooperate with both left-hand thread and right-hand thread.
Two kinds of nuts with different rotation direction are used in connection. The nut on the working bearing surface is called the fastening nut, and the A194 nut on the non bearing surface is called the lock nut. When using, the fastening nut shall be pre tightened, and then the locking nut shall be pre tightened.
Under the condition of vibration and impact, the fastening nut tends to be loose. However, since the loosening direction of the fastening nut is the tightening direction of the lock nut, tightening the lock nut only avoids tightening the fastening nut. The fastening nut should not be loose.
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