Once the bolt connection in mechanical equipment is loose, it will cause the bolt to fall off, resulting in major safety hazards, or the bolt loosening preload will decrease, resulting in a significant shortening of the fatigue life of the bolt connection. Therefore, appropriate anti-loosening measures should be selected in the design to ensure that the bolts do not loosen in actual use.
The following are some commonly used anti-loosening measures in design:
1. Double nut anti-loosening Double nut anti-loosening is also called top nut anti-loosening. When two top nuts are tightened, there is always mutual pressure between the two top nuts. If any of the two nuts wants to rotate, it needs to overcome the friction between the screw threads. Even if the external load changes, the pressure between the top nuts always exists, so it can play a role in loosening.
2. Self-locking nuts
Self-locking nuts generally rely on friction. The principle is that the embossed teeth are pressed into the preset holes of the sheet metal. Generally, the aperture of the preset hole is slightly smaller than that of the rivet nut. The nut is connected to the locking mechanism. When the nut is tightened, the locking mechanism locks the bolt thread. Embedded nylon self-locking nut
Deformed thread lock nut
Two-in-one wedge and hammer for nuts
Wedge action locknut
3. Thread locking adhesive Thread locking adhesive is an adhesive composed of (meth) acrylate, initiator, accelerator, stabilizer (inhibitor), dye and filler in a certain proportion.
4. After tightening the split pin nut, insert the split pin into the nut slot and the bolt tail hole, and pull the split pin tail apart to prevent the nut and bolt from rotating relative to each other.
5. Slotted nuts Slotted nuts are used in conjunction with screw hole bolts and cotter pins to prevent relative rotation between the bolt and nut.
6. Series steel wire anti-loosening Series steel wire anti-loosening is to insert the steel wire into the hole of the bolt head, connect the bolts in series, and play a role of mutual restraint. This anti-loosening method is very reliable, but it is more troublesome to disassemble.
7. Pre-tightened high-strength bolt connections generally do not require additional anti-loosening measures, because high-strength bolts generally require a relatively large pre-tightening force. Such a large pre-tightening force creates a strong pressure between the nut and the connected part. This pressure will produce a friction torque that prevents the nut from rotating, so the nut will not loosen.
8. After tightening the stop washer nut, bend the single-ear or double-ear stop washer against the side of the nut and the connector respectively to lock the nut. If two bolts need to be double-locked, double brake washers can be used to brake the two nuts against each other.
9. Spring washers Open spring washers
Conical spring washer
10. Double stack self-locking washers
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