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The importance and working principle of fasteners

The importance and working principle of fasteners

2020-08-04

The importance and working principle of fasteners

Fasteners are widely used and occupy an extremely important position in the automotive industry! On a car, an average of about 500 types/50Kg/4000 fasteners per car; and a heavy-duty vehicle requires various types of fasteners There are more than 88Kg/7100 pieces, of which high-strength fasteners account for about 1/3. The cost of fasteners on a car accounts for about 2.5% of the cost of the whole car, 40% of the total number of basic parts of the whole car, and the workload of fastening and connecting on the assembly line accounts for about 70%!

1. The importance of fasteners

If the force is too small, the washer may not be in place; if the force is too much, the thread will be worn. According to recently published data, 23% of maintenance problems in the automotive industry are caused by loose fasteners, and 12% of new cars have incorrect fastener tightness. Bolts are one of the most important factors that determine the quality of assembly. The failure of threaded fasteners to reach the corresponding capacity is an important cause of assembly accidents!

2. The principle of tightening fastener bolts

The bolt connection must be able to resist external force, so that the assembled parts will not move in the direction of separation, otherwise it will cause the bolt joint to loosen, damage or fall off.

Therefore, we design the minimum clamping force of the bolt to prevent the clamping part from being separated due to external force, and to maintain friction clamping or ensure sealing, etc.

The bolt is inserted into the connected part, and the bolt is stretched and deformed by tightening the nut or internal thread. This elastic deformation produces an axial pulling force that squeezes the clamped parts together, which is called pre-tightening force.

In theory, as long as sufficient clamping force is generated, the clamped parts can be guaranteed to work safely in harsh environments such as vibration, high and low temperatures, without using auxiliary methods such as glue coating.

3. Clamping force of fasteners

The only purpose of the tightening procedure is to maintain the clamping force within the corresponding tolerance range!

During assembly, the clamping force must be large enough to ensure that the assembled parts will never move relative to each other. But at the same time, it must be ensured that the clamping force applied during tightening does not cause damage or plastic deformation of the bolt.

Clamping force control is the core purpose of bolt assembly. Improper clamping force control will cause serious consequences.

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