High strength bolts are used in high strength bolts, the strength grade (after heat treatment) is 10, and the use of 10.9 grade bolts.
The mechanical properties and calculation methods of high-strength bolts and ordinary bolts are different. The force of high strength bolt is firstly by exerting pre tension P in its interior, and then the frictional resistance produced on the contact surface between the joints to bear the external load, while the ordinary bolt is directly subjected to the external load.
High strength bolt connection has the advantages of good mechanical performance, simple construction, removable and fatigue resistance, and it is a very advantageous connection method.
The high strength bolt is a special wrench to tighten the nut, which makes the bolt produce huge pretension and easy to be controlled, and the same size pre stress is produced by the nut and the backing plate. In the pre pressure, obviously along the surface of the connecting parts will produce more friction, as long as the axial force is less than the friction member will not slip, connection will not be destroyed, which is the principle of high strength bolt connection.
High strength bolt connection is the frictional force on the contact surface between the connecting piece to prevent the sliding between the contact surface, as there is enough friction, we must improve the clamping force component and the friction coefficient of components. The clamping force between the components is realized by applying pretension to the bolts, so bolts must be made of high strength steel, which is called the high strength bolt connection.
In the high strength bolt connection, the friction coefficient has great influence on the bearing capacity. The experimental results show that the friction coefficient is mainly affected by the form of the contact surface and the material of the component. In order to increase the friction coefficient of the contact surface, sandblasting and steel brush cleaning are often used to deal with the contact surface of the joint.