What does the bolt do?
The mechanical properties and calculation methods of ordinary bolts and high-strength rivet nuts are different. The high-strength rivet nut is first subjected to pre-tension in its interior, and then generates frictional resistance on the contact surface between the connected parts to bear the external load, while ordinary bolts directly bear the external load.
The high-strength rivet nut connection has the advantages of simple construction, good stress performance, removable, fatigue resistance, and no loosening under dynamic load, which is a promising connection method.
In high-strength bolt connections, the friction coefficient has a great influence on the bearing capacity. Tests 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, methods such as sandblasting and wire brush cleaning are often used to deal with the contact surface of the components in the connection range during construction.
High-strength rivet nut connection is to prevent mutual sliding between the contact surfaces of the connecting parts. In order to make the contact surface have sufficient friction force, it is necessary to increase the clamping force of the component and increase the friction coefficient of the contact surface of the component . The clamping force between the components is achieved by applying a pre-tension to the bolt, so the bolt must be made of high-strength steel, which is why it is called a high-strength bolt connection.
The high-strength rivet nut is used to tighten the nut with a special wrench to make the bolt generate a huge and controlled pre-tension. The nut and the backing plate also generate the same amount of pre-pressure on the connected parts. Under the effect of pre-pressure, a large frictional force will be generated along the surface of the connected parts. Obviously, as long as the axial force is less than this frictional force, the member will not slip and the connection will not be damaged. Principle.
There are actually two types of high-strength rivet nuts: friction type and pressure type. The criterion for friction type high-strength bolts to bear the shear force is that the shear force caused by the design load does not exceed the friction force. Pressure-bearing high-strength bolts are based on the design criteria that the shaft is not sheared or the plate is not crushed. In addition, high-strength bolts cannot be reused.