Under What Circumstances Are High Strength Bolts Used

  It is used in high-strength bolt pairs. The strength grade (after heat treatment) is grade 10, which is used with grade 10.9 bolts.

  the mechanical properties and calculation methods of ordinary bolts and high-strength bolts are different. The stress of high-strength bolts is first applied by pre tension P inside them, and then generate friction resistance on the contact surface between the connected parts to bear the external load, while ordinary bolts directly bear the external load.

   high strength bolt connection has the advantages of simple construction, good mechanical performance, detachable and replaceable, fatigue resistance and no loosening under dynamic load. It is a promising connection method.

   high strength bolts use a special wrench to tighten the nut, so that the bolt produces a huge and controlled pre tension, and the same pre pressure is generated on the connected parts through the nut and base plate. Under the action of preload, a large friction force will be generated along the surface of the connected part. Obviously, as long as the axial force is less than this friction force, the component will not slip and the connection will not be damaged. This is the principle of high-strength bolt connection.

   high strength bolt connection relies on the friction between the contact surfaces of the connector to prevent them from sliding. In order to make the contact surface have sufficient friction, it is necessary to improve the clamping force of the component and increase the friction coefficient of the contact surface of the component. The clamping force between components is realized by applying pretension to the bolt, so the bolt must be made of high-strength steel, which is called high-strength bolt connection.

   in high-strength bolt connection, the size of friction coefficient has a great impact on the bearing capacity. The test shows that the friction coefficient is mainly affected by the form of contact surface and the material of components. In order to increase the friction coefficient of the contact surface, the contact surface of components within the connection range shall be treated by sand blasting and wire brush cleaning.

   there are actually two types of high-strength bolts: friction type and pressure bearing type.

   the criterion for bearing shear force of friction type high-strength bolts is that the shear force caused by design load does not exceed the friction force.

   the design criterion of pressure bearing high-strength bolts is that the rod body is not sheared or the plate is not crushed.