Advantage of High Strength Structure Bolts
High strength structure bolts
High strength structure bolts can be called high strength bolts. High strength bolts are mostly used to connect bridges, rails, high-pressure and ultra-high-pressure equipment. The fracture of these bolts is brittle fracture. High strength bolts are used in ultra-high pressure equipment. Bolts, in order to ensure the sealing of containers, need to apply larger prestressing force on several concepts of high-strength bolts. 1. According to the stipulated performance grade of bolts above 8.8 level, they are called high-strength bolts. Currently, the national standard only lists M39. For large size specifications, especially high-strength bolts whose length is more than 10-15 times, they are outer six. Angle bolt high strength T-grooved bolt.
Advantages
High-strength bolt connection has many advantages, such as simple construction, good mechanical performance, removable, fatigue resistance, and no loosening under dynamic load. It is a promising connection method. High strength bolt is a special wrench to tighten the nut, so that the bolt produces a huge and controlled pre-tension, through the nut and cushion plate, the same size of pre-pressure is produced on the connecting parts. Under the action of pre-pressure, there will be greater friction along the surface of the connector. Obviously, as long as the axial force is less than this friction, the component will not slip and the connection will not be destroyed. This is the principle of high strength bolt connection. High-strength bolt connection is based on the friction between the contact surfaces of the connectors to prevent them from sliding. In order to make the contact surface have enough friction, it is necessary to increase the clamping force of the components and the friction coefficient of the components’contact surface. The clamping force between components is achieved by applying pre-tension force to bolts, so bolts must be made of high strength steel. In high strength bolted connections, the magnitude of friction coefficient has a great influence on the bearing capacity. The test 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, sand blasting and wire brush cleaning are often used to treat the contact surface of components within the connection area. There are actually two types of high strength structure bolts: friction type and compression type. The criterion of bearing shear force for friction type high strength bolts is that the shear force caused by design load does not exceed the friction force.
Relevant problem
What are high strength bolts designed for?
Bolts are usually designed on the basis of direct tensile stress with a large factor of safety. The initial tension in the bolt may be estimated by an empirical relation P 1 = 284 d kN, where the nominal bolt diameter d is given in mm. The relation is used for making the joint leak proof.
