The stress degree of the torsional shear bolt
The stress degree of the torsional shear bolt
High strength torsion shear bolts apply pre tension and friction force to transfer external force. The common torsional shear bolts are connected by the shear of the bolt rod and the pressure of the hole wall to transfer the shear force, and when the screw cap is tightened, the pretension is very small, and the influence can be ignored. But the high strength torsion shear bolt, in addition to its high material strength, also exerts a great pretension to the torsion shear bolt, so that the extrusion pressure is produced between the connecting members, thus making the vertical screw perpendicular to the screw. The direction of the rod has great friction, and the pre tension, anti slip coefficient and type of steel directly affect the bearing capacity of the high strength torsion shear bolt. According to the force characteristics, they are divided into pressure bearing type and friction type.
The minimum specification M12 for high strength torsion shear bolts is commonly used for M16~M30. The performance of the large size torsion shear bolts is unstable and should be carefully used in the design. The difference between the friction type and the pressure type connection of the high strength torsion shear bolt: the high strength torsion shear bolt connection is clamped by the large tightening pretension within the torsional shears, which can produce large friction force, thus improving the integrity and stiffness of the connection, when the shear force is different, according to the design and the force requirements. It can be divided into two kinds of high strength torsional shear bolt friction connection and high strength torsional shear bolt bearing type connection. The essential difference between them is that the limit state is different. Although it is the same kind of torsional shear bolt, it is very different in the calculation method, the requirement, the scope of application and so on.
In the shear design, the frictional connection of the high-strength torsion shear bolt is the maximum possible friction force provided by the external shear force to the contact surface of the plate, which is provided by the torsional shear bolt tightening force, which is to ensure that the shear force is not more than the maximum friction force during the whole operation. The relative slip deformation will not occur between the plates (the original gap between the screw and the hole wall is always maintained), and the connecting plates will be stressed according to the elastic whole. In the shear design, the shear strength of the high strength torsion shear bolt allows the external shear to exceed the maximum friction force, and the relative slip deformation occurs between the connecting plates until the torsional shear bolt contacts with the hole wall, and then the connection depends on the shear of the torsional shear bolt body and the pressure of the hole wall and the friction force between the contact surfaces of the plate. Finally, the shear stress state is taken as the ultimate state of shear connection. In short, the friction type high strength torsion shear bolts and the bearing high strength torsion shear bolts are actually the same kind of torsion bolts, but only whether they consider slippage.
The friction type high strength bolt can not slide, the bolt does not bear the shear, once the slip, the design is considered to be damaged state, the technology is more mature; the pressure type high strength bolt can slide, the bolt also bears the shear, and the final damage is equivalent to the failure of the ordinary bolt (bolt shear broken or plate crushed).
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