To have sufficient pre-tightening force, the tightening mechanism of the bolt can be obtained by converting the torque applied to the bolt. The pre-tightening force causes the bolt to generate tensile stress, and at the same time, the coupled member generates compressive stress for fastening purposes. The bolt stiffness is C1, the tensile deformation is δ1, the stiffness of the joint is C2, the compression deformation is δ2, the tensile force and compression force of the bolt are equal to F1, and the bolt is combined with the force deformation diagram of the coupled part. Together, F1 is the preload.
The pre-tightening force is set by the fastener to set the pre-tightening force to ensure that the screen box and the steel frame are always in a safely closed state under any working condition. The preload force is determined by the force state described in the previous section. It should allow the fastener to reliably withstand the maximum inertia pulling force and reliably transmit the lateral maximum inertial friction shear force by means of the tightening friction. And leave enough safety margins. In the case of flat screen work, the maximum inertia pulling force of the joint bolt to withstand the screen box is equal to the maximum inertia friction shear force. However, for the bolt force, the latter is much larger than the former, because the friction shear force is tangent to the pre-tightening force, and it is necessary to find the equivalent pre-tightening force that matches the friction shear force.
Long bolt connection Our factory is still producing flat-shaped steel pipe structure flat screen, screen box-steel frame connecting fasteners, bolts crossing the upper and lower beams between the screen box and the steel frame and the width of the two special-shaped steel pipes, so that the bolts are doubled. Growth, fatigue resistance is greatly improved, and the number of bolts is large, so that the bolt stress level is significantly reduced. Therefore, the low-carbon steel ordinary bolts used in the early stage have also met the work requirements.
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