Two methods of bolt production stress tightening

1. Only axial stress is generated in the bolt product

Belonging to this method, one end of a tension bolt uses its reaction force to squeeze and deform the bushing ring equivalent to a nut to fix it, or it refers to the method of inserting a heated bolt and using its cooling shrinkage to introduce In terms of bolt axial force and other methods. Or you can also consider tensioning the bolt thread head, input most of the bolt axial force, and then screw the nut back a little bit. The commonly used method is to rotate the nut to tighten the bolt with the thread. Not only the axial stress is generated on the bolt, but also the shear stress is generated due to the inversion. When using this method to judge the bolt axial force, there is a certain relationship between the torque added to the nut and the pulling force of the introduced bolt, so the method of judging its axial force is called the torque control method or torque method for short. (Guide: The advantages of aluminum alloy fasteners)

2. The method of judging the tension of the bolt by the amount of extension produced on the bolt

Although this can be quite accurate in the laboratory to measure the extension of the bolt, but from the on-site construction, the rotation of the nut is used to judge. This method is called the nut rotation method (referred to as the angle method).

Although the stress generated on the bolt has a high stress concentration under the bolt head with a large change in the shape of the bolt to the shaft and the threaded part, when determining the size of the lower part of the bolt head, it is generally applied to static load and repeated load It is safer than the threaded part, so the stress state during tightening mainly lies in the threaded part.

More related hardware stamping parts industry news: