Nut and method for accurately controlling pretightening force of bolt

Abstract

The invention discloses a nut and a method for accurately controlling pretightening force of a bolt. The nut is composed of an inner nut sleeve and an outer nut, the inner nut sleeve is provided withan inner thread and an outer thread, the outer nut is provided with an inner thread, the inner thread of the inner nut sleeve and the bolt form a threaded pair, the outer thread of the inner nut sleeve is opposite to the inner thread of the inner nut sleeve, and the outer nut and the inner nut sleeve form a threaded pair. The method for accurately controlling the pretightening force of the bolt sequentially comprises the following steps that 1, the combined nut is screwed to the bolt on a connected workpiece, and the bolt is stretched by a bolt stretcher according to the set pretightening force; 2, the combined nut is screwed, the upper end of the inner nut sleeve abuts against the lower end face of a stretching nut of the bolt stretcher, and the lower end face of the outer nut abuts against the surface of the workpiece; and 3, the bolt stretcher is disassembled, and the stretching nut is separated from the bolt. Therefore, the nut is simple in structure, and the method has the advantages that accurate control over the pretightening force of the bolt can be completed, few operation steps are needed, and the technology is simple.

Description

technical field [0001] The invention belongs to the technical field of bolt connection, and relates to a nut and a method for controlling the pretightening force of bolts. Background technique [0002] Bolted connection is a widely used detachable fixed connection. In some occasions with high assembly quality requirements, such as petrochemical, nuclear power, aerospace and other fields, bolted connection must be reliable, so it is necessary to accurately control the axial direction of the bolt. Preload, that is, axial tensile force. To achieve this goal, there are currently the following control methods: 1. Direct torque control method, 2. Torque control + rotation angle monitoring method, 3. Rotation angle control + torque monitoring method, 4. Yield point control method (slope control method or elastic limit method), 5. Bolt length method (elongation control method), 6. Bolt tensioner stretching method. [0003] The above method 1 is based on the relationship between th...

AI Technical Summary

Problems solved by technology

This method always has such a situation that there is a gap a between the fixed position of the nut and the tension nut of the bolt tensioner, see figure 1 , when the bolt tensioner releases the bolt, the deformation energy of the bolt a segment disappears freely, resulting in the pretightening force of the final fastening section of the bolt not equal to the pretightening force given by the bolt tensioner to the whole bolt

Due to the existence of the gap a, its size is random, so the current bolt tensioner does not involve the control accuracy of the bolt pretightening force.

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