Method for controlling pre-tightening force of bolt based on axial force and elongation

Abstract

The invention relates to a method for controlling the pre-tightening force of a bolt based on axial force and elongation. The method comprises the steps that when the bolt is tightened for the first time, the acoustic time difference of the bolt in the free state and the tightened state is measured through ultrasonic waves, the elongation of the bolt is calculated based on the acoustic time difference, and the pre-tightening force of the bolt is obtained according to the elongation so that the pre-tightening force of the bolt can be accurately controlled; for an in-service bolt, based on the linear relation between the propagation time of ultrasonic transverse waves and longitudinal waves in the bolt and the axial stress of the bolt, the residual pre-tightening force of the bolt is obtained so as to determine whether the in-service bolt needs to be re-screwed or not. The pre-tightening force of the bolt and the residual pre-tightening force of the in-service bolt during first-time fastening can be accurately measured, and the purpose of accurately controlling the pre-tightening force of the bolt is achieved.

Description

technical field [0001] The invention belongs to the technical field of wind power, and in particular relates to a method for controlling the pretightening force of bolts based on axial force and elongation. Background technique [0002] Bolted flange connection is a detachable static sealing connection structure widely used in wind power generation, pressure vessels, petrochemical equipment and pipelines. The main failure mode of the flange bolt connection system is leakage, and bolt preload is one of the important links to ensure that the connection surface does not leak. In the bolt connection, the bolt must be tightened during installation, that is, before the connection bears the working load, it is pre-acted by force. This pre-loaded force is called pre-tightening force. The purpose of pre-tightening is to enhance the reliability of the connection. and tightness to prevent gaps or relative slippage between the connected parts after loading. Therefore, in the flange bo...

AI Technical Summary

Problems solved by technology

Among them, the bolt pre-tightening force is insufficient, resulting in loose bolts, excessive vibration of parts or equipment, and shear fracture of bolts under long-term service, resulting in a large proportion of major accidents.

The reason, first, is that the quality of the bolt itself is not good enough, and there are problems in the design and manufacturing process; secondly, the pre-tightening force of the bolt is insufficient during the installation and maintenance process, and the vibration caused by the operation process

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