Ultrasonic pre-tightening force measuring method for bolt made of low-elasticity-modulus material

Abstract

The invention discloses an ultrasonic pre-tightening force measuring method for a bolt made of a low-elasticity-modulus material, and belongs to the technical field of ultrasonic nondestructive testing. The method comprises the following steps of: selecting a calibration bolt; in a zero-stress state, measuring the calibration bolt through ultrasonic waves to obtain a reference waveform; under different stress states, measuring the calibration bolt through ultrasonic waves to obtain calibration data; fitting a low-elastic-modulus bolt pre-tightening force formula by using calibration data through a least square method to obtain a bolt pre-tightening force coefficient; measuring a to-be-measured bolt through ultrasonic waves to obtain a measurement waveform; performing noise reduction processing on the measurement waveform, and performing calculation by using a time delay algorithm to obtain ultrasonic time delay between the measurement waveform and the reference waveform; and substituting the ultrasonic time delay between the measurement waveform and the reference waveform into the low-elastic-modulus bolt pre-tightening force formula for calculation to obtain the pre-tightening force of the to-be-measured bolt. By adopting the method to measure the pre-tightening force of a bolt made of a low-elasticity-modulus material, the measurement precision can be effectively improved.

Description

technical field [0001] The invention relates to a method for measuring ultrasonic pretightening force of bolts made of low elastic modulus material, and belongs to the technical field of ultrasonic nondestructive testing. Background technique [0002] As an important connection method in engineering production, bolt connection has the advantages of simple structure, convenient loading and unloading, high efficiency, and low cost. It is widely used in important equipment such as aerospace, traffic bridges, building structures, and chemical products. [0003] In actual engineering construction, inappropriate bolt pretightening force will damage the quality of the bolt connection pair, and directly affect the integrity and reliability of the equipment. Therefore, accurate, intuitive and convenient measurement of bolt pretension plays a vital role in its wide application in the industrial field. The traditional bolt pretightening force measurement methods include torque wrench ...

AI Technical Summary

Problems solved by technology

However, for bolts with low elastic modulus, due to their small elastic modulus, the elongation of the bolts is much larger than that of carbon steel or stainless steel bolts under the same pre-tightening force. The change of the ultrasonic propagation time will increase with the increase of the bolt elongation, which leads to the fact that the acoustic elastic effect cannot be ignored when the bolt pretightening force of the low elastic modulus material is measured by the ultrasonic method, making the ultrasonic propagation time and the bolt pretension Tight force is no longer a simple proportional relationship

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