Research On Bolt Stress Measurement Method Based On Ultrasonic Elastic Effect

In recent years,with the development of ultrasonic technology,ultrasonic detection technology has become a very important part in the field of acoustic image reconstruction,which is widely used in medical acoustic image reconstruction,military sonar positioning and other fields.The bolt stress detection system based on ultrasonic elastic effect has the characteristics of accurate and efficient measurement,convenient operation and low hardware cost.Based on Ultrasonic Elastic Effect and high precision time measurement technology,an intelligent measurement system for bolt stress is developed,which can be used to measure bolt stress in railway bridges,industrial and civil buildings,ships and aerospace fields.Its core content includes three aspects: firstly,ultrasonic echo signal is generated based on piezoelectric effect.Its design goal is to apply high-voltage pulse signal to piezoelectric ceramics through digital pulse excitation circuit to realize the mutual conversion between electric energy and mechanical energy,and form regular ultrasonic echo signal through multiple rebound of mechanical wave;The second is the accurate measurement of flight time.The high-precision digital time chip is used to capture the time of flight(TOF)accurately,and the temperature compensation algorithm based on arm is designed to remove the noise caused by the ambient temperature change during the measurement,so as to further improve the signal-to-noise ratio of TOF and improve the accuracy of sound time calculation;The third is the bolt stress calibration experiment.Based on the piezoelectric effect principle of PZT piezoelectric ceramics,the intelligent bolt is developed,and the bolt TOF stress calibration experiment platform is built.Through the calibration experiment,the functional relationship between the bolt stress and its internal propagation TOF is determined.The results of pilot test show that the intelligent measurement system of bolt stress adopts the point contact measurement method,and the whole measurement process is completed in 1 s.The TOF measurement resolution of bolts of different materials and diameters is within 19 PS,and the stress detection resolution is 0.063 MPa.For the same bolt,the repeatability measurement error can be stabilized within0.14 ?,It can fully meet the measurement requirements of most adhesive intelligent bolts at this stage.