Research On The Application Of Bolt Stress Detection Based On The Ultrasonic Measurement Technology

As an important connector in engineering application,bolts are widely used in bridge construction,aerospace,nuclear chemical industry,new energy and other industrial fields,which act as a connection,positioning and sealing,etc.When the applied load is large,the high-strength bolt is mainly used,and the prestressing force applied on the high-strength bolt directly affects the performance,life and safety of the connection.Therefore,it is great significance to taking effective methods to detect the prestress of high-strength bolts in practical engineering application and judge their connection state.Different from ordinary bolts,high-strength bolts were generally used for permanent connection,and conventional bolt stress detection methods have obvious limitations.In view of this problem,this paper selects the high-strength bolts of wind turbine as the experimental research object based on the relevant principles of ultrasonic technology,and the main research contents are as follows:1.This paper introduces the importance of bolt stress detection in practical engineering application,compares their advantages and disadvantages in bolt stress detection with the current conventional bolt stress detection methods,emphasizes on the principle and application prospect of ultrasonic technology in bolt stress detection,and summarized the relevant theoretical development and equipment development situation at home and abroad through reviewing a large number of documents,2.Beginning with the definition and propagation characteristics of ultrasound,combined with the classical solid acoustics and acoustic elastic effect,the relationship between the propagation velocity of ultrasonic waves and the stress in different modes was deduced by combining the classical solid acoustics and the harmonic elastic effect,and their sensitivity to stress was compared.Based on the theory of acoustic elasticity,it was established the relationship between ultrasonic wave velocity and bolt stress.Combined with the practical engineering application,factors such as bolt material coefficient,temperature effect and uneven stress distribution are considered and the calculation formula is modified,and the function relationship between the accurate calculation of bolt stress and ultrasonic transit time was finally obtained by combining the linear and nonlinear angles.3.According to the acceptance and emission form of ultrasonic signal,the characteristics of ultrasonic transducer are analyzed in detail.Combined with the design principle of piezoelectric transducer,a piezoelectric transducer suitable for bolt stress detection was designed and studied.According to the coupling characteristics of ultrasonic transducer,a gel based coupling for ultrasonic testing of high-strength bolts was selected through engineering application and experimental comparison.4.The physical field acoustic analysis of the designed piezoelectric transducer was carried out by using COMSOL finite element simulation software,the finite element model of ultrasonic propagation in solid was established,the function of ultrasonic excitation signal was determined,and the process of transmitting and receiving the signal of the self transmitting and self receiving piezoelectric transducer is simulated based on the coupled physical field,and the normalized amplitude and the signal diagram of transmitting sound are obtained.An experimental platform for stress detection of high-strength bolts of yaw brake was built based on ultrasonic technology,the experimental results show that the detection data show a linear relationship consistent with the theoretical analysis,and the ultrasonic detection error of high-strength bolts of yaw brake is less than 10 MPa,which can meet the practical engineering application.