Research On Ultrasonic Stress Detection Technology Of Steel Structure Based On Multiple Sampling Rate

In people's long-term practice of using various materials,there are a lot of material damage phenomena,which bring people a lot of catastrophic accidents.In many cases,the failure of these materials is closely related to the residual stress and the loading stress on the components made from it,so it is necessary to measure the stress on the components.Based on the acoustic elastic theory of ultrasonic surface wave,this paper studies the relationship between the propagation characteristics of ultrasonic surface wave and the surface stress on the surface of solid media,establishes the relationship between the surface stress and the propagation time difference of surface wave,optimizes the formula of acoustic elasticity,and provides a theoretical basis for ultrasonic stress detection.A portable ultrasonic signal transmitting and receiving system is designed,which makes the experiment process more simple and provides a basis for the subsequent implementation of portable on-line monitoring.The brief introduction of the research content of the paper is as follows:Firstly,the background and significance of the research are introduced,and then the research status and development of ultrasonic stress surface wave detection technology and ultrasonic signal processing are introduced.Made a detailed introduction the several types of ultrasonic,the advantages and disadvantages of different ultrasonic detection method is introduced and the choice of surface wave detection,this paper analyzed the characteristics of surface wave and the influencing factors of surface wave velocity,draw out the stress testing based on surface wave is elastic theory,and deduces simplified formula based on acoustic elasticity theory testing used.Then,the ultrasonic signal transmitting and receiving circuit system based on FPGA is designed and made.Among them,the ultrasonic signal transmitting and receiving circuit system includes ultrasonic excitation signal amplifying circuit,analog front-end signal conditioning circuit,ADC sampling circuit,data acquisition transmission circuit and power supply circuit,and the selection of some key devices is given.After that,the noise characteristics of ultrasonic echo signal are analyzed,and the signal pretreatment method is selected.Aiming at the problem that the experimental results are not accurate due to the low sampling rate,the multi-sampling rate signal processing method combined with the digital correlation method is proposed to analyze the signal time difference and improve the accuracy of the results.Finally,the ultrasonic signal transmitting and receiving system is used in the ultrasonic stress detection experiment,and the ultrasonic surface wave signal data acquisition experiment is carried out under the condition of different stress loading,and the experimental data is analyzed.Compared with the theoretical results,the accuracy of the experimental results is proved,which can be applied to the engineering measurement.