Study On Nondestructive Determination Of Plane Stress In Structural Steel Members Using The Ultrasonic Shear-wave Method

The stress state of building steel members is an important index of structural safety performance evaluation,so it is very important to conduct the research on stress nondestructive measurement of steel members.At present,the research of axial stress measurement method based on the principle of acoustic elasticity is relatively mature.However,when stress measurement is carried out by ultrasonic method based on the principle of acoustic elasticity,the velocity of wave is not sensitive to the change of stress and the accuracy is difficult to guarantee.What’s more,the research of stress measurement mainly focuses on the measurement of axial stress,and the realization of plane stress measurement is the key to obtain the true stress state of building steel components.Therefore,based on the shear wave birefringence effect and spectral analysis technology,a new method which is not only suitable for the measurement of axial stress,but also for the measurement of plane stress is proposed in this paper.The main research contents are as follows:The theory of plane stress measurement for steel members based on ultrasonic spectrum is established.In this paper,the shear wave birefringence effect under the action of plane stress is analyzed,and a mathematical model is established to obtain the phase difference function representing the plane stress state.By analyzing the periodicity of the maximum of the phase difference derivative function,the expressions of the phase spectr um response frequency and the polarization angle of the shear wave components are obtained,and then the functional relationship between the phase spectrum characteristic and the plane stress is obtained.Finally,the theoretical formula of plane stress measurement of steel components based on the phase spectrum is deduced through the separation of the normal stress.Theoretical analysis and experimental research on axial stress measurement of steel members based on ultrasonic spectrum are condu cted.By analyzing the relationship between the axial stress and the plane stress measurement,the theoretical formula between the axial stress and the response frequency of the phase spectrum is obtained,and the capture process of the response frequency is simplified.The hardware system and software system of stress measurement are built,and then the axial stress measurement test is carried out.In order to verify the accuracy of theoretical research,the error analysis is carried out.The influence of the thickness of test components and the sampling rate of oscilloscope on the measurement results are analyzed.The advantages of this method are obtained by comparing the proposed method with the amplitude spectrum method.A plane stress measurement method for steel components based on ultrasonic phase spectrum is established.The acoustic-elastic effect of shear wave propagation in plane stress field is studied.A method of separating plane normal stress based on ultrasonic phase spectrum is p roposed.A method of measuring plane stress of steel component based on ultrasonic phase spectrum is established.By designing the shape and loading form of the specific steel members,the plane stress field is obtained.Based on the theory and method of plane stress measurement,the parameters of the formula for plane stress measurement of steel members are calibrated,and the plane stress field is identified.The results agree with the strain gauge method.The effectiveness of the proposed plane stress measurement method is verified.