| As a key component of the transportation system,bridges play an important role in people’s daily life.However,during the construction and operation of the bridge structure,due to external environmental factors and the deterioration of the performance of the bridge material itself,various components of the bridge structure will be damaged to varying degrees during the operation period.Therefore,in the operation of the bridge,damage detection of the main components of the bridge structure has very urgent practical significance.However,traditional bridge safety inspection methods are difficult to accurately evaluate structural component damage,so this paper studies the use of ultrasonic guided waves for component damage detection,which has the advantages of fast speed and wide detection range.But when the degree of structural damage is small,it is difficult to distinguish.Therefore,the index based on Tsallis wavelet entropy is introduced,which can identify the change of ultrasonic guided wave signal,so as to realize structural damage detection.The content of second chapter introduces the law of ultrasonic guided wave propagation in rod structure.This chapter introduces the three modes of longitudinal mode,torsion mode,and bending mode,and combines the numerical method to solve the dispersion equation of each mode,and obtains the dispersion of various modes of ultrasonic guided waves propagating in the rod member.curve.In addition,this chapter also studies the propagation speed of guided waves in rod structures at different frequencies,and discusses the dispersion characteristics of guided waves in rod structures with different diameters.The content of chapter 3 introduces the numerical simulation based on the spectral element method.The spectral element method is based on the wave equation in the middle and high frequency bands.Compared with other similar methods,a single spectral element can be used to simulate,thereby greatly reducing the number of units.Therefore,the spectral element method can provide a high-precision and high-efficiency analysis method for structural damage detection based on guided waves.In this paper,the spectral element method is used to model various working conditions of the rod structure,a semi-infinite rod cracked rod spectrum element is used to analyze the wave propagation in the damaged rod structure,and the damage of the rod structure to the guided wave is analyzed.The impact of spread.This chapter focuses on the research on the local damage of the structure.It discusses the influence of different diameters,damage depths,damage locations and damage lengths on the propagation of guided waves in the rod.At the same time,it compares the difference in the response signal of the structure under damage and health..Finally,a quantitative analysis of the working conditions of different rod lengths and damage positions in the experiment was carried out,thus verifying the effectiveness of the spectral element method in non-destructive testing.The content of chapter 4 introduces the detection method based on Tsallis wavelet entropy.In the process of damage detection based on guided waves,because the measured guided wave signals have obvious non-stationary characteristics,this paper introduces the damage location method based on Tsallis wavelet entropy,introduces the basic principles of Tsallis wavelet entropy,and uses numerical simulation examples.The validity of Tsallis wavelet entropy is verified,and it is combined with the spectral element method to detect damage to the structure.The content of chapter 5 tests the propagation of guided waves in the rod.Excite healthy members and specimens under different damage conditions respectively,collect their acceleration responses,and identify the damage status of different components through the method proposed in the paper,which verifies the feasibility of the method. |
