Study On Defect Detection Of Semi-grouting Sleeve Based On Ultrasonic Guide Wave

At present,the national ecological civilization development strategy puts forward new requirements for the development of construction industrialization,and the development of prefabricated buildings is an important part of it.The quality control and detection technology of currently assembled monolithic concrete buildings is relatively lagging behind.There is no good method for low-cost and effective detection of the quality of grouting at the connection points(vertical and horizontal directions)of assembled concrete components at the connection point of the component.In order to ensure the quality of sleeve grouting,the relevant departments have formulated corresponding specifications and regulations,which have detailed regulations in terms of raw materials,construction techniques and methods,and personnel training.However,in the actual inspection process,the quality of the grouting cannot be guaranteed.This paper proposes a method for non-destructive testing of the quality of grouting using ultrasonic guided wave technology.First,in order to determine the optimal excitation frequency and the number of waveform cycles of the ultrasonic guided wave,according to the structural characteristics of the semi-grouting sleeve,the dispersion characteristics of the ultrasonic guided wave propagating in the semi-grouting sleeve structure were studied,and the ultrasonic guided wave period and frequency were analyzed.The influence on the detection effect determines the selection range of the frequency and period of the ultrasonic guided wave excitation signal.Using the two-dimensional finite element model of the semi-grouting sleeve,this paper obtains the propagation path of the ultrasonic guided wave and the change process of the guided wave energy attenuation.Secondly,this paper establishes a finite element model of four defect gradient semi-grouting sleeve structures,and uses the numerical simulation method to analyze the relationship between the ultrasonic guided wave received signal and different degrees of grouting defects.Based on the energy attenuation theory of guided waves,this paper analyzes the amplitude of the first wave of the received signal.The results show that the greater the degree of grouting defects,the lower the energy attenuation of the received signal.In order to characterize the grouting defects intuitively,this paper uses the time-domain energy change rate of the first wave of the received signal and the energy change rate of the reconstructed signal after wavelet packet decomposition to construct an index that can characterize the grouting defects of different degrees in the semi-grouting sleeve.The results show that both indicators can effectively identify the degree of grouting defects.The index value increases with the degree of grouting defects in the semi-grouting sleeve,and the growth rate continues to increase.Finally,this paper builds a set of ultrasonic guided wave detection grouting defects system.The ultrasonic transducer is set on the steel bar sections on both sides of the semi-grouting sleeve structure to excite and receive ultrasonic guided wave signals This paper uses the grouting defect evaluation index proposed in Chapter 4 of this paper to evaluate and verify the grouting defects,and compares and analyzes it with the numerical simulation results.The change trend of the two kinds of defects evaluation index values of the energy change rate of the signal is completely consistent with the numerical simulation method.The feasibility of ultrasonic guided wave detection method is proved,and the accuracy of numerical simulation method is further verified.