Lamb Wave Tomography Technique For Structural Crack Monitoring And Evaluation

Structural Health Monitoring has the strong ability of on-line real-time monitoring, so it is regarded as one of the most effective ways to ensure the structural safety. The damages of the structure are always at the initial state of cracks. Therefore, it is important to detect the positions and sizes of the cracks to ensure structural safety. Due to the strong concealment and harmfulness, structural crack monitoring has been one of the hot and difficult problems in structural health monitoring. Based on the analysis of Lamb wave propagating varieties influenced by the crack, Lamb wave tomography technique for structural crack detection is proposed in this paper to monitor and evaluate the crack damages. The research content can be generalized as following:(1) The research background and contents of structural health monitoring are given. The popular methods of Lamb wave tomography technique, presented in the latest ten years, are introduced. Meanwhile, the existing problems of the methods mentioned above are pointed out.(2) The propagation characteristics of Lamb wave are investigated theoretically. Based on the analysis of lamb wave actuation, the monitoring principle and limitations of RAPID(Reconstruction Algorithm for the Probabilistic Inspection of Damage) tomography technique are in-depth studied.(3) On the basis of traditional RAPID tomography technique, the cross orthogonal scanning method is put forward to monitor the direction of the crack. The length of the crack can be evaluated by the location relationship of the each sensor in the sensor array and the signal difference coefficient distribution. Furthermore, the simulation experimental researches are carried out to detect the cracks at different positions.(4) An integrated experimental system is designed for crack detection based on Lamb wave tomography technique. Hardware part includes waveform actuation, power amplifier, charge amplifier and data acquisition equipment. Software part includes the development of waveform actuation and data acquisition system. Then, this experimental system is employed for the monitoring and evaluation of the crack damage in the aluminum plate.The experimental results show that the proposed method can detect and evaluate the crack effectively in the tomographic images with high accuracy and precision. Furthermore, it provides technical method for crack online monitoring and evaluation with a good application foreground.