Research On The Metal Structural Damage Detection By Using LAMB Wave Based On The PZT

The wide use of metal structure, as well as the working condition of bearing complications, such as alternating load, environmental corrosion, would cause tiny cracks which are inevitable. Once the cracks extend, it will reduce its working ability, and even a safety hazard. Promptly and accurate finding the initial small cracks in structures in order to reduce the incidence of accidents and economic loss has become an important issue in the field of nondestructive testing. This paper, by using functional piezoelectric ceramics(PZT), in combination with LAMB wave sensitivity to the distribution of the matrix organization, proposes the use of wavelet packet energy spectrum value in order to identify the defect rate. Related tests have been carried out through the finite element simulation calculation and experiment respectively.Main research contents of this paper:(1) Carry out some further study of LAMB wave modal parameters, combined with LAMB wave dispersion equation and simulate of LAMB wave phase curve of the steel plate. Analyze window function, the number of cycles and the excitation frequency, respectively to conclude the appropriate optimal incentive mode of LAMB wave parameters.(2) The damage of LAMB wave propagation characteristics and the location of different methods were discussed in this paper. Summarize their respective application limits, and put forward the change rate of damage identification based on wavelet packet energy spectrum value.(3) Establish finite element model of different damage condition of steel plate, simulate calculation respectively. Compare and analyze defecting status for response. Combining the wavelet packet decomposition theory, the acquisition is decomposed step by step, response and sensitive attenuation curve are obtained. Via frequency band energy spectrum value through isometric point layout, to obtain decay curve fitting of the energy spectrum of each patch response value. With the existence of defects, it will lead to the whole response signal within a certain frequency band signal enhancement, while in another band signal is abate. In sensitive spectrum decomposition layer area is much more subdued response intensity, so by looking for energy spectrum value decay curve node outliers, defect positioning can be realized.(4) Design the whole experimental platform, through the dynamic data acquisition instrument, real time collection point response data, to collect by the voltage signal. Piezoelectric body is obtained by inverse piezoelectric effect of vertical vibration acceleration, the attenuation characteristics of combining wavelet packet decomposition to realize the damage location. Demonstrate the PZT stimulation of the superiority of LAMB wave energy spectrum value, and the feasibility of LAMB wave packet in the damaged rate of substrate.