Abstract
Early damage, such as microcrack, occupies most of the fatigue life of materials, and timely detection of early damage and positioning has great engineering and economic value. In this paper, a matrix scanning and positioning imaging method based on a probabilistic algorithm is proposed. Cooperating with the single-mode (S0) lamb wave, the microcrack in the thin plate material can be efficiently positioned. Taking the S0 mode lamb wave as the fundamental wave can effectively reduce the influence of the dispersion effect on the signal analysis. Meanwhile, in order to reduce the noise interference, the signal is reconstructed by empirical mode decomposition (EMD) to achieve the filtering effect. Then, the ABAQUS finite element simulation software is used to compare the positioning results under different locations of microcrack and different arrangements of probe. Finally, the feasibility of the localization algorithm is verified by the RAM-5000 SNAP nonlinear ultrasound system. The experimental results are consistent with the simulation theory, and the microcrack is effectively positioned. This facilitates our timely remedial action or further assessment of the remaining value of the material.
Highlights
Metallic materials are widely used in aerospace, transportation, construction, and other fields.the metal materials may generate defects due to fatigue loading
Because the ultrasonic wave will attenuate during the propagation process, when scanning the damage, the center line of the path from excitation to reception is the direction of propagation of the lamb wave
It can be seen that the microcrack positioning imaging figures are ideal when the excitation and reception probes are all five and symmetrically distributed, so the experiment adopts the same arrangement and compares the microcrack positioning results at
Summary
Metallic materials are widely used in aerospace, transportation, construction, and other fields. Lamb wave is chosen as the fundamental wave for nonlinear ultrasonic testing to detect early damage in the sheet. It is affected by microcrack and other defects during the propagation process [17]. The positioning algorithms for sheet material rarely consider the influence of the dispersion effect and have not noticed the value of using a single mode to detect damage. This paper pays attention to the influence of the lamb wave dispersion effect on the signal analysis and positioning results, so the S0 single-mode lamb wave is used as the detection fundamental wave.
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