| LI Geng,ZHANG Zhi-fen,QI Rui,DU Zheng-yao,WEN Guang-rui,HE Wei-feng.Exploring the Law of Elastic-plastic Wave Propagation of Aluminum Alloy LSP based on Acoustic Emission Signal[J],51(11):20-34 |
| Exploring the Law of Elastic-plastic Wave Propagation of Aluminum Alloy LSP based on Acoustic Emission Signal |
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| DOI：10.16490/j.cnki.issn.1001-3660.2022.11.003 |
| KeyWord:laser shock peening acoustic emission elastic-plastic wave plastic deformation waveform entropy time- frequency analysis |
| Author | Institution |
| LI Geng |
Xi'an Jiaotong University, Xi'an , China |
| ZHANG Zhi-fen |
Xi'an Jiaotong University, Xi'an , China |
| QI Rui |
Xi'an Jiaotong University, Xi'an , China |
| DU Zheng-yao |
Xi'an Jiaotong University, Xi'an , China |
| WEN Guang-rui |
Xi'an Jiaotong University, Xi'an , China |
| HE Wei-feng |
Xi'an Jiaotong University, Xi'an , China;Air Force Engineering University, Xi'an , China |
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| Abstract: |
| In order to improve the acoustic emission (AE) monitoring accuracy of laser shock peening (LSP), combined with the AE monitoring technology and the elastic-plastic wave theory in the LSP field, based on the time domain and time-frequency domain information of the AE signal, the internal elastic-plastic wave propagation law of the aluminum alloy 7075 plate during the LSP process is explored, which provides a theoretical basis for the follow-up LSP monitoring research. Firstly, combined with the elastic-plastic wave theory, LSP experiments under different laser power densities are designed, and the AE piezoelectric sensing technology is used to obtain the impact signal in the processing process in real time, The PGI3D aspheric surface measuring instrument was used to measure the surface plastic deformation degree of the aluminum alloy 7075 plate after laser shock strengthening. Secondly, in order to facilitate the subsequent data analysis and processing, based on the time-domain waveform of the AE signal, an envelope Euclidean distance method is proposed to determine the Fragment of Interest (FOI) sensitive to the processing quality; further based on FOI, combined with actual processing conditions, a new cumulative AE waveform entropy feature is defined. Finally, according to the multi-modal and non-stationary characteristics of the AE signal, modal decomposition and wavelet time-frequency analysis are performed on the AE signal to define the instantaneous peak energy curve (IPEC), and further extract the characteristics of peak change and the peak delay time , so as to explore the propagation law of elastic-plastic waves and measure the advantages and disadvantages of different sensors. The experimental analysis results show that the time-domain waveform of the AE signal containing only elastic waves is obviously different from the AE signal of the elastic-plastic double wave, and the propagation speed of the plastic wave inside the plate is obviously behind that of the elastic wave. The segment of interest determined by the envelope Euclidean distance method based on the time-domain waveform of the AE signal can distinguish the elastic-plastic wave well. Compared with the original AE waveform entropy feature, the new accumulated AE waveform entropy feature defined in combination with the processing conditions can be very good. Different degrees of elastoplastic waves are well differentiated. Different from elastic waves, plastic waves in aluminum alloy 7075 plates are mainly concentrated in the middle and low frequency bands (below 200 kHz). The IPEC curve proposed based on AE time-frequency domain information can not only accurately determine the 31 kHz mode as the main component of plastic waves, At the same time, the peak variation and peak delay time extracted on the basis show that the broadband sensor is more sensitive to plastic waves than the resonant sensor. In this paper, for the first time, the multi-modal characteristics in the AE signal are combined with the shock wave theory in the LSP processing process, the methods and features proposed in this paper explore the propagation law of elastic-plastic waves from the time domain and time-frequency domain, respectively. The conclusions obtained provide theoretical support and guidance for standardizing and improving the AE monitoring technology of LSP. |
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