The real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal
Liu Xuejun1,3, Wu Jiajun1,2, Qiao Hongchao1,2, Zhao Jibin1,2, Li Changyun3, Zhang Yinuo1,2, Wan Lanjun3     
1. Shenyang Institute of Automation, Chinese Academy of Science, Shenyang, Liaoning 110016, China;
2. Institutes for Robotics and Intelligent Manufacturing, Chinese Academy of Sciences, Shenyang, Liaoning 110016, China;
3. School of Computer, Hunan University of Technology, Zhuzhou, Hunan 412007, China

Overview:Laser shock processing (LSP) is an innovative surface treatment technique. It involves irradiation of the thin opaque coating layer with high-energy short-width laser pulses causing instantaneous vaporization of the surface layer into high-temperature high-pressure laser-induced plasma. The expansion of the laser-induced plasma generates high speed compressive shock waves that propagate into the components. Then the metal material is plastically deformed and generates compressive residual stress in the surface. The surface residual compressive stress is generally used to evaluate the effect of the process of LSP. The main methods of measuring surface residual compressive stress are off-line and low efficiency. It is necessary to develop the non-destructive online detection technology of LSP. The correlation analysis showed the laser-induced plasma acoustic waves can comprehensively reflect the parameter characteristics in the process of LSP. The analysis and extraction of the characteristics of acoustic wave can be used for real-time online detection of the LSP. The real-time acquisition and analysis software system for laser-induced plasma acoustic wave signal based on SIA-AEDAC-01 acoustic emission acquisition card is developed in this work to realize the online detection of LSP. Firstly, the laser-induced plasma acoustic wave signal propagating in air is collected and its energy is obtain by the software system. The residual stress of the test pieces after the treatment of LSP was measured by an X-ray stress analyzer to verify the reliability. The experimental results show that the laser-induced plasma acoustic wave signal can be collected and analyzed in real-time by the software system which can accurately get the acoustic signal energy. At the same time, both the acoustic wave signal energy and the surface residual stress of the test pieces are increased with the laser energy, and their change curve is consistent. In conclusion, the software system can satisfy the requirements of online detection of LSP with accurate and reliable performance.

Supported by NSFC-Liaoning Province United Foundation (U1608259), National Natural Science Foundation of China (51501219), National Key Development Program (2016YFB1192704), and National Key Technology Research and Development Program of the Ministry of Science and Technology of China (2015BAF08B01-01)