The online monitoring method research of laser shock processing based on plasma acoustic wave signal energy

Abstract

Abstract Aiming at the phenomenon of plasma acoustic wave during laser shock processing, the online monitoring method of laser shock processing based on plasma acoustic wave signal energy is proposed. The TC4 titanium alloy samples, after the vibration stress relief treatment, were treated by a Nd:YAG laser system with a wavelength of 1064nm, a pulse width of 12–18\u2009ns, and a single pulse energy of 0–7\u2009J. The plasma acoustic wave in air is sampled, stored, digitally filtered, and analyzed by the laser shock processing online monitoring system during laser shock processing. Then the system gets the plasma acoustic wave signal energy. The surface residual stress of material after the treatment of laser shock processing were measured by a Photo-LXRD X-ray diffraction device. The experimental results show that the residual compressive stress is generated on the surface of material after laser shock processing. Both the surface residual stress of the material and the plasma acoustic wave signal energy are increased as the laser pulse energy increases from 3J to 7J, and their growth trend is consistent. Finally, the empirical formula between the surface residual compressive stress of the material and the plasma acoustic wave signal energy is obtained by polynomial fitting, which will provides a theoretical basis for the development of laser shock processing online monitoring technology.