Characteristics of audible acoustic signal in the process of laser cleaning of paint on metal surface

Abstract

Laser cleaning is widely used for paint removal. Audible acoustic waves are generated during the process of laser cleaning of paint. The analytical methods of the time domain, frequency domain and time-frequency domain were adopted in this study. The results show that the time-amplitude (TA) spectra, frequency-amplitude (FA) spectra and time-frequency (TF) spectra have different characteristics at different laser fluences. In the FA spectra, the frequency corresponding to the point of maximum amplitude is 0.04 kHz at the cleaning threshold or above the cleaning threshold. The number of laser pulses that are needed to remove paint with an undamaged substrate can be obtained from the peak numbers of the TF spectra. The TF spectra with the damaged substrate have more peak numbers than the actual number of laser pulses needed to remove paint. By combining the characteristics of the FA spectra and TF spectra, an acoustic monitoring method is established, which can evaluate whether the paint is removed and whether the substrate is damaged. This study provides a new basis for audible acoustic monitoring method in the process of laser cleaning of paint on metal surfaces.