关键词: 电弧声, 时频分析, 小波降噪, 窄间隙MAG焊

Abstract: The control of arc-sidewall distance is the key to ensure good sidewall fusion in the process of narrow gap metal active gas welding(NG-MAG) welding. Through pretreatment and analysis of arc sound in NG-MAG pulse vertical welding, it is found that there exists periodic “ringing” attenuation phenomenon in the time-domain waveform, and its frequency is equal to the pulse frequency of welding power. The frequency distribution of arc sound energy varies from 0.3 kHz to 12.0 kHz. And energy mainly concentrates in two bands, range of 0.3-3.0 kHz and 9.0-12.0 kHz. Spectrum distribution of arc sound is highly relevant to arc-sidewall distance. On this basis, noise reduction and time-frequency analysis of arc sound are achieved by use of wavelet transform(WT) and joint time-frequency analysis(JTFA). The results show that low-frequency energy distribution of arc sound is always present, show “intermittent-continuous-intermittent”, with gradually increasing of arc-sidewall distance. While high-frequency energy distribution of arc sound only present arc-sidewall distance more than 2.6 mm, show “intermittent-continuous”. The monitoring and early warning of arc-sidewall distance can be realized based on time-frequency distribution of arc sound in NG-MAG pulse vertical welding, which provides a new way for condition monitoring in the process of NG-MAG welding.

Key words: arc sound, joint time-frequency analysis, narrow gap MAG welding, wavelet noise reduction