Explorative approach of the spectral analysis tools to the detection of welding defects in lap welding

The study of the voltage and current signals during welding can give information on the process, especially in case of defects. A signal processing software using Fourier and Wavelet transforms has been used to analyse the signals produced during welding under normal conditions and during artificially created defects. Then the fundamental frequency shift, or pitch, has been measured and the frequency variation for each case has been studied. Results showed specific features for each defect type.