Monitoring of YAG Laser Spot Welding : Detection of Porosity Defect by Acoustic Signal

摘要

Sound is generated during laser spot welding; this is useful for monitoringrnthe welding operation. In the present experiments, the sound is detected byrna microphone for inspecting the generation of porosity defect in YAG laser spotrnwelding. Laser beam conditions are the energy of 2.0 J and pulse duration of 5rnms; the welding is done on plates of stainless steel of 1.0 mm in thickness byrnsingle pulse. The Short Time Fourier Transform (STFT) analysis is applied forrnobtaining the time dependence of the generated sound. Though great differencerncannot be observed in the sound signals detected by the microphone, the clearrndifference can be observed by the STFT. The intensity of 11-15 kHz is lower inrnthe welding with defect than in without defect. This is also confirmed in thernwelding by laser beams of 2 J, 4 ms, 2 J, 3 ms and 1.8 J, 3 ms. The result showsrna possibility of detecting the welding defect by the sound analysis in the productionrnsystems.