Investigation on defect dynamic echo waveform of friction stir welding

This paper regards aluminum clad defect,channel defect and lack of penetration(LOP) of friction stir weld(FSW) as the research object.The defects dynamic echo waveforms were acquired by travering scan and lateral scan of ultrasonic testing.The characteristics of the defects dynamic echo waveforms were described.The formation reasons of the defects dynamic echo waveforms were analyzed.The results show that the generation of the ultrasonic echo wave from the aluminum clad defect was resulted from the weak-bonding of the interface between the aluminum clad and aluminum alloy because of almost same acoustic impedance of the both sides at the interface.Based on the characteristics of the defects dynamic echo waveforms that were acquired by travering scan,channel defect can be distinguished from aluminum clad defect and LOP.Therefore,the characteristics can provide a thereunder for the preliminary qualitative analysis of the ultrasonic testing for FSW.