铝合金脉冲MIG焊接熔滴过渡行为的声发射信号时频域表征

通过在线检测铝合金脉冲MIG焊接过程的结构负载声发射信号,研究熔滴过渡模式和行为的时频域表征.结果表明,熔滴过渡声发射信号波形以及熔滴过渡声发射事件的有序性和周期性可以反映脉冲MIG焊接过程熔滴过渡的稳定性和周期性.随着脉冲频率和焊接热输入的增大,熔滴过渡模式由短路过渡转变为射滴过渡,过渡熔滴体积得到逐步细化,表现出递减的声发射能量释放特征.当熔滴过渡为短路过渡模式时,熔滴过渡声发射信号的频域范围较宽,且较为集中在高频部分;当熔滴过渡为射滴过渡模式时,熔滴过渡声发射信号的频率分布范围更窄,且集中在低频部分.随着熔滴过渡模式由短路过渡模式逐渐转变为射滴过渡模式,由熔滴过渡引入的能量变化呈现出先减小再增大的趋势.

Time and frequency domain analysis of metal droplet transfer by acoustic emission signals during pulse MIG welding of aluminum alloy

The structure-borne acoustic emission (AE) signals during pulse MIG welding of aluminum alloy were detected in real-time and analyzed to investigate the time and frequency characteristics of metal droplet transfer. The results show that the order and periodicity of metal droplet transfer during pulse MIG welding were characterized by AE signals waveform and AE event of metal droplet transfer. As the pulse frequency and welding heat input increased, the metal droplet transfer was transformed from short circuiting transfer mode to spray transfer mode. The volume of metal droplet was refined gradually, which showed decreasing characteristics of AE energy release. With short circuiting transfer mode, the frequency domain of AE signals of metal droplet transfer was broad and distributed around the high frequency region. With spray transfer mode, the frequency domain of AE signals of metal droplet transfer was narrow and distributed around the low frequency region. As the metal droplet transfer was transformed from short circuiting transfer mode to spray transfer mode, the energy variation induced by metal droplet showed a parabolic trend.