铝合金回填式搅拌摩擦点焊缺陷的超声检测及信号识别

Ultrasonic Testing and Signal Identification of the Defects in Aluminium Alloy Refill Friction Stir Spot Welding

目的利用水浸聚焦超声C扫描对2524铝合金回填式搅拌摩擦点焊(RFSSW)接头进行检测并完成缺陷识别。方法以A扫描时域信号为对象,绘制能量谱与金相作对照,确定焊合区;分析未焊合、聚集型孔洞及弥散型孔洞的时域和频域波形特征,并对频域信号进行小波分析,提取特征量。结果缺陷区反射回波的归一化能量不低于0.02;不同形式的缺陷(聚集型孔洞、弥散型孔洞、弱连接)其频谱形状特征不同,具有不同的峰值个数。结论通过金相验证,表明超声波C扫描对接头缺陷可进行有效的检测和区分。

The paper aims to conduct immersion ultrasonic C-scan test for identifying different defects of the 2524 aluminum alloy joints with refill friction stir spot welding(RFSSW). With A-scan signal as the object, the energy spectrum was compared with the microstructures to determine the welded area. The time-domain and frequency-domain waveform characteristics of the unwelded, aggregated and dispersed holes were analyzed. The frequency-domain signal was analyzed by wavelet analysis to extract the feature. The normalized energy of reflection echo in the defect zone was not less than 0.02;different defects(aggregated, dispersed holes and kissing bond) had different frequency spectrum features and different peaks. The result of metallographic verification demonstrates that ultrasonic C-scan can effectively detect and distinguish defects of the joints.