薄镀锌钢板点焊超声谐振检测

研究了低频超声探头的谐振特性,并将这种谐振特性用于镀锌薄板的点焊检测中.采用接触式低频探头对点焊进行检测时,检测探头能够接收到未焊薄基板产生的半波谐振高频信号,这些半波谐振信号的高频部分处于探头频带外的奇数次谐振频率附近.通过小波包变换的方法可以将这些高频信号从检测信号中分离出来并用于点焊的质量评价.分析小波包变换中各尺度信号,获取了能够评价焊核质量的超声波特征值并将这些特征值与点焊力学性能联系起来,提供了一种能够定量评价点焊质量的超声无损评价方法.此外,采用低频探头对点焊进行检测较之普通检测方法将大大降低检测成本.

Ultrasonic low-frequency resonant test of spot welding of zinccoated steel sheet

High order resonance of the ultrasonic transducer was investigated and adopted to inspect spot weld.The transducer can receive the half-wavelength resonance frequency signals from non-welded thin steel sheet because of the ultrasonic multiple reflect in steel sheet, and the frequency of signals is near the high order resonance domain which is out of the bandwidth of the transducer. These signals can be picked up through wavelet packet transform (WPT) because of their special spectrum localization.Thus, the WPT can be adopted to evaluate the joining quality of resistance spot welding of zinc-coated steel sheet.Through analyzing the signals in different scale, the characteristic number which can determine the quality of the spot weld was obtained.This non-destructive evaluation may be used to quantitatively estimate the quality of spot welds. As the low frequency transducer is used, the testing cost is obviously decreased in comparison to the normal testing.