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相控阵超声检测中,相关法时间延迟估计是实现自适应聚焦的关键技术之一。为了消除噪声、模板窗口大小和缺陷特征等因素对相关法时间延迟估计的影响,结合检测超声回波信号的特点,提出了基于小波变换的相关法时间延迟估计方法。理论仿真和实验均证明该方法能有效抑制上述因素的影响,提高时间延迟估计精度。仿真计算表明:在可信度为0.95的情况下,信噪比提高了3.2dB,最小窗口大小从无穷大变成了3倍于探头中心频率对应周期,模板有效范围扩展了60%。
Phased array ultrasonic testing, correlation method time delay estimation is one of the key technologies to achieve adaptive focusing. In order to eliminate the impact of noise, template window size and defect characteristics on time delay estimation of correlation method, combined with the characteristics of ultrasonic echo signal detection, a time delay estimation method based on wavelet transform is proposed. Both theoretical simulation and experiment prove that this method can effectively restrain the above factors and improve the estimation accuracy of time delay. Simulation results show that the SNR increases by 3.2dB with a reliability of 0.95, and the minimum window size changes from infinity to three times the probe center frequency. The effective range of the template is extended by 60%.