基于幅度加权编码激励的不锈钢焊缝TOFD成像检测研究

发布时间：2018-01-21 17:20

本文关键词： 超声TOFD成像检测编码激励幅度加权奥氏体不锈钢焊缝　出处：《机械工程学报》2017年12期 　论文类型：期刊论文

【摘要】：通过Hamming窗加权方法设计了幅度加权调频编码激励信号,将这种新型的激励方法与TOFD(Time-of-flight diffraction)检测方法相结合,综合提高了粗晶奥氏体不锈钢焊缝缺陷检测的时间分辨力、检测信噪比和缺陷定量定位精度,有效改善了粗晶焊缝超声检测中的难点问题。为分析设计的幅度加权调频编码激励信号的检测能力,针对奥氏体不锈钢母材试件和焊缝试件中的横孔缺陷,采用5 MHz探头分别进行了编码激励和常规激励的TOFD成像检测对比试验,结果表明:在相同的检测条件下,幅度加权调频编码激励可提高了图像和信号质量,使检测信号中的杂波和噪声得到抑制,缺陷上端和下端衍射波被准确区分,使各波形的时间宽度降低了30%,有效提高了TOFD检测的时间分辨力;获得的缺陷定位定量测量的平均相对误差为3.8%,较常规激励降低了47%,这种激励方法可在不提高激励电压和增益条件下,使不锈钢焊缝中缺陷检测的信噪比达16 d B以上,较常规激励平均提高了7 d B。
[Abstract]:The amplitude-weighted FM coded excitation signal is designed by Hamming window weighting method. The new excitation method is combined with the TOFD(Time-of-flight diffusion detection method. The time resolution, signal-to-noise ratio (SNR) and quantitative localization accuracy of weld defects of coarse austenitic stainless steel are improved. In order to analyze the detection ability of amplitude weighted frequency modulation code excitation signal, the transverse hole defects in austenitic stainless steel base material and weld specimen were analyzed. 5 MHz probe was used to carry out the contrast tests of coded and conventional excitation TOFD imaging detection. The results show that: under the same detection conditions. The amplitude weighted frequency modulation code excitation can improve the image and signal quality, suppress the clutter and noise in the detection signal, and accurately distinguish the diffraction waves at the top and bottom of the defect. The time width of each waveform is reduced by 30%, and the time resolution of TOFD detection is improved effectively. The average relative error of quantitative measurement of defect location is 3.8, which is 47% lower than that of conventional excitation. This method can be used without increasing the excitation voltage and gain. The SNR of defect detection in stainless steel weld is more than 16 dB, which is 7 dB higher than that of conventional excitation.
【作者单位】：中国工程物理研究院电子工程研究所;哈尔滨工业大学先进焊接与连接国家重点实验室;
【基金】：国家自然科学基金资助项目(51175113,51575134)
【分类号】：TG441.7
【正文快照】： 0前言1奥氏体不锈钢由于具有良好的抗腐蚀性能和高温力学性能,易于加工和焊接,因而被广泛应用于核电、石油化工、航空航天等领域,尤其是用在一些重要的压力容器与管道的焊接结构中。奥氏体不锈钢焊接接头内部常见的裂纹、气孔等缺陷在特殊环境下易于扩展且难于被察觉[1],通常

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