声学编码信号检测混凝土质量研究

发布时间：2018-03-16 17:24

本文选题：混凝土　切入点：质量检测　出处：《华北水利水电大学》2016年硕士论文　论文类型：学位论文

【摘要】：在目前的水利工程质量检测中,水工构筑物缺陷的检测主要使用超声法,如混凝土裂缝深度检测、混凝土强度检测等。随着水利工程设计要求的提高和建设规模的加大,深远距离的超声检测所占比重越来越大。大功率的声学震源(电火花、空气枪)虽然能够增加探测距离,但分辨率较低,且具有一定程度的破坏性,限制了其在水利工程质量检测中的应用。声学编码信号是近年来在医用超声领域研究较多的新方法,该方法探测距离较远,在一定程度上可以提高分辨率。声学编码信号应用于超声检测与成像和传统脉冲回波成像的不同之处体现在两个方面:其一,在发射端采用调制编码激励,发送经过调制的大时宽T、大带宽B信号,即编码激励;其二,在接收端通过相应的解码,获得与信号带宽的倒数1/B相对应的窄脉冲信号,即解码处理。解码得到高信噪比的目标回波信号,从而提高分辨率。将声学编码信号引入到影响混凝土质量的结构缺陷检测中,首先用实验分析了换能器带宽对接收信号压缩效果的影响。实验结果证明换能器的有限带宽限制了任意时带积信号的激发。为激发较大能量的线性调频(LFM)信号,在激励端要结合换能器的响应特征设计LFM信号。然后,利用有限差分方法计算了含缺陷的混凝土模型波场特征。计算结果表明,LFM信号能够提高信号能量,并提高信噪比和分辨率。最后,利用声学编码信号对制作的混凝土缺陷模型进行检测。检测结果表明采用声学编码信号进行检测时,回波信号经过脉冲压缩后能够得到主瓣较窄、幅值较高的缺陷反射信号。实验以线性调频信号检测为主,同时使用Barker信号对模型进行检测,检测结果充分说明了声学编码信号应用于混凝土质量检测的可行性。理论分析和实验结果均证明利用声学编码信号检测混凝土质量具备一定的技术优势,期望该技术应用于水利工程质量检测。
[Abstract]:In the current water conservancy engineering quality inspection, the hydraulic structure defect detection mainly uses the ultrasonic method, such as the concrete crack depth detection, the concrete strength detection and so on, along with the water conservancy engineering design request enhancement and the construction scale increasing, The proportion of deep range ultrasonic detection is increasing. The high power acoustic source (electric spark, air gun) can increase the detection distance, but the resolution is lower, and it is destructive to a certain extent. The acoustic coded signal is a new method which has been studied in the field of medical ultrasound in recent years. To a certain extent, the resolution can be improved. The difference between ultrasonic detection and imaging and traditional pulse echo imaging is reflected in two aspects: first, modulation coding excitation is adopted at the transmitter. Transmitting modulated signals of large time width T, large bandwidth B, that is, encoding excitation; second, obtaining a narrow pulse signal corresponding to the reciprocal 1 / 2 B of the signal bandwidth through the corresponding decoding at the receiving end. That is decoding. Decoding the target echo signal with high signal-to-noise ratio (SNR) to improve the resolution. The acoustic coded signal is introduced into the structural defect detection which affects the quality of concrete. Firstly, the influence of transducer bandwidth on the compression effect of received signal is analyzed experimentally. The experimental results show that the limited bandwidth of the transducer limits the excitation of the band product signal at any time. At the excitation end, the LFM signal should be designed in combination with the response characteristics of the transducer. Then, the wave field characteristics of the concrete model with defects are calculated by using the finite difference method. The results show that the signal can improve the signal energy. Finally, the acoustic coding signal is used to detect the concrete defect model. The detection results show that the acoustic coded signal is used to detect the concrete defect model. When the echo signal is compressed by pulse, the defect reflection signal with narrower main lobe and higher amplitude can be obtained. In the experiment, the linear frequency modulation (LFM) signal is the main detection method, and the Barker signal is used to detect the model. The results show that it is feasible to apply acoustic coded signals to concrete quality detection. Both theoretical analysis and experimental results show that the use of acoustic coded signals to detect concrete quality has certain technical advantages. It is expected that this technology will be applied to water conservancy engineering quality inspection.
【学位授予单位】：华北水利水电大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TV544

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