混凝土结构中超声传播特性及其图像重建的研究

The research on the application of computed tomography for quality inspection of concrete is being done， it will be very appropriate for regular testing and in situnondestructive testing during concrete construction exists. The ultrasonic wave for nondestructive testing of concrete was repeatedly identified as being of high priority. Currently, the content of concrete inspection is cracked and holes. Ultrasonic time of flight use ultrasonic signal which through the interior of measured object to reconstruct ultrasonic images. At the ultrasonic time of flight computed tomography, the spatial distribution of sound velocity is estimated, so using ultrasonic time of flight we can get concrete structure images. This research aims to evaluate the internal structure of concrete material configuration using ultrasonic computed tomography imaging technique. We propose ultrasonic volatility transmission to reconstruct concrete image, explore the relationship between the ultrasonic volatility transmission and accurate reconstruction of ultrasonic images. The main contents of our research: (1) Concrete has an anisotropic property for ultrasonic, it is influential to accurately find the position of the holes in reconstruction images. So, construction of ultrasonic wave propagation for concrete inspection by ultrasonic CT on the basis of the Ordered Subsets Expectation Maximization (OSEM) method is the first research. (2) Driver sine wave Fourier transforms will be researched in our ultrasonic system. The relative difference method of time of flight data will be proposed to remove distortions in the imaging process of concrete. Furthermore, interpolation of time of flight data was applied to enhance image quality in OSEM imaging process. (3) Ultrasonic imaging algorithm optimization based global time of flight data. This research is expected to reveal the relationship between the ultrasonic wave propagation and ultrasonic imaging reconstruction, achieve empty or not dense area of concrete quantitative analysis and detection.

针对超声波CT在混凝土内部结构检测时难以直接成像进行定量检测的问题，本研究通过带有混凝土内部结构信息的超声渡越时间参数（Time of flight，TOF），基于有序子集最大期望值迭代算法，开展基于超声波传播特性的图像精准重建的创新性研究，构建近似医疗CT的混凝土超声成像系统。本项目主要研究内容为：（1）研究超声波基于波动性传播的图像重建模型，构建基于混凝土特性的超声成像系统；（2）超声波动传播中驱动正弦波傅立叶变换与渡越时间参数正规化；（3）研究针对测量物体渡越时间参数的全域化，对已经成功应用于医疗的成像算法进行改进，使之适应于混凝土成像。本研究预期揭示混凝土内部超声波波动传播与超声图像重建之间的关系，实现混凝土内部空洞或不密实区甚至混凝土内部钢筋结构的定量分析与检测，项目研究成果可为混凝土质量的科学检测进一步奠定理论和方法基础。

混凝土灌注凝固后由于其坚硬整体性及内部结构复杂的物理特性，使混凝土内部结构的定量检测相对困难，混凝土构件质量检测技术及手段目前主要是定性或半定量阶段，难以满足混凝土实际工程应用需求。混凝土超声波检测技术目前所面临的一个重要课题就是对被检混凝土进行层面信息全域化，检测出混凝土内部缺陷的位置、大小、分布状态等。本项目以混凝土内部结构图像精准重建作为目标，研究被测混凝土构件内部越时间参数的全域化的同时，揭示了混凝土构件内部超声波动传播与图像重建之间的关系，实现了基于超声渡越时间参数围绕混凝土内部结构的可视化。通过带有混凝土内部结构信息的超声渡越时间参数，利用有序子集最大期望值迭代算法和数据插补，对混凝土柱内部结构进行了图像精准重建。. 基于研究目标和进度计划，实现了混凝土构件的图像重建系统，能够多种类型混凝土构件进行了图像重建，研究结果表明对混凝土内部的钢筋、空洞、钢管等音速异常部位均可进行图像重建。本项目的研究揭示了混凝土内部超声波波动传播与超声图像重建之间的关系，实现了混凝土内部空洞或不密实区甚至混凝土内部钢筋结构的定量分析与检测，项目研究成果可为混凝土质量的科学检测进一步奠定理论依据。