混凝土介质隐患超声波CT探测技术研究

发布时间：2018-03-29 02:10

本文选题：超声CT　切入点：正演模型　出处：《安徽理工大学》2015年硕士论文

【摘要】：混凝土结构由于施工不当和外力作用,及其建筑材料性质的影响,造成内部结构的介质隐患。混凝土结构中的介质隐患主要有蜂窝空洞、裂缝和局部不密实。由于这些缺陷,使混凝土结构的不完整,从而导致其抗压抗拉强度和耐久性严重降低。因此需要对工程现场中混凝土构件进行快速检测,对保证工程建设的安全具有重要意义。目前混凝土无损检测方法主要有回弹法、冲击回波法和雷达法。这些方法在检测过程中各具弊端,受限于探测混凝土表面质量情况,不能反映混凝土介质内部情况、仪器比较昂贵且受钢筋的影响较大,现场探测不好展开以及对于尺度较小的介质隐患分辨率较低。超声波法检测可以有效的解决这些问题,此类方法因具有极强的穿透力、较高的分辨率、检测设备简单、极易操作的特点,因此在检测成本上以及后期数据反演效果方面较其他方法有很大的优势。本文首先对已知模型进行数值模拟。基于数值模拟计算所得结果,提取相关波场快照,初步研究超声波在混凝土结构中的传播规律。从波场快照中可以得出,超声波在设置有不同地质隐患的混凝土介质中显现出明显的传播差异。其次本文又通过数值模拟来研究观测系统对超声波CT成像分辨率的影响,在设置相似的数值模拟模型、布置不同的观测系统的基础上,通过对比CT图得出适合混凝土无损检测的最佳观测系统,研究得知实测阶段尽量采用多种观测系统相互比较对比、相互印证得出结论。文中做了超声波CT探查混凝土中夹层、空洞缺陷的数值模拟研究,得到超声CT图其收敛性较好,较清晰地反映出异常区的位置和尺寸。最后应用数值模拟和物理模型试验相结合的方法,相互解释相互指导,结果表明超声CT在实测阶段可行性较高且具有良好的分辨率。最后论文也指出了超声CT在混凝土无损检测方面存在的不足及今后的研究方向,文中所做的物理模型因其尺寸较小且所设置的介质隐患种类较少,因而检测效果虽好但不具有一定代表性。实际工程中混凝土结构复杂,而且体型较大,其实际探测效果还有待于进一步的实验研究。
[Abstract]:Due to the improper construction and external force, and the influence of the properties of the building materials, the concrete structure causes the medium hidden danger of the internal structure. The medium hidden danger in the concrete structure mainly includes honeycomb cavity, crack and local uncompactness. Because of these defects, Because the concrete structure is not complete, the compressive and tensile strength and durability of the concrete structure are seriously reduced. Therefore, it is necessary to carry out the rapid detection of concrete members in the engineering site. It is of great significance to ensure the safety of engineering construction. At present, the methods of nondestructive testing of concrete mainly include rebound method, impact echo method and radar method. These methods have their own disadvantages in the detection process, and are limited by the detection of concrete surface quality. It can not reflect the internal condition of concrete medium, the instrument is expensive and influenced by the steel bar, the field detection is difficult to spread out and the resolution of the medium hidden trouble is low. Ultrasonic testing can effectively solve these problems. Because of its strong penetration, high resolution, simple detection equipment and easy to operate, this kind of method has a great advantage over other methods in detecting cost and the effect of data retrieval in the later stage. In this paper, first of all, the known model is numerically simulated. Based on the results of numerical simulation, the relevant wave field snapshot is extracted, and the propagation law of ultrasonic wave in concrete structure is studied preliminarily. It can be obtained from the wave field snapshot. There are obvious differences in the propagation of ultrasonic wave in concrete medium with different geological hidden dangers. Secondly, the influence of observation system on the resolution of ultrasonic CT imaging is studied by numerical simulation, and a similar numerical simulation model is set up. Based on the arrangement of different observation systems, the best observation system suitable for nondestructive testing of concrete is obtained by comparing CT images. The study shows that various observation systems are used to compare and contrast each other in the stage of actual measurement as far as possible. The conclusion is drawn by mutual verification. The numerical simulation of ultrasonic CT to detect the sandwich and cavity defects in concrete is carried out, and the results show that the ultrasonic CT image has good convergence. The location and size of the abnormal area are clearly reflected. Finally, the method of numerical simulation and physical model test is used to explain and guide each other. The results show that the ultrasonic CT is feasible and has good resolution in the measured stage. Finally, the paper also points out the shortcomings of ultrasonic CT in nondestructive testing of concrete and the future research direction. The physical model made in this paper is smaller in size and less in the types of medium hidden dangers. Therefore, although the detection effect is good, it is not representative. The concrete structure is complex and the size is large in practical engineering, and the actual detection effect still needs further experimental study.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU37;P631.5

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