曲面超声相控阵聚焦与成像特性研究
文献类型：学位论文
| 作者 | 师芳芳 |
| 学位类别 | 博士 |
| 答辩日期 | 2009-05-31 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 曲面超声相控阵 聚焦与成像 时域有限差分 井壁成像 |
| 其他题名 | Research on Focusing and Imaging Characteristics of Curved Ultrasonic Phased Array |
| 学位专业 | 声学 |
| 中文摘要 | 超声相控阵能动态地进行聚焦发射和聚焦接收，方便灵活地进行声束控制，可以实现多种扫描方式，并且不受被检物体的形状限制，具有较高的灵敏度、分辨率和信噪比等优点，是目前无损检测领域的研究热点。本文针对超声相控阵在石油井下探测和管材检测中的应用，开展了关于平面线阵、凹面线阵和柱面线阵换能器辐射声场及散射声场的理论和实验研究，对这几种曲面线性相控阵的聚焦和成像特性进行了深入的研究和分析。 针对石油井下的实际环境，设计和研制出可用于井下前视的旋转式平面相控阵列和用于井壁扫描的柱面线性相控阵列，这两种相控阵换能器的工作频率都为500kHz，动态阵元数都为16，最大外径和实际测井仪器相同。用于前视的旋转式平面相控阵列包含40个阵元，用于井壁扫描的柱面超声相控阵探头有112个阵元，它们为均匀分布在圆柱表面的条形阵元。 对于相控阵辐射声场，我们从理论和实验上，分别对平面线阵、柱面线阵和凹面线阵这几种曲面相控阵列的辐射声场进行了深入的研究和分析，研究了聚焦辐射声场的轴向、侧向以及全空间声场分布，并对阵元间距、阵元数目、f数等参数对声场的影响展开了详细的探讨。 对于相控阵散射声场的计算方法，我们结合套管中的相控阵声场问题，开发出了2.5维和2维时域有限差分计算程序，并对套管中的相控阵声场进行了数值模拟，研究了套管中的波场特性。首先，采用2.5维时域有限差分方法对有窜槽的套管井声场进行了模拟，详细分析了窜槽对实际声场的影响。在此基础上，我们对存在裂缝的套管中的相控阵声场进行了仿真，并对采用柱面线性相控阵换能器对存在不同大小裂缝的套管进行扫描和成像的过程做了模拟，展示了套管中相控阵声场传播的物理过程。 实验上，对柱面相控阵在套管中的聚焦和成像特性进行了大量的实验研究，针对不同类型的套管以及不同类型裂缝、穿孔等缺陷，利用柱面相控阵进行了井壁扫描和成像的实验测量，对不同孔径的套管、不同尺寸的裂缝进行了成像实验。跟采用时域有限差分方法进行成像模拟得到的结果进行了分析和对比，两者符合得很好，表明了我们计算结果和实验结果的可靠性。另外，我们还分析了扫描实验过程中噪声产生的原因及相应的改进方法。 |
| 英文摘要 | Ultrasonic Phased Array can accomplish dynamic focusing and testing for the measured objects with complex geometry. Also it can improve greatly the detection sensitivity, resolution and SNR, which lead to its high recognition in NDT research domain. Aiming at the application of the ultrasonic phased array inspection in petroleum borehole and pipe, the radiation and scattering sound fields of the linear array, concave array and cylindrical array are studied theoretically and experimentally in this thesis. Focusing and imaging characteristics of these curved phased arrays are studied and analyzed comprehensively. According to the practical environments under the borehole, we designed and fabricated a rotating linear phased array and a cylindrical phased array for forward-looking and borehole-wall inspection in the borehole respectively. Both of these two phased array transducers work with central frequency 500kHz, active elements number 16 and maximum external diameter 92mm. The total element number of the linear phased array for the forward-looking is 40. The cylindrical phased array for borehole-wall inspection contains 112 elements which are finite strips distributing on the surface of the cylinder. Comprehensive analysis of the radiation sound fields has been carried out for the linear array, cylindrical array and concave array respectively. The axial, lateral and the whole space distribution of the focusing acoustic field and affect factors including distance between elements, number of elements and F number have been also investigated in detail. We developed programs for calculating scattering sound field of the phased array in cased borehole by means of 2.5 dimensional and 2 dimensional finite difference methods in time domain, and studied wave propagation characteristics in the casing. Firstly, the acoustic field in the cased borehole and the influence of the grooves on the casing borehole wall are analyzed. On this basis, the sound field of the phased array in the casing with cracks is simulated. The imaging process of the casing with different fractures using cylindrical phased array is also simulated. The wave propagation process is showed up in the thesis. Many experiments about the focusing and imaging characteristics of the cylindrical phased array for casing inspection have been conducted. Imaging experiments for different size casing and cracks have been done using the cylindrical phased array. The imaging results agree well with the simulated imaging results. It shows that both the experimental and simulated results are reliable. Furthermore, the reasons of the noises in the scanning experiment and relevant approaches to improvement are analyzed. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 145 |
| 源URL | [http://159.226.59.140/handle/311008/462]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 师芳芳. 曲面超声相控阵聚焦与成像特性研究[D]. 声学研究所. 中国科学院声学研究所. 2009. |
入库方式： OAI收割
来源：声学研究所
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