Abstract

The paper proposes to use the ultrasound tomography method based on the solution of the inverse coefficient problem to reduce the level of pattern noise. Mathematical models used in ultrasound tomography well describe such physical effects as refraction, diffraction, and rescattering. It is logical to expect that reconstruction of the internal structure of metallic samples using ultrasound tomography is more efficient compared to digital antenna focusing (DFA) techniques. Due to the nonlinearity of the inverse problem of ultrasound tomography, an iterative MultiStage method is used to ensure convergence to the global minima of the residual functional. The paper presents the results of numerical experiments to reconstruct the image of the internal structure of a welded joint that may contain side drilled holes and crack models. A domain of welded metal is represented in the form of sections constructed according to the principle of Voronoi diagrams. In each section, the velocity is constant and its value is randomly distributed. In the model adopted in the paper, the pattern noise is formed due to multiple scattering at the boundaries of sections with different sound velocities. It was assumed that the antenna array is located on the outer surface of the test object of known thickness. The obtained results show that the tomographic method allows one to determine the shape and speed of sound in low-contrast reflectors, for which the DFA method is ineffective.

中文翻译：

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基于反系数问题的超声断层扫描作为对抗图案噪声的方法

 抽象的

本文提出使用基于反系数问题求解的超声断层扫描方法来降低图案噪声水平。超声断层扫描中使用的数学模型很好地描述了折射、衍射和再散射等物理效应。与数字天线聚焦（DFA）技术相比，使用超声断层扫描重建金属样品的内部结构是合乎逻辑的。由于超声断层扫描反问题的非线性，采用迭代MultiStage方法来确保残差泛函收敛到全局最小值。本文介绍了重建焊接接头内部结构图像的数值实验结果，该焊接接头可能包含侧面钻孔和裂纹模型。焊接金属的域以根据 Voronoi 图原理构造的截面的形式表示。在每个部分中，速度是恒定的，其值是随机分布的。在本文采用的模型中，图案噪声是由于不同声速截面边界处的多次散射而形成的。假设天线阵列位于已知厚度的测试物体的外表面上。所得结果表明，断层扫描方法可以确定低对比度反射体中声的形状和速度，而 DFA 方法对此无效。