焊接接头超声检测CT成像的双线性内插算法

超声波具有明显的衍射特征,当被检焊接接头不均匀程度较大时,超声CT在投影定理的推导、重建算法上存在一定的困难。依据非均匀介质的波动方程,采用双线性内插后的直接傅立叶反变换算法重建物体的二维图像。文中论述了双线性内插的详细算法和软件流程,并用此方法对模拟的焊接接头断面形状进行了图像重建,获得了满意的成像效果,表明了该方法的有效性。

A Bilinear Interpolation Algorithm for Ultrasonic-CT Image Reconstruction Needed for Fault-Detection in Welded Joint with Some Non-Uniformity

Aim.To our knowledge,we are the first in China to offer an algorithm for U-CT image reconstruction needed for detecting faults in a welded joint.When there exists some non-uniformity in a welded joint,the direct Fourier transform inversion is hardly usable for building image reconstruction algorithm.In the full paper,we explain the algorithm in some detail;in this abstract we just add some pertinent remarks to listing the two topics of explanation.The first topic is: bilinear interpolation algorithm.In this topic,we point out that the bilinear interpolation algorithm makes the direct Fourier transform inversion usable in reconstructing the U-CT image of a welded joint.We also select suitable parameters to represent the sampling data and identify the relationship between two types of parameters,thus acquiring the sampling data distributed in the points of a rectangular grid and then acquiring the function of a 2D image.The second topic is: the design of software for the algorithm.In this topic,we improve the mode of interpolation and present the flow chart of bilinear interpolation subroutine as summarized in Fig.4 in the full paper.Finally we simulate the image reconstructed by the algorithm,and the simulation results,shown in Fig.6 in the full paper,indicate preliminarily that the image of the section faults of a welded joint is satisfactory.