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针对混凝土质量检测的特点,采用弯曲射线进行超声层析成像。首先建立波速分布的网格模型,并引入最短路径法进行射线追踪,然后采用联合迭代重建技术(SIRT)反演成像。为使算法适应弯曲射线,对SIRT的计算步骤进行调整,增加外层迭代,以便对修正后的路径进行下一轮反演;为提高反演精度,根据射线传播距离、幅度衰减、频率突变等信息建立和调整信号可信度系数,并依据该系数在求取网格慢度修正值时进行加权平均;为缩短计算时间,动态调整网格节点个数,并进行双向最短路径追踪。经过数值模拟及对混凝土基桩的实测,证明该方法在计算准确性和精度上有明显改进,计算速度也可以满足工程应用的需要。
According to the characteristics of concrete quality testing, the use of bending radiography ultrasound tomography. Firstly, the grid model of wave velocity distribution is established, and the shortest path method is introduced for ray tracing. Then, the joint iterative reconstruction (SIRT) inversion imaging is used. In order to adapt the algorithm to the bending ray, the calculation steps of SIRT are adjusted to add the outer iteration to make the next inversion of the corrected path. In order to improve the accuracy of the inversion, according to the ray propagation distance, amplitude attenuation, frequency mutation Information to establish and adjust the signal reliability coefficient, and based on the coefficient in calculating the grid slowness correction when the weighted average; To shorten the calculation time, dynamically adjust the number of grid nodes, and two-way shortest path tracking. After numerical simulation and measurement of concrete foundation piles, it is proved that the method has obvious improvement on calculation accuracy and precision, and the calculation speed can meet the needs of engineering application.