结构混凝土超声波层析成像的反演算法研究

针对混凝土超声波层析成像结果不唯一和稳定性差的问题,首先依据超声波在混凝土中的传播特点,在反演算法中引入物理意义明确的自然权矩阵,对走时较小的射线和射线较密的成像单元加以重权.然后通过混凝土速度反演的数值模拟和模型试验,对反演算法进行了比较研究.结果表明,相对于最小二乘法和阻尼最小二乘法,基于自然权的加权阻尼最小二乘算法,由于利用了正确的先验信息,不但使反演过程收敛,而且具有数值稳定、抗噪能力强的优点,其成像结果能真实有效地反映对象内部缺陷,因此更适用于混凝土的超声波速度反演.

Inversion Algorithm Study on Ultrasonic Computerized Tomography for Structural Concrete

Considering the nonuniqueness and instability of ultrasonic computerized tomography for structural concrete as well as the ultrasonic transmission characteristics in concrete,a natural weight matrix with clear physical meaning was introduced in the inverse algorithm.Ultrasonic rays with short travel time and image meshes passed by more rays were given heavy weights.Different algorithms were compared in the numerical simulation and model experiment of concrete velocity inversion.The results showed that,compared with the least-square solutions and the damped least-square solutions,the damped and natural weighted least-square solutions reflected the inner defections of the tested object more reliably and exactly due to the usage of correct priori information,which benefited the suppression of noises and made the iterations of inverse stable and convergent.