结构混凝土超声波层析成像的反演算法研究
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摘要
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.
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.
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.
引文
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[2]JENS TRONICKE,DARYL R TWEETON,PETER DIET-RICH ERWIN APPEL.Improved Crosshole Radar Tomographyby Using Direct and Reflected Arrival Times[J].Journal of Ap-plied Geophysics,2001,47(2):97-105.
[3]UETA K,TANI K,KATO T.Computerized X-ray Tomogra-phy Analysis of Three-dimensional Fault Geometries in Basement-induced Wrench Faulting[J].Engineering Geology,2000,56(1):197-210.
[4]任建喜,葛修润,蒲毅彬,等.岩石单轴细观损伤演化特性的CT实时分析[J].土木工程学报,2000,33(6):99-104.REN J X,GE X R,PU Y B,et al.Real-time CT Test on theMeso-damage Evolution of Rock Under Uniaxial Compression[J].China Civil Engineering Journal,2000,33(6):99-104.(InChinese)
[5]MARTINA J,BROUGHTON K J,GIANNOPOLOUS A,et al.Ultrasonic Tomography of Grouted Duct Post-tensioned Rein-forced Concrete Bridge Beams[J].NDT&E International,2001,34(2):107-113.
[6]石林珂,孙懿斐.声波层析成像技术[J].岩石力学与工程学报,2003,22(1):122-125.SHI L K,SUN Y F.Technique of Acoustic Tomography[J].Chi-nese Journal of Rock Mechanics and Engineering,2003,22(1):122-125.(In Chinese)
[7]黄靓,黄政宇.线性插值射线追踪的改进方法[J].湘潭大学自然科学学报,2002,24(4):105-108.HUANG L,HUANG Z Y.An Improved Method of Linear Inter-polation Ray Tracing[J].Natural Science Journal of Xiangtan U-niversity,2002,24(4):105-108.(In Chinese)
[8]宋林平.阻尼加权最小二乘地震走时层析成像[J].计算物理,1995,12(4):499-504.SONG L P.Damped and Weighted Least-Square Solution for Seis-mic Traveltime Tomography[J].Chinese Journal of Computation-al Physics,1995,12(4):499-504.(In Chinese)
[9]BERRYAN J G.Fermat’s Principle and Nonlinear TraveltimeTomography[J].Physical Review Letter,1989,62(25):2953-2956.
[10]黄靓.混凝土超声CT的数值模拟与试验研究[D].长沙:湖南大学土木工程学院,2003.HUANG L.Numerical Simulation and Test Study for Concrete Ul-trasonic CT[D].Changsha College of Civil Engineering of HunanUniversity,2003.(In Chinese)
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