基于混沌模拟退火回火算法的结构混凝土超声层析成像

针对混凝土超声波层析成像结果不惟一和稳定性差的问题,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,形成了二次增广目标函数方程;然后,通过混沌模拟退火回火算法来寻求其全局最小值,从而得到各网格单元的声速计算值。在寻优过程中,其初始值由反投影法求得。模型试验表明,由于利用了正确的先验信息,加上混沌模拟退火回火算法在寻找函数极值方面具有优良的特性,不但反演过程收敛,而且数值稳定,其成像结果能真实有效地反映对象内部缺陷,因此,该算法适用于混凝土的超声波速度反演。

Ultrasonic computerized tomography for structural concrete based on chaotic simulated annealing and reannealing algorithm

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,which gave heavy weights to ultrasonic rays with short travel time and image meshes passed by more rays,was introduced in the inverse algorithm.In order to get a quadratic augmentic goal function,the chaotic simulated annealing and reannealing algorithm was proposed,so as to search the global minimum of this function,which was also the velocity values of the meshes.In this process,the initial value was obtained through the back projection algorithm.The model experiment results show that not only the inverse process is convergent,but also the numerical value is stable.That is contributed to the usage of the corrct priori information and the excellent characteristic of the chaotic simulate annealing and reannealing algorithm in searching the global minimum value of function.The image result reflects the inner defections of the tested object reliably and exactly.As a result,this algorithm is applicable to ultrasonic velocity inversion for structural concrete.