【摘要】 超声波层析成像(CT)技术是最近发展起来的一种新型无损检测方法,该方法具有对被测对象无损伤、成像精度高、操作简单方便、结果可视化程度高等优点,在混凝土结构检测中得到广泛应用。超声波层析成像技术一般采用初至波的走时进行分析计算。因此,对走时提取的准确性至关重要。传统的超声波层析技术是利用最小走时射线追踪算法来计算初至波走时,计算效率低,且在复杂介质中存在不稳定性问题。为了快速、可靠地计算初至波走时,本文基于程函方程的有限差分形式,利用快速扫描算法实现了初至波走时的快速计算。将该方法应用于理论模型计算,并和现场采集的实测数据层析结果作对比,结果表明该方法可以取得与传统最小走时射线追踪相当的计算精度,但计算效率得到大幅提升。更多还原

【Abstract】 Ultra-sonic computer tomography(CT)technology is a new nondestructive detection method.The advantages of ultra-sonic wave CT are nondestructive to components of building,high resolution of image,convenience and high visualization effect etc.,which has been widely used in nondestructive detection of concrete structure.Ultra-sonic tomography is based on the accurate calculation of first arrival travel-time,thus the accuracy of extraction of the travel time is very important.Ray-tracing is the traditional method to get first arrival travel-time,which is limited by low efficiency and poor stability in complex structure.In this paper,the fast sweeping method(FSM)to get the first arrival traveltime stably and efficiently is used based on the finite differential operator of the Eikonal equation.Both this method and the traditional ray-based tomography are applied to theoretical models and field data.Tomography results indicate that the fast sweeping method-based tomography can retrieve velocity structure with similar accuracy as traditional ray-based tomography,while the computation efficiency is greatly increased.更多还原