基于伪谱法合成零偏移距记录的结构损伤探测与成像

该文讨论了如何利用伪谱法合成零偏移距记录进行结构损伤探测与偏移成像。从二维标量波动方程出发推导了不同情况下的数值计算公式。采用反周期扩展法对边界吸收问题做了有效处理,消除了边界反射产生的假象和干扰波场。用波场外推法合成得到了能适应复杂损伤形态和横向变速介质的零偏移距记录。根据波动方程分析了伪谱法的数值频散性、奇异性以及波场形态、位移、振幅、能量、动应力集中系数等力学特征,通过波动方程的位移解得到波场快照图和时间剖面图,实现了结构损伤可视化探测与识别。数值算例证明了伪谱法偏移成像的适用性。

STRUCTURAL DAMAGE DETECTION AND IMAGE BASED ON THE ZERO MIGRATION RECORD OF THE SYNTHETICAL PSEUDO-SPECTRUM

The structural damage detection and migration image based on the zero migration-record of synthetical pseudo-spectrum are discussed. The different forms of numerical calculation formula are deduced from the scalar wave equation of two dimensions. The problem of boundary absorbility is handled by the counter-cyclical extension, which eliminates the illusion of boundary reflection and the disturbance wave. The zero migration record which synthesized by the wave field extrapolation can adapt the complex damage form and the medium in which transverse velocity changes obviously. The dynamic characters of pseudo-spectrum, such as bizarrerie, frequency dispersion, wave shape, amplitude, displacement, energy and concentration coefficient of dynamic stress, are analyzed according to the wave equation. The snapshot and time section of the wave field are obtained which realize the visual detection and recognition of the structural damage. The numerical example shows a good feasibility of the pseudo-spectrum migration to engineering structures detection.