Damage Detection of a Plate Using Migration Technique

This paper demonstrates a feasibility study of applying migration, which is widely used as an advanced data processing technique in geophysical exploration, to detect damage in a plate. This technique suggests a scheme that may build a real time, in situ, and quantitative health monitoring system. A linear actuator/sensor array is placed along a horizontal central axis on a square homogeneous isotropic plate. A technique is proposed to utilize piezoelectrics as both actuators and sensors to generate and collect the flexural waves in the plate. Migration technique is then adopted to interpret the recorded data and image the damage that formed in the plate. The wave field reflected from the damage is synthesized by using a two-dimensional explicit finite difference method to model the plate using Mindlin plate theory. A one-way version of flexural wave equation is derived. The one-way wave equation based poststack reverse-time migration is then used to back-propagate the synthetic wave field to their secondary sources, and the damage is imaged by applying appropriate imaging condition. The data pre-processing procedures before migration, such as muting direct arrival, deconvolution and stacking, are also discussed. The satisfactory determination of the locations and dimensions of the damages in several numerical simulation examples validates the feasibility of proposed monitoring system.