Guided Wave Phased Array for Inspection of Plate Structures

This paper describes a general approach for processing data from an omni-directional guided wave transducer array for the rapid inspection of large plate structures. A basic phased array algorithm is presented that can be applied to any array geometry. The beam forming is the method in which the phase-coherent signals at different sensors are superimposed such a way that the sum will have maximum amplitude. This phase-coherent line in fact coincides with the front line of the propagating wave and thus the shape of the wave front is determined to be similar to the spatial shape of the array. Because the circular array which must be in general uses due to its symmetricity to all directions has the different shape to the wave front, its beam pattern is poor with high sidelobe levels. By projecting the array onto the wave front, the compensating weights are proposed to reduce the sidelobes. The proposed beam enhancement weights improve the inspection performance with well designed and established beam pattern. For guided waves on plate, beam steering algorithm is derived and the corresponding beam pattern to the array shape is well obtained. The processing algorithms are sufficiently investigated by applying to some simulation and experimental cases. The results show well the usefulness of the proposed methods in guided wave phased array for structural inspections.