IMAGING LAMINAR DAMAGE USING PLATE WAVE ULTRASONICS AND PROPOSED METHODOLOGY FOR DESIGNING OPTIMAL TRANSDUCER NETWORKS

摘要

This paper presents the application of plate wave ultrasonic beam forming and diffraction tomography to detect, locate and characterise laminar damage in plates. Beam forming is using a network of transducers that are used to sequentially scan the structure before and after the presence of structural damages by transmitting and receiving guided wave pulses. An image of the damage is reconstructed by analysing the cross correlation of the scatter signal with the excitation pulse and enables the detection and location of potential damage areas. Plate wave diffraction tomography attempts to quantitatively evaluate damage information using a one-to-one linear relationship between scatter field measurements and the 2D Fourier transform of variation functions that describe material parameters within the damaged region. The results of systematic simulation and experimental investigations illustrate the potential of these methodologies, which are capable, for example, to detect damage with locating inaccuracies in the order of a few millimeters within inspection areas of 300 x 300mm2 using only four transducer elements and in some cases damage well outside the inspection area. The paper also briefly discusses strategies to design optimal transducer networks using methodologies adapted from probabilistic system optimisation theory with the aim to determine the optimal number and location of transmitter and receiver elements for a particular damage case.