Guided wave topological energy method for quantitative evaluation of corrosion in metal plates and tubes

Monitoring and controlling corrosion defects in metal components is a major challenge for various industries, such as nuclear or oil & gas. Guided ultrasonic waves have already shown great potential for the rapid characterization of this kind of damage in thin-walled structures, including in hard-to-reach areas. The objective of this work is to apply the topological energy imaging method to ultrasonic waves guided in plates and tubes. Its applicability to the quantitative assessment of corrosion defects will be examined with a focus on determining defect contours and quantifying thickness loss, as the guided wave tomography methods would attempt to do. The method is based on numerical models and experimental measurements. The propagation of ultrasonic waves is modelled in the time domain by finite elements. First, a corrosion thickness loss is simulated by introducing a calibrated defect in the form of a flat bottom hole (FBH). Then, a corrosion defect with a more realistic shape and an irregular profile in the depth is taken into account. The experimental validation is performed for an aluminium plate and a steel tube. The presented results are obtained for monomodal propagation, using one of the fundamental Lamb modes. They show that it is possible to characterize the defect with a resolution in the order of one wavelength by optimizing the design of the sensor network.