Quantification and localization of a surface crack in a thick aluminum plate using Rayleigh waves electromagnetic acoustic transducers

Surface cracks are measured and analyzed in different materials, structures, or some of its components to determine its severity, rate of growth, and potential impact on integrity. In different research materials, structural health monitoring, and civil engineering like areas, the evaluation of cracks is very critical. To accurately quantify the depth of surface crack using conventional nondestructive testing techniques it is very challenging. The current work includes the development of a novel Velocity-Time (V-T) graph approach that uses Rayleigh wave to quantitatively evaluate the depth and localization of surface-breaking cracks. Structure of aluminum alloy with slots of various depths was studied both experimentally and numerically. To investigate the interaction between surface breaking cracks of varying depths and Rayleigh surface waves generated by a point Rayleigh wave EMAT, a two-dimensional (2D) numerical model based on the finite element approach was developed. Rayleigh waves are utilized to quantify the depth of surface cracks in a metallic structure based on proposed approach. This method makes use of Rayleigh waves that are directly related between a fixed transmitter and a uniformly moveable receiver. A pair of similar electromagnetic acoustic transducers (EMATs) operating in a pitch-catch mode were employed to generate, propagate and receive Rayleigh waves at the surface of the structure. An analytical expression for the evaluation of crack depth has presented. The experimental results has showed that this time-of-flight method can be utilized to properly measure the depth of crack and agreed well with the numerical simulation. This study has provided a feasible idea to analyze thick plates using Rayleigh wave EMATs to quantitatively estimate the depth of surface-breaking cracks. Results have showed that this novel approach has significantly amplified the accuracy of surface crack localization and quantification (with a maximum error of 6.7%).