Beam divergence calculation of an electromagnetic acoustic transducer for the Non-Destructive Evaluation of plate-like structures

Ultrasonic guided waves are now proving to be a viable method for real-world long-range Non-Destructive Evaluation (NDE) applications. In order to generate a specific guided wave mode optimally, knowledge of the sensor parameters becomes imperative. This paper attempts to experimentally measure the beam divergence in an Electro-Magnetic Acoustic Transducer (EMAT) that is used to generate Shear Horizontal (SH) guided waves in a mild steel plate. The commercial finite element package ABAQUS™ is then used to run 3D simulations to validate these experimental results. Based on these results, a planar defect study is also carried out. From all these investigations, the minimum degree of rotation of the EMAT can be set when used in a real-time ultrasonic guided wave omni-directional inspection system.