Abstract
There is an increasing demand for better and more accurate non-destructive evaluation and testing techniques for ferromagnetic materials, in particular, steel structures, which span diverse industrial sectors. Among the available methods, the measurement of the harmonic content and the corresponding distortion due to the material non-linearity is one of the most widespread approaches, with significant implications in the steel industry. Although these approaches have been in use for several decades with considerable success, crucial aspects, including the sensor design, the fine-tuning of the method, and, most importantly, the processing and interpretation of the acquired signals, remain, to a certain degree, empirical. Meanwhile, significant progress in simulation and data processing techniques has been reported in recent years, whose potential in the further development of the existing measuring technology cannot be overstated. In view of this rapidly changing landscape, the present review article aims to provide an overview of the state-of-the-art of the harmonic distortion measurement technique from the perspective of the recent advances in simulation and inversion methods.