Prediction of plastic strain in Fe-Co magnetostrictive alloy using magnetic Barkhausen effect

Structural health monitoring techniques play a significant role in pre-service and in-service inspection of infrastructure, machinery, plant and equipment. In particular, in order to quickly detect fatal damage to a structure after an earthquake, the nondestructive and simple measurement of the local plastic strain and the internal damage of the structure is strongly desired. When a steel material is plastically deformed, the microstructures such as vacancies and dislocations, which affect the local magnetic properties, are drastically changed. Here, we focused on a noise-like magnetic signal called Barkhausen noise which is caused by the interaction between magnetic domain walls and microstructures in magnetization process. In this study, the waveform or the root-mean square value of Barkhausen noise depending on the plastically strains were investigated by an interrupted tensile test using tough and high magnetostrictive Fe-Co alloys. From the relationship between Barkhausen noise and dislocations, we propose a quantitative evaluation method of strain damage, which makes it possible to prolong the life of infrastructure structure.