Magnetic response from micro and macro scale is widely used for stress evaluation in Non-destructive testing and evaluation. The basic principle is that the magnetic domain pattern and magnetic domain dynamics is highly depend on the applied tensile stress. Understanding the evolution of magnetic domains under the action of multi-field coupling is critical for developing novel magnetic non-destructive testing technologies. In this work, the effect of stress on magnetic domain and magneto-acoustic emission signals in polycrystalline materials was investigated based on the magneto-optical Kerr imaging and magneto-acoustic emission detection system. From the macroscopic scale, the mapping relationship between the magneto-acoustic emission signal and stress is established. Microscopically, the influence of the stress and grain boundaries on the magnetic domain patterns were investigated. And the correlation between supplementary domains and stress are built. Finally, the interrelation between the domain wall dynamics and the magneto-acoustic emission signal is revealed from the nucleation of supplementary domains and their stress-dependent evolution.
The results indicated that the magnetoelastic effect reduces the density of supplementary domains and 90° domains, which weaken the magneto-acoustic emission signal. The stress-magneto-acoustic model and the influence of the stress on the magnetic domain in this work reveals mechanism of magneto-acoustic emissions technique for stress measurement. It also provides a theoretical foundation for advancing stress-magnetic-acoustic models and magnetic non-destructive testing technology.