A magneto-mechanical model on differential permeability and stress of ferromagnetic material

Stress has long been known to have major effects on magnetic properties of ferromagnetic materials. For many non-destructive inspection techniques this is usually an undesirable complication although it can also be exploited both to enhance defect signals and as a technique for monitoring stress. This require to know the effects of stress on the magnetic characteristic. However, the rele- vant research report on the relation of stress and differential permeability hasn’t been seen up to now. A magneto-mechanical model on differential permeability and stress was put forward according to dif- ferent investigators, which can be seen as an equation of the coupling relation between stress and mag- netic for ferromagnetic materials.