Discussion Forum

Hi,

I am trying to model magnetostricitve behaviour using COMSOL 5.2a magnetostricive physics. But I have some unexpected results, and I am hoping that somebody could shed some light on what is happening.

I set up a 2D model with a stationary study, of a beam, 1 m by 0.1 m, fixed at one end, this is my magnetostrictive element. I then set up a surround box, that is Air, where I place a uniform background magnetic flux density that is in the direction along the length of the beam. The structural mechanics for this example are set up for an nonlinear isotropic magnetostriction. I use a parametric sweep to sweep through a range of background magnetic fluxes.

If the boundary conditions for the air box are set to magnetic insulation nothing really happens, there is a very small spike at one point, that I attribute to statistical noise. If i change the boundary condition to external magnetic vector potential then more expected results occur, there is a strain in the beam of the order i would expect. Why does this boundary change make a difference to my simulation?

However, in this case there is also a deflection in the beam which I do not expect. I expect it to strain only in the direction of magnetic field and to be uniform. I also tried a different set up using coils for the field, for a solenoid with uniform field, which gave the same deflection.

And also when I change the thickness of the beam, i.e. reduce it, the deflection that I see also changes, it increases.

Why am I seeing this deflection in my beam?

Any help would be appreciated. Thank you in advance. Best Regards David