I'm having troubles with a refine mesh size of 0.1mm

Hello! i was doing a refine process of the mesh in another more complex model than I show below, to get the stress results convergence with mesh independence. When I ran the solver Optistruct, it was stuck more than two hours in 0.00%, so I aborted the solver.

I tried to found out what was happening, so I did a simpler model like a cantilever beam with the same situation, a refinement box with a 0.1mm mesh size, and it happened the same. 

I show in the image below the cantilever beam with a 0.1mm refinement box:

What's happening? I hope somebody can help me, thanks!