3PB Impact Test

Do you try to calculate with different mesh density?

Yes. I've tried from 6mm characteristic length elements until 1mm and the solution appears to be well converged

Yes. I've tried from 6mm characteristic length elements until 1mm and the solution appears to be well converged

You say there're 20% different comparing to experimental results, but that's deformation or stress?

Applied force over time

The deformation is imposed by the punch's constant velocity

Maybe try to refine more your mesh?

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I've figured it out. I had inertial problems due to poor sizing of the structure. The paper I am using considers the section's characteristic length as the inner dimension (to which you add the thickness) and not the average one. The section I was using was then undersized and therefore the bending force the beam was able to sustain was lower. 

Thanks anyway! Using a more refined mesh is helping me reaching a better solution

Always using a more fine mesh will give a better solution but will increase the solving time. So, keep the best element size which will give good results and meanwhile solves quickly.