I am completely new to PreProMax. I am trying to run an analysis on this model which is a bracket to mount on the ceiling holding a display item.
I have not tried getting fancy with screws/bolts yet. The green surface is a fixed BC where the screws would go in the ceiling rafters. This is intended to go in to a corner along a wall and the yellow surface is a compression only constraint. This wall has only drywall and thin chipboard behind it, so no screws are planned but it will resist deformation in to the wall. The blue is a pressure load.
If I don’t include the compression only constraint, this passes. But once I include this constraint, it fails to solve due to lack of convergence.
I’d be appreciative of any feedback you all may have. I’m excited to bring home engineering up another level with FEA, but definitely need to learn this a fair bit more.
Hard to say without seeing the file, but do you have Nlgeom enabled ? Try changing the default settings of the compression-only constraint - reducing the stiffness and increasing the tensile force.
Also, if the geometry is simply extruded, it would be better to use Extrude Mesh to get a hex-dominated first-order mesh.
Yes, I have Nlgeom enabled. I will try changing the forces and see if that helps. If it’s helpful to share the file, I’m assuming sharing the PreProMax file? And just attach it to the post?
Yes, you can share it directly here, use some hosting website or send it via pm.
Thank you! With that said, decreasing the spring constant worked.
Yeah, the default stiffness is very high (10^12 N/mm), similarly to hard contact. It may have negative impact on convergence, so it often makes sense to reduce it to a reasonable level (not too much, of course). This usually helps the solver converge, just like using linear (softened) contact between the parts.
1 Like
