End Cap Pressure on FEA Pipe Model

[m_ridzon]

Folks,

My apologies as I feel like this answer should be obvious to me, but unfortunately I'm having a brain freeze. The attached image shows a pressurized pipe being modeled in FEA. Although not shown, both ends have bolt flanges that attach to nearby rigid equipment. Therefore, I fixed both ends of the pipe in the FEA model. I run the FEA and get reaction forces at one end that do not match the other end (not even close). Then I started to wonder about how/if "end cap" pressure is the reason and somehow needs included in the model. Since the pipe is firmly attached to rigid equipment, I don't think it needs to include "end cap" pressure. However, I'm trying to understand the reason for mismatched reaction forces at the ends.

 

[cbPVme]

Is the inner bore diameter the same on each end? I am not sure if it is just the model orientation, but the right side bore diameter looks smaller which would give a smaller reaction force. Otherwise I think either you are missing pressure on an inner surface or the mesh is not fine enough.

 

[m_ridzon]

Thanks folks. I think I found the answer after chatting with colleagues this morning. After further thought, I don’t think the reaction forces need to be equal and opposite, for a given axis, since both ends are fixed. Both ends are merely restricting the applied pressure. In other words, the applied pressure in each vector direction will vary depending on the pipe faces (i.e., applied footprint) normal to that particular axis. I went further to calculate SRSS reactions in the YZ plane and they match, which was good. That tells me the YZ SRSS vector of applied pressure is being equally resisted at both ends.

Is the inner bore diameter the same on each end? I am not sure if it is just the model orientation, but the right side bore diameter looks smaller which would give a smaller reaction force. Otherwise I think either you are missing pressure on an inner surface or the mesh is not fine enough.

To answer your question...yes the bore is constant throughout. Yes, the applied pressure is applied to all inner faces throughout. I do appreciate another set of eyes on my work.