Modeling pipe with elbow and shell elements

[Kat_kat]

Hello, I have a question concerning elbow elements in Abaqus.

I am trying to model a pipe that is made from a mix of elbow elements and shell elements under a constant internal pressure. I read that Abaqus assumes a closed-end condition for ELBOW elements and if an open-end condition is to be modeled, a compensating point load should be added at the open end. How should I go about applying that load? Is it as simple as calculating the force (F=p*A) and applying a concentrated force at the end of the elbow section? What direction should that force have?

Also, to see if Abaqus calculates correctly the axial force at the closed ends due to internal pipe pressure I modeled an elbow section with the BCs: u1=u2=u3=0 at both ends and applied constant pressure. But I didn't get the results I expected. Is my way of thinking flawed? Has anyone tried something similar?

Thank you in advance!!

 

[FEA way]

That’s right, the approach you described is used when calculating stresses in pipes. This concentrated force should be applied in the axial direction.

Kinematic boundary conditions are applied to elbow elements as usually. Their choice depends on what kind of pipe system you want to model and which assumptions are appropriate for you.

 

[Kat_kat]

If I have an elbow section, followed by a shell section, followed by an elbow section (elbow - shell - elbow) with the appropriate tie constraints, is it necessary to add the compensating loads or because the model is symmetrical, the forces that Abaqus calculates due to the closed end condition will cancel each other out?