Thank you! I'm glad I could help.

First, thanks for watching! It is a bit more nuanced than just saying everything happens at a node or integration point (I was trying to keep it simple). In the context of elasticity, the typical finite element formulation constructs the solution from nodal displacements that are interpolated over an element using shape functions. Integration points are used with these shape functions for the construction of the stiffness matrix, essentially turning a kind of energy minimization problem over a volume (requiring integration over that volume) into a set of algebraic equations. Once we reduce the problem to a system of equations in the form of Stiffness*Displacement = Force, we solve for the displacements, and these quantities reflect nodal displacements. However, the strains and stresses that we derive from these displacements (because they come from derivatives of displacement which depends on the particular choice of shape function) are NOT nodal values. This means it is correct to say, as you have done, that the stress and strain solutions are evaluated at the integration points and then extrapolated to the nodes, but at the same time the displacements themselves are nodal quantities that are interpolated throughout the element.

It's tough to diagnose what is wrong here just using your error message, but my guess is that you did not define CONC higher up in the model. It could also be something weird going on in 2024 R2 (I don't have that version, so I can't easily check that...) Anyway, try creating a material assignment in the Materials section of your model tree. Select whatever geometry you want to have the material for CONC for the scoping method, then give it some arbitrary material assignment. Preferably, for sake of organization, give it a unique material that you are not using somewhere else in the model, but it doesn't matter what the material properties actually are because we will change all that in the APDL script later. Finally, create a Command for that material assignment (right-click on the material assignment and Insert >> Commands). The only line of code you need in this command is... CONC = matid That should create the CONC variable and set it equal to the material ID of the material assignment you just created. Now when you use CONC in later commands, it knows that it should only apply to that specific material ID.

hi

Well, I'm glad it helped in some way, even if I didn't answer your question. Good luck with your modeling!