Introducing imperfection in model

[Kat_kat]

Hello, I am trying to model a pipeline with internal pressure. I want to introduce an imperfection to the model through the *IMPERFECTION command. I tried:

(a) *IMPERFECTION, INPUT=Imperfection_Data.txt, and
(b) *IMPERFECTION (with the nodes and imperfection components in each direction below)
(*Imperfection_Data.txt is file containing lines with node number, x-displacement, y-displacement, z-displacement)

There aren't any errors or warnings while I run it, but if I import the .inp to Abaqus CAE end test the distance between nodes, the imperfection doesn't seem to be introduced. Do you have any suggestions as to what I'm doing wrong or how to check if the imperfection is introduced?

Also, I would like to clarify something, when I enter the x,y,z, displacement due to the imperfection, do I have to specify the final coordinates of the node or just how much it should "move" in each direction?
(For example, if I have node 55: (x,y,z)=(1,2,3) and I want the imperfection to move it to (x,y,z)=(1,5,7), I would have to write:
55,0,3,4 or 55,1,5,7)

Thank you in advance!

 

[FEA way]

Usually inperfections are introduced in form of scaled eigenvalue buckling modes from previous analysis. This recent thread might be useful for you:

https://www.eng-tips.com/viewthread.cfm?qid=478365

Also check the documentation chapter "Introducing a geometric imperfection into a model".

When you specify imperfections directly, you have to provide the node number first and then components of imperfection in each direction.