Hello, I am a new user of ABAQUS.
I am trying to extract the eigenfrequency of the pipe to generate the dispersion curves. Now, the problems are ...
1. If I have a section of pipe in axisymmetric model, how can I make the same condition of the nodes at both ends like Ux (top) = Ux (bottom) and Uy (top) = Uy (bottom).
2. For wave propagation, there are 3 modes namely longitudinal, torsional, and flexural. If I use the axisymmetric model, I can get only the longitudinal modes because I can obtain the modes which are deformed in x-y direction.
How can I obtain the torsional modes which are deformed in z direction? I think that I have to use 3 DOF elements. Is it right? And how can I set this such type of elements in axisymmetric mode?
Dear Adisorn,
For your first problem, i'm assuming that the boundary conditions you have specified are fixed boundary conditions. If that is the case, then you can select the top and bottom regions while defining the boundary conditions in Load module.
For your second problem, it's better to use the 3D model instead of axi-symmetric. Because the frequency extraction is a linear perturbation analysis and Abaqus doesn't need much time to solve the frequency extraction analysis.
Hope my answer helps. Please let me know if you have any questions.
Thanks & Regards,
Ranjith.
Hello Ranjith,
Thank you very much for your help. Please let me explain more about my question.
For the first question, I am trying to link the displacement between both ends ... it likes a coupling, so the displacement of nodes on both ends are the same. Is it the fixed boundary condition?
For the second question, if I used 3D model, can I create only section of the pipe? If i can do this, how to make the program know that it is a section of pipe not just a plate?
Thank you very much
Dear Adisorn,
It seems that you are trying to apply a periodic boundary condition to model a lengthy pipe. Please correct me if i'm wrong. If so, you can define the periodic boundary condition in Abaqus.
If you really want to reduce the problem size you can create a 1/4 th of the cross-section of the pipe and apply cyclic symmetry boundary condition. As i mentioned earlier, linear perturbation analysis will not take lot of time, so it's better to model the complete cross-section of the pipe.
If possible, could you please send me a small picture explaining your model. It will be really helpful to give a suggestion. Based on your picture, i can create a simple model in Abaqus and send it across.
Thanks & Regards,
Ranjith.
Hello Ranjith,
Thank you very much.
I attached the file explaining about the problem in this comment.
Could you please help me to sort it out?
Yours sincerely,
Adisorn P.
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