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  1. Kat_kat

    Convergence problem during analysis

    Because I am a beginner, I am not sure how to interpret some of the results in the .msg file so I'm uploading it here in case someone wants to take a look. Thank you.https://files.engineering.com/getfile.aspx?folder=5593560d-22ce-4325-9f10-875bf4741a27&file=Imperfection_Riks_2.msg
  2. Kat_kat

    Convergence problem during analysis

    The imperfection isn't from a buckling analysis. I calculated the node coordinates based on a given f(x) and defined each node in the .inp file. I also tried adjusting the amplitude of the imperfection but with no result. Thank you for the link to read msg files, I didn't know something like...
  3. Kat_kat

    Convergence problem during analysis

    Hello, I am trying to run a Riks analysis on a straight pipeline with an initial small imperfection. I define the nodes, apply pressure and weight loads and then I start the Riks analysis. I have tried many many times but the model doesn't seem to converge. Not even when I apply the pressure or...
  4. Kat_kat

    Introducing imperfection in model

    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)...
  5. Kat_kat

    Modeling pipe with elbow and shell elements

    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...
  6. Kat_kat

    Modeling pipe with elbow and shell elements

    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...
  7. Kat_kat

    Model buckling of pipe with shell elements

    Thank you, i'll check it out. I have one last question. I tried modeling the same exact problem but instead of the 2 coupling constraints at the ends I used 2 parts that basically act like the pipe's ends. I used the same shell elements as the pipe and a material with a much higher Young's...
  8. Kat_kat

    Model buckling of pipe with shell elements

    Thank you for your reply. Yes, the analytical result is 249418.72 N. I tried what you suggested and the first eigenvalue comes to around 227162 N. Is there any way to decrease the error between the analytical and the abaqus result? Maybe increasing the elements number or changing the element type?
  9. Kat_kat

    Model buckling of pipe with shell elements

    Sorry for taking so long to respond. The boundary conditions are: Left end: ux=uy-uz=0 (pinned) Right end: ux=uy=0 (roller) For the shell elements i used S4R elements For the thickness: first i sketched the cross section with the internal radius and set the length of the pipe using extrusion...
  10. Kat_kat

    Model buckling of pipe with shell elements

    Hello, I'm having a problem modelling a straight thick pipe under compressive axial load with shell elements. I'm interested in finding the eigenvalues/eigenmodes of the pipe using a linear perturbation step (buckle). Before that, I have tried to model the pipe with elbow31 elements and the 1st...

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