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  1. KyleSong

    Riks method cannot progress to the designated axial displacement after buckling occurred

    If not displacement control, can you suggest me an alternative way to be the load scheme? I want to nominate the compression load at the very beginning, but how to determinate the magnitude of this applied load, so that the program can break it down and carry out a series of increments...
  2. KyleSong

    Riks method cannot progress to the designated axial displacement after buckling occurred

    I just imitate the situation in experimental testing, which use displacement control. Can you inform me what is the normal way to exert loading scheme? By the way, the model give reasonable prediction for the modelling process before peak load. Regards, Mengli
  3. KyleSong

    Riks method cannot progress to the designated axial displacement after buckling occurred

    Dear All users for Riks: It is such a gospel to have Riks as a numerical tool to model structure buckling behaviour. However, there is a puzzle for me, when I model a column with solid square cross-section under compression. I used displacement control as loading method. the model can nicely...
  4. KyleSong

    Does anyone know what is the difference between general static and general Riks algorithm?

    Dear mates here: I got a question if I don't introduce any imperfection to General Riks, and load the same structure with the same load, what is the difference between General Static and General Riks? From the previous topic, there is an answer from Martin: Riks is best suited to problems...
  5. KyleSong

    How to apply pressure with different magnitudes along the axial direction of the bar?

    Hi all friends: I am modelling a round bar under axial compression, and want to impose pressure to the body through out the lateral surface, and I want the magnitude of the pressure varies along the axial direction of the bar, I cannot find any suitable way to give this load in the list of load...
  6. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Dear TGS4 and other friendly mates here: I am coming back, I got another tough issue that sounds very silly, but it still makes me struggle a lot, I beg for your help again！ I am modelling a steel bar that under compression, and want to find its non-linear buckling behaviour, and I use C3D8...
  7. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Yeah, I agree with you largely, but based on the attached diagram I got from bar buckling introduction in Wikipedia, for a bar during elastic state, it should shows a bifurcation buckling. But you said a collapse of my structure, actually it won't collapse at all, I use Riks to analyse...
  8. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    sorry TGS4! My problem is: acting compressive load to a steel bar, which has round section shape, diameter is 12mm, two ends are pinned boundary conditions, I used displacement control to impose load to the bar. At this stage, I try to model its non-linear buckling behaviour, as well as...
  9. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    sorry TGS4! My problem is: acting compressive load to a steel bar, which has round section shape, diameter is 12mm, two ends are pinned boundary conditions, I used displacement control to impose load to the bar. At this stage, I try to model its non-linear buckling behaviour, as well as...
  10. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Dear TGS4: Thanks very much for your fast reply! Yes, I understand what you mean by now! and yes, not too many people consider the imperfection in actual design, and this is definitely a problem for designing. And from your information provided, the challenge of introducing geometrical...
  11. KyleSong

    What I should do if the critical buckling load doesn't make any sense?

    Dear Mustaine3: Thanks for your kind reply! Yes, it is a good idea to set the load as close to the estimated value as possible, but since we know the critical load equals to the load I set in load module multiplied by the corresponding eigenvalue, if set it as 1, the critical load could be...
  12. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Dear TGS4: Thanks for all your previous kind help, now I successfully captured the buckling critical load, but the load decrease sharply right after the buckling point in the load-displacement diagram, so I think the imperfection introduced into the riks may not be the appropriate one, and I...
  13. KyleSong

    What I should do if the critical buckling load doesn't make any sense?

    Dear friends here: Thanks for your reply to my previous questions, and I learnt really a lot from this forum, thanks everyone who helped me, May all the things goes well on you! Now, I found a serious problem when I using buckling in linear perturbation. I know the critical load equals to the...
  14. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Yes, I got the same feeling it indeed a art work in scientific research, yes, that is a good idea to find a actual failure example and calibrate the imperfection to reoccur the result! Thanks very much for your kind reply! And there is a course carried out by SIMULIA, do you think the content...
  15. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Dear TGS: 2016 already arrived, May all the thing goes well on you in the new year! After you tell me the method of including the imperfection and I just do as you told me to include imperfection to my model through editing keywords according to the documentations you referred. But I got two...
  16. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Thank you TGS4,I got it, thank you very much!
  17. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    And TGS4, does the "seeds" you mentioned defined in " initial state field" in the initial step, or where I can specifically define it? Thank you very much!
  18. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Thank you very much for your insightful answer, and these things I even never heard of... And may I ask you a question, Where did you know these details? The abaqus official documentation? If it is okay to let me know, just tell me the source to know the method, I feel so stressful at the...
  19. KyleSong

    Riks in ABAQUS: Is this the forth stopping criteria for Riks?

    Thanks very much TGS4, you are right, if no initial imperfection or perturbation, the result is definitely just about yielding, but that bring up another issue, how to input a initial imperfection, I know we can run a eigenvalue step at first, and then follow it with Riks step. For this，in...
  20. KyleSong

    Linear Buckling and Symmetry

    Yes, if you find you got different results when you use full model and half model under the same circumstance, I think we are in the same trouble, I am also sincerely ask for help from someone who know the trick of this. I got a similar problem, for a simple bar under compression, and since the...

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