General Mechanical

General Mechanical

Large Deflection Feature

    • ot2020
      Subscriber
      Hi, nI am conducting a bond-slip behaviour between rebar and concrete. When I run the model without specifying a bilinear model and only apply force that is equivalent to the rebar's yield strength with the large deflection ON, the model runs without error. nHowever, when I add a plasticity model (Bilinear isotrophic hardening) and keep everything else the same as previous, I get an error that says there are element that is highly distorted. nCould someone please suggest to me why this is happening and what I can do to fix this error? Mesh size used is 2mm. nPlease help! n
    • Gary Stofan
      Ansys Employee
      Click on Solution Information. In the Detail of Solution Information. Set Identify Element Violations to a number like 3.nRun the solution again. Several objects should now up under Solution Information. These should graphically show which elements have distortions.nLarge deflection and nonlinear materials require a more refined mesh. It is difficult to give an exact remedy, but I might start by using a 1mm mesh to nsee if the issue improves. You may also have to use much finer timesteps. nGarynn
    • ot2020
      Subscriber
      I have tried 1mm mesh. But the same problem persists? nI haven't utilised any APDL commands. I have just been using the structural steel given in the data library and added a bilinear model. nCould it be that I haven't modelled Concrete as a NL material? Because I am not sure how to do that. n
    • Gary Stofan
      Ansys Employee
      It seems as if your material properties are not defined correctly. nWhat I might do is analyze a single rebar by itself as if a cantilever, and make sure the deformation and stresses match expected values. This would prove that your material properties are reasonably accurate. nThere are many examples of Reinforced Concrete on Youtube. Search for Ansys Tutorial Reinforced Concrete Beam.nMany of the examples explain the non-linear material properties that are needed for a rebar analysis. nI would look for an example that is most similar to yours and work through it. From that, you can apply the material properties to yours. n
    • ot2020
      Subscriber
      nThank you for your reply. Could you elaborate on material properties are not defined correctly? Because all I did was add a Bilinear Property to the structural steel that is given in the engineering data library. This has worked for the videos shown in Youtube? Could there be any other reasons? nThanks! n
    • Gary Stofan
      Ansys Employee
      Anytime you add nonlinearities to a model, you often have to improve the mesh, and apply the loads more slowly. nTry reducing your load to 1/100 or 1/1000 of the value. Does it then solve OK? If so, you may have to adjust the timesteps when applying the full load. nTimesteps:. nIn the solver controls, set the Time Stepping to OnnThen,nInitial Timesteps 25nMinimum 10nMaximum 10000nAlso, Try refining the mesh. Say if you are using 1mm elements, try a little smaller, like 0.75mm or 0.5. Does it then solve OK?n
    • ot2020
      Subscriber
      nI have tried increasing the time steps, however have the same issue? nThe mesh size is set to 1mm because I would exceed the element and node limit if I make it smaller? nWould there be any other reason? nThanks!n
    • Gary Stofan
      Ansys Employee
      I cant offer much more suggestion without seeing the model. But we are not permitted to download any files.nHowever, if you clean all data and create an archive wbpz, perhaps one of the other users on the forum can take a look. n
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