General Mechanical

General Mechanical

I get a different behavior when I select different numbers of loading steps

    • 19yuuki91
      Subscriber
      HinnI am doing a simple compression test simulation of a mortar cube. It has been defined using solid65 element and as far as I know everything in this aspect works fine. However, I have noticed some peculiarities. The load imposed is a negative vertical displacement, if I only use one loading step, I get a non linear behavior of the element. However, if I utilize more loading steps but the final value is the same as the case before, I get a completely different behavior, In some cases it even remains in the linear range. As I am doing a static structural modelling I understand that each load step is applied statically, so there should not be any concerns regarding a loading speed or rate. I would like to ask your opinion about this, maybe there is something I am misunderstanding regarding loading steps.nnThank you very much for your help.n
    • Daniel Shaw
      Ansys Employee
      Do you have the load step applied or ramped applied? If the load is step applied in a non-linear solution, the results may be different than if the load is ramped applied. Also, do you have automatic time stepping active? n
    • Kai
      Ansys Employee
      can you explain what you mean by linear range and nonlinear range? Did you turn on large deflection under analysis settings? Do you have any screenshots to show the results discrepancies? n
    • 19yuuki91
      Subscriber
      Do you have the load step applied or ramped applied? If the load is step applied in a non-linear solution, the results may be different than if the load is ramped applied. Also, do you have automatic time stepping active?nHi @danielshaw, thanks for your answer and I apologize for the lack of specificity in my question. Automatic time stepping in on. The next screenshots show the load being applied in one step and in 100 steps, both reaching the same maximum value. In both cases the load (displacement) was applied using tabular data, if the displacement is applied as constant, which then makes it appear as ramped then there is no solution convergence.nArrayArrayArrayArraynnI did a comparison of both behaviors (the results of 1 step vs 100 steps) and as you can see there is a slight difference towards the end. Additionally, they both have different values of max strain. Do you think it has to do with the length of the load step that is causing this difference? As I have discovered with your inquire is that indeed I do not understand the difference when a load is applied using tabular data or ramped. Thank you very much for your help and I apologize if my problem ends un being trivial.nnBest regardsn
    • 19yuuki91
      Subscriber
      can you explain what you mean by linear range and nonlinear range? Did you turn on large deflection under analysis settings? Do you have any screenshots to show the results discrepancies?n thanks for your answer. My model does not have large deflections on. I apologize for not being specific enough, with 's comment, I realized that there is a difference when the displacement is applied as ramped or in tabular data. For more details please look at my comment replying to.nnBest regardsn
    • Kai
      Ansys Employee
      I recommend that you turn on large deflection in order to get more accurate results. The results look suspicious, for example, I don't understand why the orange line (100 steps) is a polyline towards the end. Instead, strain should always increase.n
    • 19yuuki91
      Subscriber
      thanks again for taking your time and providing an answer. I turned large deflections on and it still presents that weird behavior where the curve goes back and forth. That makes me think that I might have an error in another part of my model. I will check other aspects of it and comeback with my findings, if I am able to detect any error. Thank you n
    • 19yuuki91
      Subscriber
      I am sorry for taking this long, but I was able to solve my problem. In general, my error was that I was plotting data of different points of my model. As in, I was taking the stress data of one point, and the strain of another. That is why I had that zig zag behavior on the plot and also why I experienced variation when I selected a different number of steps. nOnce I made sure I was plotting data from the same point, I got the same behavior even if I changed the amount of loading steps. Thank you for your help.nnnBest regards.n
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