LS Dyna

LS Dyna

Geometry does not seem to ‘fall’ under gravity load

    • myvue
      Subscriber

      Hello Everyone,

      I am applying gravity load on a geometry (consisting of blocks in touching each other and fixed at the bottom) in LS-Dyna. I am using *Load_Body_Z keyword to simulate gravity. For contacts, I am using ''Automatic Surface to Surface Tiebreak''. However, in the results, the unsupported/unfixed geometry does not fall under its own weight in the animation. I want to see it falling. Any idea why this is happening?

    • Akshay Maniyar
      Ansys Employee

      I think the issue is with the contact. TIEBREAK allows the modeling of connections which transmits both compressive and tensile forces with optional failure criteria. So if there is TIEBREAK contact between parts then it will not fall under gravity as it is glued with supporting part which is resting on other part. Can you try with some other contact and check.

      regards amaniyar
    • myvue
      Subscriber

      Thank you for your reply. I changed the Tiebreak contact to 'Automatic Surface to Surface' contact. However, the result remains similar. The parts on the left (or any parts for that matter) do not seem to deform or fall under the force of gravity.
    • Erik Kostson
      Ansys Employee
      Hi

      Do you simulate long enough to see them falling or ?

      Also try one part to see if it is behaving .

      Thank you

      Erik
    • Akshay Maniyar
      Ansys Employee

      Yes, I agree with Erik's point.
      Also, the stack you modelled seems to be stable. So with any type of bonded contact it will not fall under gravity. Can you increase the overhand length and then try.
      regards amaniyar
    • myvue
      Subscriber
      Thank you and what you said about the 'length of the simulation' might actually be the problem. I changed (increased) some time-related values and I am getting some results.
      My ENDTIM in *Control_Termination keycard is 0.1 sec. So, I changed the curve (*Define_Curve) corresponding to the gravity load to 0.1 (as maximum value on the horizontal axis). Is this what you guys meant when you said the simulation should be long enough? (To clarify, I didn't want to increase the termination time because the solver takes longer time, so I changed the curve values to correspond to the termination time. Is that correct?).
      Also, to be on the right side, should my curve for gravity load go beyond the termination time to get the actual effect of gravity on my geometry? Or should my termination time go beyond the extent of my curve? I mean, what would give me the 'complete' result to see the effect of gravity?

      Thank you!!


Viewing 5 reply threads
  • You must be logged in to reply to this topic.