Pendulum

GermanGerman
I'm trying to simulate a pendulum, but I get very strange results.
x and y displacemente seems to be parabolic instead of sinusoidal.

Comments

  • GermanGerman
    edited August 15
    I defined the pendulum element with a very rigid spring, but it does not keep its lenght.
    The same occurs using a rigid bar.
    Same behavior with DynamicResponse 2D analysis.
  • GermanGerman
    The same occurs changing the pivot restriction.

  • VictorVictor
    edited August 15
    You need to use the Nonlinear dynamic response 3D analysis type for this because of the large rotation. Just change that and set solver to CCX and it works.

    EDIT: Also add a Z constraint at the pivot for 3D. Pardiso can solve without that but Spooles can't.


  • JohnMJohnM
    Mecway-
    https://youtube.com/shorts/W6l1npfaYto?si=YpzsQC5Q1OaIsMgW
  • MishalMishal
    Just my 2cents, the large rotation is one part of the problem, the other is the fact that even with small displacements the linear solution does not account for the actual position of the system in space. For a rigid pendulum system you can apply transformations to project the results to be the same as the nonlinear solution
  • VictorVictor
    You're quite right @Mishal I used that term a bit sloppily. Even a simple sin(theta)=theta pendulum won't work.
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