LS Dyna

LS Dyna

Kinetic Energy Tracker Error

    • ashek

      Hi all,

      I have a problem involving a dropped object onto a component, the impactor is specified to have a kinetic energy of 5 kJ as it impacts the test component.
      When I check the mass properties through Ansys, I can see the mass is 275.71lbm.

      I specify the initial velocity as 352.8 in/s and I calculate the kinetic energy of the impactor to be 5020 J.

      However when I check the kinetic energy tracker of the impactor I see that the kinetic energy is 4.64 BTU (4895.5 J).

      Has anyone had a similar experience to me and are there any explanations to this discrepancy?


      Edit, found out it's something to do with applying a symmetry boundary condition

    • Chris Quan
      Ansys Employee

      Can you check the mesh density of the impactor in your model? If you refine its mesh and run the model again, will the predicted kinetic energy have a more accurate value?

      The mass properties under geometry is calculated from geometry while the predicted kinetic energy is calculated from elements. It is possible to observe some difference in kinetic energy between the predicted and actual value if mesh is coarse and the geometry is complicated. 

      If you think that the refined mesh will take longer running time and thus want to avoid it, you can adjust the density of the impactor to compensate the mass lose due to coarse mesh and match the predicted kinetic energy to the actual kinetic energy. 

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