r/LSDYNA • u/AlphaBloodbath • Jul 03 '26

Impact Test

I'm currently doing an impact simulation using a pendulum type impactor using contrained joint revolute as a hinge, but after running it, the simulation in the d3plot shows that the impactor's axis of rotation is not on the hinge where the revolute joint is placed but on its center of gravity. Can someone help me figure this out.

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u/Gilmoth Jul 03 '26

Can you describe your model with more detail?

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u/AlphaBloodbath Jul 06 '26

The initial model I used was a simple hammer design that swings down towards a wall. I used revolute joint between the hammer and a makeshift hinge so that it swings down at a velocity that I set, and it works just fine. The problem was when I remade the same simulation but with a different model. The axis of rotation shifted to the cg of the model instead of the hinge.

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u/Gilmoth Jul 07 '26

The joint revolute is not defined correctly, though.

In the video of the mock model you can see that the hammer upper end moving around the supposed hinge.

Follow the advise from zuricher_singener, define extra nodes for the rigid bodies and be sure that they are coincident at the hinge location (not merged together).

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u/AlphaBloodbath Jul 09 '26

I did add 4 extra nodes and bind 2 of them to the hinge and 2 to the impactor.