Proper set for the lumped mass

Wisawanart

Hello, I have been confusing about the lumped mass setting on crash analysis, which way is the best for representing the entire weight of the vehicle.

For my questtions,

1. What should I set for the ICOG card ? normally, I tried with 1 or 3 but I didn't know the exactly definition yet.

2.  What is the most suitable cases to set the number of node for RBE? I should select only the nodes at the edge or more ? (the green one ,as a figure below)

3. Generally, I define the inertia mass in RBE2 using card edit directly, but it also has ADMAS manager which will add the mass into the node instead.

What is the best way to deal with it?

 

Best regard

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Altair Forum User

Hi,

1. ICoG is the center of gravity computation flag for the rigid body. Suppose in your model you have chosen an indepenedent node for the/RBODY and ICoG=1 is defined. In that case once the run starts the master node is computed internally by the solver and it will be moved to the computed center of gravity. Whereas in ICoG=3, the master node is not moved and the same node selected by the user will be maintained as the master node throughout the run.

2.It depends on application. If you select only the edge nodes, the mass assigned will be distributed only between those nodes. But please remember that if you select all the nodes for making rigid the component will become a non-deformable object, that is rbody will make the component with infinite stiffness.

3.Assign mass in a rigid body is comparatively easy way, but if you don't want to make the component a non-deformable one then go for ADMAS.