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bocaj22

Angular momentum of solid part

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Hello,

 

I am interested in extracting the angular momentum of a p14_solid part after a RADIOSS impact. When I create output block, I am able to request XXMOM, YYMOM, and ZZMOM. The results in the time history file are all zero however. In fact, I am unable to retrieve anything but zeros for the following outputs:

 

XXMOM YYMOM ZZMOM

XCG YCG ZCG

IXX IYY IZZ IXY IYZ IZX

RKE

 

There is clear movement and rotation. I am able to retrieve linear momentum and mass. Additionally, I have a separate part that is p1_shell, which I am able to extract all of the above parameters. Are these requests not allowed for solid parts, or is there some other piece I am missing?  Thanks for your help.

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Ivan,

 

Thanks for trying it out. Can you think of any alternative methods to acquire the same information? Do you think this is a bug, or a feature that doesn't exist?

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Hopefully, someone from Altair support team can look into this and clarify. 

There is also an option to output angular momentum of /THPART/GRBRIC, but unfortunately I don't know how.

 

Since the angular momentum output works for shell components and because angular momentum is simply a product of  moment of inertia and angular speed I propose the following workaround:

 

1. create a skin of shell elements on the solid component with tools>faces panel. Assign negligible thickness on dummy shells as not to influence the momentum or stiffness of the solid part. Define output block request on dummy shell component and run the simulation.

2. Open starter .out file (runname_000.out) and find PART MASS & INERTIA summary. Calculate the ratio between solid and shell component's moment of inertia in all three directions (Ixx, Iyy, Izz)

3. Open Hypergraph and plot angular momentum of dummy shell component. Go to Define curves and apply the calculated scale factor (solid divided by shell moment of inertia) in appropriate directions.

momentum.jpg

rotate1_0000.rad

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