Rule of thumb for sub modelling cut boundary 1

[morris9791]

Dear Experts,

Is there a rule of thumb regarding the distance of the cut boundary relative to the point of interest. I find I have to try different distances /re analyse to verify that the cut boundaries of the submodel are far enough away from the concentration


Thanks

Eddie

 

[johnhors]

Three diameters for tubes or three times section width or height (which ever is the greater) is a rough rule of thumb.

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[normm]

Morris & johnhors

I will be interested what boundary condition you apply on the cut line/surface? Fixed, Free, Spring ? What spring constant?

 

[johnhors]

normm,

I would work from a free body diagram and apply forces (and moments if necessary) as a (variable) pressure over the cut surface. The distributed loading on the cut surface would be in balance with all other loading on the model.

http://www.Roshaz.com

 

[corus]

The normal practice is to use displacements from the global model to drive the sub model. Nodal displacements in the sub model cut surface are interpolated from the global model. In general you should see a similar stress distribution at the cut surface in both the sub and global models, given that the interpolation of nodal displacements may tend to give irregular contours in the sub model. For a rule of thumb, I'd apply the cut surface where the stresses are expected to be more uniform. It's a matter of judgement really.

Tara

 

[morris9791]

Normm and johnhors,

I was referring to an FEA model regarding the sub model.

Thanks for the rule of thumb anyhow.

Ed