Part filling

[rmathan]

Dear Forum,

I have a part wth perforated holes. The part length is around one metre. will the part fill?

Does anyone experienced this kind of part filling?

Regards,

Mathankumar. R

[nordhb]

Hi,

to analyze such a pattern you can use shape equivalents for surfaces with this pattern.

For Midplane analysis technology, such complex cross-sections can be approximated by representing the area with a thinner, flat cross-section that has an equivalent material volume.

Please, see Help and
Modeling > The mesh > Mesh entities > Triangular elements >
Cross-sectional shape equivalents for surface features

Hope this helps.

Regards,
Berndt

[raalteh]

Hi,

You can make anything fill with sufficient pressure ... But you dont have infinite pressure. You can simulate it obviously.

Assuming the part.Is midplane appropriate and you have a repeated hole pattern, you can use shape factors and equivalent thicknesses to reduceelement count.

You can find some useful information here.

http://wikihelp.autodesk.com/Simulation_Moldflow/enu/2013/Help/2.0Insight/1572-The_mesh1572/1577-Mes...

http://usa.autodesk.com/adsk/servlet/ps/dl/item?siteID=123112&id=15332179&linkID=13030537

[rmathan]

Thank you to all. I have a holes with draft.So top side hole diameter and bottom side hole diameter won't match. how to model / calculate shape factor?

Regards,

Mathankumar. R

[raalteh]

A picture would help a lot here to be honest.

[rmathan]

Dear Hanno,

I have inserted a portion of a part picture below.

Warm Regards,

Mathankumar. R

[raalteh]

Hi Mathankumar,

This is a classic example of why the 'cross sectional shape' and equivalent thickness features exist (you need both).

I would strongly suggest you read the online help topic here (link) and try to understand the concept by following the example given. You can then apply this to your specific geometry.

First thing you should do is find a repeating pattern first. I highlighted one repeating pattern below, but in this case there are several. Whatever repeating pattern you take, you will end up with the same factors.

You can select the elementy you want to apply the shape factors to and select 'other' from the cross sectional shape menu (I would not use the grill with round holes option, as this assumes the holes are in a grid pattern)

Then fill in the equivalent thickness and shape factor you calculated

 

[rmathan]

Dear Hanno,

Thank you very much for clarifying in detail.

I am able to understand the concept. but still more doubts.

Not all the holes are through holes. I have attached concern in a word document

Regards,

Mathankumar. R

[raalteh]

Regarding 'concern 1'; you can choose to either model the 'rib' underneath the grill separately, or if the ribbin in the back is not substantially the filling patter, you could apply the same shape factors and treate is as a worst case scenario; if the part fills with the maximum restiction, you can be sure if will will if there is an additional rib in the part. Obvisouly, you would have to be careful with interperting things like air traps and such, as the ribbin in the back may actually affect the filling pattern.

The second concern is  a little bit harder. if the bottom of the 'hole' is very thin, than your main concern is most likely whether or not these holes will fill out or not. In that case I would not recommend the shape factor approach, as you are actually interested in a 'detailed' solution for which the shape factor/equivelent thickness apporach would provide too coarse of an answer. You may have to resort to 3D for this case. You'd probably be looking at a horrific element count. One thing worth considering to model a simplified version of the part, and then create one area witht he correct pattern to see what happens in detail (so you  know whether or not you have to worry about this or not). If the filling does not appear to be problematic, you can go back to the midplane shapefactor + equivalent thickness simplification.

Sorry that this is not a simple answer. It really depends on the level of detail you're looking for an the time available, so you may have to juggle the two camps (detailed solution vs. high level feasiblity) a little bit here.

[rmathan]

Dear Hanno,

I have done 3D mesh with the number of tetra elements of 3,800,000. but the analysis could not able to run due to lot of inverted tetras and collapsed faces in the model. and also analysis log showing coincident nodes. i have tried lot many options by freezing Dual domain aspect ratio below 10 and changing 3D mesher from advancing front to legacy, minimum elements through thickness 4, but nothing works out. Could you help me how to correct this issue?

By the way I have modeled midplane with shape factor and equivalent thickness.

Regards,

Mathankumar. R

[madhukeshwart]

Mathan,

using 3d mesh is not advisable for part having more number of holes.

It may result in more number of lelements and need high end machines and more RAM too. 

It also leads to higher simulation time.

And regarding shape factor, it is difficult apply for complicated shapes.

you need to decide, whihc is feasible to you and more ever all there are approximation only.

you can't expect 100% match with resutls but help to make decision.