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## Simulation Moldflow Insight

Contributor
Posts: 12
Registered: ‎06-01-2009

# Negative value for Volumetric Shrinkage

387 Views, 2 Replies
04-26-2012 09:17 AM

Hello,

I've this doubt for a long time...

How can I have negative values for volumetric shrinkage. I know that it happends when the material "expands" but in what circumstances?

If this result is obtained by the expression VS = average density/ density(Tamb, P0) the only way the result is negative is if one of the densitys is zero ??? What am I assuming wrong?

Thanks,

Gui

Valued Contributor
Posts: 62
Registered: ‎08-25-2008

# Re: Negative value for Volumetric Shrinkage

04-26-2012 10:27 AM in reply to: Gui_81

Hi, Gui

The formula for the VS is:

VS=(Volume(freeze)/Volume(ambient)) -1.0=(Density(ambient)/Density(freeze))-1

it becomes negative if the density at freeze time (for 2.5D solvers average density over thickness) are higher than the material density at ambient conditions

Contributor
Posts: 12
Registered: ‎06-01-2009

# Re: Negative value for Volumetric Shrinkage

05-15-2012 01:45 AM in reply to: abakharev

Hello abakharev,

Thanks a lot for the answer. now it's clear.

In AMI2013 at the help topics the formula is updated and easier to understand than one used at AMI2012.

V.S. = 100 X [ 1 - (average density / reference density) ]

reference state : pressure=0 and temperature= Tambient

Regards,

Gui