what is dilatational modulus?

[masadakhtar]

Hello,
can somebody define that, what is dilatational modulus in abaqus?
which material property/ies can effect its value?

Actually i am getting following error message for a vumat routine

***ERROR: Bad Material definition: zero or negative initial dilatational
modulus caused by bad material data. Please check your
material input and any initial conditions if necessary.

thanks
regards
Asad

[Dave Lindeman]

Bulk modulus -- the relationship between pressure and change in volume.

Regards,

Dave

-------------------------
Dave Lindeman
Lead Research Specialist
3M Company
3M Center 235-3F-08
St. Paul, MN 55144
651-733-6383

Post by masadakhtar
Hello,
can somebody define that, what is dilatational modulus in abaqus?
which material property/ies can effect its value?
Actually i am getting following error message for a vumat routine
***ERROR: Bad Material definition: zero or negative initial dilatational
modulus caused by bad material data. Please check your
material input and any initial conditions if necessary.
thanks
regards
Asad

[Celal Soyarslan]

Dilatational modulus is the Bulk modulus or the
modulus of incompressibility. If you get an error of
"Bad Material definition: zero or negative ..." that
simply means that your material data is problematic.
If you get it for a VUMAT your material response as a
consequence of bad material data is unphysical.

Post by masadakhtar
Hello,
can somebody define that, what is dilatational
modulus in abaqus?
which material property/ies can effect its value?
Actually i am getting following error message for a
vumat routine
***ERROR: Bad Material definition: zero or negative
initial dilatational
modulus caused by bad material data.
Please check your
material input and any initial conditions if
necessary.
thanks
regards
Asad
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[aaroncaba]

Asad,

My guess is that you are calculating your anisotropic material
properties incorrectly. There are mathematical restrictions on how
the values of E, G, and nu relate to each other. For isotropic
materials, the two equations are: G=E/(2*(1+nu)) and -1 < nu < 1/2.
For orthotropic/anisotropic material they get much more complex. You
can find the relations in "Mechanics of Composite Materials" by
Robert M. Jones, chapter 2.4, or probably on the web somewhere.

I think Abaqus is telling you that your material, when subjected to
hydrostatic pressure, gets bigger, i.e. the dilational modulus is
negative. Jones gives a simple and understandable explination of why
this violates the laws of thermodynamics.

Aaron

Post by masadakhtar
Hello,
can somebody define that, what is dilatational modulus in abaqus?
which material property/ies can effect its value?
Actually i am getting following error message for a vumat routine
***ERROR: Bad Material definition: zero or negative initial

dilatational

Post by masadakhtar
modulus caused by bad material data. Please check your
material input and any initial conditions if necessary.
thanks
regards
Asad