How to create new material with 2D orthotropic properties?

[potrero]

NX5.0.5

I am having trouble editing the phys_material.dat file to create a new material with 2D orthotropic properties. The point of such a material is to model an orthotropic lamina in plane stress, where the simplified compliance matrix necesitates only 4 independent material constants: E1, E2, G12, and v12.

A good example of this type of material would be a composite lamina of unidirectional carbon tape, or woven carbon fabric.

When creating a new material in the phys_material.dat file, if one attempts to set the value for the unnecesary constants (such as E3, G1, G2, etc) to "EMPTY", the software rejects the material as having an inappropriate value for that property.

Help?

 

[JohnRBaker]

Have you tried setting the unnecessary values to 'zero'?

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[potrero]

Setting the unnecesary elastic moduli and Poisson's ratio constants to zero throws the same error as before.

Setting the elastic moduli and Poisson's ratio unnecesary constants to a small non-zero number (ie: 0.1), allow material creation; the unnecesary shear moduli constants CAN be set to zero.

But would you agree, that's not the best way to represent the material properties...

 

[JohnRBaker]

I was suggesting that only because I've seen other places (and I've done it myself) where encountering a value of 0.00 is not interpreted by the software as a 'numerical value' but rather as an 'option' that triggers an alternative code path which would totally remove that value from consideration. However, in this case, it appears that the programmer/designer was not creating as elegant an interface as I was hoping they had.

John R. Baker, P.E.
Product 'Evangelist'
NX Design
Siemens PLM Software Inc.
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[potrero]

On this topic, can I get a bit of clarification with regards to the placeholders for orthotropic material properties in phys_material.dat; specifically the entries of:

Poissons_Ratio_X
Poissons_Ratio_Y
Poissons_Ratio_Z
Shear_Modulus_X
Shear_Modulus_Y
Shear_Modulus_Z

My understanding is that orthotropic material properties should follow the form:

Poissons_Ratio_XY (ie: v12)
Poissons_Ratio_YZ (v23)
Poissons_Ratio_ZX (v13)
Shear_Modulus_XY (G12)
Shear_Modulus_YZ (G23)
Shear_Modulus_XZ (G13)

Can someone clarify the conventional equivalent to the suggested form of orthotropic properties in phys_material.dat? Is my interpretation above correct?

 

[potrero]

By the way, the orthotropic material property management doesn't seem to have changed from NX5 to NX6, with regards to the input of plane-stress 2D orthotropic material properties.

 

[spongebob007]

I would like to see an enhancement request to allow materials to be created where unneeded values can simply be left blank.

For example when running a steady state CFD model where there is conjugate heat transfer all I really care about is thermal conductivity, but NX won't let me create a custom material without supplying values for structural modulus, density, and Poisson's ratio. I just enter a dummy value for all variables. But you think the software would be smart enough to know that if the analysis type was set to CFD that structural material properties would not be needed.