Highlighted

Application of formulas in Material Definition

Experimenter
Experimenter

Dear NX-NASTRAN-community,

 

the user has several options for the definition of material properties, e.g. density, elastic modulus, etc.. Normally I apply tabulated data of temperature dependent material properties and it works fine. For example:

 

T [C], elastic modulus [GPa]

20, 206

100, 200

200, 192

....

 

In case of establishing a temperature dependent formula of e.g. the material's density RHO and the definiton in NASTRAN I'm struggling with following error and have no real idea what's going on.

 

My approach is the following:

 

1. Fitting via Excel of some literature data into a temperature dependent polynomial of 2. order yields:

 

rho(T)=3.01E-02*temperature^2-1.51E+01*temperature+8.40E+03

 

2. typing the expression into the formula tab in isotropic materials definition:

 

3.01E-02*temperature^2-1.51E+01*temperature+8.40E+03

 

3. After pressing enter in the formula tab following alert appears:

 

"Dimension mismatch (binary operation)"

 

Where's my error?

 

Thanks in advance for your guidance.

2 REPLIES 2

Re: Application of formulas in Material Definition

Siemens Phenom Siemens Phenom
Siemens Phenom

The expression system does not allow temperature units to be miltiplied or raised to powers.

 

See the following online help article for a full explanation. The bottom of the article contains example methods to workaround these issues (i.e. raising a temperature to a power):

 

Temperatures in expressions

Re: Application of formulas in Material Definition

Experimenter
Experimenter

OK, best thanks for the link and the explanation!

 

It seems to be more difficult as I expected. I will try out later...