using @Brick "StandardElasticity"

[GhiathMonnet]

Dear colleagues,
I would like to use @brick "StandardElasticity". I tried to introduce the values of Young Modulus and Poisson's ratio in mtest. No matter how I call these modulii : YoungModulus, youngmodulus, Young, etc.. I always get an error message teeling me that the law does not declare such variable.
I am using the "generic" interface.
All examples I have seen are introducing the modulii inside the mfront file itself and not in mtest.
Many thanks for your help.
Cheers

[thelfer]

You may have a look at the documentation of the StandardElasticity brick for details about how elastic material properties are handled: https://thelfer.github.io/tfel/web/HookeStressPotential.html

Assuming that your behaviour is isotropic, the brick automatically declares the YoungModulus and PoissonRatio as material properties if none of the following conditions is met (those conditions are exclusive):

• The elastic properties are defined in the options to the brick, as follows:

  @Brick StandardElasticity{
      young_modulus: 150e9,
      poisson_ratio: 0.3
  };

• The elastic properties are defined by the keyword @ElasticMaterialProperties
• The stiffness tensor is defined by one of the keyword @RequireStiffnessTensor or @ComputeStiffnessTensor
• Two material properties or parameters are defined with the external name YoungModulus or PoissonRatio, as follows:

  @MaterialProperty stress yg;
  yg.setGlossaryName("YoungModulus");
  @MaterialProperty stress nu;
  nu.setGlossaryName("PoissonRatio");

See the attached example and the following code:

$ mfront-query --material-properties StandardElasticityTest.mfront 
- YoungModulus (young): the Young's modulus of an isotropic material
- PoissonRatio (nu): the Poisson ratio of an isotropic material

StandardElasticityTest.zip

[GhiathMonnet]

Thomas : Many thanks for this detailed information. OK, then I have to inset in the mtest file the following lines:
@MaterialProperty 'YoungModulus' 200e9 ;
@MaterialProperty 'PoissonRatio' 0.3 ;

Cheers.
Ghiath

[thelfer]

In this case that I sent you, yes.

[GhiathMonnet]

Dear Thomas. I tried this but it did not work.

As you suggest, I declared in mtest :

@MaterialProperty<function> 'YoungModulus' "2.6e6 * (-23.721 * Temperature + 78821)" ;
@MaterialProperty<constant> 'PoissonRatio' 0.3 ;

In the mfront file, I put :

@DSL Implicit;
@Behaviour Monnet_RPV_EVP;
@Algorithm NewtonRaphson_NumericalJacobian ;
@Description{
}
@Epsilon 1.e-14;
@Theta 1;
@Brick "StandardElasticity"; 
// when i want to compute the shear modulus as follows
@InitLocalVariables {
    mu = YoungModulus/2./(1.+ PoissonRatio);              // module de cisaillement

I have the error message : error: ‘YoungModulus’ was not declared in this scope

I tried mu = computeMu(YoungModulus,PoissonRatio). I have the same error.

Can you explain to me how can I use : @Brick "StandardElasticity, then provide the value of YoungModulus and PoissonRatio in mtest, and then compute the shear modulus in the mfront file ?

Thanks in advance.
Ghiath

[thelfer]

Hi Ghiath,

You seem to be confused by the concept of external names in MFront. In MFront, a variable x is associated with an external name by the setGlossaryName and setEntryName methods.. x is the variable that you manipulate in MFront and its external name is what you see from the solver (MTest in you case).

As mentionned in the documentation of the brick: (https://thelfer.github.io/tfel/web/HookeStressPotential.html), by default, the brick modulus will automatically define the Young' modulus and the Poisson's ratio as material properties named young and nu associated respectively with the external names YoungModulus and PoissonRatio

So you can compute the shear modulus in MFront in your example as:

mu = computeMu(young, nu);

but you'll have to define the material properties YoungModulus and PoissonRatio in your MTest file.

[GhiathMonnet]

Many Thanks.
The explanation in (https://thelfer.github.io/tfel/web/HookeStressPotential.html) is not clear for me.
What that means "if the stiffness tensor is available" ? If the solver does not provide the elastic modulii (through mtest for example), how the stiffness tensor can be available ? Who is providing the stiffness tensor when it is "available" ?

[thelfer]

The previous paragraph states:

If the elastic behaviour is orthotropic, the stiffness tensor must be available (using the keyword
@RequireStiffnessTensor) or computed by the behaviour (using the keyword @ComputeStiffnessTensor).

See the documentation of those keywords

The effect of the @RequireStiffnessTensor keywords depends on the interface. It generally works by adding additional material properties. The material properties are not accessible from the MFront file, you only have access to the stiffness tensor D.

[GhiathMonnet]

many thanks. Thomas.