The `;` keyword

The keyword ; is not documented yet

The `@Author` keyword

The @Author keyword is used to give the name of the person who wrote the mfront file.

All the following words are appended to the author’s name up to a final semicolon.

Note: The name of the person who formulated the material property, behaviour or model shall be given in the description section (see the @Description keyword).

Example

@Author Éric Brunon;

The `@Bounds` keyword

The @Bounds keyword let the user define the domain of validity of the law.

The @Bounds keyword is followed by a variable name, the keyword in and an interval. The interval may contain the infinity, represented by the ’*’ character.

Effect

What happens if a variable is found to be out of its bounds depends on the interface used. Most interfaces let the user choose one of three following policies:

None, which means that nothing is done.
Warning, which means that a message is displayed, but computations are not stopped.
Strict, which means that computations are stopped with an error message.

Example

@Bounds T in [293.15:873.15];

The `@Coef` keyword

The @Coef keyword is a deprecated synonymous of @MaterialProperty.

The `@ConstantMaterialProperty` keyword

The @ConstantMaterialPropery let the user define a specific kind of input to a model which is meant to be constant and uniform during the computations. This allows the interfaces to optimize the generated code. This keyword is followed by the names of the material properties. Those names must be valid C++ identifiers.

The following characters are legal as the first character of an identifier, or any subsequent character:

_ a b c d e f g h i j k l m n o p q r s t u v w x y z A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

External name

It is recommended to associate to a constant material property a glossary or an entry name through the methods setGlossaryName or setEntryName respectively.

Example

@ConstantMaterialProperty E;
E.setEntryName("EnergyReleasedByFission");

The `@DSL` keyword

The @DSL keyword specify the domain specific language (dsl) used.

The list of available dsl’s is returned by the --list-dsl option of mfront:

$ mfront --list-dsl

As the time of writing this notice, the following dsl’s are available:

DefaultDSL: this parser is the most generic one as it does not make any restriction on the behaviour or the integration method that may be used.
DefaultCZMDSL: this parser is the most generic one as it does not make any restriction on the behaviour or the integration method that may be used.
DefaultFiniteStrainDSL: this parser is the most generic one as it does not make any restriction on the behaviour or the integration method that may be used.
Implicit: this parser provides a generic integrator based on an implicit scheme. The elastic strain is automatically defined as a state variable
ImplicitII: this parser provides a generic integrator based on a theta method. Unlike Implicit, the elastic strain is not automatically defined as a state variable.
ImplicitFiniteStrain: this parser provides a generic integrator based on a theta method.
IsotropicMisesCreep: this parser is used for standard creep behaviours of the form \(\dot{p}=f(s)\) where \(p\) is the equivalent creep strain and \(s\) the equivalent mises stress.
IsotropicPlasticMisesFlow: this parser is used for standard plastics behaviours with yield surface of the form \(f(s,p)=0\) where \(p\) is the equivalent creep strain and \(s\) the equivalent mises stress.
IsotropicStrainHardeningMisesCreep: this parser is used for standard strain hardening creep behaviours of the form \(\dot{p}=f(s,p)\) where \(p\) is the equivalent creep strain and \(s\) the equivalent mises stress.
MaterialLaw: this parser is used to define material properties.
Model: this parser is used to define simple material models.
MultipleIsotropicMisesFlows: this parser is used to define behaviours combining several isotropic flows. Supported flow type are ‘Creep’ (\(\dot{p}=f(s)\)) ‘StrainHardeningCreep’ (\(\dot{p}=f(s,p)\)) and ‘Plasticity’ (\(f(p,s)=0\)) where \(p\) is the equivalent plastic strain and \(s\) the equivalent mises stress.
RungeKutta: this parser provides a generic integrator based on one of the many Runge-Kutta algorithm.

DSL options

A DSL’s behaviour may be changed using options defined either in the MFront file using a JSON-like syntax or as a command line argument.

The options related to a specific DSL can be retrieved using the --list-dsl-options command line argument, as follows:

$ mfront --list-dsl-options=Model
- parameters_as_static_variables: boolean stating if the parameter shall be treated as static variables.
- build_identifier              : string specifying a build identifier. This option shall only be specified on the command line.

Defining `DSL` options in the MFront file

Options can be passed to a DSL as follows:

@DSL Default{
  parameters_as_static_variables : true
};

Defining `DSL` options on the command line:

MFront have various command line arguments to define options passed to DSLs:

--dsl-option, which allows to define options passed to domain specific languages.
--behaviour-dsl-option, which allows to define options passed to domain specific languages related to behaviours.
--material-property-dsl-option, which allows to define options passed to domain specific languages related to material properties.
--model-dsl-option, which allows to define options passed to domain specific languages related to models.

For example, the --dsl-option can be used as follows:

$ mfront --obuild --interface=cyrano --dsl-option=build_identifier:\"Cyrano-3.2\" Elasticity.mfront

This example illustrates that special care must be taken when defining an option expecting a string value.

Options common to all DSLs

The following options are available for all DSLs:

build_identifier (string), which must be associated to a string value. However, the build_identifier is not meant to be directly specified in the MFront source file. It shall rather be defined on the command line.
parameters_as_static_variables (boolean), which states if parameters shall be treated as static variables.
parameters_initialization_from_file (boolean), which states if parameters can be modified from an external state file. This feature is only implemented by a few interfaces and is enabled by default.
default_out_of_bounds_policy (string), which selects the default out of bounds policy. Allowed values ar None (the default), Warning or Strict.
out_of_bounds_policy_runtime_modification (boolean), which states if the out-of-bounds policy can be changed at runtime. By default, this option is true.

automatic_declaration_of_the_temperature_as_first_external_state_variable (boolean), which states if the temperature shall be automatically declared as an external state variable.
overriding_parameters, which allows to specify overriding parameters. This parameters must be a map associating variables names and default values of the overriding parameters.

Example

@DSL Implicit;

The `@Date` keyword

The @Date keyword allows the user to precise when the mfront file was written.

All the following words are appended to the date up to a final semicolon.

Example

@Date 2008-11-17;

The `@Description` keyword

The @Description describes the material property, behaviour or model which is implemented in a mfront file.

This keyword is followed by a block containing all the relevant piece of information including:

the references of the article or technical report from which the material property, behaviour or model is extracted
the name of the authors
the modifications made

Example

@Description
{
  Corrélation établie sur la nuance V-4Cr-4Ti.

  Propriétés extraites du document :

  Propriétés et comportement mécanique d alliages
   de Vanadium avant, après et sous irradiation

  Marion Le Flem, Jean-Luc Bechade, Annick Bougault,
  Aurore Michaux, Lionel Gosmain, Jean-Louis Seran
  DMN/SRMA/LA2M/NT/2008-2967/A
}

The `@Domain` keyword

The @Domain let the user define the default domain on which a model shall be applied. This keyword is followed by the name of the domain.

This keyword is deprecated as domains shall be explicitly specified by specialisation.

Example

@Domain "Fuel";

The `@Domains` keyword

The @Domains let the user define the default domains on which a model shall be applied. This keyword is followed by an array of strings.

This keyword is deprecated as domains shall be explicitly specified by specialisation.

Example

@Domains {"MATRIX","CLADDING"};

The `@ExternalStateVariable` keyword

The ExternalStateVariable keyword introduces one or several new external state variables. It is followed by a type name and the name(s) of the variable(s) declared, separated by commas.

The external state variables names must be valid C++ identifiers.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Arrays

One may declare an array of external state variables by specifying the array size after the external state variable name.

External names

It is recommended to associate to an external state variable a glossary or an entry name through the methods setGlossaryName or setEntryName respectively.

Example

// scalar external state variable
@ExternalStateVariable strain s;

The `@Function` keyword

The @Function keyword defines a computational part of the model. This keyword is followed by a string defining the name of this part of the computation.

Example

@Function compute
{
  const real coef1 = 8.e-3;
  const real coef2 = 4.e-2;
  const real p_    = 0.5*(p+p_1);
  s = s_1 + coef1*exp(coef2-p_)*(Bu-Bu_1);
} // end of function compute

The `@Import` keyword

The @Import keyword allows the inclusion of one or several (external) mfront files. This keyword is followed by a string or an array of strings. Each string stands for a mfront file name that is meant to be imported.

This instruction interrupts the treatment of the current file and starts the sequential treatment of each file to be imported.

Search paths

Files to be imported are searched, in that order:

starting from the current directory.
starting from directories specified with one of the --search-path or the --include (-I) mfront’ command line options.
staring from directories specified through the MFRONT_INCLUDE_PATH environment variable.

Example

@Import "SlidingSystemsCC.mfront";

The `@Includes` keyword

The @Includes introduces a block were the user may define some preprocessor directives, typically #include directives (hence the name).

Example

@Includes{
#include<fstream>
}

The `@Input` keyword

The @Input keyword specifies one or several inputs of a material law. This keyword is followed by the names of the inputs, separated by commas.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Variable depth

The depth of a variable is the number of preceding values of this variable needed to perform the computations. A depth of \(0\) means that only the value at the end of the time step is required. A depth of \(1\) means that we need the value of the variable at the end of the time step and the value at the beginning of the time step.

The depth of a variable is set using the setDepth method.

If p is the variable of interest, p is its value at the end of the time step, p_1 is the value at the beginning of the time step.

External name

It is recommended to associate to an input a glossary or an entry name through the methods setGlossaryName or setEntryName respectively.

Example

@Input T,p;
T.setGlossaryName("Temperature");
p.setGlossaryName("Porosity");
// we need the value at the end of the time step and the value at the
// beginning at the time step
p.setGlossaryName("Porosity");

The `@LocalParameter` keyword

The @LocalParameter keyword let the user defines specialisation parameters. This keyword is followed by the type and the names of the parameters, separated by commas. The names of the variables must be valid C++ identifiers.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Default values

The user may attribute a default value to a local parameter through the setDefaultValue method.

Example

@LocalParameter real a;
a.setDefaultValue(1.23);

The `@Material` keyword

The @Material keyword let the user specify which material is treated by the current file. This keyword is followed by the name of the material.

This name must be a valid C++ identifier. The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Example

@Material UO2;

The `@MaterialLaw` keyword

The @MaterialLaw keyword imports the definition of a material law defined in a mfront file and compiles, as part of the current library, a function using the mfront interface. This function is available in every standard code blocks.

The @MaterialLaw keyword is followed by a string or an array of string identifying mfront files.

Search paths

Files to be imported are searched, in that order:

starting from the current directory.
starting from directories specified with one of the --search-path or the --include (-I) mfront’ command line options.
staring from directories specified through the MFRONT_INCLUDE_PATH environment variable.

Note

The mfront interface has been created to avoid names conflict.

For internal reasons, mfront reports the creation of an auxiliary library which is of no use.

Example

@MaterialLaw "UO2_YoungModulus.mfront";

The `@MaterialProperty` keyword

The @MaterialProperty keyword let the user define one or several material properties. This keyword is followed by the type of the material property and a list of material properties names separated by commas.

The material properties names must be valid C++ identifiers.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Arrays

One may declare an array of material properties by specifying the array size after the material property name.

External names

It is recommended to associate to a material property a glossary or an entry name through the methods setGlossaryName or setEntryName respectively.

Example

// scalar material property
@MaterialProperty stress young;
young.setGlossaryName("YoungModulus");

The `@Model` keyword

The @Model defines the name of the model. The name must be a valid C++ class name.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Example

@Model SolidSwelling;

The `@Output` keyword

The @Output keyword specifies one or several outputs of a material law. This keyword is followed by the names of the outputs, separated by commas.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Variable depth

The depth of a variable is set using the setDepth method.

If p is the variable of interest, p is its value at the end of the time step, p_1 is the value at the beginning of the time step.

External name

It is recommended to associate to an output a glossary or an entry name through the methods setGlossaryName or setEntryName respectively.

Example

@Output T,p;
T.setGlossaryName("Temperature");
p.setGlossaryName("Porosity");

The `@Parameter` keyword

The @Parameter keyword declares a new parameter or a list of new parameters. Optionally, the default value of the declared parameters may also be given following various C++ standard assignment syntaxes.

The default value of a parameter can also be declared after its declaration using the setDefaultValue method.

Example

@Parameter  R0 = 500;
@Parameter  Q1{1000000000},b1{0.000001};
@Parameter  Q2(0),b2(0);
@Parameter  fc;
fc.setDefaultValue(1.e-2);

The `@Parser` keyword

The @Paser keyword is a deprecated synonymous of @DSL.

The `@PhysicalBounds` keyword

The @PhysicalBounds keyword let the use define the physical domain of a variable.

The @PhysicalBounds keyword is followed by a variable name, the keyword in and an interval. The interval may contain the infinity, represented by the ’*’ character.

Effect

In implicit schemes, if physical bounds are set on an integration variable, this variable is bounded to satisfy them during the internal iterations.

If a variable is found to be out of its physical bounds, the computations are stopped. The tests are performed at different stages of the integration depending on the nature of the variable.

Example

// a temperature (in Kelvin) can't be negative
@PhysicalBounds T in [0:*[;

The `@StateVariable` keyword

The StateVariable keyword introduces one or several new state variables. It is followed by a type name and the name(s) of the variable(s) declared, separated by commas.

The state variables names must be valid C++ identifiers.

The following characters are legal as the first character of an identifier, or any subsequent character:

The following characters are legal as any character in an identifier except the first:

0 1 2 3 4 5 6 7 8 9

Arrays

One may declare an array of state variables by specifying the array size after the state variable name.

External names

It is recommended to associate to a state variable a glossary or an entry name through the methods setGlossaryName or setEntryName respectively.

Example

// scalar state variable
@StateVariables strain p;
// symmetric tensors state variable
@StateVariables StrainStensor evp,evp2;

The `@StaticVar` keyword

The @StaticVar keyword is a deprecated synonymous of @StaticVariable.

The `@StaticVariable` keyword

The @StaticVariable keyword let the user define a constant value. Unlike parameters (see the @Parameter keyword), static variables’ values can’t be changed after compilation.

This keyword must be followed by the type of the constant, its name, an equal sign and its value.

Example

@StaticVariable real A = 1.234e56;

The `@UnitSystem` keyword

The @UnitSystem keyword declares that the state variables, external state variables and parameters are expressed in a given unit system. In the current version of MFront, the only supported unit system is the international system of units, denoted SI.

One advantage of declaring a unit system is that physical bounds of variables associated with a glossary entry can automatically be declared by MFront.

For instance the declaration of the physical bounds for the temperature and the porosity is automatic if the SI unit system is used.

Example of usage

@UnitSystem SI;

The `@UseQt` keyword

The UseQt keyword (use quantities) specify if the behaviour compilation should perform compile-time units checks. It is followed by a boolean.

Note

This feature is still experimental and is disabled in most cases.

Example

@UseQt true;

Model keywords

The ; keyword

The @Author keyword

Example

The @Bounds keyword

Effect

Example

The @Coef keyword

The @ConstantMaterialProperty keyword

External name

Example

The @DSL keyword

DSL options

Defining DSL options in the MFront file

Defining DSL options on the command line:

Options common to all DSLs

Options common to all DSLs related to behaviours

Example

The @Date keyword

Example

The @Description keyword

Example

The @Domain keyword

Example

The @Domains keyword

Example

The @ExternalStateVariable keyword

Arrays

External names

Example

The @Function keyword

Example

The @Import keyword

Search paths

Example

The @Includes keyword

Example

The @Input keyword

Variable depth

External name

Example

The @LocalParameter keyword

Default values

Example

The @Material keyword

Example

The @MaterialLaw keyword

Search paths

Note

Example

The @MaterialProperty keyword

Arrays

External names

Example

The @Model keyword

Example

The @Output keyword

Variable depth

External name

Example

The @Parameter keyword

Example

The @Parser keyword

The @PhysicalBounds keyword

Effect

Example

The @StateVariable keyword

Arrays

External names

Example

The @StaticVar keyword

The @StaticVariable keyword

Example

The @UnitSystem keyword

Example of usage

The @UseQt keyword

Note

Example

`Model` keywords

The `;` keyword

The `@Author` keyword

The `@Bounds` keyword

The `@Coef` keyword

The `@ConstantMaterialProperty` keyword

The `@DSL` keyword

Defining `DSL` options in the MFront file

Defining `DSL` options on the command line:

The `@Date` keyword

The `@Description` keyword

The `@Domain` keyword

The `@Domains` keyword

The `@ExternalStateVariable` keyword

The `@Function` keyword

The `@Import` keyword

The `@Includes` keyword

The `@Input` keyword

The `@LocalParameter` keyword

The `@Material` keyword

The `@MaterialLaw` keyword

The `@MaterialProperty` keyword

The `@Model` keyword

The `@Output` keyword

The `@Parameter` keyword

The `@Parser` keyword

The `@PhysicalBounds` keyword

The `@StateVariable` keyword

The `@StaticVar` keyword

The `@StaticVariable` keyword

The `@UnitSystem` keyword

The `@UseQt` keyword