Materials file (.mat)

Files with the extension .mat include the definition of different materials through their properties. These are base materials as they can be used as templates during the Preprocessing step for the creation of newer ones.

You can define as many materials as you wish, with a variable number of fields. None of the unused materials will be taken into consideration when writing the data input files for the solver. Alternatively, they can be useful for generating a materials library.

Conversely to the case of conditions, the same material can be assigned to different levels of geometrical entity (lines, surfaces or volumes) and can even be assigned directly to the mesh elements.

In a similar way to how a condition is defined, a material can be considered as a group of fields containing its name, its corresponding properties and their values.

The format of the file is as follows:

MATERIAL: material_name

QUESTION: field_name['#CB#'(...,optional_value_i,...)]

VALUE: default_field_value

...

QUESTION: field_name['#CB#'(...,optional_value_i,...)]

VALUE: default_field_value

END MATERIAL

MATERIAL: material_name

...

END MATERIAL

If a material has a variable property (an example would be where a property was dependent on temperature and was defined with several values for several temperatures) a table of changing values may be declared for this property. When the solver evaluates the problem, it reads the values and applies a suitable property value.

The declaration of the table requires two lines of text:

The first is a QUESTION line with a list of alphanumeric values between parentheses.

QUESTION: field_name:(...,optional_value_i,...)

These values are the names of each of the columns in the table so that the number of values declared is the number of columns.

This first line is followed by another with the actual data values. It starts with the words VALUE: #N#, and is followed by a number that indicates the quantity of elements in the matrix and, finally, the list of values.

VALUE: #N# number_of_values ... value_number_i ...

The number of values declared for the matrix obviously has to be the number of columns multiplied by the number of rows to be declared.

This kind of material specification is most likely to be used in thermo-mechanical simulations, where the problem is exposed to a temperature variation, and the properties of the materials change for each temperature value.

All the fields must be filled with words, where a word is considered as a string of characters without any blank spaces. The strings signaled between quotes are literal and the ones within brackets are optional. The interface is case-sensitive, so any uppercase letters must be maintained. The default_field_value entry and various optional_value_i entries can be alphanumeric, integers or real numbers, depending on their type.

The numbers of the materials have to be consecutive, beginning with number 1. There is no need to indicate the overall number of materials or the respective number of fields for each one. This last one can vary for each material.

Note that in this file, you cannot include blank lines between different material definitions, nor between questions and values.

Note: There are other options available to expand the capabilities of the Materials window (see Special fields ).

Example: Creating the materials file

Here is an example of how to create a materials file, explained step by step:

  1. Create and edit the file (problem_type_name.mat in this example) inside the problem_type_name directory (where all your problem type files are located). As you can see, except for the extension, the names of the file and the directory are the same.
  1. Create the first material, which starts with the line:

MATERIAL: Air

The parameter is the name of the material. A unique material name is required for this into this materials file (do not use blank spaces in the name of the material).

  1. The next two lines define a property of the material and its default value:

QUESTION: Density

VALUE: 1.0

You can add as many properties as you wish. To end the material definition, add the following line:

END MATERIAL

  1. In this example we have introduced some materials; the .mat file would be as follows:

MATERIAL: Air

QUESTION: Density

VALUE: 1.01

END MATERIAL

MATERIAL: AISI_4340_Steel

QUESTION: YOUNG_(Ex)

VALUE: 21E+9

QUESTION: SHEAR_MODUL

VALUE: 8.07E+9

QUESTION: POISSON_(NUXY)

VALUE: 0.3

QUESTION: ALPX

VALUE: 0.0000066

QUESTION: DENSIDAD_(DENS)

VALUE: 0.785

END MATERIAL

MATERIAL: Concrete

QUESTION: Density

VALUE: 2350

END MATERIAL

  1. The materials defined in the .mat file can be managed in the Materials window (found in the Data menu) in the Preprocessing component of GiD.

Materials window in GiD Preprocessing