Material Models

Numerous material models are available in NairnMPM and OSUParticulas.

Define a Material

To use a material in calculations, you first must define it in the the input commands. This definition will create a material name (or ID or number) that can be used to assign that material to particles. When using NairnFEAMPM or NairnFEAMPMViz, a material is created with the command block:

Material ID,name,type
   Property value
   Property2 value
      .
      .
Done

where

• ID is the material ID (any string) that is used to reference this material in other commands.
• name is a name that will appear in output files to describe the material
• type is the type of material, which can be select by type name or number from the available material models.

Each material property is on a line with the property name and its value. Refer to each material type to see the properties needed. The property names are case sensitive (although NairnFEAMPM can usually handle any case).

A material definition in a XML input file has the form

<Material Type='1' Name='Polymer'>
   <Property>value</Property>
   <Property2>value</Property2>     
     .
     .
</Material>

where

• Type is the material type and must be entered by number corresponding to that material model.
• Name is any user-defined description of the material (limit 200 characters).

Note that in XML files a material does not have an ID, which is used in scripting files to refer to that material in other commands. Instead, other XML commands refer to defined materials by number or name as follows:

By Numbers

In this method, you use mat='#' attributes to refer to materials where # is the material number. The materials are defined by numbers in the order they appear in the output file with the first material being number 1. You have to be careful to use the correct number. If you add new materials to a file, it is best to add them to the end of the materials list, otherwise previous commands that referenced materials after an inserted material, will point to the wrong material.

By Name

In this method, you use matname='Mat_Name' attributes where 'Mat_Name' matches the Name attribute of any defined material in the file. You can use these names even before the materials are defined, but errors will occur if you reference materials that are not eventually defined or if the defined materials do not have unique names. When referring to materials by name, you must be sure that all materials Name attributes have unique strings.

When referring to materials by name, the defined materials will appear in the output file in the ordered referenced rather than in the order defined in the input file. For this reason, you should not refer to some materials by name and others by number in the same file. The eventual ordering will likely mean the numbers will refer to the wrong material. The naming method is preferred in hand-edited XML files. If you use both mat and matname attributes in a single command, the matname one will be used and the mat will be ignored.