Material Command Block

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To use an MPM material, an FEA material, or a traction law in calculations, you first must define it in the input commands. The method for defining materials and traction laws depends on the type of input commands file you are writing.

Scripted Input Commands

When using NairnFEAMPM or NairnFEAMPMViz, a material or traction law is created with the scripting command block:

Material (id),(name),(type)
   Property value
   Property2 value


  • (id) is the material ID (any string or number) 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 set by using material type name or material type ID from the available material models (see material tables on this page for each material's name and type number)

Each material property is specified on a line with a property name and its value. Refer to each MPM material, FEA material, or traction law type to see the available properties and which ones are required properties. The property names are case sensitive (although NairnFEAMPM can usually handle any case).

XML Input Commands

A material or traction law definition in a XML input file has the form:

<Material Type='(num)' Name='(name)'>


  • (num) is the material type and must be entered by material number corresponding to that MPM or FEA material type (see material tables for each material's type number).
  • (name) is any user-defined description of the material.

Each material property is specified in a single XML element matching the property name and the content of the element as the value. Refer to each MPM material, FEA material, or traction law type to see the available properties and which ones are required properties.

Referencing Materials in XML Files

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

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 an error will occur if you reference materials that are never defined. When referring to materials by name, you must be certain that all material Name attributes have unique strings.
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.

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 matname and mat attributes in a single element, the matname attribute will be used and the mat one will be ignored. A few options that refer to materials (e.g., some material properties and custom task settings) can only use material number. When using such settings, it is probably better to reference all materials by number rather then by name.