MPM Input Files

The introduction list some key features of OSParticulas and NairnMPM with links to where those features are doucmented in this help. The remaining section are the possible sections for input command files.

Introduction

This page documents all the options for the OSParticulas and NairnMPM code engines. The capabilities and features of these code engines are embedded in the documentation of input commands for each option. Some highlights of capabilities (with links to input commands) are:

• 2D, Axisymmetric, and 3D
• Various Shape Functions
• Many Material Models
• Explicit Cracks, Fracture Mechanics, and Cohesive Zones
• Multimaterial Mode
• Models from Images
• Coupled Diffusion and Conductivity
• VTK Archiving
• Rigid Particle Features
• Custom Tasks

XML File Overview

All input files for MPM calculations are XML files. When using NairnFEAMPM or NairnFEAMPMViz to set up calculations, the input files are creating using a scripting language. When these scripts are interpreted, the XML file is created for you (and you can therefore skip this section).

If you are manually writing XML files, however, they conform to the structure defined in this section. All XML command files for MPM calculations must begin with an XML declaration, an optional document type declaration, and the main input file tag and end with the corresponding closing tags. For MPM calculations, the global file structure is:

<?xml version='1.0'?>
<!DOCTYPE JANFEAInput SYSTEM "NairnMPM.dtd"
[
  <!ENTITY maxtime "1e-03">
  <!ENTITY width "100">  
]>
<JANFEAInput version='3'>
   ...
   (XML Command to define the calculation)
   ...
</JANFEAInput>

The !DOCTYPE element defines the file type and has the SYSTEM option to provide a path to a Document Type Definition (or DTD) file. The path is needed when you run the code with the validation option (-v), which is highly recommended. The required DTD file for MPM calculations is provided in the /input folder of the source code files.

The !DOCTYPE element can define any number of entities. These entities can be used elsewhere in the text of the XML file and they will be replaced by the text in the entity definition. For example, the above MPM file can use the entity &maxtime; and it will be replaced with the text 1e-03. Entities can define values that make it easier to read input XML files and easier to modify them for new calculations.

The remainder of the file is included withing a JANFEAInput block. The version attribute is currently not needed, but may be important in the future. When input files are validated using the DTD file (as recommended), the sections must appear in the specified orderdefined in the table of contents on this page. Elements that are not used can be omitted, but all needed elements must be in that specific order. A sample MPM input file shows a sample calculation of two colliding disks.

Main Header

This section, which is required in XML files, defines the type of analysis to be done. In XML files, the header block is

<Header>
  (commands)
</Header>

When using scripting language, the header is created by commands in this section. The possible header commands are

• Analysis Command
• Description Command
• Setting Developer Flags

Defining Material Models

Each material point is assigned a material type. NairnMPM and OSParticulas support numerous material models. For plasticity materials, each material type can choose from among a set of hardening laws. Finally, when using explicit cracks, the material points along the cracks can be assigned to various traction laws. The information on these options are in the following sections:

• Material Models
• Hardening Laws
• Traction Laws