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This documentation wiki is for the computational mechanics software from Oregon State University in the research group of John A. Nairn. This software package focuses on material point method (MPM) calculations (OSParticulas and NairnMPM), but also includes basic finite element analysis (FEA) calculations (NairnFEA).

Getting Starting

The calculation engines for material point method (MPM) simulations are called OSParticulas and NairnMPM. The calculation engine for finite element analysis (FEA) is called NairnFEA. These are all object-oriented, C++, platform-independent code engines. The first steps to using these tools are:

• Download Source Code
• Compile the Code Engines
• Options for Running Calculations

Input Files for Calculations

MPM simulations using OSParticulas or NairnMPM or FEA calculations using NairnFEA are controlled by input from an XML input file. This input file can be created manually by using any text or XML editing software. It is usually preferred, however, to use a higher-level scripting language to set up the calculations and then have an interpreter format those commands into the XML files needed by the code engines. This scripting method allows for more powerful input files that are much easier to customize for a range of simulations. Scripting calculations can be done by using either the NairnFEAMPM application (Mac only) or the NairnFEAMPMViz (Java tool) application. The scripting languages in these two applications are almost identical.

MPM and FEA Input Files

The bulk of the documentation in this wiki is involved with describing the features of the software and explaining the input commands needed to use those features. The features and input commands documentation for MPM or FEA calculations are in the following sections:

• Input Files for MPM Calculations
• Input Files for FEA Calculations

Documentation Notes

Scripted input files are comprised of a series of commands and XML input files are comprised of a series of XML elements. This documentation will explain these commands and elements using the style:

 Command (arg1),(arg2),<(arg3)>,<(arg4)>
 <Command attr1='(arg1)' attr2='(arg2)'>(arg3)</Command>

where

• Command is the command name.
• (arg1),(arg2), etc., specify arguments whose function will be explained along with the command.
• <(arg3)> - enclosing an argument in angle brackets indicates an optional argument. If the argument is omitted, the code will assume some default value.
• attr1, attr2, etc., are attributes to the XML element.

Visualization

The various code engines do the calculations. Visualization of results is usually using either NairnFEAMPM (preferred, but Mac only) or NairnFEAMPMViz (Java program for Windows or Linux). For 3D analysis, some things can be visualized in NairnFEAMPM. Alternatively, calculation results can be archived as vtk files and then visualized in ParaView or an other software that can read standard vtk files. For custom visualization options, you can use the ExtractMPM tool to extract selected data in various formats and input that data and to any visualization tool you have available.

Format of Output Files

The provided visualization tools automatically read output files created by these code engines. If you need even more customization, you can always write you own software to read output files; to make that task possible you can refer to documentation on the format of the archive files.