Creating MPM Materials

This section explains how to write C++ code create a new material class for use in NairnMPM.

Getting Started

The first steps are to create source files for the new material class, to give the material a unique name, and to allow the main NairnMPM code to instantiate the material class when it is needed for a particle.

Class Source Code

The best way to create the source code is to duplicate the NewMaterial.cpp and NewMaterial.hpp files, which are templates for a new material class. Edit the files and change NewMaterial to the new material's class name (e.g., MyMaterial). The NewMaterial template is a subclass of MaterialBase. Normally the new material will be a subclass of another class. If so, change MaterialBase references, as needed, to the actual parent class. These changes are needed whenever a method in the new material class needs to pass control to its immediate super class.

Material Class Hierarchy

The new material should be inserted into the NairnMPM material class hierarchy with its name (from previous step) and a unique ID (an integer). In the new material's header files, replace NEWMATERIAL with a defined constant representing the new material's ID (which by convention is in UPPERCASE) and replace the number in the new constant's definition with the new material's ID. For example:

#define MYMATERIAL 102

All documented materials use low numbers (starting with 1). To avoid conflicts, those working on custom materials should use large numbers (>100).

Editing Required in Core Code

Almost all coding will be done in the new material class files, but for that material to be recognized as an option in NairnMPM, two places in the core code have to be edited first. These should be the only changes needed outside the new material's class files.

1. Include the new material's header file at the top of Common/Read_XML/MaterialController.cpp:

    #include "Materials/MyMaterial.hpp"
   

   or the appropriate relative path to the new material's header file.

2. In MaterialController::AddMaterial(int matID,char *matName) add a new case in the switch(matID) section to call the default constructor of the new material when matID matches the new material's constant defined in the previous section.

   case MYMATERIAL:
      newMaterial=new MyMaterial(matName);
      break;
   

   If needed you can define a custom constructor and use that in this code (this need is very rare).