OOF2: The Manual

2.3. Materials

The physical characteristics of an OOF2 Microstructure are contained in one or more Material objects. Materials are created by assembling lists of Property objects, and are assigned to Microstructure pixels in the Materials Page.

2.3.1. Properties

Properties come in a variety of categories. Most, such as Elasticity or ThermalExpansion represents terms in constitutive equations. Others, such as Orientation, modify those terms, and at least one, Color, serves only a decorative function.

All of the Properties predefined in OOF2 are listed by category in Section 6.4.1 in Chapter 6. Chapter 7 explains how to add new Properties.

Many Properties have subcategories. For example, Elasticity is divided into Isotropic and Anisotropic, and Anisotropic is further divided into Cubic and all the other crystal symmetries. Generally, a Material may contain only one Property from each category. Some categories of Properties make sense only if a property of another category is defined in the same Material -- for example, it's an error to include a Cubic elasticity without also including an Orientation. OOF2 will notify you of badly formed Materials when you solve a Mesh.

When OOF2 starts, it creates a single unnamed instance of each type of Property. New instances may be created by copying a Property and giving it a name. Both named and unnamed Properties may be used in Materials. The commands in the OOF.Property.Parametrize menu set the parameters (e.g, Young's modulus, conductivity, or color) for Properties. Parameters may be set in either named or unnamed Properties.

Properties are arranged in a hierarchical tree structure, which is shown in the Property pane of the Materials task page. The path to a Property is a colon separated list of the names of the levels of the tree leading to the Property. For example, the path to cubic elasiticity is 'Mechanical:Elasticity:Anisotropic:Cubic'. The path to a named property is created by appending the name to the path to its unnamed version: 'Mechanical:Elasticity:Anisotropic:Cubic:salt' is a cubic elasticity Property named salt. Most commands that work on Properties in scripts refer to them by their paths. The exceptions are the OOF.Property.Parametrize and OOF.LoadData.Property menus, which instead embed the Property name in the name of the command. That is, the command to parametrize a cubic elastic property is OOF.Property.Parametrize.Mechanical.Elasticity.Anisotropic.Cubic, and the command to parametrize a cubic elastic property named salt is OOF.Property.Parametrize.Mechanical.Elasticity.Anisotropic.Cubic.salt. (Fortunately, the user rarely has to type these names in full.) The arguments for the named and unnamed forms are the same, and are listed in the documentation under OOF.Property.Parametrize.

2.3.2. Orientations

Many Properties are anisotropic: their values depend on the orientation of the crystalline axes. In OOF2, although the calculations are two dimensional, crystalline orientations are full three dimensional rotations. They can be specified in a number of ways as subclasses of the Orientation class.

Any Material that contains an anisotropic Property must also contain either an Orientation Property or an OrientationMap Property. The difference betweeen them is that an Orientation Property has an argument which specifies the orientation, whereas an OrientationMap Property gets the orientation from the Microstructure's Orientation Map. The existence of the Orientation Map in a Microstructure does not automatically imply that the Microstructure's Materials will derive their orientations from it. The OrientationMap Property must also be present. This allows some Materials to get their orientations from the map while others do not.