$\newcommand{\Dev}{\operatorname{Dev}}$ $\newcommand{\dev}{\operatorname{dev}}$ $\newcommand{\grad}{\operatorname{grad}}$ $\newcommand{\divg}{\operatorname{div}}$ $\newcommand{\Ei}{\operatorname{Ei}}$ $\newcommand{\tr}{\operatorname{tr}}$

For math parameters, add the type=”math” attribute to the parameter's definition. The value of the parameter tag can then be any mathematical expression. The upper case letters X, Y, Z, are used to denote material coordinates. The letter t denotes time. The algebraic operators +, -, *, /, ^ are supported, as well as the list of functions listed in Appendix C.

<material id="1" name="my_material" type="neo-Hookean">
  <E type="math">X+Y+Z</E>
  <v>0.3</v>
</material>

You can also use the component's other parameters inside mathematical expressions.

<material id="1" name="my_material" type="neo-Hookean">
  <density>1.0</density>
  <E type="math">2*density+0.1</E>
  <v>0.3</v>
</material>