Add a State Variables node () under Definitions>Variable Utilities in a model component or under Global Definitions>Variable Utilities to define states that are updated using an update expression at the beginning or end of each completed solver step. States are dependent variables in the model and stored as such in solutions, but they are explicitly updated by the solver after each converged time or parameter step rather than solved for in the usual sense. Use state variables to, for example, store the previous-step value of some expression. This is useful, for example, when implementing material models with history dependence or hysteresis.

The Settings window contains the following sections:

For a State Variables node in a component, use this section to define the geometric entities where the state variables should be defined at integration points in each element.

Enter state variable names in the State column and corresponding initialization expressions in the Initial value column. These initial values are handled in the same way as for other dependent variables, depending on study and solver settings. Then specify an Update expression for each state variable. This expression is evaluated either after completion of a (time or parameter) solver step or at the very beginning of each new solver step. You can select this behavior by choosing to Update either Before step or After step. The default is to update Before step, which is appropriate for variables representing a value from the previous converged step.

When the State Variables node belongs to a component, select the Order of integration points in which the state variables will be defined. Allowed orders are even numbers between 0 and 14. The state variable degrees of freedom are defined in the same way as a standard dependent variable using Gauss point data shape functions. Typically choose the same order as the integration order used by the physics equations in the model. States defined in that way are suitable for storing material property history data locally at each point where it is used by the equations.

Optionally specify a custom Description for each state and select the Allow complex values check box to allow complex-valued state values when the solver is set to split complex values in real and imaginary parts.