***parameter#

Description#

Using the coefficient mechanism, material behavior may depend on both internal variables calculated by the material law, and external user specified parameters which are essentially problem loading. The coefficient syntax is discussed in the ***behavior chapter in the Z-mat manual.

Use of the parameter mechanism may also intervene directly in the material law such as thermal deformations which depend on a temperature parameter. This temperature field may be the output of previous calculations to provide immediate capability of un-coupled or weakly coupled multi-domain solutions. Other non-standard parameters are also permissible allowing user data to be used in the calculation. One example is specifying a distribution of the density, and then making the elastic modulus depend on this density.

There are several methods of specifying the parameters within a geometry.

Syntax#

The baseline syntax for external parameters follows.

***parameter type  parameter_name [ *node | *ip | *node_averaged ] \(~\,~\,\)

type

a **-level sub-command for the type of external parameter input which is desired. The different types are described in the pages which follow, including their specific values. In the absence of a type (input starts directly with *-level commands, or data entry fields, the type **file is taken as the default.

parameter_name

Character name of the parameter. The naming of parameters is inherently open in the code. However, the use of certain names have particular signification for different options in the material behavior or global loading. An important example is the name temperature which is searched by the thermal strain material objects.

*node

indicates that the parameter exists at nodal locations, and will be interpolated to integration points. Record sizes are the number of nodes. This is the default.

*ip

indicates that the parameter exists at integration points. The record size will be the number of integration points in the mesh.

node_averaged

indicates that the parameter exists at nodes. Record sizes are the number of nodes. The nodal values are averaged, so one value of parameter for each element is obtained.

Important

It is imperative that the parameters be defined at all times from \(t=0.\) to the end time of the problem. Between the times for which the parameter is defined through file, function or uniform the value will be linearly interpolated. It is therefore desirable that the times of parameter definition correspond to the end sequence times. Uniform values may be applied in an analogous manner as the boundary conditions with the use of tables.

Examples#

Two simple examples are shown below.

***parameter temperature
   0. uniform 125.
   1. uniform 175.
   2. uniform 175.
   3. uniform 125.

***parameter humidity
  *ip
   0. uniform  0.25
   1. uniform  0.25
   2. uniform  0.75
   3. uniform  0.25