Nonlinear Steady Thermal Analysis
You have to run a nonlinear steadystate thermal analysis for models which have:
• materials with temperaturedependent thermal conductivity
• temperaturedependent convection conditions
• radiation conditions
To define a nonlinear steadystate thermal analysis the Nonlinear / Use Load Histories check box on the Steady Thermal Analysis Definition dialog box must be selected. This check box is selected by default if the model has any of the above listed nonlinearities. The dialog box displays the possible causes of nonlinearity and highlights the applicable cause.
Select load and constraint sets from the
Loads and
Constraints areas. For a nonlinear steadystate thermal analysis you can create a
table function for the time dependence of each constraint and load set. The time dependence function is the factor by which a load or constraint is magnified in a constraint or load set. You can create a function where the independent variable is time and the dependent variable is a quantity without units. The default function for constraint and load sets is the
ramp function.
When you define a time dependence table function the equivalent load acting on a model is the value of the load multiplied by the value of the time dependence function at a given time. You can specify the output steps at which you want results to be calculated. For a specified time step, results will be calculated for the corresponding value of load.

You cannot create a symbolic function for time dependence.


When you specify load histories for a steady state thermal analysis, the loads are assumed to be applied slowly relative to the time it takes the temperature in the model to reach equilibrium. Thus, the steps only define the order of loading, and true transient effects are neglected.

You can only run nonlinear steadystate thermal analyses with the quick check and single pass adaptive method of convergence. The multi pass adaptive method of convergence is not supported for a nonlinear steadystate thermal analysis.