Below are some error messages that may be encountered when running a thermal analysis. Unless indicated otherwise, these messages appear in either the statistics file, the summary file, or both.
AMG solver could not reach to specified accuracy.
Specified tolerance = n.nnnE-nn
Final relative residual (of scaled system) = c.cccE-cc
Condition of the preconditioned system = 1.0000E+00
Number of iterations used = X
The iterative solver was used to solve the analysis, but it was unable to converge to a solution. (See the page Setting Up and Performing the Analysis: Types of Solvers Available for more details on the different solvers.) After X iterations, it was able to solve the system of equations to a residual of c.cccE-cc compared to the target residual of n.nnnE-nn. The options are to try a different Type of solver, or change the Convergence tolerance or Maximum number of iterations. All these parameters are entered on the Solution tab of the Analysis
Parameters.
ERROR: ALL TEMPERATURES EQUAL 0.0D0
The analysis did not complete, possibly due to a lack of loads. Look for other warnings in the summary file which may be the real cause of the problem, and check the load multipliers. Also, make sure there is a source of heat, and for a steady-state analysis, a way to remove the heat.
error: element temperature outside material table
Orthotropic, temperature-dependent material properties were specified, but either an initial temperature or a calculated temperature exceeded the range of temperatures in the table. Check that the temperatures are in ascending order and that the first and last material temperatures bracket the temperatures throughout the analysis.
Error: view factors sum = X must be >= 0 and < 1.
(tolerance used=Y) for an open enclosure.
This is not the case for surface N!
The calculated view factor for body-to-body radiation, the value X in the error message, is not in the allowable range of 0 to 1 (plus or minus the user-entered tolerance value of Y). The element with the problem is identified by its radiation surface number N. Because the view factor is out of range, the calculated temperature results are likely to be inaccurate or wrong.
Use the radiation log file (.LRD) to correlate the radiation surface number (Rad. Surf in the List of Radiation Surfaces) with the part number (Egroup) and Element number. Then locate the element in the Results environment (Results Inquire Inquire Element Information) to get an idea of where the problem is occurring.
The cause of the problem and solution could be one of the following. Items 1 and 2 are set under the body-to-body radiation input dialogs. See the page Setting Up and Performing the Analysis: Thermal: Loads and Constraints: Body-to-Body Radiation for details.
- The Shadowing option was not included; therefore, the element is able to radiate to more faces than theoretically possible. Activate the Shadowing option if appropriate.
- Elements whose faces are separated by a small gap can benefit from the more accurate View factor calculation method of the String rule/contour integration. The Point-to-point option is suited for faces that are well separated.
- Use a finer mesh.
It is not suggested to increase the tolerance value Y to bypass the error. The tolerance is provided only because of the mathematical unlikelihood of calculating a view factor of exactly 1.
error: your model isn't tied down enough. make sure each DOF is set somewhere nnn
Your model may not have any loads. Check that your loads are defined and activated.
Orthotropic orientation nodes not defined. Part (n) Error. Invalid or missing data
When using an orthotropic material model, the orientation of the three material axes is defined in the Element Definition by specifying three node numbers. This error message indicates that the node numbers were not specified for part n. Use the Results environment to get the node numbers to specify the orientation, then enter those numbers for the part.
SOLUTION DID NOT MEET CONVERGENCE CRITERIA
For steady-state analysis with orthotropic, temperature-dependent material properties or radiation, the Advanced tab in the Analysis Parameters screen is used to set up the iterative process. However, the model failed to converge within the number of iterations that were specified. Based on how the model was converging (or not) during the analysis as indicated by the corrective and relative norms in the summary file, make some changes to the iteration parameters and run the model again.
SPECIFIC HEAT CANNOT BE <= 0.0
The specific heat is required for a transient heat transfer analysis. However, the material input includes negative or zero values for specific heat. Edit the materials and enter nonzero values.
Temperature results file has x nodes, but the model has y nodes.
For a transient analysis in which the initial nodal temperatures are being read from another heat transfer analysis, the two models must have the same number of nodes. Otherwise, the automatic transfer of the temperatures will not work properly. This message appears in a pop-up window; it does not appear in the summary file. Also, the analysis continues to run after closing the pop-up, but the initial nodal temperatures are not set.
Temperature results file not found.
For a transient analysis in which the initial nodal temperatures are being read from another heat transfer analysis, the previous results could not be located. Check the path and filename entered on the Global: Options tab.
This message appears in a pop-up window; it does not appear in the summary file. Also, the analysis continues to run after closing it.
THERMAL CONDUCTIVITY MUST BE 1.0E-09
The thermal conductivity must be greater than zero. Change the material properties.
Warning: Matrix reformulation will not be done. Element based loading will not depend on Load Curves.
The user input instructed the processor to not update the matrix during the analysis. Therefore, any time dependent or temperature dependent effects may not be calculated properly. See the paragraph Controlling the Matrix Calculation on the page Setting Up and Performing the Analysis: Thermal: Analysis Parameters: Transient Heat Transfer for details.
WARNING: Model has non-linearity through temperature-dependent thermal conductivity. Nonlinear flag has not been set by user. This may lead to inaccurate results. Use runtime option NL to set up nonlinear analysis.
For steady-state analysis, use the Advanced tab in the Analysis Parameters screen to set up the iteration process for the nonlinear material. This is required when orthotropic, temperature-dependent material properties are in the model or when radiation is applied.
warning: your model may not be tied down enough or you may have a change in stiffness somewhere in your model which is too abrupt. Check DOF: nnn
Your model may not have any loads, or the elements may be distorted and causing stiffness problems during the solution. Check that your loads are defined and activated. Check the quality of the elements. For more details on what can be done for this see: Model Not Tied Down Enough.