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Chapter 3: Adaptive Meshing

The ANSYS program provides approximate techniques for estimating mesh discretization error for certain types of analyses. Using this measure of mesh discretization error, the program can then determine if

a particular mesh is fine enough. If not, the program will automatically refine the mesh so that the measured error will decrease. This process of automatically evaluating mesh discretization error and refining the mesh, called adaptive meshing, continues through a series of solutions until the measured error drops below some user-defined value (or until a user-defined limit on the number of solutions is reached).

The following adaptive meshing topics are available:

3.1.Prerequisites for Adaptive Meshing

3.2.Employing Adaptive Meshing

3.3.Modifying the Adaptive Meshing Process

3.4.Adaptive Meshing Hints and Comments

3.5.Where to Find Examples

For more information about error-value approximation, see The General Postprocessor (POST1) in the

Basic Analysis Guide.

3.1. Prerequisites for Adaptive Meshing

The ANSYS program includes a macro named ADAPT.MAC for performing adaptive meshing. Your model must meet certain criteria before you can successfully activate the macro. (In some cases, models

not conforming to the criteria can be adaptively meshed using a modified procedure, as discussed below.) The requirements include the following:

The standard adaptive meshing procedure is valid only for single-solution linear static structural and linear steady-state thermal analyses.

Use only one material type, as the error calculations are based in part on average nodal stresses, and would thus often be invalid at the material interfaces. Also, an element's error energy is affected by its elastic modulus; therefore, even if the stress discontinuity is the same in two adjoining elements,

their error energy will be different if they have different material properties. Also, avoid abrupt changes in shell thickness, as such discontinuities cause similar stress-averaging problems.

Use meshable solid model entities. (Avoid characteristics that will cause meshing failure.)

Some elementand material-type limitations apply. For more information, see the documentation for the PRERR command.

3.2. Employing Adaptive Meshing

The general process for running the adaptive meshing macro follows:

1.As in any linear static structural or steady state thermal analysis, enter the preprocessor (/PREP7 command or menu path Main Menu> Preprocessor) and specify the element type, real constants, and material properties (according to the prerequisites).

Release 15.0 - © SAS IP, Inc. All rights reserved. - Contains proprietary and confidential information

 

of ANSYS, Inc. and its subsidiaries and affiliates.

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