Use nonlinear mesh adaptivity (NLAD) to modify the mesh (according to specified criteria) during solution, either to simulate some problems that otherwise cannot be simulated, to improve the accuracy of simulation results, or to reduce the degrees of freedom in unnecessarily fine-meshed regions. Nonlinear mesh adaptivity is completely automatic, requiring no user input during solution.
Nonlinear mesh adaptivity is available for 2D and 3D analyses.
Nonlinear mesh adaptivity criteria are the rules used to determine whether the mesh must be modified and, if so, what parts of the mesh should be modified. Several criteria types are available. You determine how frequently the criteria should be checked.
When the defined criteria are met, mesh modification occurs either by splitting, general remeshing, or morphing:
Splitting applies to contact-based (NLADAPTIVE,,,CONTACT,NUMELEM), energy-based (NLADAPTIVE,,,ENERGY), and position-based (NLADAPTIVE,,,BOX) criteria. It is the only option for PLANE183, but can also be used for PLANE182, PLANE222, and SOLID285 (NLMESH,REFA,SPLIT).
During splitting, the current elements are divided into elements having a half-edge length. The program creates some transition layers to connect the refined regions to the unrefined regions. Some topology changes and morphing occur during 3D tetrahedral element splitting to improve the quality of the new mesh; for 2D meshes, only morphing occurs after the element-splitting operation. General remeshing applies to:
Mesh-quality-based criteria, used with either the 2D lower-order quadrilateral elements PLANE182 and PLANE222, or 3D tetrahedral elements SOLID187 and SOLID285. During remeshing, the selected region is completely remeshed to obtain a high-quality mesh.
Contact-based (without the wear option), energy-based, and position-based criteria. It is the default option for PLANE182, PLANE222, SOLID187, SOLID227, and SOLID285. During remeshing in such cases, the selected region is completely remeshed to obtain a refined mesh, but the mesh quality may not necessarily be improved.
Contact-based (CZM), energy-based, and position-based criteria with the coarsening option. During remeshing, the selected region is remeshed to obtain a coarser element size in the new mesh based on the original equivalent element size. However, the mesh quality may not necessarily be improved, especially in transition zones to unselected regions. Refinement and mesh-quality criteria always take precedence over coarsening.
Morphing applies to contact-based criterion with the wear option (TB,WEAR and NLADAPTIVE,,,,WEAR) only.
During morphing, the mesh topology remains constant, and only nodes are moved based on the contact wearing. Contact-based criterion with CZM option
Mesh refinement and coarsening can be applied together. Coarsening can lessen processing time when modeling debonded regions of cohesive zone problems. Mesh regions where the active cohesive zone meets the criterion are refined, and the debonded (damaged) regions are coarsened (by remeshing those regions with larger element sizes automatically).
The following topics about nonlinear mesh adaptivity are available:
- 2.1. Nonlinear Mesh Adaptivity Benefits
- 2.2. Nonlinear Mesh Adaptivity Usage Considerations
- 2.3. Nonlinear Mesh Adaptivity Requirements and Limitations
- 2.4. Understanding the Nonlinear Mesh Adaptivity Process
- 2.5. Nonlinear Mesh Adaptivity Criteria
- 2.6. Specifying Criteria-Checking Frequency
- 2.7. Generating the New Mesh
- 2.8. Convergence at Substeps with the New Mesh
- 2.9. Controlling Nonlinear Mesh Adaptivity
- 2.10. Multiple Remeshings with Nonlinear Mesh Adaptivity
- 2.11. Restarting from a Nonlinear Mesh Adaptivity Analysis
- 2.12. Stabilization in a Nonlinear Mesh Adaptivity Analysis
- 2.13. Nonlinear Mesh Adaptivity Hints and Recommendations
- 2.14. Postprocessing Nonlinear Mesh Adaptivity Results