5.4. NLAD-GPAD Best Practices

Standard nonlinear mesh adaptivity recommendations apply to an NLAD-GPAD analysis.

Because NLAD-GPAD supports only small-deformation analysis (NLGEOM,OFF), only the following two refinement and coarsening criteria are available:

The mesh-splitting method for generating a new mesh (NLMESH,REFA,SPLIT) is not supported.

Although SOLID285 and SOLID187 are both supported, Ansys recommends against using SOLID285 for sequentially refining geometries exhibiting high curvature, especially with a very coarse starting mesh.

To avoid mesh over-refinement when using NLAD-GPAD, adjust one or more of the following settings as necessary:

  • Increase VAL2 on NLMESH,SRAT as required within a load step.

  • Limit the number of elements for remeshing (NLMESH,ELSZ or NLMESH,NSTR).

  • Increase the energy coefficient when using the energy-based criteria. A value of 10 is recommended.

If the remeshing executable fails to generate a new mesh during solution, it may be due to one of these reasons:

  • The initial mesh is too coarse or the quality of the initial mesh is topologically poor.

  • The remeshing regions have geometry profiles that are too thin and therefore difficult to remesh.

To improve the chance of a successful remesh, enable aggressive remeshing (NLMESH,AGGR,ON).

To make the element sizes larger in regions of the mesh with no critical features, use the coarsening option. If coarsening is enabled in regions with an existing coarse mesh, however, GPAD may instead refine them to enforce acceptable element-shape criteria and accurate projection of the nodes to the boundary of the model geometry.

For an NLAD-GPAD analysis with initial-mesh-based loading and constraints, Ansys recommends enabling load-stepping (KBC,1).

If the element size due to refinement during NLAD-GPAD analysis falls below the defeature size specified on the initial mesh in the Mechanical Application interface, topological errors or mapping issues may occur after that remeshing.