Following are the supported analysis types, elements, materials, loads, boundary conditions, and other nonlinear mesh adaptivity requirements. Also see Other Requirements and Limitations.
| Support Category | Support Details | ||||||||||||||||||||||||||||
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Solid elements | |||||||||||||||||||||||||||||
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Contact elements |
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Contact pair behavior | |||||||||||||||||||||||||||||
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Surface-effect elements | |||||||||||||||||||||||||||||
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Materials | |||||||||||||||||||||||||||||
| Analysis types |
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Loads and boundary conditions (BCs)[s] |
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| Region to be remeshed[w] |
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[a]
method only.
[b] All stress states are supported: plane strain, plane stress, axisymmetric, and generalized plane strain. Pure displacement formulation or mixed u-P formulation is supported. Plane stress with tabular input of thickness is not supported.
[c] Remeshing methods supported: splitting, general remeshing, morphing.
[e] Remeshing methods supported: splitting, general remeshing.
[f] Supported stress states include plane strain, plane stress, and axisymmetric. Pure displacement formulation or mixed u-P formulation is supported. Plane stress with tabular input of thickness is not supported.
[h] Remeshing method support: general remeshing, morphing.
[i] NLADAPTIVE does not support elements with dropped mid-side nodes in element components.
[j] Remeshing method support: general remeshing.
[k] KEYOPT(1) = 11 only.
[l] General contact is not supported. For element removal analyses, KEYOPT(2) = 2, 3 and 4, KEYOPT(14), and the CNCHECK,DMP command are not supported.
[m] For flexible-flexible contact pairs, any large initial penetration approaching or exceeding a single-element depth may cause remeshing to fail. In such cases, Ansys, Inc. recommends assigning different material and/or element types to the contacting bodies.
[n] For contact elements with cohesive zone material (NLADAPTIVE,,CONTACT,CZM), only KEYOPT(12) = 5 or 6 are valid.
[o] Target elements and pilot node cannot be remeshed.
[q] Only normal and tangential pressures applied on SURF153 and SURF154 are supported. SURF153 is not supported for element removal analyses.
[r] For linear analyses with linear elastic materials
and small-deflection effects
(NLGEOM,OFF), the iterative
Newton Raphson solution procedure is set
automatically. The smallest possible number of
substeps must also be set (either directly via
NSUBST or indirectly via
DELTIM) to a value that ensures
remeshing. Guidance for setting the number of
substeps can be taken from the
NLADAPTIVE,,ON,VAL1
value specifying the remeshing frequency.
[s] Do not remove nodal constraints (DDELE, FDELE, BFDELE, SFDELE) during solution before remeshing. DDELE supports structural degrees of freedom only (UX, UY, UZ, ROTX, ROTY, and ROTZ) and TEMP in a nonlinear adaptivity analysis.
[t] For analyses with large deflection (NLGEOM,ON), a tabular load cannot be a function of position.
[w] Initial state, element birth and death, and cyclic symmetry analysis are not supported.
[x] For initially coarse meshes on curved surfaces, the Euler rotation angles of the nodes may be improperly interpolated onto the newly meshed region of the same curved surfaces. If applied nodal boundary conditions (such as displacement) exist on those nodes, they are mapped incorrectly, as the boundary conditions are specified on the local nodal coordinate system (defined by the Euler angles). Curved surfaces should therefore have a reasonably fine mesh. Adjacent nodes on a boundary cannot have different nodal coordinate systems, if this boundary is selected for remeshing.
Nonlinear adaptivity criteria are applied on element components.
Those components must be defined and selected before issuing the first SOLVE.
Nonlinear mesh adaptivity does not require restart files (except for distributed-memory parallel (DMP) solutions).
Issuing RESCONTROL,,NONE, however, is neither necessary nor allowed.
Restarting from a given substep in a nonlinear mesh adaptivity analysis require the .rd
nnand .rnnnfiles (in addition to other restart files).For information about how to write these files, see RESCONTROL.
Nonlinear adaptivity cannot be applied on supported lower- and higher-order elements simultaneously in the same model.
For example, in a 3D model, it cannot be applied to one component with SOLID285 elements and another component with SOLID187 elements.
During the nonlinear adaptive solution procedure, only components defined with nonlinear adaptive criteria are preserved.
The elements in the region are not remeshed if:
the elements in the same region have more than one component name, and
a nonlinear adaptive criterion associated with one of the component names is disabled.
Unless you have specified the refinement algorithm with mesh splitting (NLMESH,REFA,SPLIT), this behavior applies even if the nonlinear adaptive criteria associated with the other component is enabled.
The coordinate-truncation defaults for nodal locations of meshes during remeshing (NLMESH,TCOR) work well in most cases and should be modified with caution.
If coordinate truncation is disabled (NLMESH,TCOR,OFF), solution repeatability is affected due to the finite-precision arithmetic used by Mechanical APDL.
In cases where coordinate truncation is enabled (NLMESH,TCOR,ON) but the target, contact, or surface elements are not generating properly, or the loads and boundary conditions are not being mapped properly, try disabling coordinate truncation to improve the solution.
The character string "_NLAD" is invalid.
When using general remeshing for refinement or for removing distortion, the character string "_NLAD" cannot appear in component names, in the job name, or in the main title of input defined via /TITLE.
External constraint equations and coupling constraint equations (CE and CP) are supported to a limited extent.
The nodes participating in these external constraints are maintained throughout the analysis. Only CE/CP nodes on the edges are maintained. Nodes internal to the domain and nodes on the surface of the domain, excluding nodes on edges in 3D, are not maintained since these nodes may be remeshed. Any new nodes introduced between these maintained nodes (in 2D) or near these nodes (in 3D) will not be incorporated into the external constraint equations defined by CE or CP.
If external CE and CP constraint equations are used in a region of the mesh, it is best not to remesh that region to ensure that the external constraint equations behave consistently throughout the analysis.
If both PLANE182 and PLANE222 elements exist in each element component assigned for remeshing, those elements cannot have shared nodes. PLANE182/PLANE222 elements can exist together in such components only if they are bonded together via the contact capability.
A similar limitation applies to the SOLID187/SOLID227 element combination.
Nonlinear adaptivity is available for contact elements (CONTA
nnn). Interface elements (INTERnnn) are not supported.In mode II / mode III debonding, solid elements are not selected for coarsening if they are located under target elements no longer scoped to contact elements. See the example in Figure 2.25: Restriction for CZM-Based Coarsening Under Target Elements for Mode II Debonding.
Coarsening with element-type-change nonlinear adaptivity is not supported.
Coarsening with splitting remeshing is not supported.
Splitting remeshing is not supported for element removal analyses.
DDELE is supported in a nonlinear mesh adaptivity analysis for the following degrees of freedom: UX, UY, UZ, ROTX, ROTY, ROTZ, and TEMP.
When issuing DDELE to remove the degree-of-freedom constraints (defined via D), ensure that you have selected appropriate nodes in the region where you intend to removed the constraints.
During remeshing, the program maps degree-of-freedom constraints on nodes in the region to the new mesh. Therefore, if you issue DDELE to delete the constraints after remeshing occurs, the original nodes on which the constraint was applied cannot be used with the current DDELE command.
When you issue DDELE before remeshing occurs, the program calculates and applies the resulting reaction forces on the existing and newly created nodes in the specified region by default. (You can change the default behavior via the
IRSTRTFLAGargument so that the program ignores the reaction forces.)If displacements have been applied along a discretely connected line (or curve) and you issue DDELE to delete them, the program does not map reaction forces to the new nodes along that line (or curve) within the remeshed region.
SFCONTROL is supported in a nonlinear adaptivity analysis with the following limitation: The command does not support options
KTAPER= 2,KAREA= 1, orKFOLLOW= 1 with large-deformation effects (NLGEOM,ON).Issue /CLEAR,NOSTART before performing a restart of a previous nonlinear mesh adaptivity analysis via ANTYPE,,RESTART,,,CONTINUE or ANTYPE,,RESTART,,,ENDSTEP.
