Specifying ALE adaptive mesh controls for an Abaqus/Explicit analysis

From the main menu bar, select OtherALE Adaptive Mesh ControlsCreate.

A Create ALE Adaptive Mesh Controls dialog box appears.

In the dialog box, type a name for the ALE adaptive mesh controls, and click Continue.

The Edit ALE Adaptive Mesh Controls dialog box appears.

Choose a mesh smoothing Priority:

• Choose Improve aspect ratio to perform adaptive meshing that minimizes element distortion and improves element aspect ratios at the expense of diffusing initial mesh gradation. This objective is recommended for problems with moderate to large overall deformation. For more information, see Specifying a uniform mesh smoothing objective.

• Choose Preserve initial mesh grading to perform adaptive meshing that attempts to preserve initial mesh gradation while reducing distortions as the analysis evolves. This objective is recommended only for adaptive mesh domains with reasonably structured graded meshes undergoing low to moderate overall deformation. For more information, see Specifying a graded mesh smoothing objective.

Click the arrow to the right of the Smoothing algorithm field, and select a method for calculating adaptive mesh smoothing:

• Select Determined by analysis product to accept the default for the analysis product you are using (in this case, Abaqus/Explicit).

• Select Enhanced algorithm based on evolving geometry to use geometrically enhanced forms of the basic smoothing algorithms as a technique to mitigate distortion.

• Select Conventional smoothing to use the conventional forms of the smoothing algorithms.

For more information on adaptive mesh smoothing, see Mesh smoothing methods.

Choose a Meshing predictor option:

• Choose Current deformed position to perform adaptive meshing based on current nodal positions. This method is recommended for all Langrangian-like problems and for problems with very large distortions. For more information, see Positioning nodes in Lagrangian domains.

• Choose Position from previous ALE adaptive mesh increment to perform adaptive meshing based on the positions of the nodes at the end of the previous adaptive mesh increment. This technique is recommended for Eulerian-like problems where material flow is significant compared to the overall deformation. For more information, see Positioning nodes in Eulerian domains.

In the Curvature refinement field, enter a value for the curvature refinement weight, ${\alpha }_C$. An appropriate value allows you to ensure that there is sufficient mesh refinement near highly curved boundaries. The default, ${\alpha }_C=1$, works well on a wide variety of problems. For more information, see Solution-dependent meshing based on concave boundary curvature.

Calculation of the new mesh in Abaqus/Explicit is based on some combination of three basic smoothing methods: volume smoothing, Laplacian smoothing, and equipotential smoothing. You must specify the weighting factor for each method in the Volumetric, Laplacian, and Equipotential fields. For more information, see Mesh smoothing methods.

In the Initial feature angle field, enter the initial geometric feature angle, ${\theta }_I$, in degrees ($0^{\circ }\le {\theta }_I\le {180}^{\circ }$). This angle is used to detect geometric edges and corners. The default value is ${\theta }_I={30}^{\circ }$. Setting ${\theta }_I={180}^{\circ }$ will ensure that no geometric edges or corners are detected or enforced.

In the Transition feature angle field, enter the transition geometric feature angle, ${\theta }_T$, in degrees ($0^{\circ }\le {\theta }_T\le {180}^{\circ }$). This angle is used to determine when geometric edges and corners should be deactivated to allow remeshing across them. The default value is ${\theta }_T={30}^{\circ }$. Setting ${\theta }_T=0^{\circ }$ will ensure that no geometric edges or corners are deactivated.

In the Mesh constraint angle field, enter the mesh constraint angle, ${\theta }_C$, in degrees ($5^{\circ }\le {\theta }_C\le {85}^{\circ }$). The default value is ${\theta }_C={60}^{\circ }$.

When adaptive mesh constraints are applied to nodes on Lagrangian or sliding boundary regions, the analysis will terminate if the angle between the normal to the boundary region and the direction of the prescribed constraint becomes less than ${\theta }_C$. When adaptive mesh constraints are applied to nodes that are part of a Lagrangian or active geometric edge, the analysis will terminate if the angle between the prescribed constraint and the plane perpendicular to the edge becomes less than ${\theta }_C$.

Choose an algorithm for remapping solution variables after adaptive meshing has been performed:

• Choose First order to use a first order method based on donor cell differencing.

• Choose Second order to use a second order method based on the work of Van Leer.

For more information, see Advection methods for element variables.

Choose a method for advecting momentum:

• Choose Element center projection for the least expensive method.

• Choose Half-index shift for a method that is more expensive computationally but which may demonstrate better dispersion properties.

For more information, see Momentum advection.

Click OK to save the named set of controls and to close the editor.