17.11.1 Meshing multiple three-dimensional solid regions

ABAQUS/CAE assigns a default meshing technique to each region depending on its geometry and topology. However, sometimes the default meshing techniques applied to adjacent regions of a three-dimensional part or part instance are not compatible, and ABAQUS/CAE cannot generate a compatible mesh.

For example, ABAQUS/CAE cannot generate a compatible mesh over the entire part instance in Figure 17–73 using the default meshing techniques because the nodes from the structured mesh on the left cannot be merged with the nodes of the swept mesh on the right. (The cube on the right side of the part instance is a swept region because it is joined to the cylinder, which is also a swept region.)

Figure 17–73 A compatible mesh is impossible using these default meshing techniques.

The mismatch that would occur between the nodes of the structured region and the nodes of the swept region is obvious if you mesh the two regions separately, as shown in Figure 17–74.

Figure 17–74 The structured region and the swept region meshed separately.

If you initiate the meshing procedure and ABAQUS/CAE cannot generate a compatible mesh using the default meshing techniques, ABAQUS/CAE attempts to replace the default meshing techniques with new meshing techniques. These new techniques are determined not only by the region's geometry and topology but also by the characteristics of neighboring regions in the part or part instance. ABAQUS/CAE evaluates the interfaces between regions and tries to minimize the number of incompatible interfaces.

For example, the default meshing technique for the cube on the left side of the part instance in Figure 17–73 is structured, and the resulting incompatible mesh is shown in Figure 17–74. However, this cube can also be meshed using the swept meshing technique. Therefore, ABAQUS/CAE changes the meshing technique assigned to this region from structured to swept, and a compatible mesh is generated over the whole part instance. (The element shapes assigned to a region remain unchanged when ABAQUS/CAE changes the meshing technique assigned to the region.)

When you initiate the meshing procedure for a three-dimensional part or part instance, ABAQUS/CAE determines if a compatible mesh can be generated using the default techniques assigned to each region. If a compatible mesh is possible, meshing proceeds. If a compatible mesh cannot be generated using the default techniques, ABAQUS/CAE checks to see if it can replace the default meshing techniques with different techniques that will allow a compatible mesh to be generated.

If a compatible mesh cannot be generated, you can try one of the following approaches:

In general, the following restrictions apply to generating a compatible mesh on a three-dimensional solid part or part instance:

Different regions of the same part or part instance can be meshed with hexahedral and tetrahedral elements as shown in Figure 17–78.

Figure 17–78 Different regions of the same part or part instance can be meshed with hexahedral and tetrahedral elements.

You can use the hexahedral elements where accuracy is important, such as adjacent to contact surfaces or in areas of special interest that require a fine mesh. You can use tetrahedral elements in other regions, and ABAQUS/CAE creates tied surfaces where the regions connect. When you mesh one region, ABAQUS/CAE does not adjust an existing mesh on adjacent regions.