The concept of partitioning in Abaqus/CAE refers to dividing geometry (parts/instances) into subregions. It has many applications, but the most important one is preparing geometry for hexahedral mesh generation. Most available techniques for generating this type of mesh require the part to be divided into simpler shapes. In Abaqus/CAE, this is immediately visible thanks to the default color coding in the Mesh module - orange indicates areas unsuitable for hex meshing, while green and yellow indicate regions meshable using the structured and sweep techniques, respectively.
Other common applications of partitioning include:
Partitions can be created at three levels: edges, faces, and volumes. Tools for creating them can be found on the vertical toolbar or under Tools → Partition. Like other geometry-based features, partitions can always be suppressed or deleted from the model tree.
Edge partitioning divides an edge into two segments by introducing an additional vertex between them (which itself can be useful for further operations). The following techniques are available:
1. Specify parameter by location – splits the edge directly at the location selected with the cursor. Useful for quick, less precise partitions when the exact vertex location is not important.
2. Enter parameter – splits the edge at the location defined by a specified parameter value - a fraction of the edge's normalized length - value between 0 and 1 (an arrow shows the direction of increase from 0 to 1). For example, 0.5 splits the edge in the middle, while 0.25 creates a partition at one-quarter of the length from the arrow's start.
3. Select midpoint/datum point – splits the edge at its midpoint or at a datum point lying on the edge.
4. Use datum plane – splits the edge at the point of intersection with a previously created datum plane.
Face partitioning divides a face into smaller regions by creating additional edges. In addition to being used for shell geometries, it's often useful for defining areas for boundary conditions, loads, or other analysis features, or as a base for volume partitioning. The following techniques are available:
1. Sketch – direct sketching of the partition pattern on the face (or on another face/datum plane and then projecting it - necessary for faces that are curved or not lying in the same plane). This method enables the creation of even very complex, arbitrarily shaped partitions. It's especially useful for defining regions for analysis features and is the most commonly used method for face partitioning.
2. Use shortest path between 2 points – splits the face along the shortest path between two selected points lying on that face. If the face is curved, the resulting edge will also be curved. This method is useful and can serve as a base for volume partitioning.
3. Use datum plane – splits the face at the location where it intersects with the selected datum plane.
4. Use curved path normal to 2 edges – splits the face along a Bézier curve normal to two edges of the face. The curve can be positioned by selecting two points anywhere between the two edges. The angle between the edges must be less than 180 degrees. This method is rarely used in practice.
5. Extend another face – splits the face at its intersection with an extension of another face.
6. Intersect by other faces – splits the face at its intersection with one or more other faces (they may intersect it or be tangent to it). This method is rarely used in practice.
7. Project edges – splits the face by projecting edges perpendicularly from the face to be partitioned. Optionally, the edge(s) can be extended to complete the face partition. This method is also not commonly used in practice.
In the Mesh module, there is an additional option called Auto-partition. When generating a mesh using quadrilateral elements with the free meshing technique, Abaqus internally partitions the face into regions with 3-5 edges. The Auto-partition option allows users to preview and optionally modify this partitioning.
Partitioning at the volume level (referred to as a cell in Abaqus terminology) divides the volume into smaller sections by creating additional faces. This is most often used to enable hexahedral meshing, but it can also be useful for dividing a solid part into regions with different materials assigned. The following techniques are available:
1. Define cutting plane – splits the volume using a datum plane defined when creating the partition. There are three ways to define the plane
This is a very commonly used technique (especially the Point & Normal option) and can often eliminate the need to create a separate datum plane beforehand, as required by the next method.
2. Use datum plane – splits the volume at its intersection with a previously created datum plane. Although datum planes have a finite visual representation, they are treated as infinite during such operations. Available methods for creating datum planes include offset from the global coordinate system, offset from any plane or face, three points, line and a point away from it, point and edge defining the normal direction, midway between two points, and rotation about another plane or face. This technique is frequently used in practice.
3. Extend face – splits the volume using the extension of a selected face, which is treated as an infinite plane. This is one of the most commonly used methods.
4. Extrude/Sweep edges – splits the volume by extruding (with infinite length) the indicated edges (profile) in the direction defined by the selected edge or by sweeping the edge (profile) along a selected path (straight or curved). This method is often used in practice.
5. Use n-sided patch – splits the volume using a closed contour composed of a loop of connected edges (they can be straight or curved, but they must be connected and fully pass through the part being partitioned). There are two methods for defining the contour:
This method is somewhat less commonly used in practice but can still be helpful in certain cases, especially with the Select Edges → loop option.
6. Sketch planar partition – splits the volume by intersecting it with a sketch. This is usually a sketch on a datum plane that cuts through the part, although an existing face can also be used. This method can be useful for creating crack surfaces in fracture mechanics analyses, but aside from that, it is rarely used in practice.
Partitioning in Abaqus is a crucial step in model preparation for meshing, following geometry simplification and repair. In the case of hexahedral meshes, which are often the desired outcome, multiple partitions might be necessary. These partitions must be defined in a way that creates simple regions suitable for meshing with sweep or structured techniques. Selecting the appropriate method to divide a part into such regions is often the most challenging aspect, but a good understanding of the available partitioning tools can significantly help.
It is also worth noting that the 3DEXPERIENCE platform includes an automated tool for volume partitioning.