Rigid Patch

The Rigid Patch realization is a common modeling practice for the Explicit Analysis where the bolts are represented with a rigid mesh and Constrained Rigid Bodies are used to tie the various subsystems together.

Figure 1.


Table 1 shows the support in different profiles.
Table 1.
Profile Support
LS-DYNA Constrained Rigid Bodies, Mat20 on the Patches
OptiStruct Rigid Bodies, RBODY and RBADD
Radioss GROD of nodes and RBODY of the GRNOD set
Note: If you use Attachments with Rigid Element, this realization will generate a Merge_RBODY instead.

Connectivity

Existing Only
A minimum of one hole per layer must be available. If holes do not exist, the realization fails. This is the default method and must be used for any type of solid meshes.
Hole Mesh
Can be used to change the hole mesh.
None
Leaves the hole mesh as is. Default for most operations.
Fill
Fill detected holes during fastener realization. There are various quad patterns available, which cause a remeshing of the area around the hole.
Holes can also be filled with pie pieces. If the number of pie pieces is defined, the surrounding mesh is remeshed. The pie pieces preserve option also creates pie pieces, but takes the existing hole nodes into account and prevents the remeshing.
Density
Adjust the number of nodes around the hole.
Number of nodes
Specify the exact number of nodes (default is eight). The surrounding mesh gets remeshed.
Element Size
Specify an element size (default is 5.0). The number of elements around the hole is calculated based on this size. This is the preferred option for extremely different hole diameters. The surrounding mesh gets remeshed.
Auto
Perform a node distribution based on the underlying mesh size. The number of nodes is always rounded to an equal number.
Washer Layer
For 2D holes, one or two washer layers can be created, after which the surrounding mesh gets remeshed.
The width of the washer can be defined by factoring the hole radius and directly specifying the exact width.
Rebuild Washer
Perform a rebuild operation on the created washer in cases where the washer is close to a feature edge. This will potentially change the shape of the washer to snap to feature edges to avoid poor mesh quality.
Create Missing
If there are not any holes on a certain layer, they are punched into that layer at the position of the projection point. The diameter of the new hole is defined under the Realization Details heading. This method is used if the model does not contain the appropriate number of holes per fastener, but holes are required for specific realization types.
Hole Mesh
Can be used to change the hole mesh.
None
Leaves the hole mesh as is. Default for most operations.
Fill
Fill detected holes during fastener realization. There are various quad patterns available, which cause a remeshing of the area around the hole.
Holes can also be filled with pie pieces. If the number of pie pieces is defined, the surrounding mesh is remeshed. The pie pieces preserve option also creates pie pieces, but takes the existing hole nodes into account and prevents the remeshing.
Density
Adjust the number of nodes around the hole.
Number of nodes
Specify the exact number of nodes (default is eight). The surrounding mesh gets remeshed.
Element Size
Specify an element size (default is 5.0). The number of elements around the hole is calculated based on this size. This is the preferred option for extremely different hole diameters. The surrounding mesh gets remeshed.
Auto
Perform a node distribution based on the underlying mesh size. The number of nodes is always rounded to an equal number.
Hole Search
Not all the holes found in the given connector tolerance can be considered for the various fastener realizations.
The connector tolerance, especially when set to a large value, detects many holes. To prevent detecting holes which are far away from the connector position and are not aligned with the other hole(s), the consideration cylinder excludes outer holes from the detection.
Since the existence of a hole is not necessarily requested anymore, a space must be defined where the holes are expected to be. It is no longer sufficient to use just the connector tolerance, therefore the Hole Consideration Cylinder option performed along the projection path becomes necessary. All the holes the cylinder touches or contains can be considered for the various fastener realizations.
Tolerance Factor
Factors tolerance diameters to help filter the hole search.
Input
Used to specify an exact diameter. The default diameter is 15.0.
Set Hole Diameter
New
Create new holes with the specified diameter.
All
Create new holes with the specified diameter and adjust existing holes with the specified diameter.
Washer Layer
For 2D holes, one or two washer layers can be created, after which the surrounding mesh gets remeshed.
The width of the washer can be defined by factoring the hole radius and directly specifying the exact width.
Rebuild Washer
Perform a rebuild operation on the created washer in cases where the washer is close to a feature edge. This will potentially change the shape of the washer to snap to feature edges to avoid poor mesh quality.
Align Hole
Moves the center of a hole into the position of the projection point.
Unrealize Fill Hole Created
The created holes during the realization are filled when the connector is unrealized, returning the surface back to its original configuration before realization.
Use Available
Creates hybrids (hole on one side only), but other combinations are allowed. On the mesh side (no hole), the connection is realized via the head elements defined in the chosen realization type. The head element(s) is/are created between the appropriate body element node and the nodes inside the diameter (no hole connection diameter) defined under the Realization Details heading. This option is used for realization types which are not eager for holes.
Hole Mesh
Can be used to change the hole mesh.
None
Leaves the hole mesh as is. Default for most operations.
Fill
Fill detected holes during fastener realization. There are various quad patterns available, which cause a remeshing of the area around the hole.
Holes can also be filled with pie pieces. If the number of pie pieces is defined, the surrounding mesh is remeshed. The pie pieces preserve option also creates pie pieces, but takes the existing hole nodes into account and prevents the remeshing.
Density
Adjust the number of nodes around the hole.
Number of nodes
Specify the exact number of nodes (default is eight). The surrounding mesh gets remeshed.
Element Size
Specify an element size (default is 5.0). The number of elements around the hole is calculated based on this size. This is the preferred option for extremely different hole diameters. The surrounding mesh gets remeshed.
Auto
Perform a node distribution based on the underlying mesh size. The number of nodes is always rounded to an equal number.
Hole Search
Not all the holes found in the given connector tolerance can be considered for the various fastener realizations.
The connector tolerance, especially when set to a large value, detects many holes. To prevent detecting holes which are far away from the connector position and are not aligned with the other hole(s), the consideration cylinder excludes outer holes from the detection.
Since the existence of a hole is not necessarily requested anymore, a space must be defined where the holes are expected to be. It is no longer sufficient to use just the connector tolerance, therefore the Hole Consideration Cylinder option performed along the projection path becomes necessary. All the holes the cylinder touches or contains can be considered for the various fastener realizations.
Tolerance Factor
Factors given diameters, which include create hole diameter (2D), create/adjust hole diameter (2D), adjust hole diameter (2D), and no hole connection diameter. The first available diameter is used. The default factor is 1.5.
Input
Used to specify an exact diameter. The default diameter is 15.0.
Set Hole Diameter
All holes in the realization will be adjusted to the specified diameter.
Selection Diameter
Connect a link without an available hole by joining the nodes found inside the circle with the specified diameter around the projection point via head elements. Used if holes are not required when using the use hole if available option or fill and remesh hole if available option.
Align Hole
Moves the center of a hole into the position of the projection point.
Remove
Use this option when you do not want the shape of holes to interfere with the mesh flow in the fastener region. The detected holes are closed and a remesh of the new elements and a few additional rows of adjacent elements is performed. The connection is realized via the head elements defined in the chosen realization type. The head elements are created between the appropriate body element nodes and the nodes inside the diameter (no hole connection diameter) defined under the Realization Details heading.
Hole Search
Not all the holes found in the given connector tolerance can be considered for the various fastener realizations.
The connector tolerance, especially when set to a large value, detects many holes. To prevent detecting holes which are far away from the connector position and are not aligned with the other hole(s), the consideration cylinder excludes outer holes from the detection.
Since the existence of a hole is not necessarily requested anymore, a space must be defined where the holes are expected to be. It is no longer sufficient to use just the connector tolerance, therefore the Hole Consideration Cylinder option performed along the projection path becomes necessary. All the holes the cylinder touches or contains can be considered for the various fastener realizations.
Tolerance Factor
Factors tolerance diameters to help filter the hole search.
Input
Used to specify an exact diameter. The default diameter is 15.0.
Selection Diameter
Connect a link without an available hole by joining the nodes found inside the circle with the specified diameter around the projection point via head elements. Used if holes are not required when using the use hole if available option or fill and remesh hole if available option.