Working with model instances

You can create instances of other models in your main model, allowing you to add complete subassemblies in addition to individual parts. Model instances are created in the exact same way as part instances and can be positioned and manipulated in a similar fashion.

The following topics are discussed:

When you create a new model instance, the main assembly of the referenced model is instantiated in the assembly of the current working model. The instance produces a subassembly from the contents of the other model. Since the referenced model assembly may in turn contain other model instances as children, multiple levels of complex subassemblies are possible.

The external model to be instantiated must be included in the current model database (.cae) file to be available. If the model you want to instantiate is contained in a different model database, use FileImportModel to import it into the current model database. A model database file can always contain multiple models.

Characteristics of model instances

Model instances have the following characteristics:

  • A particular model can be instantiated multiple times, and you can instantiate as many different models as desired.

  • Model instances are always dependent, not independent.

  • You can freely mix model instances with part instances.

  • Model instance subassemblies can contain either geometric parts or orphan mesh parts.

  • Model instances can be positioned and oriented in the main assembly by using transformations (Translate, Translate To, Rotate) and positioning constraints. The transformations and constraints must be applied to a complete model instance subassembly, not to any of its children. If you select a child instance within a model instance, the transformation or constraint will be applied to the entire parent model instance.

  • Linear and radial patterns are not supported and cannot be used with model instances.

  • Part instance commands such as Suppress/Resume, Hide/Show, Delete, Show Parents/Children, and Switch Context can also be used on model instances.

    The Suppress and Delete commands cannot be used on the child instances of a model instance, only on the model instance itself. If you suppress a child instance (part or model) in the original (referenced) model assembly, it will be suppressed in the main model as well. To see that the suppressed instance is correctly suppressed in the main model, you must use the Model list in the context bar to switch from the original (referenced) model to the main model. Moving to the main model in the Model Tree will not regenerate the model instance children consistently. (For information about the context bar, see Components of the main window.) The child instance must then be resumed in the original model.

  • Replace, Exclude from Simulation, Merge/Cut, and Link Instances are not supported and cannot be used on model instances.

  • The Partition toolset is not supported and cannot be used with model instances.

  • The Query toolset is supported and can be used to determine the position and attributes of model instances.

  • All sets and surfaces defined in the referenced model are brought into the model instance, maintaining the Model Tree hierarchy of features. These sets and surfaces will be available in the main model.

  • Surface-to-surface contact and self-contact interactions defined in the initial step (along with their contact interaction properties) are the only history-level features defined in the referenced model that are brought into the model instance; other history-level features such as steps, loads, boundary conditions, other interactions, and amplitudes are not brought into the model instance. Some model-level features—fasteners and other engineering features—defined in the referenced model are not brought into the model instance.

  • Model instances are supported and selectable in Display Groups and in the Instance tab of the Assembly Display Options.

  • The Virtual Topology toolset is not supported for model instances.

Any part-level attributes that are needed in your subassembly (referenced) model must be created and assigned in that original model and cannot be created in the main model assembly. For example, materials, sections, orientations, and skin/stringer assignments must be created in the original model. Meshing can be performed on the original independent part instances, and the meshes will appear in the model instance.

When you create a model instance, all of the part instances of the referenced model assembly are added to the main model assembly as child part instances. Any suppressed part instances or instances that are excluded from the simulation will retain the same status in the subassembly.

If you modify or delete an existing part instance or model instance subassembly in the main model assembly, Abaqus/CAE automatically regenerates the child instances from all parent instances (parts and models) whenever you switch out of and back into the Assembly module of the main model.

If you try to create a new model instance from another model that in turn contains child model instances, any problems with model referencing circularity will be prevented by Abaqus/CAE. Abaqus/CAE will prevent you from creating this kind of problematic instance.

Abaqus/CAE ensures consistency of the modeling space for model instances—if all instances in the main model are three-dimensional, any other models to be instantiated must also be three-dimensional.

Model instance data saved in input files

When Abaqus/CAE generates the input (.inp) file for a model assembly that contains model instances, a single flattened assembly is generated. All model instance subassemblies are written as a flat list of instances under the single assembly block.

Most features from the original model of a model instance are saved in the input file, with some exceptions:

  • Surface-to-surface contact and self-contact interactions defined in the initial step are the only history-level features from a model instance subassembly that are saved in the input file. The contact interaction property name and surface names are prepended with the model instance name in the main assembly; for example: 

    model-instance-name#contact-property-name
model-instance-name#Surf-1, model-instance-name#Surf-2

  • Model-level features from a model instance are saved in the input file; for example, materials, section assignments, connector section assignments, skins, stringers, and orientations. Materials and element controls defined in a model instance are prepended with the model name in the main assembly; for example, 

    model-name#material-name

    Connector sections assignments are prepended with the model instance name in the main assembly; for example: 

    model-instance-name#Wire-3-Set-1

    Other model-level data such as initial conditions and amplitude definitions from a model instance are not saved in the input file.

  • Engineering features such as mass and inertia elements, springs, and dashpots defined at the part level in the model instance are saved to the input file, but engineering features defined at the assembly level in the original model are not.

  • Sets and surfaces from a model instance are saved in the input file. These set and surface names are also prepended with the model instance name in the main assembly; for example: 

    model-instance-name#Set-1

  • Constraints, reference points, attachment points, attachment lines, and wires from a model instance are saved in the input file.

  • For constraints the model instance name will be prepended to the constraint name; for example: 

    model-instance-name#constraint-name

  • Attachment points, attachment lines, and wires will be available through sets created in the subassembly.

The following limitations exist:

  • Generation of a flat input file is not supported for a model containing model instances.

  • Restart analysis is not supported for a model containing model instances.

  • Instances of models containing substructure instances are not supported.

  • Instances of models containing assembled fasteners are not supported.