Modeling abstractions (Abaqus)

You can generate matrices and define a substructure using two steps available in Structural analyses in the Abaqus environment:

• Use the Matrix Generation step to generate a matrix representing the stiffness, mass, viscous damping, structural damping, or load vectors in a model. The software stores the matrices in a .sim file, which you can output to various matrix files and formats. The Matrix Generation step corresponds to the Abaqus *MATRIX keyword. For more information, see Generating matrices in the Abaqus Analysis User’s Guide.

• Use the Substructure Generation step to generate substructures, collections of elements from which the internal degrees of freedom have been eliminated. You can also use the substructure to define a flexible body.The Substructure Generation step corresponds to the Abaqus *SUBSTRUCTURE keyword. For more information, see Substructuring in the Abaqus Analysis User’s Guide.

Supported elements and properties

All elements supported for Structural analyses are supported for the Matrix Generation and Substructure Generation steps.

For more information, see Abaqus elements.

Supported loads and constraints

All loads and constraints supported for Structural analyses are supported for the Matrix Generation and Substructure Generation steps.

For more information, see Abaqus boundary conditions.

Specifying options for the Matrix Generation step

When you define a Matrix Generation step, use the tabs on the Solution Step dialog box to specify the following:

• Matrix generation procedure optionsUse the options on the General tab to control the matrix generation procedure, including the types of matrices to generate. You can specify to generate global matrices for a model in assembled form or generate global matrices in element-by-element form. You can also select to generate matrices for only the structural portion of the model, and other options such as friction. Note: Acoustic elements are not supported in the Abaqus environment. If you select to generate matrices for the acoustic field only and the FE model does not contain any acoustic elements, the solver issues an error message.The options correspond to the Abaqus ELEMENT BY ELEMENT, SOURCE, and FIELD parameters of the *MATRIX GENNERATE keyword.

• Matrix generation checkUse the options on the Other Step Options tab to check the quality of the generated global stiffness and mass matrices. The solver saves the check results in the data (.dat) file. You can specify the origin of the coordinate frame. The options correspond to the Abaqus *MATRIX CHECK keyword.

• Output optionsUse the options on the Output tab to select what you want types of matrices you want to output and to what types of files. The options correspond to the Abaqus *MATRIX OUTPUT keyword.

Specifying options for the Substructure Generation step

When you define a Substructure Generation step, use the tabs on the Solution Step dialog box to specify the following:

• Substructure generation procedure optionsUse the options on the General tab to control the generation of the substructure, including specifying a unique identifier for the substructure and specifying the matrices to be generated. You can also specify the degree of freedoms to be recovered, the frequency at which frequency-dependent material properties are evaluated, whether to evaluate friction, and that gravity load vectors be calculated. The options correspond to the Abaqus TYPE, MODEL DATA, MASS MATRIX, VISCOUS DAMPING MATRIX, STRUCTURAL DAMPING MATRIX, RECOVERY MATRIX, FRICTION DAMPING, PROPERTY EVALUATION, and GRAVITY LOAD parameters of the *SUBSTRUCTURE GENERATE keyword.

• Eigenmodes, matrix generation check, and flexible body generationUse the options on the Other Step Options tab to:Specify the eigenmodes to be used in the substructure generation, The options correspond to the Abaqus *SELECT EIGENMODES keyword. Check the quality of the generated global stiffness and mass matrices. The solver saves the checked results in the data (.dat) file. You can specify the origin of the coordinate frame.The options correspond to the Abaqus REFERENCE NODE parameter of the *MATRIX CHECK keyword. Generate a flexible body from the substructure in several flexible body types. The options correspond to the Abaqus *FLEXIBLE BODY keyword.

• Output optionsUse the options on the Output tab to select what you want types of matrices and vectors you want to output. The options correspond to the Abaqus *SUBSTRUCTURE MATRIX OUTPUT keyword.

Where do I find it?

Application	Pre/Post
Prerequisites	A Simulation file as the work part and displayed partAbaqus as the specified solverStructural as the specified analysisSubstructure Generation or Matrix Generation as the specified step
Simulation Navigator	Right-click a Simulation file→New Solution

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