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Simulations

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    One or more simulations are maintained within the part or assembly document. Each document can have any number of simulations. The simulation result files, which can be large, are maintained separately and linked to the document unless you specify otherwise.

    A simulation contains:

    • Simulation Type
    • Parameters
    • Materials
    • Loads
    • Constraints
    • Contacts
    • Mesh

    for the purpose of:

    • Evaluating the structural loading conditions and frequency.
    • Comparing the results of using different materials and parameters.
    • Analyzing behavior of different geometric configurations.
    • Importing motion loads from Dynamic Simulation.
    NoteInventor creates a set of nested folders and nodes for each simulation.

    To examine the performance of a model, replicate the environment the model can experience. Start by building an assembly model containing all pertinent components. Then create simulations for each operating condition to examine.

    In setting up a simulation, consider specific questions, such as:

    • What is the design objective for this simulation?
    • What materials to use?
    • Which parts of the geometry can I change?
    • What are the underlying physical forces?
    • How is model movement constrained?

    As you refine a design, analyze the results of the simulation to determine the relationships between the criteria. Then proceed to the next step or iteration of the design.

    Simulation Types

    • Static Analysis evaluates structural loading conditions.
    • Modal Analysis evaluates natural frequency modes, including rigid body movements.

     

    Procedures

    Create a simulation

    The first time you enter the Stress Analysis Environment with a model, only a few commands are available, these are for creating a simulation and specifying global settings.

    Create a simulation:

    1. On the ribbon, click Stress Analysis tabManage panelCreate Simulation.
    2. The Simulation Properties dialog box displays. Specify:
      • Simulation name
      • Design Objective
      • Simulation type and options, according to the type selection
        NoteIn this step you also specify whether motion loads from a dynamic simulation are used.
      • Contact tolerance and Default type
      • Model representations to use (Design View, Positional Representation, and Level of Detail)
      • iAssembly or iPart member name, if applicable
    3. Click OK

    Activate a simulation

    To activate an inactive simulation, double-click the inactive simulation node in the browser. The action:

    • Selects and activates the simulation.
    • Collapses non-active simulation nodes.
    • Expands the active simulation nodes providing access to the design criteria for the simulation.

    The active simulation has a white background in the browser. Inactive simulations have a gray background. You can immediately identify which simulation you are working with and editing.

    Browser update notices

     
    When switching between simulations, the data can become stale. You see a browser node decoration, lightning bolt, indicating the need to update those items before you view the results. To update the data, right click the node and click Update.

     

    Copy a simulation

    To produce variations of a simulation, use the Copy Simulation command on the context menu of a simulation.

    1. Right-click the simulation you want to copy and select Copy Simulation.
    2. A copy of the simulation is created and numbered consecutively. The copy is now the active simulation. You can edit it to produce the variation.

    Limitation of Copy Simulation

    • Associativity between the copied object and the pasted object is not maintained.

     

    Copy objects

    To copy simulation objects, constraints, loads, manual contacts, and material overrides, do the following:

    1. Right-click the browser node of the object and select Copy. Multi-select of the same object type is supported.
    2. In the browser, right-click the simulation you want as the target for the paste action, and select Paste. Or, use the Paste command from the Edit menu.

    Within the Copy command, the following applies:

    Supported

    • Only objects that are deemed healthy have the copy command enabled.
    • Pasted object uses the original object name with the instance number generated incrementally by 1.
    • You are notified of any missing references.

    Limitations of Copy (simulation object)

    • Does not maintain associativity between the copied object and the pasted object.
    • Does not paste:
      • Simulation settings into the simulation.
      • Mesh settings into the simulation.
      • Convergence settings into the simulation.
      • Exclude states into the simulation.

     

    References

    Create New Simulation

    Access:

    Ribbon: Stress Analysis tab Manage panel Create Simulation

    Displays the Simulation Properties dialog box where you define the type of simulation you want to run. Once you click OK to create the simulation, the following occurs:

    • The browser populates with a simulation node.
    • Nested within the Simulation node are subnodes for the component (part or assembly), material overrides, constraints, loads, contacts, meshes, and results.
    • The available commands on the Stress Analysis ribbon enable.

     

    Create New Simulation and Edit Simulation Properties - Simulation Type tab

    Simulation properties are unique for each simulation. The properties are populated with values from the Stress Analysis Settings and representation information from the assembly. Then, based on the simulation needs, you specify the properties. The dialog box contains general controls and tabs for specific controls.

    Simulation Type properties provide you the option to select either Static or Modal analysis and properties associated to those types. If the simulation requires something other than the default, modify the settings as needed.

    Access:

    Presented as the Create New Simulation dialog box when Create Simulation command is used.

    Presented as the Edit Simulation Properties dialog box when you right-click the Simulation browser node and click Edit Simulation Properties. The Simulation Properties dialog box displays the Simulation Type tab by default.

    The following controls are common to the dialog box, regardless of the selected tab:

    Name

    A user assigned name that defaults to Simulation, followed by a colon and a numeric indicator indexed from 1 to ‘n’. Each new simulation is named with the next higher value. The name is used for all user-visible references to the simulation.
    Design Objective

    Specifies the objective of the simulation. Select from either of the following:

      Single PointUse when you want to evaluate one set of geometry. New simulations default to this type.
      Parametric Dimension

    Use when you want to optimize or change feature geometry through the use of design parameters. The simulation reports results for the various parameter values you specify.

    Reset

    Replaces the current settings with those found in the Stress Analysis Settings.

    NoteThe new settings may not reflect the values that were set when the simulation was newly created. You can Cancel the dialog box without clicking OK or use Undo to reverse the action after using OK.

    Does not affect the following:

    • Design Objective
    • Simulation Type
    • Contact Settings
    OKAccepts the setting modifications and applies them to the selected simulation.
    CancelCancel the current dialog box session. Modifications made during the session that have not been applied are discarded.
    ApplySets or revises the simulation settings based on current dialog box values.

    Simulation Type tab

    There are two simulation types available: Static and Modal.

    Static Analysis

    Evaluate the model without motion to determine stresses and displacement.

      Detect and Eliminate Rigid Body ModesRemoves the rigid body modes in problems where not enough constraints are defined, but they have a balanced load with a valid elasticity solution.
      Separate Stress Across Contact SurfacesSelect to have explicit representation of discontinuous stress across the contact interface in the FEA formulation. Some components of the stresses can be discontinuous due to different materials of the contacting parts.
      Motion Load Analysis

    Select to transfer motion loads of a single part from Dynamic Simulation. This selection enables Part and Time Step controls.

    • Part: lists available parts whose motion loads were exported
    • Time Step: lists available time steps associated with the part selection.

    All other bodies are excluded and the associated Dynamic Simulation loads are imported.

    Modal Analysis

    Determine the natural frequencies of vibration for the model.

      Number of Modes

    Enter the number of resonant frequencies to find, for Structural Frequency.

    Frequencies corresponding to rigid body movements are included. For example, in a free vibration analysis the first six modes occur at 0Hz, corresponding to the six rigid body movements.

      Frequency Range

    Enter the range of frequency for the desired modal frequencies, when using this option. We recommend that you indicate both the range and the number of modes within the range. If the number of modes is not known, Stress Analysis calculates up to 100 modes within the range.

      Compute Preloaded Modes

    Select to compute stress on a model and then compute modes for the prestressed condition.

      Enhanced Accuracy

    This option increases the accuracy of the calculated frequency values by an order of magnitude (10).

    Contacts

     
      Tolerance

    Specify the maximum distance between faces or edges to consider in automatic detection. Faces or edges falling outside the distance are eliminated from participating in automatic contacts.

    You can enter the value in a different linear unit than the default document value.

      Default TypeFrom the list of contact types, select the type to generate automatically when the simulation builds contacts. You can edit individual contacts and change the type later.
      Normal StiffnessSpecifies the equivalent normal stiffness value. Applicable to Spring contact only.
      Tangential StiffnessSpecifies the equivalent tangential stiffness value. Applicable to Spring contact only.
    NoteNormal and tangential directionality is based on the best approximation between the two faces that follow each other in a parallel way. Examples are parallel planes, concentric cylinders, and so on. Otherwise it can be ambiguous.

    Simulation Properties - Model State tab

    On the Model State tab, specify the assembly representations you want to use in relation to the simulation. Additionally, if the component is part of an iAssembly factory you can specify which member is presented in the simulation.

    Access:

    Presented as the Create New Simulation dialog box when the Create Simulation command is used.

    Presented as the Edit Simulation Properties dialog box when you right-click the Simulation browser node and click Edit Simulation Properties.

    The following controls are common to the dialog box, regardless of the selected tab:

    Name

    A user assigned name that defaults to Simulation, followed by a colon and a numeric indicator indexed from 1 to ‘n’. Each new simulation is named with the next higher value. The name is used for all user-visible references to the simulation.
    Design Objective

    Specifies the objective of the simulation.

      Single PointUse when you want to evaluate one set of geometry, materials, constraints, and loads. New simulations default to this type.
      Parametric Dimension

    Use when you want to optimize or change feature geometry through the use of design parameters. The simulation reports results for the various parameter values.

    Model State tab

    Representations

    Each assembly simulation maintains an association to each representation type. As you activate different simulations, the corresponding representation is activated for that simulation. You can change the representation association at any time. If you do so after a simulation has been run, the results can be out of sync. If so, rerun the simulation.

    You cannot associate a representation with a Part document.
      Design View

    Specifies the design view representation to use in conjunction with the simulation.

    Not available for Parts.

      Positional

    Specifies the positional representation to use in conjunction with the simulation. Use positional representations to place components into a specific position or relationship with other components.

    Not available for Parts.

      Level of Detail

    Specifies the level of detail representation to use in conjunction with the simulation. This selection can help simplify the model thereby reducing simulation and meshing time.

    Not available for Parts.

    iAssembly/iPart Member

    iAssemblies

    Specifies the iAssembly member to be associated with the simulation. If the component is a factory member, the member selection is disabled. Available only when the assembly is an iAssembly factory.

    iParts

    If the part document is an iPart factory, you can associate a specific iPart member with the simulation.