OS-SL-T: 1030 Preloaded Modal Frequency Response Analysis

This tutorial demonstrates how to solve a modal frequency response analysis for a Differential housing model by including the effect of pretension of bolts as preload.

Before you begin, copy the file(s) used in this tutorial to your working directory.
The following exercises are included:
  • Set up the problem in SimLab
  • Apply Loads and Boundary Conditions
  • Solve the job
  • View the results
  • Plot graph

Launch SimLab

Launch SimLab.

Import the Model

  1. From the menu bar, click File > Import > Database.
    An Import File dialog opens.
  2. Select the Differential_Housing.gda file you saved to your working directory from the Differential_Housing.zip file.
  3. Click Open.
    The Differential_Housing.gda file is loaded into the current SimLab database.

Set Up Problem

Create Solid Bolds for Assembly

  1. From the menu bar, click Advanced > Bolt Modeling.
    The Bolt Modeling Ribbon opens.
  2. From the Bolt Modelling Ribbon, 3D Bolt group, click the Create Bolt tool.
    The Create Solid Bolt dialog opens.
  3. In the Create Solid Bolt dialog, enter the values as shown below.


    Figure 1. Bolt Parameters
  4. For Washer face Input, select the disc faces of the Cover body in the modeling window.


    Figure 2. Select Disc Faces of Cover Body for Washer Face
  5. For Thread face Input, select the cylindrical faces of the carrier body in the modeling window.


    Figure 3. Select Cylindrical Faces of Carrier Body for Thread Face
  6. For D2 based on D3, set the Shrinkage value to 0 and click OK.
    Ten solid bolts are created.
  7. In the Assembly tab of the Model Browser, select the 10 solid bolts, right-click in the modeling window, and select Merge from the context menu.
    In the Assembly tab of the Model Browser, the bolts are merged into a single bolt.
  8. Merge the assemblies.
    1. In the Assembly tab of the Model Browser, select the Merged_Model.gda and Differential_Housing.gda assemblies.
    2. From Geometry ribbon, click the triangle next to the Model group label and select Merge Models from the context menu.
    All bodies are merged under one assembly.

Create Solution

  1. From the Solutions ribbon, Physics group, click the Structural tool.
    The Create Solution dialog opens.
  2. In the Create Solution dialog, define the following options:
    1. For Name, enter MFreq_with_Pretension.
    2. For Solver, select OptiStruct.
    3. For Solution type, select Static, Dynamic and Heat Transfer Analysis.
    4. For Select bodies, select all the bodies from the Assembly tab of the Model Browser and click OK.


      Figure 4. Create Solution

Assign Property to Bodies

In this step you will assign the Cast Iron property for both the Carrier and Cover bodies and Steel property for the Bolts.

SimLab has default materials defined, so there is no need to define materials.

  1. From the Analysis ribbon, Property group, click the Property tool.
    The Analysis Property dialog opens.
  2. In the modeling window, select the Carrier body.
  3. In the Analysis Property dialog, enter the values as shown below and click Apply.


    Figure 5. Carrier Body Property
  4. Create a property for the Cover body.
    1. In the modeling window, select the Cover body.
    2. In the Analysis Property dialog, enter the values as shown below and click Apply.


    Figure 6. Cover Body Property
  5. Create a property for the Bolts.
    1. In the modeling window, select the Bolts.
    2. In the Analysis Property dialog, enter the values as shown below and click OK.


    Figure 7. Bolts Property
The created properties are displayed in the Property tab of the Model Browser.

Apply Loads and Boundary Conditions

The first loadcase is the non-linear static analysis where pretension is applied on the bolts and constraints are defined on the end of the carrier body. The second loadcase is the modal frequency response analysis in which a pressure load is applied on the inner face of the cover body and excitation load is created using the pressure load. The pretension effect of the bolts in the first loadcase is included in the second loadcase. Contacts are created between each part of the model.

Create Loadcase

  1. In the Solutions tab of the Model Browser, right-click on MFreq_with_Pretension and select Define using Load case from the context menu.
    LoadCase1 is created.
  2. Right-click on LoadCase1, select Rename from the context menu, and enter Pretension_Case.
  3. Under the Pretension_Case loadcase, right-click on Type: Linear Static and select Analysis type > Non Linear Static from the context menu.

Create Pretension Load

  1. From the menu bar, click Advanced > Bolt Modeling.
    The Bolt Modeling Ribbon opens.
  2. From the Bolt Modeling Ribbon, 3D Bolt group, click the Solid Pretension tool.
    The Create Solid Pretension dialog opens.
  3. In the Create Solid Pretension dialog, enter the values as shown below.


    Figure 8. Create Solid Pretension for Bolts
  4. In the modeling window, select the bolts body and click OK in the Create Solid Pretension dialog.
The pretension faces of the selected bolts are identified and a force of 15000N is applied.

Create Constraints

  1. From the Analysis ribbon, Loads and Constraints group, click the Constraints tool.
  2. From the secondary tool set, select the Fixed tool.
    The Fixed Constraint dialog opens.
  3. In the Fixed Constraint dialog, enter the values as shown below.


    Figure 9. Fixed Constraint
  4. In the modeling window, select the cylindrical faces of the Carrier body and click OK in the Fixed Constraint dialog.


    Figure 10. Select Fixed Constraint Faces

Define Loadcase Parameters

  1. In the Solutions tab of the Model Browser, right-click the Pretension_Case loadcase and select Loadcase Parameters from the context menu.
    The Loadcase Parameters dialog opens.
  2. In the Loadcase Parameters dialog, enter the values as shown below and click OK.


    Figure 11. Loadcase Parameters Non Linear Analysis

Define Frequency Response Analysis Loadcase

  1. From the Solutions tab of the Model Browser, right-click LoadCase and select Create Loadcase from the context menu.
    LoadCase2 is created with linear static analysis.
  2. Right-click on LoadCase2, select Rename from the context menu, and enter Preloaded_MFreq.
  3. Under the Preloaded_MFreq loadcase, right-click Type: Linear Static and select Analysis Type > Modal Frequency Response from the context menu.

Create Face Group for Pressure Load

Multiple faces must be selected to create a pressure load on the inner face of the cover body.

  1. In the modeling window, select the face in the cover body.


    Figure 12. Select Face
  2. Right-click in the modeling window and select Select Adjacent Layers from the context menu.
    The Select Adjacent Layers dialog opens.
  3. In the Select Adjacent Layers dialog, enable the Create group checkbox and enter the name as Pressure Faces.


    Figure 13. Create Group of Faces
  4. In the modeling window, select the limit faces and click Apply in the Select Adjacent Layers dialog.


    Figure 14. Select Limit Faces
The Pressure Faces group is created in the Groups tab of the Model Browser.

Create Pressure Load

  1. From the Analysis ribbon, Loads and Constraints group, click the Loads tool.
  2. From the secondary tool set, select the Pressure tool.
    The Pressure dialog opens.
  3. In the Pressure dialog, enter the values as shown below.


    Figure 15. Pressure Load Input
  4. In the Group tab of the Model Browser, select the Pressure_Faces group and click OK in the Pressure dialog.
The pressure load is applied to the entities of the group.

Create Excitation Load

  1. From the Analysis ribbon, Loads and Constraints group, click the Loads tool.
  2. From the secondary tool set, select the Excitation tool.
    The Excitation Load dialog opens.
  3. In the Excitation Load dialog, click Create next to Amplitude table.
    The Create Table dialog opens.
  4. In the Create Table dialog, select Frequency-Amplitude as the Loading Typer, enter the values as shown below, and click OK.


    Figure 16. Define Amplitude Table for Excitation Load
  5. In the Excitation Load dialog, enter the values as shown below and click OK.
    The Pressure_Load defined will automatically be set as the Excitation load.


    Figure 17. Excitation Load Input

Add Fixed Constraint

In the Solutions tab of the Model Browser, under the Pretension_Case loadcase, right-click on the Carrier_Fixed constraint and select Add to Current Loadcase from the context menu.
The Carrier_Fixed constraint is added to the Preloaded_Mfreq loadcase.

Define Loadcase Parameter and Result Request

  1. In the Solutions tab of the Model Browser, right-click on the Preloaded_MFreq loadcase and select Loadcase Parameters from the context menu.
    The Loadcase Parameters dialog opens.
  2. In the Loadcase Parameters dialog, enter the values as shown below and click OK.


    Figure 18. Loadcase Parameters Frequency Response Analysis
  3. Right-click on the Preloaded_MFreq loadcase and select Result Request from the context menu.
    The Result Request dialog opens.
  4. In the Result Request dialog, enter the values as shown below and click OK.


    Figure 19. Result Requests for Frequency Response Analysis

Create Contacts

  1. From the Analysis ribbon, Loads and Constraints group, click the Contact tool.
    The Define Contact dialog opens.
  2. Create Cover_Bolts contact.
    1. In the Define Contact dialog, enter the values as shown below.
    2. In the modeling window, select the Cover for the main body and select the Bolts for the secondary body.
    3. In the Define Contact dialog, click Apply.


    Figure 20. Contact Between Cover and Bolts
  3. Create Carrier_Bolts contact.
    1. In the Define Contact dialog, enter the values as shown below.
    2. In the modeling window, select the Carrier for the main body and select the Bolts for the secondary body.
    3. In the Define Contact dialog, click Apply.


    Figure 21. Contact Between Carrier and Bolts
  4. Create Cover_Carrier contact.
    1. In the Define Contact dialog, enter the values as shown below.
    2. In the modeling window, select the Cover for the main body and select the Carrier for the secondary body.
    3. In the Define Contact dialog, click OK.
    This contact is created to prevent the overlapping of Carrier and Cover bodies.


    Figure 22. Contact Between Cover and Carrier

Solve and View Results

Solve the Solution

In the Solutions tab of the modeling window, right-click on Results and select Update from the context menu.
The Solution begins to solve.

Interpret the Results

After the model setup has been successfully solved, the results are automatically appended to the input model.

  1. In the Results panel, change the Load Case to view the results of the Preloaded_MFreq loadcase.
    The Simulation of Results panel lists all the frequencies for which the results are computed.


    Figure 23. Change Loadcase
  2. Use the Results panel to change the result component.
Example resultant displacement results of Preloaded_MFreq at different frequencies are shown in Figure 24.


Figure 24. Example Displacement Results

Plot Graph

In this step you will plot a graph of resultant displacement at different frequencies of the Preloaded_MFreq subcase.

  1. From the Results ribbon, Results group, click the XY Plot tool.
    The X Y Plot dialog opens.
  2. In the X Y Plot dialog, change the Data type to Loadcase/Frequency.


    Figure 25. Change Data Type
  3. For X Data, click Loadcase.
    The Loadcase dialog opens.
  4. In the Loadcase dialog, enable the checkbox for Subcase2 (Preloaded_MFreq) and click OK.


    Figure 26. Select Subcase to Plot Graph
  5. In the modeling window, select any node from the model and click Plot in the X Y Plot dialog.


    Figure 27. Example Graph