Variability (Stochastics) Study

Study the effects of parameter variations on squeak and rattle issues.

The manufacturing of parts is often related to variations of tolerances and quality of materials. Also, the assembly process adds a set of variations on dimensions and connection of stiffnesses resulting in a unique product at the end of each build. These two major processes contribute to the quality and performance of the final product.

Squeak and Rattle are phenomena that are tightly related to the quality of the built parts, and performance can vary through the population of produced products.

The Manufacturing Variations Study workflow will take the you through the steps of setting up a variability study to analyze the risk and effects of the manufacturing problems. Below is an illustration for Manufacturing Variations Study.
Note: SnRD requires a runnable solver model, which should either contain a Dynamic or Static Loadcase. This is required since HyperStudy works on the principle of comparing results of a nominal run with the consecutive run results.
Below is an illustration of the workflow that shall be covered in this usecase:
Figure 1.
Objective
  • Prepare the FE model for analyzing Squeak and Rattle issues.
  • Setup variability study for the following-
    • Material Parameters
    • Attachment Stiffness
    • Thickness, and
    • Damping
  • Run analysis and post-process the results.
Starting Point

Choose the workflow according to your need and refer to sections mentioned above for the procedures.

Files Required

Files required to complete the usecase.

Use the solver deck exported from Detailed Risk and Root Cause Analysis usecase.
Once you import the Dynamic Loadcase solver deck, you can proceed with Variability (Stochastics) Study setup.

Step 5: Variability Study Setup and Export

Define variability study setup for various parameters and export the solver deck.

Variability Study Setup

Below are the steps to setup variability study(s).

  1. From Setup group, select Variability Study.
    Figure 2.
    A guide bar will appear.

Material Parameter Study- Youngs' Modulus

You will setup a variation study for all the materials in the model.

  1. Using window selection in the graphics area, or click in the guide bar to open advanced selection option. Select all the materials from the list.
    This selects five materials in the model. A microdialog appears.
    Figure 3.
  2. Select E from the list, enter 20 for and value fields.
    This defines the parameter variation percentage for the study. Click to expand the microdialog. You can define a desired name for the study or retain the default.
    Figure 4.
  3. Click .
    This creates the material Youngs' Modulus (E) variation study.

Material Parameter Study- Density

  1. Using window selection in the graphics area, or click in the guide bar to open advanced selection option. Select all the materials from the list.
    This selects five materials in the model. A microdialog appears.
  2. Select RHO from the list, enter 20 for and value fields.
    This defines the parameter variation percentage for the study.
  3. Click .
    This creates the material Density (Rho) variation study.

Attachment Stiffness Study

  1. Select Attachment Stiffness from the guide bar.
  2. Click in the guide bar to open advanced selection option.
  3. Select following properties from the Advanced Selection window.
    • ControlPanel_IPSub_Snaps
    • GloveBox_RubberBumper
    • ClusterBezel_IPSub_Clips
    • DriveSidePanel_IPSub_Snaps
  4. Select K1, K2 and K3 stiffnesses from the microdialog.
  5. Click .
    This creates the Attachment Stiffness variation study.

Material Thickness Study

  1. Select Thickness from the guide bar. Select the following components from the graphics area-
    • IPSubstrate
    • Glove Compartment
    • Driver Side Panel
    • Lower Control Panel
  2. Retain the default values in the microdialog and click .
    This creates a study for the material Thickness variation study.

Damping Study

  1. Select Damping from the guide bar.
  2. Click in the guide bar to open advanced selection option.
  3. Select all the damping curves from the Advanced Selection window.
  4. Click .
    This creates the material Damping variation study.

To review variability study

  1. Select Review Variations.
    Figure 5.
    A table will appear containing all the variations and its related parameters. Click Close after verification.
    Figure 6.

Export Solver Deck

  1. From Analyze group, select Export OptiStruct Solver File.
    Figure 7.
    Model Export window will appear.
    Figure 8.
  2. Check Export Variability Study box.
    Variability Study properties are displayed.
    Figure 9.
  3. Accept the default options and click Export.
    A folder selection window will appear.
    Note: You can modify any property(s) in the dialog.
  4. Browse and select the required folder.
    This will export the OptiStruct solver deck, along with the XML and TPL files to the selected folder. Click Close to close the model export option.
Use the exported TPL template file to solve on HyperStudy.

Step 6: HyperStudy Database Generation

SnRD exports the variability study parameters into the following files, which are required by HyperStudy for results database generation-
  • TPL,
  • XML

The template (TPL) file us created with the required parameters that are readable by HyperStudy.

Stochastics Runs

Below are the steps to generate results database and summary files. These files will be later used in SnRD Post-processing.

  1. Launch HyperStudy 2021.
  2. Click Open.
    A file browser option will be displayed. Browse and select tutorial XML file.
  3. Once the XML file is loaded, a session tree will populate in HyperStudy and the process will start from Sto 1 node.
    Figure 10.
    Note: Green check boxes signify that the respective data is available. Any Yellow, Red or empty boxes mean inputs are required.
  4. Click Next to proceed to Sto 1 > Definition > Test Models task.
    Note: You can skip Define Models and Define Input Variables tasks since they are pre-defined.
    Figure 11.
  5. Click All under Test column.
  6. Click Next to proceed to Define Output Responses and click Evaluate.
  7. Click Next to proceed to Specifications and click Apply .
    Figure 12.
  8. Click Next to proceed to Evaluate.Click Evaluate to run the stochastics variations.
    Figure 13.
    Note: Evaluation tasks will take considerable amount time to complete. Please do not interfere with HST when the process is running.
    Figure 14.

    Once the evaluation is completed, remaining tasks, I.e Post-processing and Report turn green.

  9. Click Next twice to skip Post-processing and navigate to Report task.
  10. Click Create Report .
    This generates a .data file, which will be the results database that will be utilized later in SnRD Post.

    You can navigate to Tutorial working model folder and verify the files. The respective files will be created in the export folder.

    Tip: Learn more about Altair HyperStudy.

Step 7: Stochastics Post Processing

Note: Copy the summary.data files created which were created in the rpt/sto_1 after Create Report steps from HyperStudy, to approaches/sto_1 .
  1. Select SnRD > SnRD-Post.
    SnRD Post Processing tool is launched.
    Figure 15.
  2. Using the file browse option , select the OptiStruct solver file which was exported in Step 4 for Model File.
    Note: Pre output CSV file containing the E-Lines definition is sourced automatically.
  3. Load the model and CSV file in Post Processing tab, and then switch to DoE/Stochastics tab.
  4. Click HyperStudy Results Database radio button.
  5. Click against HyperStudy Results Database. A file browser window will appear.
  6. Browse and select the XML file generated in Export Solver Deck step.
  7. Click Calculate .
    This will start the Compose 2021 in the background to perform the stochastics runs evaluation.
    Note: Since the number of runs is high, a considerable amount time will taken. Please do not interfere with process.
  8. Once the calculation is complete, a confirmation message will be displayed.
    Figure 16.

    Click OK to close the message.

    Note: To run the results processing for the second time, you can use the SnR Database XML that was created during the calculation can be utilized.
  9. Select the following options from the Selection lists -
    1. All from E-lines
    2. All from Line ID
    3. SnR Index from Results
  10. Select All radio button from Show Runs
  11. Select Value radio button from Vary Variable by
  12. Click All check button from Show Variables.
  13. Click Apply Filters
    This will filter all the runs in the Run Selection table
    Figure 17.

Run & Display Selection

  1. Click Display Results.
    This plots the results for the all the filtered runs.
  2. Also, you can select the required runs from the Run Selection table.
  3. Click Display Selection. This will plot the results for the selected runs.
    Figure 18.