Simcenter Testlab Transfer Path Analysis: Component Editing

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The Component Editing add-in of Simcenter Testlab Transfer Path Analysis (TPA) is used to simulate modifications to a source-path-receiver model.  By trying out potential modifications, the best and most effective changes to reduce sound or vibration can be understood.

 

Potential modifications include:

  • Modifying Individual Paths or Multiple Paths
  • Reducing Structural Sensitivities, adjusting Mount Stiffness Spring Rates
  • And more…

This article contains instructions on using the Component Editing Add-in with an existing Transfer Path Analysis model.  Sections include:

  1. Getting Started and Background
  2. Modifying Structural Sensitivity
  3. Modifying Mount Stiffness
  4. Saving Modified Model

 

1. Getting Started and Background

 

In the Transfer Path Analysis (TPA) model results shown in Figure 1, a path called “body:1:+Z” is the biggest contributor to the total sound at the target location.

 

TPA_Model.pngFigure 1: Transfer Path Analysis results showing the path “body:1:+Z” as the largest contributor to sound level at target location.

To better understand why a particular path is the largest contributor, click on the “Path Specific” minor of the “TPA Results” worksheet as shown in Figure 2.

 

TPA_Results.pngFigure 2: In the “TPA Results” worksheet, click on the “Path Specific” minor worksheet to analyze the paths in more detail.

 

The “Path Specific” minor worksheet breaks down the path into its constituent parts.  For example, a mount stiffness path would consist of accelerations, mount stiffnesses, structural sensitivities, etc.   This is shown in Figure 3.

 

TPA_Path_Specific.pngFigure 3: In the “Path Specific” minor worksheet, the target/path/load is selected. All related path data is displayed on the right.

On the left side of the worksheet, the user can select the target location, the path of interest, and the load condition (order, spectrum, etc).  In Figure 3, the selections consist of:

  1. Target: An acoustic target called “mic:1111: S”
  2. Path: The path called “body:1:+Z” is selected
  3. Load: Third order is selected

On the right side of the worksheet, the selected path data is displayed:

  1. Mount Accelerations (green): The accelerations on both the active side and passive side of the mount. These accelerations are double integrated and subtracted to calculate the displacement across the mount (x).
  2. Mount Stiffness (blue): The mount stiffness (k) is multiplied by the displacement (x) to calculated the force (f)
  3. Calculated Force (yellow): The calculated force from the mount is displayed.
  4. Structural Sensitivity FRF (orange): The Frequency Response Function (FRF) is multiplied by the force to get the total for the path
  5. Totals (red): In the totals display, the contribution of the selected path is shown (magenta in this case) against the calculated total of all paths. The calculated total is also shown against measured total.

In the totals display shown in the lower right corner, three curves are shown by default (Figure 4).

 

TPA_Totals_Original.pngFigure 4: The measured 3rd order sound level (green) of a dynamic system is shown. It is displayed against the calculated total (blue) from the Transfer Path model and the contribution (magenta) of one of the paths (body:1:+Z).

The curves in the display are as follows (note that the colors can vary depending on software settings):

  1. Measured Total – The 3rd order (green) measured at target location.
  2. Calculated Total – Sum of all paths (blue) in the TPA model. The blue and green curve should match well to know that the model reflects the dynamic system.
  3. Contribution of Selected Path – Contribution of path “body:1:+Z” (magenta) to the total.

Seeing how the path “body:1:+Z” contributes significantly to the total, the next step would be to try some virtual modifications to reduce the sound level at the target location.

 

Modifications can be done using the Component Editing add-in.  From Simcenter Testlab Transfer Path Analysis, choose “Tools -> Add-ins” and select “TPA Component Editing” as shown in Figure 5.

 

TPA_addin.pngFigure 5: Under “Tools -> Addins” turn on “TPA Component Editing”.

If using Simcenter Testlab Token licensing, the TPA Component add-in occupies 45 tokens.

 

One modification to try would be to reduce the structural sensitivity of path “body:1:+Z”.  The path “body:1:+Z” is by far the largest contributor, and has a resonant peak at the same frequency range as the peak in the measured response.

 

2. Modifying Structural Sensitivity FRF

 

After turning on the Component Editing Add-in, the “Open Edit” button at the top of the screen is sensitive.  Click on it and cursors appear in the displays.  The cursors can be used to identify the frequency range to be modified (Figure 6).

 

OpenEdit.pngFigure 6: Press the button “Open Edit” at the top of the “Path Specific” displays. Cursors appear to select a frequency range to edit. In this case, a reduction of the peak in the structural FRF (middle right) will be done to reduce the overall response level (lower right).

The cursors are positioned around a large resonance in the structural sensitivity Frequency Response Function (FRF)

 

To reduce the amplitude of the resonance, press the “Edit” button above the FRF display (Figure 7).

 

FRF_Edit.pngFigure 7: Press the “Edit” button above the FRF curve to reduce the amplitude of the resonance.

In the resulting menu, different editing options are available.  To reduce the resonance in the FRF, the modification called “Remove Peak” will be selected (Figure 8).  A reduction factor of 90% will be used.

 

EditMenu.pngFigure 8: Modification Options available in Component Editing TPA.

Press the “OK’ button when finished.  In the lower right, the results of the modification are shown (Figure 9).

 

FRF_Modification_Results.pngFigure 9: Reduction in overall level (blue) and path contribution (red) due to reduction of peak in structural FRF on selected path. The measured level (green) at the TPA target location is shown, as well as the original path contribution (magenta).

The possible dB reduction is shown in the lower right. After applying the modification:

  1. Measured Total – The 3rd order (green) measured at target location.
  2. Modified Calculated Total – Sum of all paths (blue) in the TPA model, including the modified FRF. The blue curve is now lower than the measured.
  3. Original Contribution of Selected Path – The original contribution (magenta) of path “body:1:+Z” to the total. It is possible for the contribution of an individual path to be higher than the total due to phasing between paths.
  4. Modified Contribution of Selected Path – The modified contribution (red) of path “body:1:+Z” due to the FRF peak reduction.

Reducing the resonance of the FRF has reduced the peak significantly in the overall response.

However, instead of modifying the structural sensitivity FRF, a different modification could be tried and evaluated. For example, the mount stiffness could be reduced.

 

3. Modifying Mount Stiffness

 

To modify the mount stiffness used in the operational force calculations, press the “Edit…” button above the mount stiffness curve display as shown in Figure 10.

 

mount_modification.pngFigure 10: Press “Edit…” above the mount stiffness curve display.

To change the mount stiffness across the entire frequency range, the cursors were positioned at the beginning and end of the display.

 

The modification “Add offset” was selected, and the mount rate lowered by 6 dB.  After pressing the “OK…” button, the new calculated totals and path contribution are displayed in the lower right (Figure 11).

 

mount_mod_results.pngFigure 11: Reduction in overall level (cyan) and path contribution (red) due to mount stiffness and structural FRF modification on selected path. The measured level (green) at the TPA target location is shown, as well as the original path contribution (magenta). The result of the first modification overall level (blue) is also shown.

The results of the mount stiffness reduction:

  1. Measured Total – The 3rd order (green) measured at target location.
  2. Modified Calculated Total #1 – Sum of all paths (blue) in the TPA model, with the modified FRF only.
  3. Modified Calculated Total #2 – Sum of all paths (cyan) with both the modified FRF and new mount stiffness.
  4. Original Contribution of Selected Path – The original contribution (magenta) of path “body:1:+Z” to the total. It is possible for the contribution of an individual path to be higher than the total due to phasing between paths.
  5. Modified Contribution of Selected Path – The modified contribution (red) of path “body:1:+Z” due to the FRF peak reduction and mount stiffness change..

The results of the modifications can be stored for later use. 

 

4. Saving Modified Model

 

To save the modified model, click on the “Save Snapshot” button in the lower left as shown in Figure 12.

 

Save_Snapshot.pngFigure 12: Click on the “Save Snapshot” button in the lower left and provide a name for the modification results.

Provide a name for the modifications and press the “Save” button.

 

Then click on the “Close Edit” button at the top as shown in Figure 13. This will end the editing operations.

 

CloseEdit.pngFigure 13: Click on the “Close Edit” to stop editing the TPA model.

A warning is shown that any edits performed after the “Save Snapshot” will not be stored.  Press “OK”.

 

In the lower left, it is now possible to switch the view from the original TPA model to the modified (Figure 14).

 

Model_Switch.pngFigure 14: Click on the “Close Edit” to stop editing the TPA model.

This makes comparing models very easy.  There are several places in the TPA software where this can be used.  For example, in Time Domain TPA, results can be generated for both the original and modified model by switching as needed.

 

Questions?  Email peter.schaldenbrand@siemens.com, post a reply, or contact Siemens PLM GTAC support.

 

Also check out the Transfer Path Analysis White Paper.

 

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