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:
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
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.
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.
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.
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:
On the right side of the worksheet, the selected path data is displayed:
In the totals display shown in the lower right corner, three curves are shown by default (Figure 4).
The curves in the display are as follows (note that the colors can vary depending on software settings):
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.
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).
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).
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.
Press the “OK’ button when finished. In the lower right, the results of the modification are shown (Figure 9).
The possible dB reduction is shown in the lower right. After applying the modification:
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.
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).
The results of the mount stiffness reduction:
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.
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.
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).
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.
Also check out the Transfer Path Analysis White Paper.