Sensitivity Analysis

Use Sensitivity Analysis to study modal contribution.

The standard post-processing in SnRD offers the functionality to generate time domain displacement plots of each of the node-pairs of all the E-Lines that are present in the model. The purpose of the Sensitivity Analysis is to study the root cause of rattle and/or squeak at each E-Line.

Two main diagnosis functionalities are enabled in SnRD sensitivity analysis step:

Determination of Relative Modal Contribution to squeak and rattle of complete E-Lines and as well as at specific points on each E-Line.
Capability to check the effect of changing the percentage of modal contribution on the squeak and rattle performance.

Select the Sensitivity Analysis tab in the tool.
The Sensitivity Analysis tab opens.
Select the required result file from the Result File list.
Select the subcase from the Subcase name list.
Browse and select relevant H3D file for Modal Results File (.h3d).
Select required E-Line from E-Lines list.
Select a point on the E-Line or checkbox to select the complete Line for Select Pair option.
Select direction from Select Direction list.
Optional: Enable the Display Excitation load checkbox to plot the excitation load.
Optional: Enable the Squeak 2D Plot checkbox to plot the relative displacement in the XY plane (Contact Plane).
Click Load Time History.
Loading time history and relative displacement plots for the selected E-Line and the pair are generated and plotted.

Modal Sensitivity Studies

Study the modal contribution and sensitivity.

Calculate the relative Modal Contribution of the required E-Line to be analyzed.
Observe the change in results. Specifically, when the modal contribution is varied buy either including or excluding a certain mode from the result calculations with the help of Modal Sensitivity study.
The relative modal contribution for a particular E-Line can be calculated and studied in two ways:
- Study the modal contribution of the complete E-Line.
- Study the modal contribution of a particular node pair of an E-Line.

Maximum Peak

Max. Peak is available only for studying modal contributions based on nodes as the selected pair.

Select Max. Peak radio button.
Use to navigate in the plot to view the Relative Displacement peaks and time of occurrence.
The plot highlights the peaks values in relative displacement using horizontal and vertical dashed lines and also shows labels to highlight the same.
Select a value from Select Top Contributors list.
Click Analyze.
This plots and displays the selected number of top contributing modes in descending order of effect on squeak and rattle.

Percentage of Highest Peaks

% of Highest Peaks is enabled only when studying modal contributions based on complete E-Line as the selected pair

Enter the percentage value of peaks that you want to study.
Select a value from Select Top Contributors list.
Click Analyze.
This plots and displays the selected number of top contributing modes in descending order of effect on squeak and rattle.

Modal Sensitivity

The Modal Sensitivity study can be performed on complete E-Line or a selected Node pair belonging to an E-Line. Once the Modal Contribution study is done and you have determined the modes that exhibit maximum contribution to the relative displacements that lead to squeak and rattle, you can study the effect of particular mode(s) on the total response.

SnRD computes the total response (relative displacement) based on the equation of motion without need to simulate again. This enables to understand the potential of a design change that leads to damping or eliminating a certain mode shape.

Chosen modes can be Included or Excluded from the results and displacements recalculated to observe their effect on the squeak and rattle performance.

Click Modal Sensitivity.
Select Include or Exclude from Select Contributors to list.
Define the percentage value of the mode to be considered for evaluation in % to Include/Exclude field.
Select required mode from the Modes table.
Enable the Plot in same graph checkbox.
Click Analyze.
This plots the new and the original maximum relative displacement for the selected E-Line.

Sensitivity Analysis Options

Result File

List contains the results file loaded in the Post Processing tab.

Subcase Name

List containing the subcases of the selected results file.

Modal Result File (h3d)

H3D file containing the modal contribution results.

Display Excitation Load

This option will be active only for a node pair and not for complete line option.

Displays the excitation load as a curve in a HyperGraph window.

2D Squeak Plot

Adds an additional plot with the relative displacement in contact plane (XY) for squeak lines.

This plot is useful to fully understand the movement in the contact plane and the principal directions.

Modal Contribution

Max. Peak: To study the relative displacement study for the peaks and time of occurrence.
% of Highest Peaks: To study a certain percentage of highest peaks.

Modal Sensitivity

Select Contributors: Include: Includes the selected modes in the recalculation of the displacements.; Exclude: Excludes the selected modes in the recalculation of the displacements.