3 Checking operational deflection shapes

Getting source characterization first-time right, can be a challenging task. To achieve good quality, it is essential to detect overloads, detached sensors, broken cables, and noise issues.

The operational deflection shapes illustrate the motion of the sensors at a specific frequency for a specific operational measurement.

At low frequencies, the ODS should mainly show the component moving like a rigid body. If that is not the case, you can understand what is going on according to the sensor movements and fix it right at the beginning.

ODS is a really helpful tool when used together with the operational consistency quality indicator. It can be used to visualize and identify which sensors and channels of a specific VP have issues.

If you follow the VIBES suggested workflow, you have already checked the ODS of the artificial excitations in DIRAC. However, you must also check the ODS of all your operational measurements in SOURCE. This is needed to ensure that nothing has changed in the test setup between the FRF and the operational measurements.

Displaying ODS

You need the src-ods license to animate ODS in SOURCE. Geometries can only be imported from a DIRAC project.

  1. ODS are shown in the 3D Viewer card of the Operational Data module.
  2. To visualize geometries, you need to import a DIRAC file.
  3. Master channels must have channel position and orientation information.
  4. The operational data channels must be mapped to the master channels.
  5. Drag and drop the desired operational dataset in the 3D Viewer.
  6. Press the Play  button.


Steps 5 and 6:

ODS settings

When animating ODS, you can change the following settings in the taskbar:

  1. Amplitude: amplitude scaling of the sensors’ movement.
  2. Quantity: when multiple quantities are available (e.g., forces and accelerations), you can decide whether to visualize one or all of them together.
  3. Block: the time block.
  4. Frequency: the frequency block.

If you select the quantity Accelerations, SOURCE will automatically convert all quantities to accelerations for a better comparison.

Personalizing ODS style

You can add lines and faces to visualize ODS better, and fully personalize them and the nodes using different colors.

Creating lines

You can connect multiple nodes with lines. All the created lines are visible in the 3D Viewer and listed in the Lines tab.

To connect two or multiple nodes, you have to:

  1. Select the nodes in the 3D Viewer.
  2. Type E.

Creating faces

You can create face elements connecting 3 nodes. All the created faces are visible in the 3D Viewer and listed in the Faces tab.

To create a face, you have to:

  1. Select 3 nodes in the 3D Viewer.
  2. Type F.

How to: Spot wrongly oriented sensors

If one sensor is rotated on the test setup compared to how it is oriented in the DIRAC file, when playing the ODS, it will move differently than the surrounding sensors at low frequencies.

A wrongly oriented sensor will also drastically reduce the operational consistency of that Virtual Point.

To fix it, you must open the DIRAC file, compare the design of experiment with the physical test setup, and rotate the sensor in DIRAC correctly. Then, you must correct the orientation in SOURCE. You can either manually type the new sensor orientation in the channels card or remove the master channels, import the corrected DIRAC file, create new master channels and redo the mapping.

How to: Spot wrong channels mapping

You must correctly map the FRF and the operational channels to perform the calculations needed for a source characterization. If something goes wrong with the mapping, sensors placed close to each other will move inconsistently in the ODS at low frequencies.

When you have wrongly mapped channels, also the operational consistency for that specific Virtual Point drops. If you have wrongly mapped channels, open the Channels card, check and correct the mapping.

How to: Spot detached sensors

You want to make sure that all sensors stay glued in place during your measurements. Due to the vibrations, sensors can detach and fall. This has to be spotted immediately after the measurement. When playing the ODS, sensors placed on the same component and close to each other should move consistently, at least at low frequencies.

The operational consistency of the whole VP group will be reduced mainly in the higher frequency range as the cable acts like a low-pass filter on the sensor. In this case, you should check if all sensors in this VP group are still well attached.

If a sensor is detached, glue it again and repeat the operational measurement.

How to: Visualize overloads with ODS

When a sensor measures a voltage higher than its measurement range, it gets overloaded. When a sensor is overloaded, you notice an increased movement at the specific time block when compared to the surrounding sensors.

When you measure overloads, the operational consistency of that operational condition decreases at specific time blocks. Overloads can also be spotted when plotting time and waterfall graphs. If you have overloads, you need to repeat the operational measurement. If you keep measuring overloads, consider using less sensitive sensors. If you replace sensors, remember to repeat artificial excitation measurements and change the sensor in DIRAC.

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