Field Data Replication (FDR)

Back to: Test Development with Recorded Data

The primary objective of random vibration testing is to bring the device under test (DUT) to failure. Random vibration excites a range of frequencies simultaneously, using a power spectral density (PSD) to determine energy distribution. When resonant frequencies are excited simultaneously, failure can occur.

High-peak Accelerations

Random vibration tests are largely more reflective of real-world conditions than sine tests. Rarely does a DUT experience one single-tone vibration at a time, but rather a combination of excitations over a range of frequencies.

However, random tests are not an exact replication of the real-world environment, only an approximation. Random vibration control assumes a Gaussian distribution of data, which is not always the case in the real world. The averaging methods software programs use for random testing can “average out” extreme peaks that could possibly be damaging.

A test without peak accelerations can result in under-testing. If an engineer determines that a peak acceleration contributes to failure, they will need to add the peak back to the random test profile or select a different/supplemental testing method.

VibrationVIEW’s Field Data Replication (FDR) software module replicates a field recording on a shaker in the lab, including high peaks. It is an option for testing a single dominant operating condition as accurately as possible.

Field Data Replication

The FDR module performs an iterative time-history playback. The test engineer imports a time-history file, and VibrationVIEW plays it back as a control reference. The purpose is to include potentially damaging peaks by replicating a waveform from the field environment. The result is 1:1 replication.

FDR quickly brings a vibration test to the full level and requires minimal setup/configuration. The test does not necessarily have to be random, as the goal of an FDR test is to replicate any environment.

Live Field Data Replication test data.

How to Use FDR

To replicate a recorded waveform, engineers can import a single data file up to 2³² samples. FDR runs one waveform at a time, but the engineer can play back up to five files in a single profile and select different channels for control.

The FDR test can re-create the waveform for a specified duration, and the waveform can be scaled up or down by any factor. Additionally, the test can run at different intensity levels for a set duration.

Watch: Fundamentals of Field Data Replication Tech Talk

Filters

Engineers can apply filters to the data stream before or during an FDR test. A low-pass filter, high-pass filter, or notch filter can be applied and modified during the live stream; the controller will automatically adjust the control.

For example, buzz, squeak, and rattle tests seek to determine how components behave in a real-world environment. The engineer may want to reject different frequencies to eliminate an irritating noise. This action will help determine if any other frequencies complement the noise or if any noises are generated from the same waveform without exciting a pre-determined failure.

FDR and Random Testing

With FDR, there is no need to approximate the field environment, and it is useful in many situations. However, this test method does not replace random vibration testing. As the replicated waveform is identical to the field data, it doesn’t capture potential variability. FDR provides a representation of one instance in the environment, while a random test provides a statistical average. As stated in “What is Random Vibration Testing?”:

“Where FDR might exactly capture what one driver experiences while driving a prescribed route, random represents the average of thousands of different drivers trying to follow the same course.”

An FDR test represents one specific environment, and most DUTs experience various conditions throughout their operating life. Some programs require engineers to test isolated conditions, and FDR caters to these types of applications.