The Future of Random Vibration Testing

Predict your product’s life expectancy through accelerated testing

If you're asking these questions, you need FDS

  • What is the best random test to simulate my product's environment?
  • How long should I be running my random test?
  • Can I accelerate my testing?

What is Fatigue Damage Spectrum?

  • Fatigue Damage Spectrum is random vibration spectrum based on Miner’s Rule of Damage.
  • Miner's Rule teaches that fatigue damage will accumulate over time until it reaches a level that causes a crack or other deformation of a product.

Time Domain Calculation

  • Calculation through time domain, not frequency domain to account for kurtosis you will likely see in the real world.
    The Fatigue Damage Spectrum is based on the response of single degree of freedom systems rather than FFTs.

    Display Imported File Statistics

  • Displays peak acceleration, velocity, displacement as well as the kurtosis of the time history file.
    This provides a quick and easy way to determine the statistics of a waveform.

    Configurable Process Parameters

  • The user can define the slope of the s/n curve (beta) and quality factor (Q).

    Reduce Test Time

  • User sets test item target life based on product specifications, as well as test duration.
    The software automatically calculates ratios that will produce the same amount of fatigue damage in shorter test time.

    Analysis to Control

  • With one mouse click, bring your new random breakpoints into a control profile.
    Go from a time waveform to a breakpoint profile and start controlling on that profile all in one program.

    Multiple Waveforms

  • Calculate the combined fatigue of multiple waveforms. Overlay and compare multiple waveforms on a single plot.

    Includes Random Import (VR9204)

  • Compare multiple methods of generating a random profile.

Technical Papers and Presentations on Fatigue Damage Spectrum

Using Fatigue Damage Spectrum for Accelerated Testing with Correlation to End-Use Environment (2MB)

The accumulated damage that a product experiences in the field due to the variety of vibration stresses placed upon it will eventually cause failures in the product. The failure modes resulting from these dynamic stresses can be replicated in the laboratory and correlated to end use environment to validate target reliability requirements. This presentation addresses three fundamental questions about developing accelerated random vibration stress tests...download to read more...

written by Tom Achatz of GM and John Van Baren of Vibration Research

Using Fatigue Damage Spectrum for Accelerated Testing with Correlation to End-Use Environment (1.4MB)

PDF of slides as presented by John Van Baren and Tom Achatz at ASTR 2014

Fatigue Damage Spectrum for Repetitive Shock Machines & the HALT/HASS Process (2MB)

Overcoming decades of shortcomings, applying a Fatigue Damage Spectrum (FDS) to Repetitive Shock (RS) machines used in HALT (Highly Accelerated Life Tests) and HASS (Highly Accelerated Stress Screening) provides an improved use and analysis. FDS can be used to benchmark RS excitations and product responses to correlate them with End-Use-Environments (EUE), ED shakers and thus quantifying severities of different excitations. FDS expands the benefits of the HALT process by addressing EUEs and shaker excitations (RS and ED) and quantifies step stress levels, product strengths and margins, proof of screen, product responses and test compression to document progress toward reliability and confidence goals. Answers the questions, “When to “Stop HALTING” and “What are you doing to my product”

PDF of slides as presented by Stephen A. Smithson of Smithson & Associates, Inc. at ASTR 2014

A Primer on Fatigue Damage and Fatigue Damage Spectra (1.5MB)

Fatigue is the result of multiple repetitions of low-level stress applied to an object. Generally, fatigue happens in three stages: crack initiation; crack propagation; and final fracture. These three stages can clearly be seen in examples of aluminum beams that experienced various levels of fatigue during experimental testing.........download to read more >>>

written by John Van Baren

Fatigue Damage Spectrum on FORD Fuel Rail System (2.5MB)

FDS was used by Ford Motor Company (FORD) to help them assess a situation they were investigating with the fuel-rail systems on their 5.0 L and 6.2 L BOSS engines. FDS helped to show that the laboratory tests that FORD was performing were over-testing the fuel-rail systems and it helped FORD predict the life-expectancy of the fuel-rail systems and test them more realistically.......donwload to read more >>>

written by John Van Baren

Accelerating Random Vibration Tests (0.7MB)

Vibration Research Corporation has two techniques to help test engineers rapidly accelerate the random vibration tests. Those two methods are Kurtosis Control and Fatigue Damage Spectrum.....download to read more >>>

written by Joel Minderhoud

Video Demonstrations of Fatigue Damage Spectrum (FDS) option

Video 1 of 3 - In this video we take field data collected from an engine run up and review it in VibrationVIEW software. The recorded waveform is opened and played back to analyze both the waveform and spectrum during the engine run up. Analyzing the data is the first step in producing an fatigue curve.

Video 2 of 3 - In this video we transform the recorded data into a random power spectral density curve and make a direct comparison between the classic method using the "average" method followed by our new Fatigue Damage Spectrum method. Kurtosis is also measured and considered in the FDS transformation.

Video 3 of 3 - In this video we use our FDS feature to address the age-old question of "is random or sine testing more severe?". This question was addressed several years ago in one of our technical articles where a user asked "given both a sine test and a random test, how can I determine which is the more severe test".

Read the original article here: "Test My Product Using Sine or Random"

Comparing Ford Mustang Road Data Using the Fatigue Damage Spectrum (FDS) option

Video 1 of 5 - Recording data – In this video we show the process for instrumenting an ECU on two Ford mustangs (old and new). We instrumented in two locations on the newer Mustang, at the base of the ECU bracket (input measurement) and then the ECU itself (response measurement).

Video 2 of 5 - Processing and analyzing recorded data (newer Mustang) – next we show how to process the new Mustang recorded road data using Fatigue Damage Spectrum software (FDS). During this process we also show how to combine multiple road environments and generate a single fatigue spectrum. Load 27 recorded data files, enter M and Q values, set target life, calculating fatigue, x and y and z axis, damage for each, then enveloping all road data (maximum values) across 6 -2000Hz.

Video 3 of 5 - Processing and analyzing recorded data (older Mustang) – next we show how to process the new Mustang recorded road data using Fatigue Damage Spectrum software (FDS). During this process we also show how to combine multiple road environments and generate a single fatigue spectrum.

Video 4 of 5 - Create a single PSD from combined FDS and exporting data – using a 500 hour target life for the ECU, we set up a random PSD test profile to run on a shaker for 5 hours. The 5 hour shaker test will provide an equivalent amount of fatigue damage to the 500 hour target life. We then export data to a spreadsheet to prepare for the creation of a scatter plot of both Mustang’s fatigue curves.

Video 5 of 5 - Create a scatter plot in Excel to compare the combined fatigue curves for each Mustang to illustrate damage vs frequency differences between the two.


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