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Re-introduce high acceleration peaks to a random test

Vibration Research’s patented kurtosis control adds a third dimension to random vibration testing when the in-service vibration environment is not Gaussian. Kurtosion® is a Random software add-on (VR9205).

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Part number 9205


Improve Random Test Profiles

Present-day methods of random testing assume a Gaussian mode of distribution where the kurtosis value equals three. However, not all data fit Gaussian distribution, and this assumption can result in under-testing.

A better method is to adjust the distribution of data to reflect the field environment, which involves the adjustment of kurtosis. Kurtosion is a closed-loop method of kurtosis control developed by Vibration Research. It allows for the adjustment of kurtosis levels while maintaining the test profile and spectrum attributes.

Add Kurtosion to a Random vibration test when

  • The vibration test needs to be more realistic to real-life situations
  • You want to break a product quickly without using more energy

Spend More Time at Peak Levels

kurtosis versus time graph

The greatest damage potential of your product is typically at peak acceleration levels. When the kurtosis value of a signal is increased, the time spent at peak levels is also increased. With kurtosis control software, your test will better reflect what occurs in the real world.

Technical Papers

Accelerate Structural Life Testing

Kurtosis control allows engineers to conduct life testing in a fraction of the time required for a Gaussian drive signal to precipitate failures. However, they must implement kurtosis control properly to circumvent interference from the Central Limit Theorem.

A unique feature within the Kurtosion process allows engineers to accelerate resonant fatigue and simple static failure tests. READ MORE.

The Third Dimension of Random Vibration Control

“Adding a third control dimension leads to more realistic random vibration tests that better match the damage potential of the field environment. That third dimension is kurtosis control…” READ MORE.


Getting the Kurtosis into the Resonances

Qualifying the Kurtosion Technique

“Vibration Research’s unique method of kurtosis control can get the kurtosis into the resonances and produce non-Gaussian output on the DUT, thereby making random vibration tests more realistic.” READ MORE.


Is your kurtosis control method effective or effectively worthless?


Kurtosion Shaker Capacity Calculator

Increasing the kurtosis value on a shaker for specific tests may decrease the manufacturer’s random lb-f rating. Engineers can use the relationship between kurtosis and the crest factor to calculate the shaker capacity for a random Kurtosion test.

Download Calculator (Excel)

Evaluate the Effectiveness of Kurtosis Control

FDS software iconThe fatigue damage spectrum (FDS) illustrates the fatigue damage a product will experience in the field. Increasing the kurtosis value of a random vibration test increases the number of peak accelerations in the test, and the FDS should show an increase across the frequency spectrum when the kurtosis is increased.

The FDS can help engineers visualize how increasing the test kurtosis will bring a product to failure more quickly. READ MORE.

Kurtosion Definition

This VR innovation in random testing is a patented method of kurtosis control. With Kurtosion, you can control the RMS and kurtosis of the random waveform to have more control over the probability distribution and more closely match your test lab to the real world.

  • Full RMS control: Acceleration is moved from the mean towards peak levels, resulting in no change in gRMS
  • Full dynamic range: The kurtosis of the acceleration is controlled without any reduction in dynamic range

What is Kurtosis?

Kurtosis is a dimensionless measurement that pertains to the average deviation of a signal from its mean value. Present-day random testing assumes a Gaussian distribution of random data with a kurtosis value of 3. However, some data do not fit the Gaussian distribution. In such instances, a kurtosis value of 3 may omit higher peak values.

What is Gaussian Distribution?

The Gaussian distribution function is the most widely used probability distribution in statistical analysis. The distribution is symmetrical; the skewness equals zero and the kurtosis equals three.

Traditional random control assumes a Gaussian distribution of data, which is highly concentrated near the mean value of zero. Therefore, traditional random test acceleration is near zero most of the time. In most environments, significantly more time is spent at peak levels than what is produced by a traditional random test.

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