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VR9500 Revolution Vibration Controller
Using Kurtosion® to Accelerate Structural Life Testing
Life testing using controlled random excitation is a long- accepted means of fnding design and/or assembly faws. Class- general broadband spectra, such as the NAVMAT profle, permit testing without initially knowing the specifc resonances of a new package. Now kurtosis control allows such tests to be conducted in a fraction of the time required for a Gaussian drive signal to precipitate failures. However, the kurtosis control needs to be properly implemented to circumvent interference from the Central Limit Theorem. A unique feature within the Vibration Research Corporation (VRC) Kurtosion® process allows resonant fatigue as well as simple static failure tests to be accelerated.
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Author: Joel Minderhoud, Philip Van BarenSound&Vibration, October 2010 pp 2-6.
Does your Controller Square with Chi?
"Why does the random test spectrum look ragged?" is a frequently asked question. It is actually a far deeper question than most interrogators realize. This article reviews the statistical nature of a random test's spectra. We will provide an answer to this nagging question; provide some valuable test planning information and present methods to evaluate your controller's statistical performance.
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Spreadsheet
Author: George Fox Lang, Philip Van Baren Sound&Vibration, October 2009 pp 8-16.
How Well Does 3 Approximate Infinity - Understanding 3 Sigma Clipping in Random Shake Tests
Random vibration testing presents a host of new and often confusing concepts to the test engineer. Among these, the notion of 'clipping' or 'limiting' the excitation signal to "±3 Standard Deviations" has caused undo confusion. This paper attempts to explain what 3 σ clipping is all about and how it came to haunt us. Given the erosion of written history with time, we will do better at the former objective than the latter.
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Authors: George Fox Lang, John Van BarenSound&Vibration, March 2009 pp 9-16.
The Fatigue Damage Spectrum and Kurtosis Control
The accumulated damage that a product experiences on the field due to the variety of stresses placed upon it will eventually cause a failure in the product. These failure modes can be replicated in the laboratory using random vibration testing. During the past several years, the vibration industry has been introduced to Kurtosis Control - a new technique that brings about these failure modes in the laboratory in a more realistic and speedy fashion. The Fatigue Damage Spectrum (FDS) is an effective tool that can show the damage a product will experience at a particular frequency and the effect Kurtosis Control has on the random vibration test. Kurtosis Control is a more effective method than traditional random vibration tests because it brings products to failure more quickly. The Fatigue Damage Spectrum shows the increasing fatigue damage across all frequencies that accompany the increased kurtosis levels that cause the faster product failure. The FDS is another great tool that clearly illustrates the effectiveness of Kurtosis Control.
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Authors: John Van Baren, Phillip Van Baren
Improving Transportation Industry Random Vibration Tests - Kurtosion and SRS
The transportation industry historically has used Gaussian random vibration tests to simulate real-world transportation data. However, examination of real-world transportation data reveals that transportation data is Non-Gaussian in nature. Consequently, transportation test engineers should simulate the real-world data using Non-Gaussian random vibration. Non-Gaussian random vibration (Kurtosis control) increases the number of large peak accelerations (that arise in field data due, in part, to the pot-holes of transportation) that the Gaussian random vibration tests "average-away" with their averaging techniques. By implementing Kurtosis control, the transportation industry would be well on its way to making their laboratory simulation tests much more realistic. And this, in turn, would result in better packaging - putting more products in the customer's hand without damage.
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Authors: John Van Baren, Phillip Van Baren
Statistical Properties of the Random PSD
This document describes the statistical properties of the PSD of a Gaussian Random waveform, including tolerance bands, confidence intervals, and degrees of freedom (DOF).
Fulfilling MIL-STD-1540D-Tolerance
Is your Random Vibration Testing fulfilling MIL-STD-1540D-Tolerance on Vibration Controllers
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MIL-STD-1540C Table III
KURTOSION® - GETTING THE KURTOSIS INTO THE RESONANCES
Traditional random tests, using a Gaussian distribution, have not satisfactorily tested products in a realistic manner because the Gaussian distribution method fails to bring into the test the large peak accelerations which cause product failure. The key to bringing those large peak accelerations into the random vibration test is to use a kurtosis control method. Kurtosion® , the patented technique developed by Vibration Research Corporation, is a kurtosis control method that can effectively bring large peak accelerations into the random vibration test. This technique has been criticized by some who appeal to the Papoulis Rule a rule that indicates that all systems tend towards Gaussian distribution. However, while the Papoulis Rule indicates the output of highly filtered systems tend towards a Gaussian distribution, it does not claim they actually are Gaussian. Test results obtained at VRC with their newly developed kurtosis control technique clearly show that non-Gaussian distributions can indeed be created at product resonances, regardless of the Papoulis Rule.
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SAVIAC 2007 Presentation
Examining the Dynamic Range of Your Controller
Dynamic range is one of the fundamental metrics describing the capability of a shaker controller. We all know that dynamic range describes the span of small-to-large acceleration amplitude that can be properly controlled during a test. Since modern controllers are digital instruments, we also know the dynamic range to be six times the number of bits in the analog/digital converter. But what do we really know? Let's examine the dynamic range of a vibration controller more scientifically.
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Authors: George Fox Lang, Philip Van Baren Sound&Vibration, August 2007 pp 12-20.
The Missing Knob on Your Random Vibration Controller
Random vibration testing is the industry workhorse for simulating the environment for a broad range of products. Tests are typically specified by defining a spectrum shape and overall RMS amplitude. The test controller then causes a measured reference acceleration to match these specified parameters. The controller forces a shaped-random response with a normal or Gaussian amplitude distribution. However, experience has shown that such tests may be too conservative for some product/environment combinations. The test does not produce the same damage statistics observed in the field. Adding a third control dimension provides more realistic random vibration tests that better match the damage potential of the actual environment. That third dimension is kurtosis control, which matches the amplitude distribution of the test to that of the environment.
Author: Philip Van Baren Sound&Vibration October 2005 pp 2-7.
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The Third Dimension of Random Vibration Control
Random vibration testing is the industry workhorse for simulating the environment for a broad range of products. Tests are typically specified by defining a spectrum shape and overall RMS amplitude. The test controller then causes a measured reference acceleration to match these specified parameters. The controller forces a shaped-random response with a normal or Gaussian amplitude distribution. However, experience has shown that such tests may be too conservative for some product/environment combinations; the test does not produce the same damage statistics observed in the field. Adding a third control dimension provides more realistic random vibration tests that better match the damage potential of the actual environment. That third dimension is Kurtosis control, which matches the amplitude distribution of the test to that of the environment.
Author: Philip Van Baren
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Kurtosis - The missing dashboard knob.
Many test personnel have recognized that random testing, while good, has shortcomings when it comes to simulating the real-world environment. As a result, over the years, there have been many vibration testing method modifications to address these shortcomings. In the automotive world, technicians often see that random tests do not find product faults that should show up when vibration testing. To make random testing more effective, they sometimes take the random spectrum, and increase the level accoreding to their own internal, home-cooked formula. The level may be increased so the random peak g levels match the real world.
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Author: John Van Baren Test Magazine October/November 2005 pp 14-16
Test your product using sine or random?
As you know, in the vibration world, there are quite a few test "types" to which you can expose your product. The major choices are Sine, Random, Classical Shock, Transient Shock, Field Recorded Time History, Sine-on-Random, Random-on-Random and Sine-and-Random-on-Random. Frequently, our customers will request advice on which of these types of test to run on their product, and in particular, how to choose between the two most common test types: sine or random. Their desire is to know which test, sine or random, is best to most quickly pinpoint flaws in their product. If they can only run one test, either sine or random, which should it be? Recently, we received an even more specific request from a customer. This customer (Don) presented both a sine test and a random test and wanted to know, given both a sine test and a random test, how he could determine which is the most severe?
Authors: John Van Baren, Philip Van Baren Test Magazine June/July 2004
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What Is Random?
There is a degree of confusion about the different kinds of vibration tests available to the vibration testing engineer. Difficulties encountered usually center on the difference between sinusoidal vibration (sine testing) and random vibration testing
Ask the IEST Testing Experts
How do I get the peak levels back up to 120 G peaks when running my random profile? There are several solutions implemented in the real world to "solve" this issue.
Author: John Van Baren Test Magazine August/September 2007
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A Comparison of Simultaneous and Sequential Single-axis Durability Testing
This article appeared in Experimental Techniques
Volume 30 Issue 5 Page 32 - September/October 2006
Authors: R.M. French, R. Handy, H.L. Cooper (2006)
Experimental Techniques 30 (5), 32–37.
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Slide Decks
This article appeared in the August 2000 issue of Shoreline Business Monthly and is reprinted by permission.
Good vibrations keeps shakers rolling at Hudsonville firm
by Rod Kackley - SBM Staff Writer
HUDSONVILLE --- Shake, rattle and roll. Not only is that phrase part of one of the classic songs of the '50s, it also can be used to describe an important part of the manufacturing process: vibration testing.
Vibration Research Corporation (Vibration Research Corporation), a Hudsonville company founded six years ago by John Van Baren, is rolling unshakably as a major player in that segment of the manufacturing business. The firm's customer list includes such Michigan industrial stalwarts as Ford Motor Co., General Motors Corp. and BF Goodrich Aerospace along with more exotic clients like the Naval Research Laboratory in Washington, D.C. and firms in Canada, Taiwan, Brazil and Italy.
The purpose of Vibration Research Corporation is to help customers find fault with and flaws in what they produce before it reaches the customer. His primary market is described as "retro-fit," replacing the old with the new.
"Over the years vibration equipment has worked well, but big advances have been made in the instrumentation that goes on that equipment. It used to be very expensive, run with expensive analog computers and then expensive digital computers. But with the advent of digital signal processing and fast computers it's a natural fit to replace all that expensive, antiquated, hard to run equipment with less expensive, easy to use PC-based equipment," Van Baren told SBM. "Thanks to the computer revolution, we have taken the price to one-fourth of what it used to be and increased the capability ten-fold."
Vibration Research Corporation engineers and sells vibration analysis, testing, monitoring and controller systems for electro-dynamic and servo-hydraulic shakers. The firm has developed its signature product, the Vibration View system, which consists of an analog I/O box, a digital signal processing card, a personal computer and software to run the system. The system provides all standard types of tests including sine, random, sine-on-random and classical shock. It also provides a system check that can be used to test and calibrate a shaker system. Vibration Research Corporation's customers hook that system up to their own testing gear to analyze data on a product before it goes to market.
Van Baren, who cut his vibration testing teeth during a 15-year tenure at now competitor Thermotron Industries, operates two offices. Vibration Research Corporation's headquarters are in Hudsonville with a companion office in Ann Arbor. The latter was opened less than two years ago to better serve Vibration Research Corporation's automotive industry customers. That segment of the business is increasing in importance because the Japanese auto industry taught American car companies a valuable dollars-and-cents lesson about the need for vibration testing. "They (American automakers) will put cars together and actually shake them from the component level to whole cars," said Van Baren of the automakers demands. "They will vibrate it to see how it performs. And they are now doing what we call squeak and rattle testing just to see if it makes any noise. They measure the sound level."
In 1995 Vibration Research Corporation broke new ground in vibration research with the development of Field Data Replication (FDR). FDR has become very popular with the automotive industry. Said Van Baren, "This technology allows you to go out into the field and measure your vibration levels and then take that vibration back into the lab and repeat that exact waveform on your shaker." Vibration Research Corporation was the first first firm to make the technology available on a single-axis shaker system. "Since then all of our competitors have copied it or attempted to copy it. But we still do it better, and I can prove that," Van Baren stressed.
Vibration Research Corporation's founder offered a broad brush view of the company's future. "For any company to be successful it has to grow. That would naturally mean more offices, more people and more products."
He envisions an expansion of the Vibration Research Corporation product line based on new customer needs and demands, plans for which are already under development. Van Baren revealed he is also working on forming strategic alliances with companies that actually manufacture the shaker systems.
