Vibration Research Corporation

Jenison, MI, United States

Vibration Research Corporation

Jenison, MI, United States

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Minderhoud J.,Vibration Research Corporation | Van Baren P.,Vibration Research Corporation
Sound and Vibration | Year: 2010

Vibration Research Corporation (VRC) has developed Kurtosion® process that allows resonant fatigue and simple static failure tests to be accelerated. Kurtosion® generates high-kurtosis random signals through a modulation process. First, a Gaussian white noise signal is generated, and this is amplitude modulated by a second random noise. The signal specifics of the second random signal determine the kurtosis of the result, which is then frequency shaped by the desired Demand and the measured H-1 frequency response of the shaker/amplifier/DUT electromechanical system. A general-application broadband profile such as NAVMAT can be used to identify fatigue-sensitive resonances and such testing can be accelerated in time by increasing the kurtosis of the controlled shake. The NAVMAT test specifies a 6gRMS random shake with a constant power spectral density (PSD) of 0.04 g 2/Hz between 80 and 350 Hz.


John,Vibration Research Corporation | Van Baren P.,Vibration Research Corporation
Sound and Vibration | Year: 2012

The accumulated damage that a product experiences in the field due to the variety of stresses placed upon it will eventually cause a failure. 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.


Van Baren J.,Vibration Research Corporation | Van Baren P.,Vibration Research Corporation
Sound and Vibration | Year: 2012

The transportation industry historically has used Gaussian random vibration to simulate real-world transportation environments. However, examination of field measurements reveals the environments to be non-Gaussian in nature. Consequently, transportation test engineers should simulate real-world environments using non-Gaussian random vibration. Non-Gaussian random vibration (kurtosis control) increases the number of large peak accelerations (arising in field measurements due, in part, to the pot-holes of typical roadways) that the Gaussian random vibration tests "average away" with their vibration controllers. By implementing kurtosis control, the transportation industry would be well on its way to making its laboratory simulation tests much more realistic. And this, in turn, would result in better packaging - putting more products in the customer's hands without damage.


Van Baren J.,Vibration Research Corporation
Sound and Vibration | Year: 2015

The Fatigue Damage Spectrum (FDS) function has been added to a vibration test controller in order to regulate the rate at which fatigue is induced into a unit under test without distorting the real-world Power Spectral Density (PSD) profile.


Van Baren J.,Vibration Research Corporation
Sound and Vibration | Year: 2012

John Van Baren, Vibration Research Corporation, Jenison, Michigan, US, shares his views on some of the features and advantages of the random vibration testing method. One of the main goals or uses of random vibration testing in the vibration testing industry is to bring a device under test (DUT) to failure. A company will desire to find out how a particular product can fail due to various environmental vibrations encountered by it. The company will simulate these vibrations on a shaker and operate their product under those conditions. Testing the product to failure will teach the company many important things about its product's weaknesses and ways to improve it. Random vibration is also more realistic than sinusoidal vibration testing, as it simultaneously includes all the forcing frequencies and simultaneously excites all the resonances of the product.


Van Baren P.,Vibration Research Corporation
Sound and Vibration | Year: 2012

Control and conduct of a random vibration test is all about probabilities. What is the chance of any single PSD spectral line being less than X? More than Y? What percentage of the test time will the amplitude at any frequency be between X and Y? Well established statistical calculations answer these important questions. In this article we present various procedures for determining the statistical properties of random waveforms. Probability and confidence interval tables are introduced for common degrees of freedom.


Dejong R.,Calvin Engineering | Jung S.G.,Calvin College | Van Baren J.,Vibration Research Corporation
SAE Technical Papers | Year: 2016

Methods for conducting accelerated vibration fatigue testing of structures, such as MIL-STD-810G, allow for the non-linear scaling of the test time with the inverse of the rms vibration amplitude based on the slope of the material S-N curve obtained from cyclic fatigue tests. The Fatigue Damage Spectrum (FDS) is used as a method to allow for different level scalings at different frequencies in a broadband vibration environment using the relative responses of resonances in the structure. A recent development in industry has been to mix impulses with random excitations to increase the vibration peak levels (as measured by the kurtosis), thereby accelerating the fatigue even more than would occur with a Gaussian excitation. This paper presents results from a study to determine the conditions under which high kurtosis, impulsive excitations actually produce high kurtosis responses in structural resonances thus increasing the level of the FDS. © 2016 SAE International.


Minderhoud J.,Vibration Research Corporation
Sound and Vibration | Year: 2013

The use of automatic phase/frequency control for sine resonance track-and-dwell (SRTD) tests is proposed. the technique makes fatigue tests consistent with real-life excitations.


Van Baren J.,Vibration Research Corporation
SAE Technical Papers | Year: 2015

Random vibration control systems produce a PSD plot by averaging FFTs. Modern controllers can set the Degrees of Freedom (DOF), which is a measure of the amount of averaging to use to estimate the PSD. The PSD is a way to present a random signal-which by nature "bounces" about the mean, at times making high excursions from the mean-in a format that makes it easy to determine the validity of a test. This process takes time as many frames of data are collected in order to generate the PSD estimate, and a test can appear to be out of tolerance until the controller has enough data to estimate the PSD with a sufficient level of confidence. Something is awry with a PSD estimate that achieves total in-tolerance immediately after starting or during level changes, and this can create dangerous over or under test conditions within specific frequency bands and should be avoided. This paper intends to treat some of the inherent properties of the PSD and some faulty PSD estimation methods that attempt to circumvent these inherent properties. Copyright © 2015 SAE International.


An apparatus, system and method for estimating power spectral density (PSD). A processing apparatus and a test system are operatively coupled where a random signal generator produces a source signal comprising known statistical properties, and a first converter converts the source signal to a power spectral density (PSD) representation. The test system receives the source signal and produce an output signal, where a second converter converts the output signal to a second PSD representation, and an estimator estimates a magnitude-squared frequency response function (MSFRF) of the output signal and source signal. A weighting module may weight an estimation error factor based on at least one of a quality of the estimate and a user preference, and a removal module, removes a portion of the estimation error from the output signal PSD.

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