Sinusoidal Vibration Testing

Dynamic deflections of materials caused by vibration can cause a host of problems and malfunctions including failed electrical components, deformed seals, optical and mechanical misalignment, cracked or broken structures, excessive electrical noise, electrical shorts, chafed wiring. Because sine vibration is basically a certain fundamental frequency and the harmonics of that fundamental, in its pure state, this type of vibration is generated by a limited but significant number of sources. Expressed as amplitude versus frequency, sine vibration is the type of vibration generated in the field by sources such as engine rotational speeds, propeller and turbine blade passage frequencies, rotor blade passage and launch vehicles.

While much of "real world" vibration is random, sine vibration testing accomplishes several important goals in product qualification and testing.

Much material and finished product was modeled on some type of sine vibe signature. A sine sweep of frequencies will determine whether the assumptions were correct and if the deviations are significant enough to cause design changes. In other words, sweep will establish if the anticipated frequency has been met and/or discovers the test item fundamental frequency.

Similarly, a sweep will help identify the test subject resonance frequencies, which may be the points at which the item experiences particularly stressful deflections. By dwelling at those frequencies in subsequent tests, premature failures due to the properties of the material may come to light before the items sees field use. Some of the following tests include fixed frequency at higher levels of the controlling variable (displacement, velocity, acceleration), and random vibration. Per customer request, NTS will run sweeps in one direction, decreasing, increasing or bi-directionally and can change frequency logarithmically or linearly.

Another typical sinusoidal vibration test, sine burst such as the teardrop, goes rapidly to peak pulse and then decays at lower rate (to prevent damage to the unit). The burst test puts a maximum load into an article at a rapid rate and particularly stresses joints and seams to identify workmanship and design issues.

NTS understand the uses of sine vibration and the parameters required to help you develop and perform a valid, useful test. We have extensive experience working with designers and manufacturers from all industries, including automotive, transportation, nuclear, aerospace and consumer.

NTS has extensive experience in vibe test fixturing, understanding how to locate and take into effect the test item's center of gravity and its placement in relationship to the driving mass of the armature and preventing side load issues.

Our engineers understand proper placement of accelerometers and force limiting instrumentation. Need high number of data channels? Our systems can accommodate 60 or more data channels and still give you the data right at the end of the test with a formal report following in less than two weeks. We're capable of frequencies from 0 Hz to 200 Hz on hydraulic shakers, and up to 5000Hz on electrodynamic shakers. and due to a large number of advanced, well maintained electrodynamic as well as hydrodynamic vibration equipment, can develop the right combination of frequency, displacement and acceleration to satisfy your vibe test requirements.

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