Random Vibration Testing

The legitimacy of random vibration as an effective tool of screening workmanship defects came about during the first manned spacecraft programs. Up until that point, limited Hertz sine vibration was applied during reliability testing. Pure sinusoidal vibration is composed of a single frequency at any given time. Comparison tests revealed that to equal the effectiveness of random vibration, the test items will have to be subjected to many sine frequencies over a longer period of time, and may unintentionally fatigue the test item. Random vibration uncovers defects faster.

Real world simulation
Most vibration in the real world is random. For example, vehicle traveling over roads experiences random vibration from the roads irregularities. A ground-launched rocket vehicle experiences non-stationary vibration during its flight - the motor ignites, the rocket travels through the atmosphere, the motor burn ends, and so forth. Even a wing, when subjected to turbulent airflow, undergoes a random vibration response. Among items typically tested with random vibration are motorcycle component, jet engines, cruise missiles, catalytic converters and any products that will see transportation.

Random vibration is composed of multitude of, a continuous spectrum of, frequencies. Motion varies randomly with time. It can be presented in the frequency domain by a power spectral density function [G2/Hz where G is GRMS]. If real world data exists, NTS can use these measurements to develop a profile and implement testing. With just general predictions, NTS can estimate PSD with a formula PSD = g2/Hz or PSD = g2/(freqend  freqstart).

NTS Random Vibe Capabilities
NTS is capable of generating up to 70,000 force pounds with tandem shakers and up to 45,000 force pounds on a single shaker. NTS has performed testing in excess of 200 GRMS in a single band. and can hook up in excess of 100 data channels. 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.

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