Random Vibration Testing

Vibration, by causing loosening of parts or relative motion between parts in the specimen, can produce objectionable operating characteristics, noise, wear, and physical distortion, and often results in fatigue and failure of mechanical parts.

The Vibration Test is used to determine the effects on component parts of vibration within the predominant frequency ranges and magnitudes that may be encountered during field service and/or transportation. Most vibrations encountered in field service and/or transportation are not of a simple harmonic nature, but tests based on vibrations of this type have proved satisfactory for determining critical frequencies, modes of vibration and other data necessary for planning protective steps against the effects of undue vibration.

Random Vibration is characteristic of modern field environments such as, for example, those produced by missiles, high-thrust jets and rocket engines. In these types of environments, the random vibration provides a more realistic test as it simulates vibration amplitudes which may vary randomly, periodically, or both. For design purposes, a swept frequency sinusoidal test may yield more pertinent design information such as resonant frequencies and modes.

Tooling is generally required to attach the component to the shaker platform. The tooling should allow the accelerometer to be mounted as close to the centerline of the component being shaken as possible. In addition, it is imperative that the tooling be run dry (without test components) in all three orientations to ascertain that the tooling does not have resonances in the frequency range of interest. Characterization of the tooling is recommended as a part of the calibration procedure before running components.

Various standards use different requirements, and are summarized here:

MIL-STD-202G for Electronic and Electrical Component Parts
Method 214A

MIL-STD-810F for Dept of Defense
Method 514.5

MIL-STD-883F for Microcircuits
Method 2026

Failure Analysis
If components fail during random vibration testing, Silicon Cert has the expertise and the equipment to perform complete failure mode analysis (FMA) utilizing cross-sectioning, electrical testing, Scanning Electron Microscopy (SEM w/EDAX), and CSAM providing a comprehensive report of the findings.