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 is 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.
Variable Frequency Vibration is the normal test specified for electronic components and assemblies. Typically the test consists of a platform driven by a simple harmonic motion from a minimum frequency to an upper frequency and return in an approximate logarithmic rate. The motion is usually limited to a peak amplitude at low frequencies and a maximum G level above a corner frequency. This corner frequency may be calculated from:
Where: a is gravitational units (G)
d is displacement of a p-p cycle (Inches)
f is frequency (Hz)
This cycle is typically repeated four times in each of three axes.