Sinusoidal vibration (Test Fc) - mechanical endurance and resonance search.
The method provides a standardized procedure for determining the ability of components, equipment and other products to withstand specified severities of sinusoidal vibration. It reveals mechanical weaknesses and degradation of packaged or unpackaged specimens.
It is used to assess product acceptability, demonstrate mechanical endurance and investigate dynamic behavior (resonances). The standard allows components to be classified according to selected severity levels.
The test demonstrates that a specimen mounted as in service withstands harmonic vibration of specified amplitude over a specified frequency range for a specified duration without damage or loss of function. It also reveals critical frequencies (resonances).
Rolling-stock vibration is broadband random and railway standards test it using IEC 60068-2-64. An “IEC 60068-2-6” entry without frequency range, amplitude and duration does not allow severity to be assessed.
The specimen is mounted on the exciter according to IEC 60068-2-47. The control signal is taken at a reference point selected from control points on the fixture, table or specimen as close as possible to the mounting points.
Frequency is varied logarithmically, with a sweep rate of one octave per minute ±10%. Sequence: initial measurements, vibration response investigation (resonance search), endurance by sweeping over the specified frequency range or endurance at fixed frequencies (critical or predetermined), intermediate measurements, recovery and final measurements.
Amplitude is specified as displacement below the crossover frequency and acceleration above it; the standard’s nomograms use crossover frequencies of 8–10 Hz and 58–62 Hz. Amplitude tolerance at the reference point is ±15%, at control points ±25% up to 500 Hz and ±50% above 500 Hz; transverse motion does not exceed 50% of the specified amplitude up to 500 Hz and 100% above.
Severity consists of frequency range, amplitude (displacement/acceleration) and duration (number of sweep cycles or time), selected by the product specification.
Check the frequency range (Hz), amplitude (mm or m/s² / g), duration or number of sweep cycles and number of axes; only this complete set has comparative value. For rolling-stock equipment, IEC 61373 (ed. 3.0, 2026) normatively references IEC 60068-2-27, IEC 60068-2-47 and IEC 60068-2-64 (random vibration); an IEC 60068-2-6 statement does not replace IEC 61373 testing.
