In this paper, the author studies the specific motion of mechanical system with low rates of mass variation. A variable mass–spring system has been developed using different materials for discharging (sand and gravel). Experimental procedure involves monitoring of the dynamics of expansion tank within the system configuration, along vertical direction, during the flow process of two materials. The spectral analysis of acquired acceleration, in terms of spectrum magnitudes and joint time-frequency spectrogram respectively, was considered, in order to evaluate the mass flow-rate equation. Comparative analysis between experimental and computational mass variation laws was performed, based on the tests acquirements and, respectively, on the available literature information.

Key words: variable mass system, experimental analysis, dynamics, mass flow-rate law, spectral analysis.

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