Experiencing rotor and fluid film bearing dynamics

Starting from fruitful past experiences on rolling bearing diagnostics, the research activity here presented has aimed since the beginning to investigate the physical phenomena that are at the base of experimental rotor dynamics, when fluid bearings are involved. An appropriate test bench was designed and a prototype assembled. The peculiarities of the test bench are the wide range of rotational speeds, the slender shaft with a massive inertia (like the Jeffcott rotor model), the adjustable resonance frequency, the motor-joint-rotor misalignment, and the chance to supply static pressure to the oil film in the bearings. An extended monitoring software was developed, which allows the tracking of flexible shaft orbit, in orthogonal sections, along its axis, which transforms the orbit signals into spectral contributions and does appropriate filtering. The main whirl and whip phenomena, together with misalignment, mass/inertia imbalances and resonant behaviour are thus investigated in detail. In particular, orbit shape and spectral content coming from a broad experimental campaign are reported and commented in details.