Chaotic responses of unbalanced rotor/bearing/stator systems with looseness or rubs

Time–frequency features of two types of coupled rub-impact faults in rotor systems

“…There is only crack fault and the corresponding frequency component is 1X and 2X in 14.25-14.6 s. Slight rub-impact occurs near 14.6 s and the system motion is period-three (P3) motion. Meanwhile, 1 3 -based fractional harmonic components such as 1X/3 and 2X/3 can be observed, which shows that high energy impacts appear in high frequency domain. With the increase of rotational speed, the motion changes from period-three (P3) to periodtwo (P2) near 15 s. During period-two motion, the frequency spectrum is composed of 1 2 -based fractional harmonic components and impacts with higher frequency components occur, which can also be observed in Fig.…”

“…12. The frequency spectrum is mainly composed of 1 2 -based fractional harmonic components and 1X/4 can also be observed with small amplitude, as shown in Fig. 12(a) Table 4 An experimental description of oil-film instability coupled with bearing rub-impact.…”

“…Some novel fault features are summarized as follows: for the crack coupled with rubimpact fault, we discovered the route to and out of chaos, which starts from period-three (P3) motion, transits to period-two (P2) motion, period-four (P4) motion, chaotic motion, and finally to period-one (P1) motion, corresponding to the process of starting from slight rub-impact, transit to serious rub-impact, finally to no rub-impact. The slight rub-impact induces 1 3 -, 1 2 -, and 1 4 -based fractional harmonic components, and the serious rub-impact can introduce irreducible and colored noise frequency components to the spectrum. The above results present a good supplement to the studies of Chu [4] by showing a chaotic path with changing rotational speed.…”

“…So far, rubimpact fault alone has been studied extensively, using various research methods. Muszynska [1] discussed chaotic responses of unbalanced rotor-bearing-stator systems with rubbing. The results showed that at low rotational speeds, the rotor's response exhibits 1X vibration as the lowest frequency component.…”

Chaos and Bifurcation in Nonlinear Inextensional Rotating Shafts

“…In one of early experiments in chaotic motion of rotor systems, Ehrich [2] observed period doubling routes to chaos in a rotor with dead-band nonlinearity. Up to now, many studies has been carried out in study of chaotic vibration in rotor-dynamics; for example chaotic responses due to rub-impacts in rotors has been studied in references [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]; the chaotic dynamics of rotors due to effects of bearing has been investigated in papers [18][19][20][21][22][23][24][25]. Most of these papers treated the rotor with strong nonlinearity.…”