scholarly journals Nonlinear Vibrations of a Rotating Shaft Supported by a Magnetic Bearing : Critical Speed of 1/2-Order Subharmonic Oscillation

2004 ◽  
Vol 2004.42 (0) ◽  
pp. 183-184
Author(s):  
Shin MURAKAMI ◽  
Takashi IKEDA ◽  
Daisuke OCHI
Keyword(s):  
Critical Speed ◽  
Nonlinear Vibrations ◽  
Magnetic Bearing ◽  
Rotating Shaft ◽  
Subharmonic Oscillation

Forced Oscillations of Rotating Shaft With Nonlinear Spring Characteristics and Internal Damping: Subharmonic Oscillation of Order 1/3 and Entrainment

1999 ◽  
Author(s):  
Yukio Ishida ◽  
Shin Murakami
Keyword(s):  
Critical Region ◽  
Critical Speed ◽  
Forced Oscillations ◽  
Ball Bearings ◽  
Internal Damping ◽  
Rotating Shaft ◽  
Nonlinear Spring ◽  
Subharmonic Oscillation

Abstract An elastic rotating shaft supported by ball bearings may have nonlinear spring characteristics due to clearance and internal damping due to friction between the shaft and the bearings. In such a system, self-excited oscillations appear in the post critical region and nonlinear forced oscillations appear at various resonance points. In this paper, a phenomenon in the neighborhood of the critical speed of the subharmonic oscillation of order 1/3 of a forward whirling mode is discussed. It is clarified that, similar to the case of the subharmonic oscillation of order 1/2 of a forward whirling mode, an entrainment phenomenon appears due to the interplay between self-excited oscillations and forced oscillations.

Contact Whirling Vibration of a Rotating Shaft Supported by a Repulsive Magnetic Bearing and the Influence of the Axial Displacement on Its Suppression

2011 ◽  
Author(s):  
Tomohiro Sugai ◽  
Tsuyoshi Inoue ◽  
Yukio Ishida
Keyword(s):  
Rotational Speed ◽  
Critical Speed ◽  
Nonlinear Coefficient ◽  
Magnetic Bearing ◽  
Axial Displacement ◽  
Damping Coefficient ◽  
Rotating Shaft ◽  
Escape Speed

A rotating shaft supported by a repulsive magnetic bearing may contact with a backup bearing during the passage of the critical speed as the damping coefficient of the repulsive magnetic bearing is small. This paper investigates the contact vibration during passage of the critical speed. Particularly, the influence of the axial displacement of the repulsive magnetic bearing on the escape speed from the contact vibration is focused. As a result, it is clarified that the rotational speed of the escapement from the contact vibration decreases as the axial displacement increases. It is explained by the change of both the linear stiffness and nonlinear coefficient in the increase of the axial displacement.

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