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Research Papers

Effects of Typical Machining Errors on the Nonlinear Dynamic Characteristics of Rod-Fastened Rotor Bearing System

[+] Author and Article Information
Yi Liu

Key Laboratory of Education Ministry for Modern
Design and Rotor-Bearing System;
State Key Lab for Strength and
Vibration of Mechanical Structures,
Xi'an Jiaotong University,
No. 28, West Xianning Road,
Xi'an, Shaanxi, China
e-mail: sfzw0016@163.com

Heng Liu

Key Laboratory of Education Ministry for
Modern Design and Rotor-Bearing System;
State Key Lab for Strength and
Vibration of Mechanical Structures,
Xi'an Jiaotong University,
No. 28, West Xianning Road,
Xi'an, Shaanxi, China
e-mail: hengliu@mail.xjtu.edu.cn

Nanshan Wang

Key Laboratory of Education Ministry for
Modern Design and Rotor-Bearing System;
State Key Lab for Strength and
Vibration of Mechanical Structures,
Xi'an Jiaotong University,
No. 28, West Xianning Road,
Xi'an, Shaanxi, China
e-mail: tyus2012@163.com

1Corresponding author.

Contributed by the Technical Committee on Vibration and Sound of ASME for publication in the JOURNAL OF VIBRATION AND ACOUSTICS. Manuscript received October 28, 2015; final manuscript received August 21, 2016; published online October 25, 2016. Assoc. Editor: John Yu.

J. Vib. Acoust 139(1), 011004 (Oct 25, 2016) (10 pages) Paper No: VIB-15-1454; doi: 10.1115/1.4034768 History: Received October 28, 2015; Revised August 21, 2016

The effects of typical machining errors on the dynamic features of rod-fastened rotor bearing system (RBS) are studied in this paper. Three micron-sized machining errors are considered in a three-dimensional (3D) rod-fastened model. The static effects of machining errors are investigated by applying finite element method. Results demonstrate that machining errors not only bring about mass eccentricity but also cause obvious rotor bending due to large pretightening force. Then, nonlinear dynamic features such as stability and bifurcation are analyzed by using target-shooting technique, track-following method, and Floquet theory. Analysis data indicate that rotor bending originated from machining errors reduces the system stability evidently. It is also observed that the vibration value continues to go up after critical speed as rotating speed increases. It is a particular property compared with integral rotor. It explains the reason why the machining precision of rod-fastened rotor is much higher than that of the corresponding integral rotor to some extent. Moreover, differences between machining errors are compared and the results show that the machining precision of axial assembly interfaces should be paid more attention in the rod-fastened rotor design.

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References

Figures

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Fig. 1

Typical rod-fastened rotor bearing system

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Fig. 3

(a) Stress of rotors, (b) stress of disk b, and (c) stress of axial assembly interfaces at 7500 rpm

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Fig. 4

Mass eccentricity and axis-center displacement of diskb

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Fig. 5

Rotor bending due to the flatness error on disk b

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Fig. 6

Stability figure for both rotor RBS with flatness error

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Fig. 7

Vibration of both defective rotor RBS

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Fig. 9

Dynamic motions for both defective RBS: (a) period-doubling motion of rod-fastened RBS at 8470 rpm and (b) quasi-periodic motion of integral RBS at 7890 rpm

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Fig. 10

Poincare map of whirling motions

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Fig. 11

Frequency spectrums of both defective rotors

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Fig. 12

Deviation of circumferentially distributed rod-holes

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Fig. 13

Unevenly distributed stress of no. 4 rod

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Fig. 14

Mass eccentricity and axis-center displacement

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Fig. 15

Stability (a) and vibration (b) diagrams of both defective rotor RBS

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Fig. 16

Whirling motions of both defective rotors

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Fig. 17

Frequency spectrums of both defective rotors

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Fig. 18

Concentricity error of disks

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Fig. 19

Unevenly distributed stress of no. 4 rod

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Fig. 20

Mass eccentricity and axis-center displacement

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Fig. 21

Stability (a) and vibration (b) diagrams of both defective rotor RBS

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Fig. 22

Whirling motions of both defective rotors

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Fig. 23

Frequency spectrums of both defective rotors

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Fig. 24

Static and dynamic comparisons between different errors. (a) Axis-center displacement and mass eccentricity, (b) stability diagram, and (c) vibration diagram.

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Fig. 25

Vibration diagram of defective rod-fastened rotor with linear bearings

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Fig. 26

Rotor's motions at different rotating speeds

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