Research Papers: Hydrodynamic Lubrication

Structural Stiffness of X-750 Alloy Bump Foil Strips for Compliant Foil Bearings With Different Heat Treatments

[+] Author and Article Information
Wenbo Duan

State Key Laboratory of Strength
and Vibration for Mechanical Structures,
Xi'an Jiaotong University,
Xi'an, Shaanxi 710049, China
e-mail: jeffery2056@163.com

Yanhua Sun

State Key Laboratory of Strength
and Vibration for Mechanical Structures,
Xi'an Jiaotong University,
Xi'an, Shaanxi 710049, China
e-mail: sunyanhua@mail.xjtu.edu.cn

Chunhua Ding

State Key Laboratory of Strength
and Vibration for Mechanical Structures,
Xi'an Jiaotong University,
Xi'an, Shaanxi 710049, China
e-mail: chding@mail.xjtu.edu.cn

Lie Yu

State Key Laboratory of Strength
and Vibration for Mechanical Structures,
Xi'an Jiaotong University,
Xi'an, Shaanxi 710049, China
e-mail: yulie001@126.com

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received April 27, 2015; final manuscript received December 12, 2015; published online March 22, 2016. Assoc. Editor: Daejong Kim.

J. Tribol 138(3), 031702 (Mar 22, 2016) (5 pages) Paper No: TRIB-15-1153; doi: 10.1115/1.4032350 History: Received April 27, 2015; Revised December 12, 2015

This paper focuses on the structural stiffness of bump foils which are used for compliant foil bearings with different heat treatments. After heat treatments in vacuum environments, the mechanical properties of the foil strips were tested, and the structural stiffness was estimated from the static load versus displacement curves obtained from the experiments. High cycle dynamic load tests were also applied to the bump foil under different cycle loads, and the shape of the foil was scanned after the tests to measure the height variation of the bumps. The results show that the modulus of elasticity and strength of Inconel X-750 strip with thickness of 0.1 mm after different treatments are lower than that with the thickness of 0.18 mm at room temperature. Moreover, the sample foil strips which have been treated with a lower solution anneal temperature at 980 °C (2 hrs) and precipitation heat treatment at 732 °C (16 hrs) have the largest modulus of elasticity and strength at room temperature. Therefore, heat treatments have a great influence on the structure stiffness of the bump foil. At last, the results of the high cycle dynamic load tests show that the bump foil with suitable heat treatment will have a good load capacity and stress-relaxation property.

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Fig. 2

The bump foil assembly on the fatigue machine: (a) the photograph of the bump foil assembly and (b) the schematic of the bump foil assembly

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Fig. 1

Specimen of the Inconel X-750 alloy foil strip and bump foils used in the tests: (a) specimen of the foil strip for tensile test and (b) bump foils for load test before heat treatments

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Fig. 3

Static load versus displacement of the bump foil with different heat treatments (1 Hz cycle frequency)

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Fig. 4

Local stiffness of the bump foil estimated from the data in Fig. 3

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Fig. 5

Height variation of the bumps during the cycle load test: (a) under different cycle loads with heat treatment No. 2 and (b) under 100 N–500 N load with different heat treatments

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Fig. 6

Section profiles of the bump foil with heat treatment No. 2: (a) profiles at different parts before test and (b) profiles under different cycle loads at the middle part



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