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Research Papers: Applications

Thorough Observation of Real Contact Area of Copper Gaskets Using a Laser Microscope With a Wide Field of View

[+] Author and Article Information
Isami Nitta

Faculty of Engineering,
Mechanical and Production Engineering,
Niigata University,
Igarashi 2-nocho 8050,
Nishi-ku, Niigata, 950-2181, Japan
e-mail: nitta@eng.niigata-u.ac.jp

Yoshio Matsuzaki

Mechanical Engineering,
Ishikawa National College of Technology,
Kitachujo, Tsubata-machi, Kahoku-gun,
Ishikawa, 929-0392, Japan
e-mail: matsu@ishikawa-nct.ac.jp

Yosuke Tsukiyama, Shuichi Sakamoto

Faculty of Engineering,
Mechanical and Production Engineering,
Niigata University,
Igarashi 2-nocho 8050, Nishi-ku,
Niigata, 950-2181, Japan

Motoshi Horita

Mechanical Engineering,
Ishikawa National College of Technology,
Kitachujo, Tsubata-machi,
Kahoku-gun,
Ishikawa, 929-0392, Japan

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received November 6, 2012; final manuscript received April 20, 2013; published online June 24, 2013. Assoc. Editor: Robert Wood.

J. Tribol 135(4), 041103 (Jun 24, 2013) (7 pages) Paper No: TRIB-12-1193; doi: 10.1115/1.4024781 History: Received November 06, 2012; Revised April 20, 2013; Accepted June 01, 2013

To quantitatively predict the leakage rates of static metal seals, it is important to observe the real contact area at seal surfaces because the leakage path consists of the noncontact portions between the flange and gasket surfaces. In a previous study, we observed the real contact situation using a thin polymer film 1 μm in thickness. In the present study, we observed the real contact area on gasket surfaces using a laser microscope with a wide field of view. With this method, observation time over the whole gasket surface could be greatly reduced compared with conventional methods. The observations indicated that the leakage paths on the gasket surfaces were in the radial direction perpendicular to a lathe-turned groove and the circumferential direction along the groove. As the closing loads increased, the leakage paths in the radial direction disappeared and only the leakage path in the circumferential direction remained. When the closing loads increased further, the widths of the leakage paths at both the inside and outside on the gasket surface became narrower. The critical contact pressure where the leakage paths in the radial direction disappear was determined from the observation of the contact surface of the gasket. The leakage rates obtained from the experiments showed good agreement with the calculated values under the assumption of laminar flow along the turned groove over the critical contact pressure.

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References

Japanese Society of Tribologists, ed., 2001, Tribology Handbook, A. Designing, Yokendo Press, Japan, p. 274.
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Nitta, I., Matsuzaki, Y., and Ito, Y., 2005, “Observation of Real Contact Area at Gasket Surfaces Using the Thin PC film,” Trans. Jpn. Soc. Mech. Eng., Ser. C, 71(701), pp. 265–271 (in Japanese). [CrossRef]
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Figures

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Fig. 1

Outline of an assembly of a gasket and two flanges

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Fig. 2

Real contact area measured with a thin polymer film 1 μm in thickness at a contact pressure of 25 MPa. (a) Measured real contact area. (b) Schematic diagram of leakage paths in the circumferential and radial directions.

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Fig. 3

Real contact area. (a) Magnified image in Fig. 2(a); white arrows show breaks in the contact mark. (b) Real contact area at a higher contact pressure of 62 MPa; the breaks in the contact marks disappear.

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Fig. 4

Shapes and dimensions of the flange and gasket. (a) Flange. (b) Gasket.

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Fig. 5

Cross-section of the experimental apparatus

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Fig. 6

Profile curves of the specimens. (a) Flange. (b) Gasket.

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Fig. 7

Laser microscope with wide field of view and rotary table with the gasket. (a) Laser microscope with a gasket. (b) Layout of the laser beam and pixel data.

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Fig. 8

Gasket rotational direction and laser scanning direction during observation and acquired image of the gasket

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Fig. 9

Observed gasket images at contact pressures of (a) 6.7 MPa, (b) 12.4 MPa, (c) 24.5 MPa, (d) 49.0 MPa, and (e) 80.7 MPa

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Fig. 15

Leakage rate as a function of contact pressure, where calculated values were obtained under the assumption of perfect spiral laminar flow

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Fig. 14

Surface profile of the gasket fitted on that of the flange at a contact pressure of 49.0 MPa and the corresponding observed image of the gasket

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Fig. 13

Surface profiles of the gasket and flange. (a) Contact pressure, 6.7 MPa. (b) Contact pressure, 12.4 MPa. (c) Contact pressure, 24.5 MPa. (d) Contact pressure, 49.0 MPa. (e) Contact pressure, 80.7 MPa. (f) Image of 80.7 MPa. (g) Flange surface profile after application of a contact pressure of 80.7 MPa.

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Fig. 12

Observed image of gasket surface with the surface profile at a contact pressure of 6.7 MPa. Noncontact portions are indicated by white arrows.

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Fig. 11

Observed gasket images for contact pressure of 49.0 MPa, corresponding to a central angle of 15 deg. (a) Observed image. (b) Magnified image of (a).

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Fig. 10

Observed gasket images for contact pressure of 12.4 MPa, corresponding to a central angle of 15 deg. (a) Observed image. (b) Magnified image of (a).

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