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Research Papers

Glass Fiber-Reinforced PTFE Gasketed-Joint Under a Retorque

[+] Author and Article Information
James P. Williams

Department of Mechanical and
Aerospace Engineering,
University of Central Florida,
Orlando, FL 32816
e-mail: jwghw@knights.ucf.edu

Addi-Neequie Stone, Ryan Reedy, Ali P. Gordon

Department of Mechanical and
Aerospace Engineering,
University of Central Florida,
Orlando, FL 32816

1Corresponding author.

Manuscript received February 5, 2017; final manuscript received December 6, 2018; published online February 21, 2019. Assoc. Editor: Sayed Nassar.

J. Pressure Vessel Technol 141(2), 021001 (Feb 21, 2019) (11 pages) Paper No: PVT-17-1023; doi: 10.1115/1.4042219 History: Received February 05, 2017; Revised December 06, 2018

Joints gasketed with viscoelastic seals often receive an application of a secondary torque, i.e., retorque, in order to ensure joint tightness and proper sealing. The importance of understanding gasketed joint behavior under various loading conditions and test parameters is paramount to a successful design. The motivation of this study is to characterize and analytically model the initial and retorque load relaxation response of a single 25% glass-fiber reinforced polytetrafluorethylene (PTFE) gasket-bolted joint with serrated flange detail by a single set of experimentally determined modeling constants. The Burger-type viscoelastic modeling constants of the material are obtained through optimization from a baseline load relaxation data and compared to a variety of test cases for both initial and reloadings. Determination of a retorque parameter, α, allowing modeling constants identified from an initial loading to predict the retorque relaxation showed the retarded elasticity or K2 term to be most influential in predicting retorque response. Finally, the validity of the viscoelastic model with the retorque parameter is shown to reasonably predict retorque relaxation responses of all test cases investigated.

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References

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Figures

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Fig. 5

Components of the experimental setup (relaxometer)

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Fig. 4

Ground umbilical carrier plate: (left) shrouded connection and (right) flange assembly

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Fig. 3

Microstructure of the PTFE-based gasket with 25% fiberglass prior to application of mechanical loading

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Fig. 2

Schematic of the four element Burger viscoelastic constitutive model, depicting the relationship between the Kelvin and Maxwell elements

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Fig. 1

Nomenclature of torque and retorque relaxation response

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Fig. 6

Dimensioned platens and specimens

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Fig. 7

Micrograph of 0.0625 in.-thick E-600 specimen loaded between serrated platens

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Fig. 8

Evolution of the microstructure of the PTFE-based gasket with 25% fiberglass after 24 h of loading

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Fig. 9

Effect of complete unloading

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Fig. 10

24 h–24 h baseline test and the effect of multiple loadings (primary, secondary, tertiary, and quaternary torques)

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Fig. 13

Data and modeling of the initial dwell period at a desired torque of T1= T2 = 226 in.-lb: (a) linear scale and (b) semilog scale

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Fig. 11

Data and modeling of the effect of torque level

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Fig. 12

Data and modeling of the gasket thickness under a desired torque of 226 in.-lb: (a) linear scale and (b) semilog scale

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Fig. 14

Effect of load-up histories and initial dwell time

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Fig. 15

Retorque factor versus the number of retorques for the stiffness (Kn) and damping (Cn) modeling constants

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