Glass Fiber-Reinforced PTFE Gasketed-Joint Under a Retorque

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.