Identification and optimization of the constitutive model for die-formed expanded graphite for sealing applications
Résumé
The die-formed expanded graphite is used in industry for sealing applications subjected to extreme pressure and temperature. Its chemical inertness, excellent elastic recovery and adaptability to damaged flanges serves the sealing function. However, in some cases, the high load required for tightening leads to significant mechanical effects related to flanges bending or radial thrust. To address this effect and support the implementation of graphite seals investigations are performed to identify a constitutive model for that specific material and describe the interaction of these seals with their environment [1]. Instrumented axial die-compaction tests are performed to characterize the load-compression curve as well as the radial pressure from the sample [2], [3]. A methodology is then developed for the identification of the coefficients related to the constitutive model, assuming a Drucker-Prager Cap model, and especially the hardening behaviour, which drives the seals compression and unloading curves. The work is based on a parametric optimization and a numerical simulation close to the test device itself. The identified model is finally used for graphite seals simulation, to address mechanical interactions with their environment and comparison with tests performed with dedicated instrumented seals validate its relevance.