flexible graphite, cap plasticity models, compacted media, identification, basic experiments

. The development of a method for experimental determination of the plastic properties of thermally expanded graphite sheets (flexible graphite) under compressive medium stresses is the subject of this study. This problem is practically not reflected in publications, with the exception of several that offer uniaxial tension and indentation tests for its solution. The conditions of manufacture and operation of sealing elements and uniformity of stress-strain state in the specimen is allowed to allocate a range of suitable tests (all-round and triaxial compression of cylinder, free and constrained compression of cylinder, compression of cylinder in an elastic pipe and compression of parallelepiped in the channel), the samples which have the form of a solid cylinder or cube and is made of discs or squares cut from the sheet. For rings made by winding graphite foil on a cylindrical core with subsequent axial compression in the matrix, tests are additionally offered for all-round compression, axial compression in the gap between the outer and inner elastic cylindrical shells, as well as stretching in half-disks. A feature of the plastic properties of flexible graphite is its dilatancy, that is coupling of shear and volumetric plastic strains. A review of the relevant models was performed, as a result of which DiMaggio and Sandler cap model was selected, its material functions and constants were associated with the values measured and controlled in the above tests. The excessive amount of data allows us to check the adequacy of the application of the cap model to describe the plastic properties of flexible graphite.

Adamov Anatoliy Arsangaleevich, Dr. Sci. Phys. & Math., Senior Researcher, Leading Researcher, Institute of Continuous Media Mechanics of UB RAS, Perm, Russia.

Keller Ilya Ernstovich, Dr. Sci. Phys. & Math., Associated Professor, Head of laboratory, Institute of Continuous Media Mechanics of UB RAS, Perm, Russia.

Podkina Nataliya Sergeevna, Head of the test area, JSC “Sealur”, Perm, Russia.