Mathematical modelling of usage conditions and refined strength analysis of flexible graphite o-ring seals

A thermomechanic model for initial operation mode description of large-series production seals (intended for plunger seal in the stop valves) is developed with the account of a cylindrical nature of anisotropy type, obtained experimental data for elastic, strength and thermophysical characteristics of flexible graphite (i.e. FG). It was supposed that o-ring seal is a thick-walled, limiting homogeneous transversally-isotropic cylinder fixed in an oil-seal housing by sealing bush. On one of the face surfaces pressure for hermetization has been set, and on the other end surface – work pressure. Axial displacements that modelled plunger reciprocation in burn-in regimes in the direction of a closing ring and in the opposite side have been set on the internal lateral surface. The influence of thermoforce loading conditions on the character of stress-strain distributions along cross-sections of FG o-ring seals and their packs has been investigated by the use of numerical FEM solutions of 3D stationary boundary-value problems. Calculations have been made of estimation of damage mechanisms (damage from tension or compression in radial, hoop and axial directions, and from transversal and antiplane shear) affection on initial strength, of a comparison of different loading modes (reciprocating motion in sealing bush or opposite direction) and slip conditions on contact surfaces between seals on the maximum values of radial, hoop, axial, and shear stresses. The locations of damaged domains obtained from experiments correspond with the results of o-ring seals exploitation.