THERMO-MECHANICAL COUPLED SIMULATION OF RUBBER O-RINGS FOR MOX FRESH FUEL TRANSPORT PACKAGES

The containment performance of transport packages which apply rubber O-rings as their containment barrier depends on the stress relaxation and compression set of rubber O-rings. In this paper, to establish a prediction method for compression set of the EP rubber O-rings, a thermo-mechanical finite element analysis code was proposed. The proposed simulation code considers the coupling problem of heat conduction and mechanical deformation of rubber materials, simultaneously. The nonlinear viscoelastic model which apply hyperelasticity to the elastic part and viscous-dashpots to the time-dependent parts, was applied to the simulation code to predict the mechanical behavior in finite deformation and thermal-dependent stress relaxation. For numerical modelling, the biaxial-loading tests for EP rubber sheet specimens were conducted to verify the material modulus for hyperelasticity. Stress relaxation tests for EP rubber O-rings were conducted to verify the relationships between relaxation times and temperature. Finally, the accelerated thermal aging tests of EP rubber O-rings were conducted and the compression sets of EP rubber O-rings were measured. In this study, a concept of the accelerated thermal aging tests was applied to the experimental and numerical simulation method. The concept of the thermal accelerating test is that rather higher temperature than real one is applied to the specimen though the duration time is shorter the real situation. This cause is that progress of the plastic deformation and stress relaxation of rubber follows the Arrhenius equation. The compression sets of the EP rubber O-ring were simulated numerically, and simulated results shows good agreement with the experimental results.