EVALUATION OF SEALING PERFORMANCE OF METAL GASKETS USED IN DUAL PURPOSE METAL CASK UNDER NORMAL TRANSPORT CONDITION CONSIDERING AGEING OF METAL GASKETS UNDER LONG-TERM STORAGE

If a metal gasket used in a dual purpose metal cask was subjected to high temperature for a long term, the residual linear loads and total spring back distance of a metal gasket might decrease due to the creep deformation of the outer jacket made of soft metal. Therefore, when the cask would receive the vibration force during normal transport operation on land or sea, the sealing performance of metal gaskets might be affected. In this paper, to examine the compressive creep characteristics of the outer jacket made of a 99.5% pure aluminum with a heat treatment, the compressive creep tests were executed under various levels of stresses, temperatures and loading durations. Based on these test results, a creep constitutive model was proposed. Moreover, in order to establish the numerical methodology of the ageing phenomena on sealing performance of the metal gasket over the long term, the compressive creep characteristics of the aluminum were introduced in the Finite Element Method code(ABAQUS), as a user subroutine. A relaxation analysis was performed considering actual over-all gasket complex configuration to calculate residual linear loads and total spring back distance of the metal gasket for a storage period of 60 years. In order to evaluate the deformation response of the metal gasket subjected to the acceleration profile measured during an actual sea transport, the impact analysis by LS-DYNA code was executed. As a result, it was found that the opening displacement of the gasket was negligible as compared with the evaluated spring back distance of metal gasket used for 60 years.