Year
2019
File Attachment
a1305_1.pdf1 MB
Abstract
The seal performance of dual purpose metal cask is ensured by bolted lid with metal gasket. When a metal gasket used in the cask is subjected to high temperature for a long term, it is necessary to take ageing effect of a metal gasket into account. The residual linear load and total spring back distance of a metal gasket might decrease due to the creep deformation of the outer jacket made of soft metal. To examine the compressive creep characteristics of the outer jacket made of aluminium with a heat treatment (A1050-O), 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 in the former paper. In this study, the creep constitutive model was re-evaluated. 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. Compared analysis results obtained by new model with the former results, effect of the creep constitutive model on the residual linear loads and total spring back distance was evaluated. In addition, effect of the friction coefficient between outer jacket and seal surface on the residual linear loads and total spring back distance was evaluated. Tensile strength of aluminium used for outer jacket of metal gasket changes because of ageing. One of the reasons of ageing of aluminum is grain growth. The sample of outer jacket used in the long-term seal test was observed metallographically. As a result, it was found that there is no big change of grain size.