| Summary: | 碩士 === 大葉工學院 === 機械工程研究所 === 84 === ABSTRACT In this work, the creep and creep rupture behavior of
both the spherical vessel and rotating disk, subjected to an
internal pressure, are studied indetails based on the local
continuum damage mechanicss approach using the element
technique. A strained-controlled creep rupture creep damage law
is derived from a more complex strained-dependent creep damage
law. This law expresses creep damage solely in terms of creep
strain, which indicates the creep strain is the only factor
controlling the creep damage. Based on this one-dimensional
creep damage law, a multi-dimensional creep damage law is
postulatedusing respectively the maximum principal tensile
strain criterion, the maximum principal tensile stress
criterion, the maximum octahedral shear stress criterion and the
mixed criterion. The solution procedure models the development
of creep damage, due to the accumulation of creep strain, and
involves the repetive solution for the associatedboundary-value
problem, which consists of two successive time period of damage.
While it is a typical boundary-vvalue problems for the first
period, it becomesa moving boundary-value problems for the
second period. During the first periodwhen the local value of
creep damage throughout the vessel is less than a criticalvalue,
the stresses redistribute and the damage developes
monotonically. Duringthe second period, an initial rupture
front propagates through the member and which leads eventually
to a complete collapse. Finally, partial analytical solution
for the spherical vessel is derived and used to verify the
validity of the numericalresults obtained.
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