Creep is considered to be the life limiting damage mechanism in many load bearing high temperature
components. A range of different parameters determine the creep life of a component, many of which
are unlikely to be known to sufficient accuracy to enable
satisfactory estimation of remnant life.
Instead,
the integrity of a component
should
be established through direct measurement of the response of the
component to the operating conditions. Creep deformation is shown to be a positive feedback
mechanism;
an
increase
in strain lead
s
to
an
increasing strain rate. It has recently been shown that as a
consequence of positive feedback the Failure Forecast Method, a generalised framework for predicting
time to criticality based on
rates of change of damage
, may be
applied for remnant life calculations. A
range of strain rate based assessments have been proposed
in the
literature but it is proposed that the
Failure Forecast Method unifies many of these techniques and provides additional insight into creep
behaviour
by virtue of the underlying positive feedback.
The methodology has been demonstrated using
e
xperiment data
sets that are pertinent to creep in
high temperatu
re pressure vessels and piping; it is
shown that failure times are accurately predicted
shortly aft
er the minimum creep strain rate.