Abstract:
After the review of the
predictive methods
in the high temperature
fatigue field the
characterization of the low
cycle
fatigue behaviour
of a nickel superalloy,
t4ARMOO2, is
carried out using one of
those
predictive methods, the Strainranqe Partitioning method.
The basic
concepts and procedures of
this method are reviewed and applied
to
NARt"O02 over the
range
750°
-
1040 C.
-These'procedures
invol
ed
the determination
of the four basic life
relationships at
P50 C
and 1040°C
and their
use
in
conjunction with a
damage rule were
then employed to assess the degree
of
insensitivity of the four
basic
strainrange versus life
relationships
to test temperature.
Three damage rules and the assumptions
behind them are
discussed
within the context of their application with
the Stra i
nrange
Partitioning
approach. An
alternative analysis
based
on
Ostergren's
method is
studied
in
a separate chapter and proved to be
an easy
and helpful
method
in
predicting high temperature lot.,
cycle
fatigue
of several superalloys.
The
characterization of the
creep-fatigue
behaviour
of
1,4F. RP"002 was
completed
by
separation of
initiation
and propagation periods within
two temperature intervals. A
situation of earl
formation
of cracks
at the higher temperature intervaa
950°-
l040 C
with accelerated
growth. at
lower tennperatures 750
-
250oC showed that great care
is
necessary when applying
MAPP"002 isothermal results to cases
where
temperature
varies.
