321 / 392
317
In Eq. (2) the
e
K
factor,
K
mat
.
This quantity is o
fracture resistance of the material is used in terms of th
btained formally from the
J
–integral or CTOD by
2
2
(1 )
(1 )
y mat
mat
mat
E
J E
K
σ δ
ν
ν
=
=
−
−
(31)
The SINTAP procedure includes different analy
main difference
ween these levels is the function
f
(
L
r
). It is defined s ch that lower levels can be app
eve
sis levels. The
u
bet-
lied
n with relatively poor input information. Due to this, the output is more conservative
as compared with more advanced levels which require more detailed input information,
but “reward” the user with more realistic results. The Default Level is the lowest level of
the SINTAP procedure. Its use is recommended only if no other data than the yield
strength of the material and the Charpy data are available.
The function
f
(
L
r
), which is the same for both FAD and CDF routes, is given by:
–
In cases where the material exhibits a Lüders strain
1/ 2
2
1
−
⎛
⎞
max
( ) 1
2
r
r
f L
L
= +
⎜
⎟
⎝
⎠
for 0
≤
L
r
≤
L
r
(32)
The cut-off
L
r
max
is defined in a conservative m
–
I
lure assessment curve
f
(
L
r
) is
described by the equation
anner as
1
max
r
L
=
(33)
f the material does not exhibit a Lüders strain, the fai
1/ 2
2
6
1
( ) 1
0.3 0.7exp( 0.6 )
2
r
r
r
f L
L
L
−
⎛
⎞ ⎡
⎤
= +
+
−
⎜
⎟ ⎣
⎦
The cut-off
L
r
max
is defined slightly less conservatively as
⎝
⎠
for 0
≤
L
r
≤
L
r
max
(34)
2.5
0.2
1
max
r
p
L
R
= +
⎜
⎟
⎜
⎟
⎝
⎠
150
⎛
⎞
(35)
1.10. Fracture Toughness
The fracture toughness was determined in terms of the crack tip opening displacement
ritish standard BS 7448, Part 1, [10]. Four tests were carried
ou
1.1
Default Level assessment.
Nine tests have been carried out at three temperatures. The result is summarised in
Table 2. The SINTAP analysis was based on the minimum room temperature Charpy
energy of 6 J.
CTOD (
δ
) according to the B
t using three-point bend specimens at room temperature. The test setup is shown in
Fig. 18, and a typical test record in Fig. 19. It shows typical pop-in behaviour. Pop-ins are
cleavage fracture events disrupting the ductile tearing process. The crack is arrested
subsequent to each pop-in. Note, however, that the specimen is subjected to displacement
control in the test machine whereas in reality load control might occur. Usually the crack
would not be arrested in such a case, but cause failure. Therefore, no benefit can be taken
from the crack arrest following a pop-in which was specified as such by the test standard.
For SINTAP analyses the lowest of the pop-in fracture toughness values was chosen.
This was
δ
c
= 0.02 mm or corresponding
K
mat
= 49.7 MPa√m.
1. Charpy energy
Information on the Charpy energy is necessary for SINTAP