Environmental Engineering Reference
In-Depth Information
4.4
The integrity-failure diagram: A - a point that reflects the
work of construction; F is the critical point.
i
i
occur if the point with coordinates
K
t t
is situated inside the
region bounded by the curve described by the expression similar
to [4.49]. In this case,
( , ()
r
1
r
1
i
r
K
t
and
i
r
S
t
are calculated differently:
()
()
i
i
i
i
i
i
t= tl t t=st t
There is no critical crack growth in the zone of ductile fracture leading
to the formation of a continuous crack (the yielding of the bridge between
the crack and the back surface) if
69
K
()
K
( )/
K
( ; ()
S
()/ ( .
R
r
1
r
C
1
r
1
eq
1
F
1
i
i
i
st
()< ()
k
t
R
,
[4.50]
1
F
1
p
0.2
i
F
k
t
is the attenuation coefficient for the
i
i-th element at time τ
l
,
(determined in accordance with Ref. 69); σ
i
(τ
l
) are the total tensile stresses
in the
i
i-th element at time τ
l
.
According to Ref. 69, critical crack growth, leading to large-scale
destruction (plastic instability in the cross section with a crack), does not
occur if
where
()
[4.51]
i
i
i i
st
()< ()
k
t ηt
R
( ,
1
F
1
F
1
i
i
RR
k
RR
(
)
0.2
i
m
m
where
ηt
()=
−
−
11
− t
() .
In determining the probability of structural failure, it is necessary to
define:
- conditional probability of the formation of a through-wall defect
and large-scale destruction from a single defect in the element under the
condition of occurrence of a calculated event
CE
k
;
- conditional probability of a through-wall defect and large-scale
destruction by the effect of several defects in the element under the
1
F
1
i
i
p
F
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