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 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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