RESIDUAL LIFE ASSESSMENT OF ELBOW WITH VOLUMETRIC SURFACE DEFECT UNDER CYCLIC INNER PRESSURE
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Transcript of RESIDUAL LIFE ASSESSMENT OF ELBOW WITH VOLUMETRIC SURFACE DEFECT UNDER CYCLIC INNER PRESSURE
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RESIDUAL LIFE ASSESSMENT OF ELBOW WITH VOLUMETRIC SURFACE DEFECT
UNDER CYCLIC INNER PRESSURE
Yukhymets Petr Sergejevich
Paton Welding Institute (Kiev)
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RESIDUAL LIFE ASSESSMENT
Defect and its modeling with half-ellipsoid
functioncurvitywhere
cb
hb
hb
cb
cb
cb
db
325
175,011
2313,048,012,12
12
)(
fKwhere
eeforKee
eeforee
e
ykaei
k
ykai
k
Stress concentation factor
Cyclic stress range
Fatigue curve
[N]
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Nominal strains
ei
straight pipe (circular ring, h=const) elbow (circular ring, h=const)
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Torus geometry
Elbows measuring results
Elbow №
Dmax, mm
Dmin, mm
Ovalityα*, %
Thickness range h, mm
I 109,7 108,0 ~1,6 5,7-6,4
II 109,1 108,1 ~0,9 5,4-6,8
III 109,6 108,2 ~1,3 5,8-6,7
IV 109,7 108,4 ~1,2 5,4-6,8
nD
DD
DD
DD minmax
minmax
minmax 100200
5.5
6
6.5
76.7
5.8
h2
U2 x( )
7
4
0 1 x
Th
icn
ess
, m
m
φ, rad
Elbow III thickness distributionextended zone
compressed zone
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Torus damage modeling
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Experimental and calculated strains
1.57 0 1.57 3.14 4.71 6.2820
40
60
80
100
120
140
160141.3
27.123
ek1
ek2
ek3
ek4
a
os 1( )
oc ( )
ov ( )
oo ( )
o1s ( )
upr ( )
6.283
2
3 3 3 3 1
σφ,
MP
a
φ, rad
Cross section model Cross section scheme
Circular ring,
h = const
Circular ring,
h = variable
Elliptical ring, h = const
Elliptical ring, h = variable
NNP NNP corrected
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Experiment details
Nominal stress determination method
Δek х10-6
NNP 17,77
NNP corrected 13.12
Elliptical cross-section, h = const
12,07
Experiment 8,27
Strain rate on the defect surface (P=0.1 MPa)
Fatigue crack
Ni, cycle Stress concentration, ασ
ΔP, MPa
10 000 2,53 6
6 500 5,25 19
Load history
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Fatigue damage estimation
Method Damage,
df
NNP 20,20
NNP corrected 4,60
Elliptical,
h = const
3,08
1 10 100 1 103
1 104
1 105
1 106
1 103
1 104
1 105
1 106
3.388 105
2.433 103
a1 N( )
10000001 N
σa,
MP
a
N, cycle
Fatigue curve (σt = 524 MPa, σy = 327 MPa, Ψ = 49%)