extra 3d crack growth
TRANSCRIPT
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Simulation of 3D Crack Growth
Thin Shells
3D Solids
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NONLINEARITIES:Predicted Curvilinear Fatigue Crack Growth
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Early Damage Tolerance Testing
on B-707 Fuselage
Single Bay Flaps
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Life Prediction in Transmission Gears
Project: NASA Lewis NAG3-1993 Allison 250-C30R Engine
U.S. Army OH-51 Kiowa
Fatigue Cracks in Spiral Bevel
Power Transmission Gear
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Geometry Update for Crack Growth
1) based on the stress intensity factors
and a growth model, new crack frontpoints are determined
2) a best-fit polynomial space curve is
fit through the new crack front points
3) edges and faces are added to connect the old
crack front to the new front
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Geometry Update for Crack Growth:
some difficult cases
new crackfront points
circularcutting
plane
r
fitted curve
oldcrackfront
intersectionpoint
crossing patch boundaries reentrant corners alongthe crack mouthreentrant corners along
the crack front
predicted fronts
that do not intersect
surfaces
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Geometry for the Demonstration Analysis
CrackTip 1
projection onto Section A - A
a2
a1
1.5"
initial notch
crack
.508"
a3
Crack
Tip 2
p 11.54 kips, R = 0.214
2.412"
3"
2"
A
A
12"
bottom view
side view
45 angleview 1
view 2
0.25R" EDM
flaw
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Solid Geometry Models
OSM Geometry
Model
Inserted Initial
Flaw
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Initial Boundary Element Mesh
Full Beam
Initial FlawFlaw Mouth
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Predicted and Observed Crack Fronts
a
Predicted Transition into Corner a
ba
Final Fatigue Crack Front
b
Predicted Transition into Corner b
Observed Fatigue Crack Shape
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Final Predicted Crack Shape
DeformedSolid
bottom face sideside
initialcrack
ExperimentFRANC3DComparison of
computed andobserved crack trace
on the surface
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A Computed SIF History and Comparisons
to Observations
B
A
a1 a2
Event Observed FRANC3D %Difference
a-Corner (cycles) 106,800 140,000 32
b-Corner (cycles) 171,000 170,000 -0.5
Last Front (cycles) 175,000 190,000 8.5
a1 (in.) 1.26 1.42 12.7a2 (in.) 1.38 1.34 -2.8
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GGGGGGGGGGGGGGGGGGGGGGGGGG
GGGGGGGG
GGG
GG
GG
G
G
JJJJ
JJ
J
J
H
H
0
0.5
1
1.5
2
2.5
3
3.5
4
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
F
a / r
Experimental
BES, applied stress
BES, applied displacements
K= S a F
a = a / cos(20)ar
0.09"
0.045"
50
r
nh
h = 0.005"
Countersunk Rivet-hole
Assumed circular crack front
Comparison of boundary element
computed and experimentally
observed results.
Crack location
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Thermal fatigue
in a housing
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A Cylindrical Shell with an Arbitrarily Oriented, Through-
Crack Subjected to Internal Pressure:
Comparison of BEM and FEM Solutions
P = 1
R = 10t = 1
a = 2
= 20 degrees = 0.3
R
2a
Pt
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Boundary Element and Finite Element Models of a
Cracked Tube
17,061 10-noded tetrahedral elements:
1 SP processor, 2.5 hours wall clock time
FEM8,696 3-noded triangular elements:
24 SP processors, 7 hours wall clock time
BEM
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Mode-I Stress Intensity Factors
0
5
10
15
20
25
30
35
40
0 0.2 0.4 0.6 0.8 1
Normalized Distance Along Crack Front
BEM
FEM
2D Analytical solution
Mode-IStressIntensityF
actor
Mo d e
IS tre s s I
nte ns ity Fa c t o r