extra 3d crack growth

7/28/2019 Extra 3D Crack Growth

1/19

Simulation of 3D Crack Growth

Thin Shells

3D Solids


2/19

NONLINEARITIES:Predicted Curvilinear Fatigue Crack Growth


3/19

Early Damage Tolerance Testing

on B-707 Fuselage

Single Bay Flaps


4/19


5/19

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


6/19


7/19

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


8/19

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


9/19

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


10/19

Solid Geometry Models

OSM Geometry

Model

Inserted Initial

Flaw


11/19

Initial Boundary Element Mesh

Full Beam

Initial FlawFlaw Mouth


12/19

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


13/19

Final Predicted Crack Shape

DeformedSolid

bottom face sideside

initialcrack

ExperimentFRANC3DComparison of

computed andobserved crack trace

on the surface


14/19

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


15/19

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


16/19

Thermal fatigue

in a housing


17/19

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


18/19

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


19/19

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

extra 3d crack growth

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