Crack Paths 2006

associated with friction between crack flanks and residual compressive stresses within the

fretted material [7]. Thus, numerous of the initiated cracks stop propagation [1].

Experimental evidences [1, 4] show the existence of relatively large broken material particles

filling the mouth of cracks. One or two cracks may be able to dominate and propagate to

cause failure.

Numerical manipulation of FF was mostly within the context of experimental setup

designed to simplify real applications. Each application has its mechanical behavior and

requires a separate manipulation. An application of particular importance is the blade-disk

dovetail attachments in aero-engines. Fretting FCI life is crucial in those attachments.

Numerical and experimental studies simulated loaded disc-blades assembly, e.g. [10, 11].

Used loads do not match loading during the normal engine cycle [12]. This work numerically

manipulates axial dovetail fixings in typical operations and predicts probable sites of fretting

FCI, the entrance angles of the initiated cracks and their development possibility. The results

suggest a surface cracking mechanism for the formation of free relatively large material

particles possibly found filling the mouth of FF cracks. The tool is a two-dimensional elastic

plastic finite element (FE) modeling.

P R E S E NWT O R K

U P P E CR O M M O N S U R F A C E

A C C E L E R A T I O N M O D E

D E C E L E R A T I O N

Zmax ( s -1 )

M O D E

F

B angular speedand

t

u

t

acceleration of the disc

Pmax (N)

Y-axis

Dmax

F

r

u

r

T I M E

m

d

A

1

L O A D I N G

2d

(b)

F

f

X-axis

T

U N L O A D I N G

b

it

1

b

2

M O D E S

\

Dmin ( s-2)

O

T

R

b

e

DOVETAIL

4

b

3

F

A

L U LD

U

ic

3 d 4 d

N O T CBHA S E

D

Fluid Pressure

(DNB)

n

16.64

ut

1.35

(a)

F

r

DISCO U T E R

C I R C U M F E R E N C E

u

5

(DOC)

7.5

r

8.11

9.05

C

Ft

20o

L O W ECRO M M O N

4

S U R F A C E

20 m m

(c)

S T R A I G HCTO N T A C T

3

113

S U R F A C E

PAIR

(d)

(e)

PAIR13

Fig. 1 Present application (a) a single sector with its boundary conditions, (b) modes

simulating loading conditions during a cycle (c) dimensions of the analysed dovetail joint,

(d) half of the analysed mesh and (e) magnification of the model lower half

A disc-blades assembly of an aero-engine compressor is assumed mounted on a circular

rotor. The blades are assembled into the disc with Coulomb frictional dovetail joints. The

disc is divided into identical sectors. The sector shown in Fig. 1(a) is analysed with inertia

forces distributed over the body. The sector is externally subject to forces acting at its border