Crack Paths 2012

Tab. 1. Mechanical characteristics and damageparameters of the Al. Alloy 2024-T3

Damagemodels

Paris law constants

Wöhler regime

Paris regime

45 M P a mA

6.128E-14

2.170E-16

f c K

m

3.6 M P a

B

0.026

0.412

thK

V0

1.86E-11 m/cycle

C’

177.4 M P a

152.0 M P a

m

4.05 a1

0.402

0.034

a4

1.480

1.270

a5

-0.958

-0.819

0.159

C

0.474

regime) and the crack propagation-dominated fatigue (Paris regime) – and by applying

the genetic algorithm (GA) procedure [9], are listed in Tab. 1.

The experimental S-N curve (continuous line) and the constant amplitude fatigue life

evaluated through the present damage model for the Wöhler regime (round symbols) are

shown in Fig. 2a. Note that the stress amplitude

a V values used to compute the model

parameters through the G A method are indicated by square symbols. As can be

observed, the present model (round symbols) satisfactorily approximates the material

fatigue curve (continuous line) even near the conventional fatigue limit region.

In Fig. 2b, the crack growth rate (expressed in m/cycle) against the SIF range

(expressed in Pa m1/2) is displayed for both the classical Donahue law

'

K

a

a S V

Kfc

(a)

AluminumAl. 2024-T3 R=-1 Vaf-1=207 M P a 1 f = 1 1 0 6cycles L o g V a8= 03108-0.096LogN(Pa)

1E+008 234

Donahuelaw V a = 100 M P a = 1 5 0 M P a 2 0

1E-021006284

D a m a g e

K th

model

Al Alloy 2024-T3

(b)

1E+006

1E+007

1E+008

SIF range, ' K (Pa m1/2)

N u m b e rofcycles to failure, N

Fig. 2. (a) Wöhler curve (continuous line) and evaluation through the present damage

model for the Wöhler regime according to Eq. (3) (round symbols), for Aluminum Al

2024-T3. (b) Crack growth rate curves obtained from the Paris law and the present

damage model.

301