Issue 50

A. Salmi et alii, Frattura ed Integrità Strutturale, 50 (2019) 231-241; DOI: 10.3221/IGF-ESIS.50.19

Tab. 3 provides the 2024T3 aluminum alloy chemical compositions [ 4].

Material 2024-T3

Cu

Fe

Si

Cr

Mg Mn Zn Ti

4.82

0.18

0.07

0.02

1.67

0.58

0.06

0.15

Table 3: Chemical composition by mass in percentage.

R ESULTS AND DISCUSSION

P

aris and Erdogan have constructed a quantitative framework of fatigue fracture mechanics, which correlates the fatigue crack growth rate to the range of stress intensity factor as follows [16]:

da C K dN  

m

(1)

is the stress intensity factor range in fatigue loading, N

where C and m are empirical material constants, ∆K = K max is number of cycles, and da is crack extension length. The following correlation gives the relation between C and m parameters: - K min

Log C = a + bm

(2)

a and b 0  where: a is the ordinate at the origin and b is the slope of the regression line. Or

m A

C =

(3)

B

da dN      

B =10 = k b p  

with A =10 = a

p

( da mm k MPa m dN cycle                ); ( ) p p

Coordinates of the pivot point [17].

The material constants in Paris equation depicted in Tab. 4 [18]:

Plate thickness 2.29 mm

Plate thickness 6.35 (mm)

m = 3.2828

m = 4.224

C = 3.63 E-13 C = 1.51 E-15 Table 4: Material constants in Paris law for aluminum panel. The total number of stress cycles N required for a short crack to propagate from the initial crack length a 0

to any crack

length a can then be determined as

z

1 i N N   

(4)

i

N i stress cycles required for the appearance of the initial crack i = 1; 2; 3; . . . ; z z number of grains transverse by the crack

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