PSI - Issue 3

Jilali Nattaj et al. / Procedia Structural Integrity 3 (2017) 579–587 Author name / Structural Integrity Procedia 00 (2017) 000–000

584

6

N

f

k  = 1.47

For Δσ= 282 MPa:

= 1786,8.10 -6 and

N

0

f

N

f

= 674.2 10 -6 and k  = 1.34

For Δσ= 352 MPa:

N

0

f

which gives C  27 10 3

and k = 0.1

The expression of damage becomes:

        1

(12)

D



i

 0,1

N

) f

  27.10 3 .

(

(13)

 

N

0

f

5. Results 5.1. Properties of steel A36

Table 1. Mechanical properties of steel A36 Specification

Propriety

σ u (MPa)

σ y (MPa)

E(GPa)

A36

621

372

180

Table 2. Chemical composition

Specification

Composition

C

M n

P

S

S i

Cu 0.2

A36

0.29

0.8-1.2

0.09

0.05

0.15-0.30

We plot the (σ -N) curves according to the equation (11).

Figure 1. (σ, N f ) curve of a notched specimen

The curve (σ -N f ) shows well the three zones of the Wohler curve (olygocyclic below 10 number of cycles beyond 10 3 up to the endurance limit tends towards the horizontal asymptote.

3 ). The part with a large