PSI - Issue 57

Amira Aboussalih et al. / Procedia Structural Integrity 57 (2024) 848–858 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

856

9

4.3.2 Impact of the amplitude of the decreasing axial stress at constant average stress The 316L steel will be stressed at 100 cycles by three different loads under sinusoidal stress having the same average stress σ mean = 75 MPa with decreasing stress amplitude σ a = (225, 200, 175) MPa, the loading conditions will be represented on the Table 4.

Table 4 : Conditions of the sinusoidal uni axial loading

Loading 1

Loading 2

Loading 3

300

275

250

max 

[MPa]

- 150

- 125

- 100

min 

[MPa]

σ mean = + [MPa]

75

75

75

225

200

175

max   −

[MPa]

a 

=

min

2

=

- 0.50

0.45

0.40

-

-

Sensitivity of the steel (Fig 10 - a, 10-b and 10- c) allowed us to analyze the influence of the amplitude of the stress on the Ratcheting and to reach different levels of plastic strain. A numerical analysis (Fig 11) has allowed admitting a decreasing Ratcheting by the comparison of the three cases of cyclic loadings through their superposition. The gaits obtained (Fig 12) clearly reflect the consequences of plastic strain produced by the effect of the amplitude of stresses.

-200 Axial Stress  xx ( Pa ) 0 200

200

-200 Axial Stress  xx ( Pa ) 0

 mean = 75 MPa  a = 200 MPa

 mean = 75 MPa  a = 225 MPa

0,00

0,01

0,02

0,03

0,04

0,05

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35

A xial Strain  xx (%)

A xial Strain  xx (%)

b)

a)