PSI - Issue 57

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

853 6

The confrontation of the cyclical hardening curves in the axial and biaxial direction of the steel 316 is represented by their superposition showing for the biaxial behavior a fall in the axial stress at zero deformation, then an increase in the stress exhibiting additional hardening (see Fig. 6).

400

-200 Axial stress  xx ( MPa ) 0 200

 xx = 0,4 %  xx = 0,4 %  x  = 0,69 %

-0,004

0,000

0,004

Axial strain  xx (%)

Fig. 6 Comparison between axial and biaxial behavior 316L steel for the same strain

4.3 Cyclic behavior under uniaxial sinusoidal controlled stress 4.3.1 Impact of increasing mean stress at constant stress amplitude

Three types of tests of simulations with cyclic uni- axial loading can be envisaged to determine the influence of the increasing average stress σ mean = (50, 100, 150) MPa with amplitude of constant stress σ a = 150 MPa with decreasing loading ratios R = (-0.81, -0.66, -0.42) on the Ratcheting. One will characterize thereafter macroscopically the behavior of each test of simulation and one seeks to know which is the relevant loading, which gives an accelerated ratcheting, which corresponds to a significant excess of plastic strain. Table 3 summarizes the conditions of cyclic loading.

Table 3 : Conditions of the sinusoidal uni- axial loading

Loading 2

Loading 3

Loading 1

250

275

200

max 

[MPa]

- 50

- 25

- 100

min 

[MPa]

σ mean = σ max +σ min 2 [MPa] max min   − [MPa]

100 150

150 150

50

150

2 =

a 

=

- 0.81

-0.42

- 0.66