PSI - Issue 23

W. Teraud et al. / Procedia Structural Integrity 23 (2019) 390–395 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

393

4

a)

b)

Fig. 1. An elongation of the specimens for  = 352MPa (a) and for  = 552MPa (b).

3.1. Static parameters

In each experiment, different values were determined, for example, table 1 shows the final parameters of the tested samples, where p * is the total longitudinal creep deformation at failure,   1.0  p is the deformation at strain localization with the parameter k 4 = 1.0 MPa, 0 p  is the rate of steady uniform creep,   1.0 1.0 0   p p   , w max and w min are the maximum and minimum widths of the specimen at fracture, 1.0  and 5.0  are the localization times corresponding to the parameters k 4 = 1.0 MPa and k 4 = 5.0 MPa.

Table 1. The parameters of the tested specimens. №  0 , MPa C H , % t * , h p *

 

1.0 

5.0  , h

1.0  p

w max , mm 4.74 4.49 4.52

w min , mm 3.67 3.71 3.72

6

0 10  p 

, h

7 8 9

541 541 541 541 345 345 345 345

0.28

1.3

0.20 0.29 0.25 0.07 0.36 0.36 0.26 0.41

0.048 0.106 0.071 0.135 0.055 0.211 0.065 0.159

27.68

0.48

0.48

0.0 0.0 0.1

22.1 20.1

2.12 1.78

13.94 11.09

17.44 16.98

15

4.6

11.20

-

-

3.34

3.64

10 12 13 14

0.28

48.2

0.89 0.18 0.28 0.15

4.56 4.37 4.59 4.25

3.13 3.29 3.14 3.11

17.16

23.84

0.0 0.1 0.0

370.8 133.6 394.0

333.00

341.42

64.43

71.19

297.30

313.34

In these experiments, the plasticity of the samples under the action of hydrogen, estimated from the rate of uniform creep 0 p  , increases by 5 times for a concentration of C H = 0.1 % and more than 10 times for a concentration of hydrogen of C H = 0.28 %. The effect of hydrogen is most pronounced on the time to failure. With an initial voltage of  0 = 345 MPa for the concentration of hydrogen C H = 0 % and C H = 0.1 %, the time t * decreases 2.8 times, and in comparison with C H = 0.28 % the time t * decreases almost 8 times . Under the action of excess hydrogen content in the crystal lattice, the localization time is significantly reduced. The localization time for C H = 0 % on average in three experiments (No. 6, 12 and 14) is 83 % of the time to failure, for experiment No. 13 ( C H = 0.1 %) it is 48 %, and for experiment No. 10 ( C H = 0.28 %) it is only 36 %. In this case, the limiting deformation p * corresponds to a statistical variation for such experiments, therefore, it can be concluded that with increasing hydrogen in the sample, deformation occurs mainly only in the localization zone. No noticeable thinning of the cervix during destruction was found.