PSI - Issue 33

M.R. Tyutin et al. / Procedia Structural Integrity 33 (2021) 765–772 M.R. Tyutin , L.R. Botvina, A.V. Ioffe / Structural Integrity Procedia 00 (2019) 000–000

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Hydrogen charging also affects acoustic emission characteristics. In the initial specimen, the total number of AE signals and the b AE -value are higher than in the specimens after charging (Table 3, Fig. 2c-e). This effect can be associated with less plasticity, causing a greater fracture localization in the specimens after hydrogen charging, which leads to a decrease in the total number of AE signals. A decrease in the b AE -value indicates an increase in the relative number of high-amplitude signals, the sources of which are the developing defects that have arisen during hydrogen charging. a b

b AE

I

III

IV

II

I

II

III

IV

1200

200

3x10 4

1200

ΣN AE

45

Ṅ, s -1

σ

2,0

1000 ΣN AE

1000

1000

1,5

Σ N AE

30 Ṅ , s -1

150

ΣN AE

800

2x10 4

800

1,0 b AE

b AE

1,5

600

100

600

σ, MPa

b AE

σ

500

400

1x10 4

400 σ , MPa

15

1,0

50

Ṅ

200

200

0,5

Ṅ

0

0,5

0

0

0

0

0

0,0

0,2

0,4

0,6

0,8

1,0

0,0

0,2

0,4

0,6

0,8

1,0

ε∗

ε*

c

d

-1

10 Ṅ AE , s

-1

20 Ṅ AE , s

I

II

III

IV

1200

2,0

1200

2,0

250

I

II

III

IV

ΣN AE

1000 ΣN AE

b AE

σ

1000

1000

1,5 b AE

8

150 ΣN AE 200

15

1,5

800

800

b AE

6

1,0 b AE

ΣN AE

σ

600

1,0

600

10

σ, MPa

σ, MPa

4

100

500

400

400

Ṅ

Ṅ

0,5

5

0,5

2

50

200

200

0

0

0,0

0

0

0

0,0

0

0,0

0,2

0,4

0,6

0,8

1,0

0,0

0,2

0,4

0,6

0,8

1,0

ε*

ε*

e

-1

20 Ṅ AE , s

I

II

III IV

1200

2,0

800

σ

1000

1,5 b AE

15

800

400 ΣN AE 600

b AE

600

10

1,0

σ, MPa

400

ΣN AE

5

0,5

200

Ṅ

200

0

0

0

0,0

0,0

0,2

0,4

0,6

0,8

1,0

ε*

Fig. 2. Relative strain dependences of stress σ , accumulated number of AE signals Σ N AE , AE activity Ṅ AE and b AE -value for specimens of 15Cr2MnMoV steel in the initial state (a), after operation (b) and after one-week exposure in hydrogen sulfide environment at load 0 (c); 0.1 σ Y (d) and 0.2 σ Y (e) The exposure in NACE media at a stress of 0.1∙σ Y causes an increase in both the number of AE signals and their intensity (Fig. 2d). During tensile deformation of the specimen after hydrogen charging at 0.2 ∙σ Y , uniform AE activity is observed, no acoustic emission gap before failure was observed. This indicates the presence of active emission sources in the material that arose during hydrogen charging and subsequent tensile deformation (Fig. 2e). This is