PSI - Issue 59

Oksana Hembara et al. / Procedia Structural Integrity 59 (2024) 190–197 Oksana Hembara et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Distribution of hydrostatic stresses (a, c, e, g, k) and concentration of diffusive hydrogen (b, d, f, h, l) along the Ox axis from the surface of the defect for different internal pressure values for various types of crack-like defects: semi-elliptical crack ( a / c =1); semi-elliptical cracks ( a / c =0.25; a / c =0.5; a / c =0.75); crack ( a / c =0.1). a b

Fig. 5. Dependence of hydrostatic stresses maximum values (a) and concentration of diffusive hydrogen (b) on the internal pressure for different defect surface shapes. 5. Conclusions An analysis of hydrogen diffusion in a steel pipe with five types of crack-like defects on the inner surface under internal pressure has been conducted. The finite element method was used for both hydrogen diffusion analysis and stress-strain analysis. The distribution of hydrogen concentration around defects was obtained by varying the internal pressure and crack depth. It was found that for a crack with a / c =0.1 the concentration of diffusible hydrogen is twice as high as that around a semi-circular crack ( a / c =1) at 7 MPa and 15% higher at 30 MPa. Maximum hydrostatic stress values for the crack ( a / c =0.1) exceed those for the semi-circular crack ( a / c =1) by 20%, regardless of the pressure. When changing the crack shape from semi-circular to semi-elliptical ( a / c =0.1), the maximum hydrogen concentration increases by up to 4% at 7 MPa, up to 6% at 10 MPa, up to 11% at 20 MPa, and up to 16% at 30 MPa. With an increase of pressure from 7 to 30 MPa the maximum hydrogen concentration increases by 47% for a semi-circular crack ( a / c =1), 49% for a / c =0.75, 50% for a / c =0.5, 51.5% for a / c =0.25, and 54.5% for a / c =0.1. Acknowledgements This work was financially supported by the National Research Foundation of Ukraine (Project No: 2020.02/0049).