PSI - Issue 33

Jesús Toribio et al. / Procedia Structural Integrity 33 (2021) 1215–1218 Jesús Toribio / Procedia Structural Integrity 00 (2021) 000–000

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5. Results and discussion Fig. 4a plots the boundary ( notch-tip ) concentration of hydrogen c Г / c o represented as a function of the load ratio F / F max . Such a boundary value clearly increases with the remote stress and slightly decreases with the notch depth, i.e., the equilibrium boundary value of hydrogen concentration is slightly higher for shallow blunt notches.

5.0

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C/D=0.1 C/D=0.2 C/D=0.3 C/D=0.4

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R/D=0.40

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0.0 0.2 0.4 0.6 0.8 1.0 C/D=0.1 C/D=0.2 C/D=0.3 C/D=0.4 F/F max R/D=0.40

/c 0

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x S (mm)

Γ

c

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(a) (b) Fig. 4. Hydrogen concentration at the boundary ( notch tip ) c Г / c o vs load ratio F / F max . (a) and depth x S of the maximum hydrostatic stress point (b). On the basis of research by Toribio (1992, 1993), the position of the maximum hydrostatic stress point towards which hydrogen mainly diffuses is of the highest interest in hydrogen embrittlement. It is the point of maximum hydrogen concentration in the steady state regime . Fig. 4b shows the maximum hydrostatic stress point depth x S as an increasing function of the of the load ratio F / F max . This important length has a relevant fractographic meaning, since it coincides with the asymptotic depth ( for quasi-static tests or steady state regime ) of the hydrogen-assisted micro-damage area ( tearing topography surface or TTS) in pearlitic steels, as reported by Toribio (1992, 1993). 6. Conclusion Results show how the boundary value of hydrogen concentration increases clearly with the remote stress (externally applied load) and slightly decreases with the notch depth, i.e., the equilibrium boundary value of hydrogen concentration is slightly higher for shallow blunt notches. The point of maximum hydrostatic stress shifts by increasing the load from the notch tip to the axis of the bar. Ayas, C, Deshpande, VS., Fleck, NA., 2014. A Fracture Criterion for the Notch Strength of High Strength Steels in the Presence of Hydrogen. Journal of the Mechanics and Physics of Solids 63, 80-93. Lillard, RS., Enos, DG., Scully, JR., 2000. Calcium Hydroxide as a Promoter of Hydrogen Absorption in 99.5% Fe and a Fully Pearlitic 0.8% C Steel During Electrochemical Reduction of Water. Corrosion 56, 1119-1132. Toribio, J., 1992. Fractographic Evidence of Hydrogen Transport by Diffusion in Pearlitic Steel. Journal of Materials Science Letters 11, 1151-1153. Toribio, J., 1993. Role of Hydrostatic Stress in Hydrogen Diffusion in Pearlitic Steel. Journal of Materials Science 28, 2289-2298. Van Leeuwen, HP., 1974. The Kinetics of Hydrogen Embrittlement: A Quantitative Diffusion Model. Engineering Fracture Mechanics 6, 141-161. Wagenblast, H., Wriedt, HA., 1971. Dilation of Alpha Iron by Dissolved Hydrogen at 450º to 800ºC. Metallurgical Transactions 2, 1393-1397. Wang, M., Akiyama, E., Tsuzaki, K., 2007. Effect of Hydrogen on the Fracture Behavior of High Strength Steel During Slow Strain Rate Test. Corrosion Science 49, 4081-4097. References