Issue 33

J. Toribio et alii, Frattura ed Integrità Strutturale, 33 (2015) 434-443; DOI: 10.3221/IGF-ESIS.33.48 442 depth 300  m. Hereafter, the hydrogen distribution is progressively decreased, approaching the equilibrium hydrogen concentration for the material free of stress and strain ( C eq / C 0 = 1). So, the maximum hydrogen amount is placed out of the contact plane at a depth from the rod surface of 300 μ m. To conclude the analysis, the hydrogen distribution in the axial direction is presented in Fig. 11 for diverse depths within the plastic strain affected zone observed previously in Fig. 5. Thus, the hydrogen concentration is highly decreased at the vicinity of the contact zone (0 < z < 1.2 mm). So, the shorter the distance from the contact area, the lower the reduction of hydrogen amount. Thus, for a depth of 700  m, the distribution of hydrogen is rather affected by the stress and strain states generated by HA-RC-MF. 0 0.2 0.4 0.6 0.8 1 1.2 0 0.5 1 1.5 2 2.5 3 x=0 x=86  m x=173  m x=216  m x=300  m x=700  m C eq /C 0 z (mm) Figure 11: Hydrogen distribution for long times of diffusion in the axial direction at diverse layers of the rod between the contacting balls. C ONCLUSIONS n a ball-on-rod test, non-uniform plastic strains are generated on the contact plane where the ball applies a huge pressure to the rod overcoming material yield strength. This state is located near the rod surface with a plastic zone spreading over a maximum depth of 300  m. A huge compressive stress appears in the vicinity of the rod surface; it is progressively reduced as the distance from the surface increases in radial, hoop and axial directions. As a result, hydrogen is accumulated out of the contact plane where a huge reduction of the hydrogen amount is achieved for long times of exposure to the environment due to the high compressive hydrostatic stress in the radial direction, thereby pumping hydrogen towards points outside the contact plane. The maximum hydrogen amount appears for a depth from the surface about 300  m at planes placed 20º out of the contact plane in the contact cross section of the bar. A CKNOWLEDGEMENTS he authors acknowledge the financial support provided by the EU Project MultiHy (http://multihy.eu ): Multiscale modelling of hydrogen embrittlement of crystalline materials (EU-FP7-NMP Project No. 263335). R EFERENCES [1] Europe's onshore and offshore wind energy potential: an assessment of environmental and economic constraints. European Environment Agency, Copenhagen, (2009). [2] Toribio, J., Lorenzo, M., Vergara, D., Kharin, V., Hydrogen-assisted rolling-contact fatigue of wind turbines bearings. Key Eng. Mater., 627 (2015) 157–160. [3] Toribio, J., Lorenzo, M., Vergara, D., Kharin, V., Numerical analysis of hydrogen-assisted rolling-contact fatigue of wind turbine bearings. Frattura ed Integrità Strutturale, 30 (2014) 40–47. I T