Study On Molecular Dynamics Simulation Of Hydrogen Damage And Damage Characterization Method For X80 Steel

In order to protect environment and depletion of non-renewable energy sources such as coal,oil and natural gas,renewable energy power generation technologies such as hydropower,wind power and photovoltaic power generation have developed rapidly,but the large geographical differences in China’s economic development,as well as the intermittent,fluctuating nature of wind and light energy,have led to serious abandonment of electricity from renewable energy sources in some areas.To make full use of renewable energy and solve its abandoned power consumption problem-hydrogen is widely paid attention as a non-polluting energy carrier,using renewable energy to generate hydrogen to convert the unconsumed abandoned power into hydrogen.The whole technical cycle includes hydrogen production,storage,transportation and utilization,among which hydrogen transportation is the key link between the upper and lower parts.The best way to transport hydrogen on a large scale is to mix it with natural gas in a certain ratio and use the existing natural gas pipeline or pipeline network.Thus,the research of hydrogen and pipeline compatibility is very necessary and urgent.In order to meet the transmission demand,the materials of existing natural gas pipelines in China are mostly high-strength steels.In this paper,a representative X80 pipeline steel is selected for study,and the following conclusions are drawn through molecular simulation and macro tensile experimental studies:1.Towards the more pure iron surface,doping surface of impurity elements have some influence on hydrogen adsorption diffusion,among which the surface under Mo doping has the most obvious effect on hydrogen adsorption hindrance,and the distance between H and surface is the farthest,1.026 (?).Ni element will promote the hydrogen diffusion behavior.The hydrogen diffusion optimization coefficient of X80 model is 0.0727 from the influence of different elements relative to the hydrogen diffusion on the iron surface and the percentage of the material interior.2.The study found that the doping of hydrogen atoms under the same strain conditions reduces the body-centered cubic structure and increases the other unknown structures,the amount of hydrogen doping determines the degree of structural disorder;with the increase of tensile strain,the body-centered cubic structure is transformed into face-centered cubic structure,which significantly reduces the mechanical properties of the material.It is found that the mechanical properties of X80 pipeline steel show a decreasing trend with the increase of hydrogen concentration,and the maximum error is 1.85% compared with the macroscopic experiment.3.By analyzing the damage evolution of X80 pipeline steel in the tensile process by acoustic emission characteristic parameter analysis and DIC technique,we can determine the fracture location in advance,and find that the increase of hydrogen concentration causes the peak of the accumulated acoustic signal count to be generated earlier and the peak value to decrease,and the proportion of high amplitude acoustic signal in each tensile stage to increase,which indicates that the incorporation of hydrogen strengthens the plastic deformation strength of the material and reduces the ductility of the material.The change in the amplitude of the acoustic signal can determine the internal hydrogen concentration of the material.