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首页> 外文会议>ASME international pipeline conference >COMPUTATIONAL ANALYSIS OF HYDROGEN CONTRIBUTION TO THE NEAR- NEUTRAL PH STRESS CORROSION CRACKING
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COMPUTATIONAL ANALYSIS OF HYDROGEN CONTRIBUTION TO THE NEAR- NEUTRAL PH STRESS CORROSION CRACKING

机译：氢源对近中性pH应激腐蚀裂纹的计算分析

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Hydrogen plays a critical role in near-neutral pH SCC in pipelines, but the precise mechanism of its effect on crack initiation and propagation is still not well understood. Fundamentally, the process starts on the atomic level and at the root is dislocation formation and propagation due to various factors. In the present study a molecular statics simulation has been applied for the analysis of the contribution of hydrogen to the near-neutral pH stress corrosion cracking. A 3D crystal structure in which the interatomic forces between the hydrogen-iron and iron-iron atoms were defined, respectively, by the Morse and modified Morse potential functions was tested numerically. The model and the code developed were applied to both a hydrogen-free bcc iron crystal with the pre-made edge slit and to a bcc iron crystal with the hydrogen atoms aggregated near the crack tip. The width of the reference structure was chosen to be large enough to avoid any significant effects of free boundaries while preserving the basic properties of the structure. The edge slit was obtained by removing of a monolayer of iron; it was assumed that this slit was formed previously as a result of dissolution and the hydrogen-assisted cracking. Simulation results demonstrated that the presence of dissolved hydrogen causes severe distortion of the lattice and results in a weakened zone of interatomic bonds in the vicinity of the hydrogen atom even before the external load is applied to the structure. This phenomenon leads to the nucleation of nano-voids and later to the formation of edge dislocations array, and to the newly nucleated voids coalescing. Consequently the sliding processes start earlier (under the smaller load) leading to a 15-20% loss of residual strength in comparison with the hydrogen free sample.
机译：氢在管道中的近中立pHCc中起重要作用，但其对裂纹引发和繁殖的影响的精确机制仍然不太了解。从根本上，该过程从原子水平开始，并且由于各种因素，根部是脱位形成和传播。在本研究中的分子模拟静力学已经应用为氢与近中性pH值的应力腐蚀开裂的贡献的分析。其中定义了摩尔斯铁和铁 - 铁原子之间的间隙力的3D晶体结构，通过MORSE和改性摩尔斯潜在功能进行了数值测试。使用预制的边缘狭缝和与氢原子靠近裂纹尖端的氢原子施加到无氢的BCC铁晶体两者的模型和典型的涂布型BCC铁晶。选择参考结构的宽度足以足以避免自由边界的任何显着影响，同时保持结构的基本性质。通过去除一单层铁来获得边缘狭缝;假设以溶解和氢辅助裂化的结果形成此狭缝。仿真结果表明，溶解的氢的存在导致晶格的严重变形，并导致甚至在将外部载荷施加到结构之前氢原子的氢原子附近的弱化区。这种现象导致纳米空隙的成核，后来形成边缘脱位阵列，以及新成核空隙的聚结。因此，滑动过程较早开始（在较小的载荷下），与氢样品相比，导致残余强度的损失15-20％。

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