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首页> 外文会议>ASME international pipeline conference 2008 >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：氢对近中性PH应力腐蚀开裂的计算分析

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摘要

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% lossrnof residual strength in comparison with the hydrogen free sample.
机译：氢气在管道的近中性pH SCC中起着至关重要的作用，但是其对裂纹萌生和扩展的确切机理仍然尚不清楚。从根本上讲，该过程始于原子级，而根源是由于各种因素引起的位错形成和扩散。在本研究中，分子静态模拟已用于分析氢对近中性pH应力腐蚀开裂的影响。数值测试了3D晶体结构，其中分别通过莫尔斯电势和修正的莫尔斯电势函数定义了氢-铁原子与铁-铁原子之间的原子间力。所开发的模型和代码适用于具有预制边缘缝隙的无氢bcc铁晶体和氢原子聚集在裂纹尖端附近的bcc铁晶体。选择参考结构的宽度应足够大，以免在保留结构基本属性的同时，避免任何明显的自由边界影响。通过去除单层铁获得边缘缝；据推测，该缝隙是由于溶解和氢辅助裂化而预先形成的。仿真结果表明，溶解的氢的存在会导致晶格严重变形，甚至在将外部载荷施加到结构上之前，还会导致氢原子附近的原子间键合区域减弱。这种现象导致纳米空隙的成核，随后导致边缘位错阵列的形成，并导致新成核的空隙聚结。因此，与无氢样品相比，滑动过程开始得更早（在较小的载荷下），从而导致15至20％的残余强度损失。

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  • 会议地点 Calgary(CA);Calgary(CA);Calgary(CA)
  • 作者

    Igor Ye. Telitchev; Oleg Vinogradov;

  • 作者单位

    Department of Mechanical and Machatronics Engineering, University of Waterloo Waterloo, Ontario;

    Department of Mechanical and Manufacturing Engineering, University of Calgary Calgary, Alberta;

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  • 正文语种 eng
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