【摘要】：高超聲速環(huán)境下材料的燒蝕破壞問題是發(fā)展高超聲速飛行器技術的關鍵問題。本文主要應用分子動力學方法對石墨受到高超聲速氧分子流燒蝕過程進行了模擬研究。本文的主要工作有以下幾個方面:(1)運用基于Reax FF力場勢的分子動力學方法模擬了雙層以及三層石墨與高超聲速氧分子流的相互作用過程。石墨在高超聲速氧分子流的持續(xù)沖擊作用下,氧原子與表層石墨原子結合;可以觀察到部分結合了氧原子的碳原子以CO2的形式從表層石墨解離,石墨出現(xiàn)缺陷,逐漸破壞。另外發(fā)現(xiàn)三層石墨的情況下表層石墨溫度上升速度較慢。(2)運用基于REBO勢的分子動力學方法對多層石墨受高超聲速氧分子流的燒蝕過程進行了模擬。對LAMMPS中只包含碳、氫原子的REBO勢函數(shù)進行修改,加入氧原子。分析了石墨氧化對其等效面內剛度的影響。研究發(fā)現(xiàn),多層石墨在受到高超聲速氧分子流沖擊燒蝕過程中出現(xiàn)逐層破壞的現(xiàn)象,且模擬隨著層數(shù)的增多,石墨破壞的時間相對延后。研究了缺陷對雙層石墨受高超聲速氧分子流沖擊燒蝕過程的影響,發(fā)現(xiàn)雙空位缺陷加速了表層石墨升溫破壞的過程,單空位缺陷的影響次之,而Stone-Wales型缺陷對燒蝕過程的影響可以忽略。氧原子以吸附的方式與石墨結合對其等效面內剛度基本沒有影響,而在缺陷處與碳原子結合則降低了石墨的等效面內剛度。(3)對研究石墨燒蝕問題時,分子動力學方法的可計算規(guī)模進行了探討。運用基于REBO勢的分子動力學方法采用單核計算對包含33516個碳原子,12000個氧原子的系統(tǒng)進行300ps的模擬,時間步長為1fs�？偟挠嬎銠C時約為10個小時,這相對于采用Reax FF力場勢所能計算的規(guī)模有了很大的提高。另外詳細描述了表層石墨在受高超聲速氧分子流沖擊作用過程中從缺陷產生、缺陷擴展到破壞解體的階段性現(xiàn)象,分析了模擬過程中表層石墨的溫度和系統(tǒng)勢能的變化。
[Abstract]:The problem of material ablation in hypersonic environment is a key problem in the development of hypersonic vehicle technology. In this paper, the molecular dynamics method is used to simulate the process of supersonic oxygen molecular ablation of graphite. The main work of this paper is as follows: (1) the interaction process of two-layer and three-layer graphite with hypersonic oxygen flow is simulated by using the molecular dynamics method based on Reax FF force field potential. Under the continuous impact of hypersonic oxygen molecule flow, the oxygen atom binds to the surface graphite atom, and it can be observed that the carbon atom which binds oxygen atom dissociates from the surface graphite in the form of CO2, and the graphite appears defects and gradually destroys. In addition, it is found that the temperature of surface graphite rises slowly in the case of three layers of graphite. (2) the ablation process of multilayer graphite subjected to hypersonic oxygen flow is simulated by molecular dynamics method based on REBO potential. The REBO potential function containing only carbon and hydrogen atoms in LAMMPS is modified and oxygen atoms are added. The effect of graphite oxidation on the equivalent in-plane stiffness was analyzed. It is found that the multi-layer graphite is destroyed layer by layer in the process of supersonic oxygen molecular flow impact ablation, and the time of graphite destruction is relatively delayed with the increase of the number of layers. The effect of defects on the ablation process of double layer graphite by hypersonic oxygen molecular flow is studied. It is found that the double vacancy defect accelerates the process of surface graphite heating destruction, and the effect of single vacancy defect is the second. However, the effect of Stone-Wales defects on the ablation process can be neglected. The adsorption of oxygen atoms with graphite has little effect on the in-plane equivalent stiffness of graphite, but it decreases the equivalent in-plane stiffness of graphite by bonding with carbon atom at defects. (3) when studying the problem of graphite ablation, The computational scale of molecular dynamics method is discussed. The molecular dynamics method based on REBO potential was used to simulate the 300ps of a system containing 33516 carbon atoms and 12,000 oxygen atoms with a time step of 1fs. The total computer time is about 10 hours, which is much higher than that calculated by using the Reax FF force field potential. In addition, the phase phenomenon of surface graphite produced from defect to destruction and disintegration during the process of hypersonic oxygen molecular flow impact is described in detail. The temperature and system potential energy of surface graphite in the simulation process are analyzed.
【學位授予單位】：南京航空航天大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：V219

【相似文獻】

相關期刊論文 前10條

1 邱海鵬,郭全貴,翟更太,宋永忠,劉朗;粘結劑對石墨材料的物理性能及微觀結構影響的研究[J];宇航材料工藝;2001年06期

2 姜荊;;碳和石墨的電化學陽極嵌入化和過氧化 Ⅰ.在濃硫酸電解質中的反應[J];武漢鋼鐵學院學報;1989年02期

3 謝有贊，，羅俊琨;不同的原子及基團對碳石墨材料性能的影響[J];碳素;1994年04期

4 任慧,焦清介,喬小晶,王長福;三元石墨插層化合物的合成與表征[J];北京理工大學學報;2003年02期

5 李文W

本文編號：2319858