納米加工晶體銅中亞表層缺陷演變及力學(xué)性能研究
發(fā)布時(shí)間：2018-09-18 17:10
【摘要】：納米技術(shù)在科技日新月異的現(xiàn)代社會已不再是遙遠(yuǎn)生疏的詞匯,基于納米加工技術(shù)的高精度、高質(zhì)量的工件產(chǎn)品被不斷運(yùn)用在科學(xué)研究、國防科技以至高端消費(fèi)等方方面面。而對納米加工機(jī)理的認(rèn)識則很大程度上制約了納米技術(shù)的發(fā)展。由于納米加工實(shí)驗(yàn)要求以及成本的限制,分子動力學(xué)仿真已成為納米加工領(lǐng)域?qū)嵱们抑匾难芯抗ぞ�。另�?納米加工領(lǐng)域存在一系列需克服的問題,其中缺乏對工件亞表層缺陷演變規(guī)律的理解是制約加工工件質(zhì)量的重要原因。針對上述問題,本文將晶體銅作為研究對象,包括單晶銅與多晶銅,進(jìn)行納米切削以及納米壓痕的分子動力學(xué)仿真與實(shí)驗(yàn),分析了單晶銅和多晶銅工件在納米切削和納米壓痕過程中工件亞表層晶體結(jié)構(gòu)的演變規(guī)律,并通過納米壓痕仿真與實(shí)驗(yàn)研究了不同切削參數(shù)條件下的工件表面力學(xué)性能。基于單晶銅納米切削分子動力學(xué)仿真,利用CNA共近鄰分析、DXA位錯(cuò)提取等分析方法,分別解構(gòu)了四面體堆垛層錯(cuò)、V形位錯(cuò)、球形團(tuán)簇等不同種類亞表層缺陷在工件切削時(shí)的演變過程,發(fā)現(xiàn)了亞表層缺陷的結(jié)構(gòu)特征以及形成規(guī)律;通過改變切削仿真采用刀具的幾何參數(shù),包括前角、后角以及刃圓半徑,分析刀具參數(shù)引起的亞表層結(jié)構(gòu)特征的變化,總結(jié)了其對切削過程中位錯(cuò)演變的影響規(guī)律。進(jìn)行多晶銅工件的納米切削分子動力學(xué)仿真,通過切削力、應(yīng)力分布等方面,研究了切削中多晶銅工件亞表層晶體結(jié)構(gòu)以及位錯(cuò)表現(xiàn)出的規(guī)律,通過切削力和工件位錯(cuò)密度表現(xiàn)出的波動規(guī)律,發(fā)現(xiàn)了多晶銅晶界對位錯(cuò)滑移的阻礙作用以及與位錯(cuò)的轉(zhuǎn)化過程,并發(fā)現(xiàn)了多晶銅晶界產(chǎn)生的應(yīng)力屏蔽現(xiàn)象;改變多晶銅納米切削仿真時(shí)的切削深度,分析切削深度對工件晶體結(jié)構(gòu)以及位錯(cuò)特征的影響,發(fā)現(xiàn)了切削深度與工件內(nèi)部位錯(cuò)密度的線性關(guān)系。分別開展單晶銅與多晶銅的納米壓痕分子動力學(xué)仿真以及加工實(shí)驗(yàn),對未加工以及經(jīng)不同切削參數(shù)進(jìn)行納米切削后的晶體銅工件進(jìn)行納米壓痕。一方面利用納米壓痕仿真分析了單晶銅的納米壓痕過程,研究了亞表層缺陷對工件壓痕再生成位錯(cuò)的影響,并發(fā)現(xiàn)亞表層缺陷將造成工件“加工硬化”的現(xiàn)象;同時(shí)通過與納米壓痕實(shí)驗(yàn)進(jìn)行對比,發(fā)現(xiàn)切削深度的變化對單晶銅工件表面力學(xué)性能的影響。另一方面,通過加工與實(shí)驗(yàn)比較了不同切削參數(shù)下多晶銅工件表面力學(xué)性能的差異,發(fā)現(xiàn)切削深度的增大在一定范圍內(nèi)使得硬化效果更明顯。將納米壓痕仿真結(jié)果與實(shí)驗(yàn)結(jié)果進(jìn)行對比,發(fā)現(xiàn)其趨勢的相同特征,從而定性地證明結(jié)論的正確性。
[Abstract]:Nanotechnology is no longer a distant and unfamiliar word in the modern society with the rapid development of science and technology. High-precision and high-quality workpiece products based on nanoprocessing technology have been continuously used in many aspects such as scientific research, national defense science and technology, and even high-end consumption. However, the understanding of nano-processing mechanism restricts the development of nano-technology to a great extent. Due to the limitation of experiment and cost, molecular dynamics simulation has become a practical and important research tool in nanofabrication field. In addition, there are a series of problems to be overcome in the field of nano-fabrication, among which the lack of understanding of the evolution law of workpiece subsurface defects is an important reason for restricting the quality of workpiece. In order to solve the above problems, we take crystal copper as the research object, including single crystal copper and polycrystalline copper, and carry out the molecular dynamics simulation and experiment of nano-cutting and nano-indentation. The evolution law of the subsurface crystal structure of single crystal copper and polycrystalline copper workpiece in the process of nano-cutting and nano-indentation is analyzed. The mechanical properties of workpiece surface under different cutting parameters are studied by nano-indentation simulation and experiment. Based on molecular dynamics simulation of monocrystalline copper nanoscale cutting, the V shape dislocation of tetrahedron stacking fault is deconstructed by using CNA conearest neighbor analysis and other analysis methods. The evolution process of different kinds of subsurface defects such as spherical clusters in the cutting process of workpiece is found. The structural characteristics and formation law of subsurface defects are found, and the geometric parameters of cutting tools, including the front angle, are changed by changing the cutting simulation. The change of subsurface structure caused by cutting tool parameters is analyzed, and the influence of tool parameters on dislocation evolution in cutting process is summarized. The molecular dynamics simulation of polycrystalline copper workpiece in nano-cutting was carried out. Through cutting force and stress distribution, the crystal structure and dislocations of polycrystalline copper workpiece were studied. Through the fluctuating law of cutting force and dislocation density of workpiece, the blocking effect of polycrystalline copper grain boundary on dislocation slip and the process of transformation with dislocation are found, and the phenomenon of stress shielding produced by polycrystalline copper grain boundary is also found. The influence of cutting depth on the crystal structure and dislocation characteristics of the workpiece is analyzed by changing the cutting depth of polycrystalline copper nanomachining simulation. The linear relationship between the cutting depth and the dislocation density inside the workpiece is found. The molecular dynamics simulation and processing experiment of nano-indentation of single crystal copper and polycrystalline copper were carried out respectively. On the one hand, the nanocrystalline indentation process of single crystal copper is analyzed by nano-indentation simulation, and the effect of subsurface defects on the dislocation formation of workpiece indentation is studied, and it is found that sub-surface defects will cause workpiece "work hardening". At the same time, the effect of cutting depth on the surface mechanical properties of single crystal copper workpiece was found by comparing with nano-indentation experiment. On the other hand, the difference of mechanical properties of polycrystalline copper workpiece under different cutting parameters is compared with experiments. It is found that the hardening effect is more obvious with the increase of cutting depth in a certain range. The simulation results of nano-indentation are compared with the experimental results, and the same characteristics of the trend are found, which proves the correctness of the conclusion qualitatively.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.11
[Abstract]:Nanotechnology is no longer a distant and unfamiliar word in the modern society with the rapid development of science and technology. High-precision and high-quality workpiece products based on nanoprocessing technology have been continuously used in many aspects such as scientific research, national defense science and technology, and even high-end consumption. However, the understanding of nano-processing mechanism restricts the development of nano-technology to a great extent. Due to the limitation of experiment and cost, molecular dynamics simulation has become a practical and important research tool in nanofabrication field. In addition, there are a series of problems to be overcome in the field of nano-fabrication, among which the lack of understanding of the evolution law of workpiece subsurface defects is an important reason for restricting the quality of workpiece. In order to solve the above problems, we take crystal copper as the research object, including single crystal copper and polycrystalline copper, and carry out the molecular dynamics simulation and experiment of nano-cutting and nano-indentation. The evolution law of the subsurface crystal structure of single crystal copper and polycrystalline copper workpiece in the process of nano-cutting and nano-indentation is analyzed. The mechanical properties of workpiece surface under different cutting parameters are studied by nano-indentation simulation and experiment. Based on molecular dynamics simulation of monocrystalline copper nanoscale cutting, the V shape dislocation of tetrahedron stacking fault is deconstructed by using CNA conearest neighbor analysis and other analysis methods. The evolution process of different kinds of subsurface defects such as spherical clusters in the cutting process of workpiece is found. The structural characteristics and formation law of subsurface defects are found, and the geometric parameters of cutting tools, including the front angle, are changed by changing the cutting simulation. The change of subsurface structure caused by cutting tool parameters is analyzed, and the influence of tool parameters on dislocation evolution in cutting process is summarized. The molecular dynamics simulation of polycrystalline copper workpiece in nano-cutting was carried out. Through cutting force and stress distribution, the crystal structure and dislocations of polycrystalline copper workpiece were studied. Through the fluctuating law of cutting force and dislocation density of workpiece, the blocking effect of polycrystalline copper grain boundary on dislocation slip and the process of transformation with dislocation are found, and the phenomenon of stress shielding produced by polycrystalline copper grain boundary is also found. The influence of cutting depth on the crystal structure and dislocation characteristics of the workpiece is analyzed by changing the cutting depth of polycrystalline copper nanomachining simulation. The linear relationship between the cutting depth and the dislocation density inside the workpiece is found. The molecular dynamics simulation and processing experiment of nano-indentation of single crystal copper and polycrystalline copper were carried out respectively. On the one hand, the nanocrystalline indentation process of single crystal copper is analyzed by nano-indentation simulation, and the effect of subsurface defects on the dislocation formation of workpiece indentation is studied, and it is found that sub-surface defects will cause workpiece "work hardening". At the same time, the effect of cutting depth on the surface mechanical properties of single crystal copper workpiece was found by comparing with nano-indentation experiment. On the other hand, the difference of mechanical properties of polycrystalline copper workpiece under different cutting parameters is compared with experiments. It is found that the hardening effect is more obvious with the increase of cutting depth in a certain range. The simulation results of nano-indentation are compared with the experimental results, and the same characteristics of the trend are found, which proves the correctness of the conclusion qualitatively.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TG146.11
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