本文選題：納米切削 + 切削原理　； 參考：《燕山大學(xué)》2015年碩士論文

【摘要】：納米切削是一種高效、直接的微尺度制造方法,對于國防、航天等領(lǐng)域至關(guān)重要。然而對于單晶硅這類脆性材料,加工中材料行為會隨尺度變化由發(fā)生韌性變形轉(zhuǎn)而發(fā)生脆性變形,即在微尺度下無法忽略材料微結(jié)構(gòu)的變化。這種微結(jié)構(gòu)的演化與變形方式的關(guān)聯(lián)性嚴(yán)重制約了加工效率與質(zhì)量的提高。本文從材料變形角度,利用分子動力學(xué)方法,探究了納米尺度切削原理與微結(jié)構(gòu)演化的關(guān)聯(lián)性關(guān)系。首先,本文簡述了分子動力學(xué)方法的基本思路,分析了金剛石單點切削工藝中的材料去除方式,并結(jié)合分子動力學(xué)特點,闡述了正交切削模型的建立過程。在合理選擇模型參數(shù)的基礎(chǔ)上,確定了勢函數(shù)等仿真參數(shù)。采用并行計算方法,基于幾何模型,構(gòu)建了單晶硅納米切削過程的分子動力學(xué)模型。其次,分析了單晶硅納米切削中塑性去除模式的特點。從切屑形成、原子遷移軌跡、切削變形三個方面闡述了塑性去除的變形機(jī)理。通過徑向分布函數(shù)、配位數(shù)等多種方法,分析了塑性去除中材料微結(jié)構(gòu)的變化規(guī)律,探究了塑性去除過程與微結(jié)構(gòu)演化的聯(lián)系。計算了塑性去除過程中單晶硅材料的應(yīng)力分布、勢能分布與自由體積變化規(guī)律,結(jié)合微結(jié)構(gòu)演化特點,說明了應(yīng)力、自由體積與微結(jié)構(gòu)演化的內(nèi)在關(guān)聯(lián)性,發(fā)現(xiàn)了自由體積與塑性流動的關(guān)聯(lián)關(guān)系,說明了宏觀切削參數(shù)對塑性去除過程的影響關(guān)系。最后,分析了單晶硅納米切削中脆性去除模式的特點�；诮饎偸瘑吸c切削工藝特點,觀察了不同未變形切屑厚度下材料變形方式的差別,分析了相應(yīng)的微結(jié)構(gòu)變化特點,從相變角度揭示了脆塑轉(zhuǎn)變過程的剪切局部化特征。通過分析剪切帶的構(gòu)成,說明了剪切帶承載能力隨未變形切屑厚度變化的規(guī)律。研究了刃口鈍圓半徑與晶向?qū)Υ嘈匀コ^程的影響。從位錯密度與位錯組態(tài)兩方面分析了缺陷在脆性去除過程中的作用,揭示了納米切削過程中單晶硅無法通過位錯機(jī)制進(jìn)行塑性變形的原因。計算了脆性去除中的勢能與應(yīng)力分布,說明了脆性變形過程對應(yīng)的工藝特點。
[Abstract]:Nano-cutting is an efficient and direct micro-scale manufacturing method, which is very important in the fields of national defense, aerospace and so on. However, for brittle materials such as monocrystalline silicon, the behavior of materials changes from ductile deformation to brittle deformation with the change of scale, that is to say, the change of material microstructure can not be ignored at microscale. The relationship between the evolution of the microstructure and the deformation mode seriously restricts the improvement of processing efficiency and quality. In this paper, the relationship between the principle of nanoscale cutting and the evolution of microstructure is studied by molecular dynamics from the point of view of material deformation. Firstly, the basic idea of molecular dynamics method is briefly introduced, and the material removal method in diamond single point cutting process is analyzed, and the process of establishing orthogonal cutting model is expounded according to the characteristics of molecular dynamics. Based on the reasonable selection of model parameters, the simulation parameters such as potential function are determined. The molecular dynamics model of monocrystalline silicon nanocrystalline cutting process was constructed based on geometric model by parallel calculation method. Secondly, the characteristics of plastic removal mode in monocrystalline silicon nanomachining are analyzed. The deformation mechanism of plastic removal is described from chip formation, atom migration path and cutting deformation. By means of radial distribution function, coordination number and other methods, the variation law of material microstructure in plastic removal was analyzed, and the relationship between plastic removal process and microstructure evolution was explored. The stress distribution, potential energy distribution and free volume variation of monocrystalline silicon in plastic removal process are calculated. The intrinsic relationship between stress, free volume and microstructure evolution is explained by combining the characteristics of microstructure evolution. The relationship between free volume and plastic flow is found, and the influence of macro cutting parameters on plastic removal process is explained. Finally, the characteristics of brittle removal mode in monocrystalline silicon nanomachining are analyzed. Based on the characteristics of diamond single point cutting process, the different deformation modes of materials with different thickness of undeformed chip are observed, the corresponding characteristics of microstructure changes are analyzed, and the shear localization characteristics of brittle plastic transition process are revealed from the angle of phase transformation. By analyzing the composition of the shear band, the variation of the bearing capacity of the shear band with the thickness of the undeformed chip is explained. The effects of the radius and orientation of the edge obtuse circle on the brittleness removal process were studied. The function of defects in brittle removal process was analyzed from dislocation density and dislocation configuration, and the reason why single crystal silicon could not be deformed by dislocation mechanism in nanoscale cutting was revealed. The potential energy and stress distribution in brittleness removal are calculated, and the process characteristics of brittle deformation process are explained.
【學(xué)位授予單位】：燕山大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TQ127.2

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本文編號：1827638