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基于分子动力学的单晶硅压痕过程计算机仿真研究 总被引:5,自引:0,他引:5
对单晶Si的压痕过程进行了分子动力学模拟。采用Morse势函数描述原子间的相互作用,以牛顿方程建立力学运动方程,使用改进后的Verlet算法解子运动轨迹,通过对MD仿真结果的分析研究,将压痕过程分为三个特征阶段,即初期弹性变形阶段,中期塑性变形阶段及非晶层形成阶段。并从原子角度分析了压痕过程中原子间势能,磨削力的变化,应力状态,磨削温度等特征,解释了微观材料的去除和表面形成机理。 相似文献
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对内部无缺陷的单晶硅纳米级磨削过程进行了分子动力学仿真,从磨削过程中瞬间原子位置、磨削力、原子间势能、损伤层深度等角度研究了纳米级磨削加工过程,解释了微观材料去除、表面形成和亚表面损伤机理。研究表明:磨削过程中,单晶硅亚表面损伤的主要形式是非晶结构形式,无明显的位错产生,硅原子间势能的变化是导致单晶硅亚表面损伤的重要原因;另外,发现磨粒原子与硅原子之间有黏附现象发生,这是由于纳米尺度磨粒的表面效应而产生的。提出了原子量级条件下单晶硅亚表面损伤层的概念,并定义其深度为沿磨削深度方向原子发生不规则排列的原子层的最大厚度。 相似文献
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纳米结构陶瓷涂层的磨削机理 总被引:2,自引:0,他引:2
用压痕断裂力学模型或切削加工模型来处理纳米结构陶瓷的磨削去除机理.把磨削中磨粒与工件的相互作用近似看成理想的小规模压痕现象,研究磨削裂纹的形成与扩展过程、材料的去除过程以及陶瓷磨削表面缺陷来评价陶瓷加工表面质量.切削加工模型证明了虽然材料去除通常由脆性去除实现,但大部分磨削能消耗与塑性变形有关. 相似文献
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应用陶瓷微观结构和磨削表面热应力的有关知识结合压痕断裂力学和损伤力学;根据几种典型结构陶瓷材料的SEM观察结果,分析了结构陶瓷磨削裂纹的产生过程、形成机理。 相似文献
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超高速磨削冲击成屑模型构建与机理研究 总被引:1,自引:1,他引:1
建立了脆性材料压痕实验的理论模型,分析了脆性材料压痕实验条件下的比能,给出了单颗磨粒总比能计算公式。对脆性材料进行了超高速磨削实验,并对实验结果进行分析,得出了超高速冲击条件下,脆性材料可以产生塑性流动破坏的结论。根据实验结果,建立了超高速磨削冲击成屑模型,分析了超高速磨削条件下磨屑形成的基本原理,提出了超高速磨削条件下磨屑形成的新构想。 相似文献
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单晶硅超精密磨削过程的分子动力学仿真 总被引:9,自引:2,他引:7
对内部无缺陷的单晶硅超精密磨削过程进行了分子动力学仿真,从原子空间角度观察了微量磨削过程,解释了微观材料去除、表面形成和亚表面损伤机理,并分析了磨削过程中的磨削力和磨削能量消耗。研究表明:磨削过程中,在与磨粒接触的硅表面原子受到磨粒的挤压和剪切发生变形,堆积在磨粒的前方,当贮存在变形晶格中的应变能超过一定值时,硅的原子键断裂,即完成了材料的去除;随着磨粒的运动,磨粒前下方的硅晶格在磨粒的压应力作用下晶格被打破,形成了非晶层,非晶层不断向前向深处扩展,造成了单晶硅亚表面的损伤;同时部分非晶层原子在压应力的作用下与已加工表层断裂的原子键结合,重构形成已加工表面变质层。 相似文献
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提出了以随机载荷作用次数为寿命度量指标框架下的零件可靠性建模方法,分别给出了强度不退化和强度退化时随机载荷多次作用下的零件可靠度与失效率计算模型,研究了不同情况下零件可靠度与失效率随载荷作用次数的变化规律。研究表明,即使零件强度不退化,零件的可靠度与失效率也会随着随机载荷作用次数的增加而逐渐减小,且失效率曲线具有浴盆曲线“早期失效期”和“偶然失效期”的特征。强度随载荷作用次数退化时,随着载荷作用次数的增加,零件的可靠度降低较为明显,失效率先减小后增大具有“浴盆曲线”的全部特征。 相似文献
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为了揭示氮化硅陶瓷磨削温度分布规律以及其对表面成形的影响,首先,建立氮化硅陶瓷纳米级切削的分子动力学模型;其次,研究切削过程中切削参数对切削温度的影响,以及加工过程中切削表面变质层的形成过程;最后,对 K 型热电偶测温和表面能谱分析的仿真与实验结果进行对比分析.结果表明:随着金刚石磨粒切削深度和切削速度的增加,原子晶格发生变形和非晶相变过程中时释放的能量增多,从而使切削温度升高;切削高温会引起氮化硅陶瓷发生非晶相变现象,非晶态原子重新与已加工表面断裂的原子键结合形成表面变质层;分子动力学仿真模型可以用来预测氮化硅陶瓷材料实际磨削加工中磨削温度变化情况,对生产加工具有参考价值. 相似文献
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A computer simulation method for investigating the form generation mechanism in the centerless through-feed grinding process
is described. The length of the contact line and the magnitude of the grinding force between the grinding wheel and workpieces,
vary with the change in the axial location of the current workpiece during grinding. Thus, a new coordinate system and a grinding
force curve of previous and/or following workpieces are introduced to treat the axial motion. Experiments and computer simulations
were carried out using four types of cylindrical workpiece shapes. To validate this model, simulation results are compared
with the experimental results. 相似文献
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A new grinding method using a torus-shaped grinding wheel and a machining path generation method with a novel moving coordinate system are proposed. With this new grinding method, the smooth spiral rake surface of a taper ball-end mill with constant helical angle and constant normal rake angle can be formed during one grinding process and the normal rake angle can be obtained accurately. The novel moving coordinate system is established based on taking account of both the cutting edge curve and the cutter body surface. By means of the novel moving coordinate system, the machining path generation becomes very simple. The proposed grinding method and the machining path generation method are verified by 3D simulation results. 相似文献
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Theoretical and experimental analysis on super precision grinding of monocrystal silicon 总被引:1,自引:0,他引:1
Guo Xiaoguang Guo Dongming Kang Renke Jin Zhuji 《Frontiers of Mechanical Engineering in China》2007,2(2):137-143
Through investigating the diamond-silicon grinding system, the grinding mechanism, including chip removal and subsurface damage,
is discussed with the aid of the molecular dynamics (MD) approach and grinding experiments. Based on MD simulation, nanometric-grinding
mechanism is analyzed from the viewpoint of instantaneous distribution of atoms, grinding force, and the potential energy
between atoms and the profile of the groove. The simulation results show that some silicon atoms are deformed and piled up
in front and on two sides of the abrasive surface because of the extrusion and cutting. When the energy in silicon lattice
reaches its maximum value, the bonds of silicon atoms are broken and the material is removed. With the advancement of the
abrasive, the silicon lattice under the abrasive surface is fractured, and then the amorphous layers are formed and propagated,
which causes the subsurface damage. At the same time, some amorphous atoms are reconstructed and the degenerating layer of
the machined surface is formed. Besides, the recovery of elatstic deformation occurs in the machined surface of the workpiece.
In addition, the grinding experiment and profile detection with the aid of the measurement for 3D profiling are performed
to verify the simulation results. The good agreement in the profile of the groove between the experimental value and the simulating
value shows that MD simulation is very effective and reliable, and successful to fulfill the investigation on nanometric machining
mechanism. 相似文献