包含联合多重空间和时间规模的问题为粒子或连续统力学的常规框架提供真实挑战。在这篇论文，四案例研究(砍乐队形成大批金属性的眼镜，分裂源于压力波浪，在一个探查尖端和样品之间的相互作用，有分子的统计热力学的 nanoindentation 的模拟)被提供说明trans规模问题的三个层次(问题由于各种各样的物理机制在宏级，问题由于在 macro/micro-level 的微结构进化，问题由于在 micro/nano-level 联合原子/分子和有限尺寸身体)并且他们的明确的表达。因此，非平衡统计力学，联合 trans 规模方程和同时的答案，和基于原子 / 分子的相互作用的 trans 规模算法作为 trans 规模力学的三个可能的模式被建议。
The formation and mechanical properties of amorphous copper are studied using molecular dynamics simulation. The simulations of tension and shearing show that more pronounced plasticity is found under shearing, compared to tension. Apparent strain hardening and strain rate effect are observed. Interestingly, the variations of number density of atoms during deformation indicate free volume creation, especially under higher strain rate. In particular, it is found that shear induced dilatation does appear in the amorphous metal.
La57.6Al17.5(Cu,Ni)24.9 and La64Al14(Cu,Ni)22 bulk metallic glasses (BMGs) were prepared by copper-mould casting method. Plastic deformation behavior of the two BMGs at various loading rates was studied by nanoindentation. The results showed that the La57.6Al17.5(Cu,Ni)24.9 BMG with a glass transition temperature of 423 K exhibited prominent serrated flow at low loading rates, whereas less pronounced serrated flow at high rates during nanoindentation. In contrast, the La64Al14(Cu,Ni)22 BMG with a glass transition temperature of 401 K exhibited prominent serrated flow at high loading rates. The different rate dependency of serrated flow in the two La-based BMGs is related to the different glass transition temperature, and consequently the degree of viscous flow during indentation at room temperature. A smoother flow occurs in the alloy with relatively lower glass transition temperature, due to the relaxation of stress concentration.
Wei Peng1), Taihua Zhang2), Yuan Liu1), Lei Li1), and Bingchen Wei1) 1) National Microgravity Laboratory, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China 2) State Key Laboratory of Nonlinear Mechanics (LNM), Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080, China
This study investigated the process parameter effects on the structural and optical properties of ZnO thin film using radio frequency (RF) magnetron sputtering on amorphous glass substrates. The process parameters included RF power and working pressure. Results show that RF power was increased to promote the crystalline quality and decrease ZnO thin film defects. However, when the working pressure was increased to 3 Pa the ZnO thin film crystalline quality became worse. At a 200 W RF power and 1 Pa working pressure, the ZnO thin film with an optical band gap energy of 3.225 eV was obtained.
Recently,people are confused with two opposite variations of elastic modulus with decreasing size of nano scale sample:elastic modulus either decreases or increases with decreasing sample size.In this paper,based on intermolecular potentials and a one dimensional model,we provide a unified understanding of the two opposite size effects.Firstly,we analyzed the microstructural variation near the surface of an fcc nanofilm based on the Lennard-Jones potential.It is found that the atomic lattice near the surface becomes looser in comparison with the bulk,indicating that atoms in the bulk are located at the balance of repulsive forces,and the elastic moduli decrease with the decreasing thickness of the film accordingly.In addition,the decrease in moduli should be attributed to both the looser surface layer and smaller coordination number of surface atoms.Furthermore,it is found that both looser and tighter lattice near the surface can appear for a general pair potential and the governing mechanism should be attributed to the surplus of the nearest force to all other long range interactions in the pair potential.Surprisingly,the surplus can be simply expressed by a sum of the long range interactions and the sum being positive or negative determines the looser or tighter lattice near surface respectively.To justify this concept,we examined ZnO in terms of Buckingham potential with long range Coulomb interactions.It is found that compared to its bulk lattice,the ZnO lattice near the surface becomes tighter,indicating the atoms in the bulk are located at the balance of attractive forces,owing to the long range Coulomb interaction.Correspondingly,the elastic modulus of one-dimensional ZnO chain increases with decreasing size.Finally,a kind of many-body potential for Cu was examined.In this case,the surface layer becomes tighter than the bulk and the modulus increases with deceasing size,owing to the long range repulsive pair interaction,as well as the cohesive many-body interaction caused by the electron redistribution.
