纯铜双晶体拉伸变形的介观力学分析

利用介观力学观察设备对Cu双晶拉伸变形行为进行了研究.结果表明,在双晶体变形过程中,取向不同的晶粒滑移方式和形变量等都不同,软取向的晶粒变形较快、变形量大,并对其它晶粒的变形产生影响.不利取向的晶粒首先在晶界附近出现无滑移区,随外应力增加出现次滑移以协调变形.云图分析表明,变形过程中晶界处有明显的应变集中.在变形过程中产生了亚晶粒.能量分析表明,变形过程中晶粒储能的升高足以引发新晶粒的生成.

固体范性形变与断裂的介观力学物理原理(英文)

本文回顾了建立在物理介视力学基础上的固体范性形变与断裂的研究概况，从物理介现力学角度看，处于载荷下的固体是一个多层次的自治体系．依尺度不变原理，在微观、介观、宏观尺度上的范性流变，本质上是相互关联的．整体介观体积在介观尺度上按照“切变加旋转”的方式运动．固体范性形变与断裂可考虑为同样过程的二个阶段．

聚氧乙烯单晶介观力学性质研究

以固定于平整硅基底上的聚氧乙烯单晶为模型体系,利用原子力显微镜的成像功能定位单晶后,用探针压穿聚氧乙烯单晶层,测量单晶层的介观力学性质.结果显示,原子力显微镜探针压穿单晶层所需要的力值为50~200 n N,随着探针曲率半径、下压速率和聚氧乙烯与溶剂界面能的增加,压穿单晶层所需要的力值也随之增加.结合分子模型证明在压穿过程中聚氧乙烯分子被原子力显微镜探针挤压到单晶外部.另外,发现在相同的下压速率和拉伸速率下,将相同数目的聚氧乙烯分子链挤压出晶体的能量与拉伸出晶体所需要的能量接近,继而从能量角度建立了聚氧乙烯晶体微观力学性质与介观力学性质的联系.

乳化和润湿反转现象的耗散粒子动力学研究

利用耗散粒子动力学方法,研究了化学驱过程中乳化和润湿反转两个重要的物理化学现象。通过合理划分流体粒子和定义粒子之间相互作用参数,模拟了十二烷基苯磺酸钠、正十二烷和水三组分体系的自发乳化现象;通过附加固壁条件,模拟了在水动力作用下吸附在岩石表面的油珠发生破裂的非自发乳化过程,以及由于表面活性剂在岩石表面吸附而引起的润湿反转现象,比较了润湿反转前后残余油珠的运动情况。模拟结果表明:作为介观力学的离散粒子动力学方法,耗散粒子动力学方法可作为研究包含物理化学现象的化学驱渗流问题的重要手段。

纳米铝合金的断裂与塑性变形

在结构非均匀的多晶材料中,局域化塑性变形不仅在微观层次而且也在介观层次上具有波动特征,并以塑性波形态进行扩展,这一现象与材料亚韧性断裂之间有相互关系。纳米晶、亚微米微晶2009铝合金试样在经受拉伸应力实验时,试样上各点的应变量在三维方向上均呈波动性变化,且随着外加载荷的增加而波动的幅度增加。塑性变形的波动的传播是在加载过程中,试样内的剪切稳定性丧失后,由于晶粒群转动,在试样上沿最大剪应力方向形成了吕得尔斯条带而逐步形成的。主剪切带形成了一个塑性变形的波峰,接下去侧生条带和次生带形成波峰和波低谷区,周而复始,形成了塑性变形的波动的传播。应力应变峰值的形成与材料缺陷所造成应力集中有关。试样于应力集中点起始迅速开裂。宏观断裂强度仅体现了材质缺陷弥散程度的统计平均数。

纳米晶、亚微米微晶2009铝合金塑性形变的波动特性

纳米晶、亚微米微晶2009铝合金塑性形变试样上各点的应变量是不相同的，并且呈波动性变化，随着外加载荷的增加而波动的幅度增加，表明在拉伸过程中，其应力传播和剪切变形传播在三维方向都具有波动特性。形成峰值与材料缺陷造成应力集中有关，实验结果表明纳米晶、亚微米微晶2009铝合金材料的塑性变形的流动行为的波动特性和非均匀特性，证明了介观力学提出的观点。即材料进入塑性变形后，晶粒群将进入平移-转动涡流，将材料的初始结构层次（包括晶粒、晶界、晶群以及试样整体）全部纳入变形范畴。

Mesoscopic Simulation of Aggregate Behaviour of Polymers in β-HMX-based PBXs

The mesoscopic structures of β-HMX （octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine）- based PBXs （polymer bonded explosives） at room temperature were investigated using dissipative particle dynamics method. The parameters and repulsive parameters of dif- ferent polymers and β-HMX, the mesoscopic structures of β-HMX-based polymer-bonded explosives at different temperatures have been studied. The results showed that the compat-ibility between β-HMX and vinylidenedifluoride （VDF）,β-HMX and chlorotrifluoroethylene （CTFE）, VDF and CTFE increased with increasing temperature. The temperature and mo-lar ratio of the polymers played an important role in wrapped process. And there exists the optimum temperature and molar ratio.

The Squeezing Effect in a Mesoscopic RLC Circuit

Using the path integral method we derive quantum wave function and quantum fluctuations of charge andcurrent in the mesoscopic RLC circuit. We find that the quantum fluctuation of charge decreases with time, oppositely,the quantum fluctuation of current increases with time monotonously. Therefore there is a squeezing effect in the circuit.If some more charge devices are used in the mesoscopic-damped circuit, the quantum noise can be reduced. We also findthat uncertainty relation of charge and current periodically varies with the period π/2 in the under-damped case.

Improved similarity criterion for seepage erosion using mesoscopic coupled PFC–CFD model

Conventional model tests and centrifuge tests are frequently used to investigate seepage erosion. However, the centrifugal test method may not be efficient according to the results of hydraulic conductivity tests and piping erosion tests. The reason why seepage deformation in model tests may deviate from similarity was first discussed in this work. Then, the similarity criterion for seepage deformation in porous media was improved based on the extended Darcy-Brinkman-Forchheimer equation. Finally, the coupled particle flow code–computational fluid dynamics(PFC-CFD) model at the mesoscopic level was proposed to verify the derived similarity criterion. The proposed model maximizes its potential to simulate seepage erosion via the discrete element method and satisfy the similarity criterion by adjusting particle size. The numerical simulations achieved identical results with the prototype, thus indicating that the PFC-CFD model that satisfies the improved similarity criterion can accurately reproduce the processes of seepage erosion at the mesoscopic level.

Recovering Navier–Stokes Equations from Asymptotic Limits of the Boltzmann Gas Mixture Equation

This paper is devoted to the derivation of macroscopic fluid dynamics from the Boltzmann mesoscopic dynamics of a binary mixture of hard-sphere gas particles.Specifically the hydrodynamics limit is performed by employing different time and space scalings.The paper shows that,depending on the magnitude of the parameters which define the scaling,the macroscopic quantities(number density,mean velocity and local temperature)are solutions of the acoustic equation,the linear incompressible Euler equation and the incompressible Navier–Stokes equation.The derivation is formally tackled by the recent moment method proposed by[C.Bardos,et al.,J.Stat.Phys.63(1991)323]and the results generalize the analysis performed in[C.Bianca,et al.,Commun.Nonlinear Sci.Numer.Simulat.29(2015)240].