触变性流体在旋转圆盘上的流动

采用甩涂过程的基本方程，导得触变性流体在旋转圆盘上流动的速度分布．并利用特征线法，得到薄膜厚度的方程．对其定性分析表明，流体的重建系数越小和破坏系数越大，将加快甩涂过程．     

刚性椭球对固定面的三维摩擦碰撞

讨论刚性椭球对固定面的三维摩擦碰撞．以法向冲量为自变量，建立碰撞过程中接触点切向速度的微分方程．利用相平面的奇点理论对碰撞过程中切向滑动的全局性态作定性分析，并导出切向滑动的解析积分．     

弹、塑性轮盘塑性区的实验应力换算

介绍一种弹、塑性状态轮盘的实验应力换算新方法．其优点是在迭代运算过程中无需反复利用拉伸曲线求割线模量E’,大大简化计算工作．     

界面裂纹的路径选择与数值模拟

利用界面断裂能和荷载混合度的概念研究界面裂纹的扩展路径，利用有限元数值方法模拟界面裂纹的扩展过程，再现界面断裂的各种几何构型．研究表明，界面的断裂能和混合度完全控制了裂纹在界面附近的扩展过程．数值预测的裂纹路径与理论结果一致     

链轮驱动系统的多刚体建模及分析

采用多刚体方法对链条链轮系统的驱动过程进行了建模和动力学分析．链节看作刚体,链轮看作等边刚性多边形,辊子看作两个链节之间的旋转副．啮合约束当作可变约束处理,当啮合力为正时,链节和链轮之间是固定约束,当力变负时,链节脱离链轮．利用龙格库塔法求解系统的拉格朗日方程．最后计算并分析了不同工况下的驱动过程,解释了系统的锁死现象,并进一步分析了两种避免锁死的处理方法．     

基于临界距离点法的混凝土Ⅰ型断裂韧度的预测

混凝土的断裂韧度是极为重要的断裂力学材料参数,本文利用临界距离理论(TCD)中的点法和混凝土标准断裂梁试样裂缝尖端应力场的近似解,提出了一种对混凝土断裂问题按临界距离的点法进行分析的方法．基于已有文献的试验材料及其实验结果,分析了这种断裂研究分析方法的可行性．将临界距离点法与双K断裂准则应用于几何相似的混凝土梁的断裂韧性和断裂过程区分析,验证了TCD点法的可靠性．实验表明：临界距离理论的点法能够获得比双K断裂准则相对安全的失稳断裂韧度,利用临界距离法还可得到相应断裂过程区长度的极限估算值．     

考虑空气阻力影响的振动筛分物料的运动分析

空气阻力对轻质物料筛分的影响是不可忽略的,本文利用达朗贝尔原理推导出物料在正向滑动、反向滑动和抛掷运动过程中的运动方程,并利用MATLAB软件仿真了物料在运动过程中的位移和速度,将结果与不考虑空气阻力时的物料运动进行对比分析,讨论了主要物理参数对物料运动的影响规律,为轻质物料的筛分提供理论参考．     

光纤模斑谱传感器复合材料固化监测研究

提出利用一种新型光纤传感器，通过测量光纤末端近场模斑谱反映光纤埋置周围树脂折射率的变化．计算了随着树脂固化过程中折射率变化的功率谱密度分布，给出截止频率与折射率的近似关系．给出了利用这种传感器进行复合材料树脂固化监测的实验结果．发现这种光纤传感器的信号可以用来反映固化凝胶点和固化结束点．由于固化后光纤仍保持光波导特性，该光纤还可以用来监测结构受环境的扰动如温度变化、振动等．     

高温下岩石SEM实时实验研究

首次利用带扫描电镜的高温疲劳试验机等目前最先进的实验手段,高温下实时观测了温度变化对石灰岩微结构的影响,有效地避免了由于岩石的热膨胀是不可逆的,它会受加温历史的影响,加热时的特性和冷却后的特性差异较大的影响．发现试样在升温过程很少发现热裂纹,但在冷却过程中反而易出现较多的微裂纹,认为是石灰岩在冷却过程中产生的残余应力所致．     

离散元法在求解三维冲击动力学问题中的应用

提出了三维连结型离散模型,建立了可实现连结型模型(用于连续介质)-接触型模型(用于非连续介质)转化的三维离散元计算程序,用来模拟连续介质转变为非连续介质的力学过程．利用该计算程序对冲击载荷下混凝土块体内(连续体情况下)的应力波传播过程进行了数值模拟．将计算结果的数值与LS-DYNA程序计算的结果进行比较,验证了该计算程序的计算精度．在此基础上,模拟了混凝土块体的动态破坏(连续介质向非连续介质转化)过程．其计算结果可用动画显示,得到的破坏形式与由实验得到的破坏形式相近．两个算例说明该离散元模型及其计算程序是模拟计算伴随有连续介质向非连续介质转变的动态破坏问题的有力工具．     

Flow and heat transfer in compression mold filling

The interaction between heat transfer and flow through temperature-dependent viscosity during compression molding of a cold charge in a hot mold is studied by numerical simulation of two-dimensional cases. The finite-element method is used to solve the equations of motion and energy with a mesh which conforms at every instant to the shape of the charge. The results show that under typical operating conditions a thin layer of warm, low viscosity fluid at the mold surface lubricates the remainder of the charge, which undergoes nearly a planar elongational deformation. For material properties and operating conditions typical of the compression molding of sheet molding compound, very little preferential flow of the material near the mold surface is predicted. The results support the assumption of a flat velocity profile in nonisothermal compression molding used by several workers, and explain the success of some isothermal mold-filling models at predicting mold-filling patterns for nonisothermal cases.     

Theoretical analysis of capillary-driven nanoparticulate slurry flow during a micromold filling process

The microcasting technique for the fabrication of microstructures mainly involves two consecutive steps, namely, the capillary-driven flow of nanoparticulate slurry in micromolds and sintering of the resulting preform. During the mold-filling step, particle settling leads to a spatial particle distribution in the preform, which affects the subsequent sintering kinetics, and in turn, and causes a shape distortion in the final sintered product. This paper presents a comprehensive theoretical model which is adopted to account for the capillary-driven flow and simultaneous particle settling behavior during the filling step. Numerical simulations are performed over a wide range of parameters to illustrate the effects of four nondimensional groups on the fill time and particle distribution, and to develop design windows, which may serve as guidelines in the design of particle properties, slurry composition, and mold dimensions to maintain a desired level of homogeneity in particle distribution.     

水下模拟失重动力学研究综述

水下模拟失重方法是国外20世纪60年代发展起来的地面模拟失重的有效方法，在载人航天中发挥了举足轻重．不可替代的作用；水下模拟失重动力学是水下模拟失重方法的理论基础．简要概述了水下模拟失重方法的产生背景、原理、发展和优缺点；综述了水下模拟失重动力学的国内外研究现状，展望了水下模拟失重动力学今后的发展趋势．     

An extended unresolved CFD-DEM coupling method for simulation of fluid and non-spherical particles

This study develops an extended unresolved CFD-DEM coupling method for simulation of the fluid–solid flow with non-spherical particles. The limitation of fluid grid size is discussed, by simulating the settling of a cylinder in a Newtonian fluid based on the resolved and unresolved CFD-DEM coupling method. Then, the calculation of porosity and the fluid–particle relative velocity based on the particle shape enlargement method for simulation of non-spherical particles is proposed. The availability of the particle shape enlargement method for the simulation of non-spherical particles with different sphericity is discussed in this work, by comparing it with the results from the equivalent diameter enlargement method. The limitation of the equivalent diameter enlargement method for non-spherical particles is revealed from the simulation results. Several typical cases are employed to elaborate and verify the extended unresolved CFD-DEM method based on particle shape enlargement method, by presenting a good consistency with the experimental results. It proves that the extended unresolved CFD-DEM method is suitable for different CFD grid size ratios, and consolidates that it is a universal calculation method for CFD-DEM coupling simulation.     

刚柔耦合定位平台结构-运动-控制一体化建模

针对微电子制造行业等领域中的长行程高精度定位问题,提出了一种刚柔耦合定位平台,并建立了其结构-运动-控制一体化动力学仿真模型。首先,根据刚柔耦合定位平台的结构特点对浮动坐标法进行修改,建立了简洁高效的动力学仿真模型。其次,结合动力学模型、3阶S型曲线和经典的PID控制方法建立了结构-运动-控制一体化仿真模型。最后,通过数值算例对仿真模型的有效性进行了验证。数值模拟结果显示,建立的结构-运动-控制一体化仿真模型能够有效地对定位平台的工作过程进行模拟,为后续的结构优化、运动规划和控制系统设计等工作创造条件。     

Simulation of stochastic loads for fatigue experiments

A simple direct simulation method for stochastic fatigue-load generation is described in this paper. The simulation method is based on the assumption that only the peaks of the load process significantly affect the fatigue life. The method requires the conditional distribution functions of load ranges given the last peak values. Analytical estimates of these distribution functions are presented in the paper and compared with estimates based on a more accurate simulation method. In the more accurate simulation method samples at equidistant times are generated by approximating the stochastic load process by a Markov process. Two different spectra from two tubular joints in an offshore structure (one narrow banded and one wide banded) are considered in an example. The results show that the simple direct method is quite efficient and results in a simulation speed of about 3000 load cycles per second using a personal computer. Finally the proposed simulation method for fatigue-load generation is tested by comparing some fatigue damage measures obtained by the simulation methods.     

On a modified Monte-Carlo method and variable soft sphere model for rarefied binary gas mixture flow simulation

The effect of new terms in the improved algorithm, the modified direct simulation Monte-Carlo (MDSMC) method, is investigated by simulating a rarefied binary gas mixture flow inside a rotating cylinder. Dalton law for the partial pressures contributed by each species of the binary gas mixture is incorporated into our simulation using the MDSMC method and the direct simulation Monte-Carlo (DSMC) method. Moreover, the effect of the exponent of the cosine of deflection angle (α) in the inter-molecular collision models, the variable soft sphere (VSS) and the variable hard sphere (VHS), is investigated in our simulation. The improvement of the results of simulation is pronounced using the MDSMC method when compared with the results of the DSMC method. The results of simulation using the VSS model show some improvements on the result of simulation for the mixture temperature at radial distances close to the cylinder wall where the temperature reaches the maximum value when compared with the results using the VHS model.     

岩石结构面直剪力学特征的颗粒流宏细观分析

目前,由于颗粒尺寸和位置随机分布而产生的粗糙度,导致在模拟过程中出现应力集中现象,从而无法利用PFC2D准确模拟岩石结构面的剪切力学行为。为了避免以上弊端,采用结构面两侧颗粒组接触判别法分别对倾角为20°和30°的三角形单锯齿结构面进行不同法向应力下的直剪模拟。模拟结果与物理试验结果基本吻合,表明此模拟方法可以真实模拟岩石结构面剪切力学行为。为了进一步验证此模拟方法在天然结构面模拟试验中的可行性,利用PFC2D对Barton标准十条节理轮廓线模型进行不同法向应力下的直剪试验,模拟结果与理论值吻合,表明模拟方法具有可行性,为剪切破坏过程和机理分析提供可靠的理论依据,为研究粗糙结构面强度特征提供了一种思路。     

A multi-scale architecture for multi-scale simulation and its application to gas–solid flows

A multi-scale hardware and software architecture implementing the EMMS (energy-minimization multi-scale) paradigm is proven to be effective in the simulation of a two-dimensional gas–solid suspension. General purpose CPUs are employed for macro-scale control and optimization, and many integrated cores (MICs) operating in multiple-instruction multiple-data mode are used for a molecular dynamics simulation of the solid particles at the meso-scale. Many cores operating in single-instruction multiple-data mode, such as general purpose graphics processing units (GPGPUs), are employed for direct numerical simulation of the fluid flow at the micro-scale using the lattice Boltzmann method. This architecture is also expected to be efficient for the multi-scale simulation of other complex systems.     

变拓扑多体系统动力学的全局仿真

对于在运动过程中系统自由度会发生改变的变拓扑复杂机械系统，提出基本系统与当前系统的概念，采用约束激活的思想，实现系统拓扑结构在仿真过程中自动切换．以笔者开发的多体系统动力学仿真软件ＤＡＭＢ为基础，将其扩展为可进行变拓扑多体系统动力学全局仿真的软件系统．文中以某型号火箭炮系统火箭弹发射动力学的全局仿真为例说明这种方法的可行性