聚合物注射成型流动残余应力的数值分析

建立了可压缩黏弹性聚合物熔体在薄壁型腔中充模/保压过程中非等温、非稳态流动 的数学模型,用数值方法实现了注射成型过程中流动应力和取向建立及松弛过程的模拟,研 究了熔体温度、模具温度和注射速率等工艺条件对分子冻结取向的影响,取得了与实验相符 的结果.     

注塑模保压过程的数值分析

 基于对注塑成型保压过程的机理研究，本文利用黏性、可压缩非 牛顿流体基本方程，得到了注塑模保压过程分析的控制方程，采用数值 方法实现了对保压过程的数值模拟，并通过实例说明如何利用数值模拟 为优化注塑模成型加工提供科学的理论根据.     

装药及外界保护介质对炸药爆轰合成超微金刚石的影响

研究了不同保护介质对超微金刚石（ＵＦＤ）生成的影响，认为爆轰产物与外部介质间的传热速度对ＵＦＤ得率影响很大；外部保护介质在爆轰产物膨胀阶段的保压作用在ＵＦＤ合成过程中有重要作用。实验结果指出，要提高ＵＦＤ得率，装药应存在一个最佳直径。用水和冰作为保护介质可使ＵＦＤ得率超过１０％，比利用马赫效应装药更适用于实际生产。     

基于ALE描述的压缩流动三维粘弹性数值模拟

塑料熔体压缩流动中在主流动平面及厚度方向均有速度变化,结合了剪切和拉伸两种流动特征。为了准确描述和模拟塑料熔体的压缩流动,本文基于粘弹性及ALE原理建立了熔体三维流动理论模型,构造了有限元求解的变分方程。为了避免整体求解计算量大、稳定性差的缺陷,提出了两重迭代解耦合算法分别求解耦合的连续方程、动量方程、本构方程、能量方程,开发了模拟程序。开展了等厚度板及变厚度板的注压成型实验及相应的数值模拟,结果表明:压缩过程中出现压力变化小于4.57%的平台现象;温度呈指数规律下降;塑料入口、流动末端第一法向应力差比平均值分别高1.73MPa、0.87MPa,变厚度区域第一法向应力差比平均值高1.16MPa。本文提出的理论模型和数值算法能够较好地表征压缩过程中熔体的压力、温度变化、应力演化。     

气体炮及其常规测试技术(二)

气体炮经过精密的安装以后,就要进入实验发射的调试阶段。在调试阶段要测量的性能参数大体上有两方面的内容:一是静态性能,主要检验加压和保压性能;抽真空和保真空性能;各联接部件的工作状态是否可靠等。这部分工作基本上属于检验机械加工和组装的质量;二是发射性能,主要检验弹道性能,其内容有高压气室工作过程中的压力变化,活塞和弹丸在管内的运动规律,弹丸出炮口的速度和姿态等。 静态检验的内容对于一级炮和二级炮都是相同的。     

埋头弹药发射过程药筒力学特性分析

埋头弹药是一种新型战场用弹药,自动机采用旋转闭锁新原理,供弹与退壳同步进行。在发射过程中埋头弹药的工况不同于传统的弹药筒,针对埋头弹药在特殊工作条件下药筒内压变化及变形特征,分析了药筒的动力学过程,获得了药筒在贴壁前、贴壁后、卸载过程的力学特性。通过数值分析发现:在最大膛压为400MPa条件下,聚乙烯药筒性能良好,卸压后能迅速弹性恢复。在此基础上设计了金属与塑料耦联的35mm埋头弹药筒,射击实验表明该药筒满足连发射击要求。     

拉杆调整监测装置

本文研制了适合塑料注射成型机拉杆调整的监测装置,并对其主要组成部份之一的拉杆调整传感器的工作原理作了较详细的叙述.该装置结构简单、制作容易、数字显示、直观可靠。     

纤维增强复合材料界面强度的细观测试方法

本文对纤维增强复合材料界面强度细观试验方法的发展及现状进行了评述，分析了各种试验方法的优点和不足。着重对纤维压入试验方法从试验的装置，试件的制备，试验的过程以及试验的理论分析方法等各方面进行了详细介绍。应用纤维压入试验测试了碳纤维增强环氧树脂复合材料的界面强度     

锥形轴对称微管道内流动特性实验研究

介绍了生物转基因显微注射的应用和存在的问题。针对显微注射所用的锥形轴对称微管道，进行了流动过程理论分析，并在微流动实验平台上对这种管道内流动进行了流量与压力特性参数的连续观测实验，详尽介绍了实验装置和实验过程，并给出了尖端直径为4～15μm的锥形管道流动实验结果。     

落柱式高压粘度装置的研制与压粘试验结果

作者研制了一台可测试润滑油在高压下的粘度和密度的落柱式高压粘度装置。本装置采用了新型高压粘性动密封和新型高压流变平垫静密封,经1200MPa试压、1000MPa压力下48小时保压和使用试验证明均无泄漏。用本装置所获得的压粘数据的重现性好、灵敏度高、可比性强。     

Numerical modelling of gas–solid fluidized beds using the two‐fluid approach

This paper details an approach to modelling gas–solid fluidized beds using the two‐fluid granular temperature model. Details concerning the difficulties associated with the boundary conditions, particularly for curved boundaries, are described along with a novel means of obtaining the internal stress of the solid‐phase, in part, by solving an implicit equation. This results in a scheme that is stable even when the solid volume fraction is close to maximum packing. A transient, mixed finite element discretization is used to solve the multi‐phase equations with a discontinuous finite element representation of the granular temperature and continuity equations. A new solution method is proposed to solve the coupled momentum and continuity equations based on Arnoldi iteration. Two fluidized beds are modelled, one in the bubbling regime and the other in the slugging regime. These simulations are compared with experiments. Copyright © 2001 John Wiley & Sons, Ltd.     

A dynamic finite element method for inhomogeneous deformation and electromechanical instability of dielectric elastomer transducers

We present a three-dimensional nonlinear finite element formulation for dielectric elastomers. The mechanical and electrical governing equations are solved monolithically using an implicit time integrator, where the governing finite element equations are given for both static and dynamic cases. By accounting for inertial terms in conjunction with the Arruda–Boyce rubber hyperelastic constitutive model, we demonstrate the ability to capture the various modes of inhomogeneous deformation, including pull-in instability and wrinkling, that may result in dielectric elastomers that are subject to various forms of electrostatic loading. The formulation presented here forms the basis for needed computational tools that can elucidate the electromechanical behavior and properties of dielectric elastomers that are used for engineering applications.     

非确定结构系统区间分析的泛灰求解方法

工程中的不确定性问题可以用区间分析、概率理论或模糊理论来求解。采用泛灰区间分析法来处理结构静力分析和设计中的不确定性问题。将结构系统中的不确定性参数用区间数来表示，用有限元法建立系统的控制方程。该控制方程是线性区间方程组。然后，在概述泛灰数的概念及其运算规则的基础上，介绍了泛灰数与区间数的转化，利用泛灰数的可扩展性对区间进行分析，研究了泛灰线性方程求解，然后将它应用于结构静力分析和设计中的不确定性问题，泛灰数不仅具有区间分析的功能，而且能解决区间分析所不能解决的问题。文中给出了两个算例，列出了本文算法与其他算法的结果比较。     

A shearable and thickness stretchable finite strain beam model for soft structures

Soft materials and structures have recently attracted lots of research interests as they provide paramount potential applications in diverse fields including soft robotics, wearable devices, stretchable electronics and biomedical engineering. In a previous work, an Euler–Bernoulli finite strain beam model with thickness stretching effect was proposed for soft thin structures subject to stiff constraint in the width direction. By extending that model to account for the transverse shear effect, a Timoshenko-type finite strain beam model within the plane-strain context is developed in the present work. With some kinematic hypotheses, the finite deformation of the beam is analyzed, constitutive equations are deduced from the theory of finite elasticity, and by employing the standard variational method, the equilibrium equations and associated boundary conditions are derived. In the limit of infinitesimal strain, the new model degenerates to the classical extensible and shearable elastica model. The corresponding incremental equilibrium equations and associated boundary conditions are also obtained. Based on the new beam model, analytical solutions are given for simple deformation modes, including uniaxial tension, simple shear, pure bending, and buckling under an axial load. Furthermore, numerical solution procedures and results are presented for cantilevered beams and simply supported beams with immovable ends. The results are also compared with the previously developed finite strain Euler–Bernoulli beam model to demonstrate the significance of transverse shear effect for soft beams with a small length-to-thickness ratio. The developed beam model will contribute to the design and analysis of soft robots and soft devices.     

曲线梁研究进展

曲线梁在工程中的应用非常广泛, 但由于曲率的影响, 导致梁内弯矩和扭矩的耦合, 使得 曲线梁的研究相对直梁非常复杂. 本文从4个方面较为详细地评述了近年来国内外曲线梁的 研究进展情况. 从曲线梁的平衡方程、几何方程和基本微分方程出发, 概述了曲线梁静动力 学的基本理论、建模及分析方法; 面内面外振动及分析方法; 非线性问题及分析方法; 特别 评述了有限元单元法在曲线梁研究中的应用, 论述了各种曲梁单元的优缺点; 对复合曲线梁 的发展及理论研究进行介绍; 推导了空间曲线梁非线性动力学方程; 最后提出了值得进一步 研究的方向及采用的方法.     

基于多块对接网格的隐式气体运动论统一算法应用研究

基于玻尔兹曼模型方程的气体运动论统一算法(gas kinetic unified algorithm,GKUA) 给出了一种能模拟从连续流到自由分子流跨流域空气动力学问题的途径. 该算法采用传统计算流体力学技术将分子运动和碰撞解耦处理,若采用显式格式将受格式稳定条件限制,在模拟超声速流动尤其是近连续流和连续流区的流动时计算效率较低. 为了提高计算效率,扩展其工程实用性,采用上下对称高斯-赛德尔(LU-SGS) 方法和有限体积法构造了求解玻尔兹曼模型方程的隐式方法,同时在物理空间采用能处理任意连接关系的多块对接网格技术. 通过模拟近连续过渡区并排圆柱绕流问题,计算结果与直接模拟蒙特卡洛方法模拟值吻合较好,验证了该方法用于跨流域空气动力计算的可靠性与可行性.      

A failure criterion based on material instability

Scaling laws for adiabatic shear bands are used to parameterize a model that is suitable for introducing shear damage within engineering calculations. One-dimensional solutions to the governing equations for a single shear band provide laws that connect the driving deformation, the imperfections, and the physical characteristics of the material to the process of stress collapse [International Journal of Plasticity 8 (1992) 583, Mechanics of Materials 17 (1994) 215]. The current model uses homogeneous material response and the scaling laws to anticipate the correct timing beyond the maximum stress at which stress collapse should occur. The model is implemented into a finite element code for wave propagation and used in the analysis of boundary value problems that are dominated by shear failure. Finally, implications of the model for simulations of material failure are discussed.