结构形状优化与智能模型化

阻碍形状优化软件广泛应用的障碍之一是依据自然设计度量描述和建立设计模型、分析模型、优化模型以及实现三个模型之间的转换.本文称这一困难为结构形状优优设计软件的适用性.本文提出了一种方法用来动态地确定平面连续体结构形状优化过程中的边界,应用基于人工智能方法的启发式规则与技术,自动生成由设计单元法表示的几何模型,也就是将一个结构自动剖分成若干个大的四边形映射单元.这些大单元对于进一步的网络生成是必要的,同时也是向全自动计算机辅助形状优化系统前进的重要一步.     

基于AutoCAD的有限元建模系统AutoFEM

介绍了基于ＡｕｔｏＣＡＤ平台开发应用程序的主要特点和在ＡｕｔｏＦＥＭ中采用的软件接口方案，数据模型及所见即所得等。     

On the Validity of Darcy's Law for Stable High-Concentration Displacements in Granular Porous Media

Recently, it has been suggested that Darcy's Law might not be applicable for modelling miscible, density-dependent flow in porous media. To investigate this, three sets of careful laboratory column experiments were performed on coarse and medium sands, consisting of upward displacement of water by sodium chloride solutions with concentrations ranging from 5 to 200g/l. Data on salt concentrations and water pressures were collected in horizontal transects along the flow direction. Salt concentration data were also collected in the influent and exit lines. The experimental data were analysed using a simplified approach based on Darcy's Law alone, applied with the assumption of a sharp interface. Darcy's Law was used to estimate porous medium permeability by fitting predictions to experimental data. Consistent estimates of permeability were obtained for each set of experiments. The results indicate that Darcy's Law adequately describes high concentration displacements through saturated coarse- and medium-grained porous media.     

有限元网格自动生成及绘制中的实用处理技巧

提出了超大单元、结点归一化相对距离判别法这一快速三维自动剖分技术，针对大型水工建筑物的特点，给出了几种常遇问题的实用处理方法；还给出了适合工程实际的超大面判断立体消隐图绘制法和基于Ａｕｔｏｌｉｓｐ语言及Ａｕｔｏ－ＣＡＤ的立体图处理方法．     

有限元网格自动生成及自动调整技术

本文给出了一种任意平面域内三角形网格自动生成及自动调整算法，并编制了相应的程序。通过对带Ｕ形槽的三点变曲试件的分析，证明本文算法是可行的，并且具有稳定性能好、收敛速度快的优点。     

粗粒土与结构接触面受载过程中的损伤

进行了粗粒上与结构接触面单调和循环加载试验,基于宏细观测量结果,扩展了损伤概念以描述该类接触面在受载过程中的物态演化,及由于物态演化导致的力学特性从初始状态到最终稳定状态的连续变化过程.揭示了接触面损伤的细观物理基础主要是接触面内土的颗牲破碎和剪切压密这两种物态演化;指出接触面的剪胀体应变可以划分为可逆性和不可逆性剪胀体应变两部分,其中不可逆性剪胀体应变可作为接触面损伤发展的宏观量度,因此其归一化形式可作为一种损伤因子的定义;提出了建立粗粒土与结构接触面一种损伤本构关系的基本思路.     

Numerical solution of Navier–Stokes equations using multiquadric radial basis function networks

A numerical method based on radial basis function networks (RBFNs) for solving steady incompressible viscous flow problems (including Boussinesq materials) is presented in this paper. The method uses a ‘universal approximator’ based on neural network methodology to represent the solutions. The method is easy to implement and does not require any kind of ‘finite element‐type’ discretization of the domain and its boundary. Instead, two sets of random points distributed throughout the domain and on the boundary are required. The first set defines the centres of the RBFNs and the second defines the collocation points. The two sets of points can be different; however, experience shows that if the two sets are the same better results are obtained. In this work the two sets are identical and hence commonly referred to as the set of centres. Planar Poiseuille, driven cavity and natural convection flows are simulated to verify the method. The numerical solutions obtained using only relatively low densities of centres are in good agreement with analytical and benchmark solutions available in the literature. With uniformly distributed centres, the method achieves Reynolds number Re = 100 000 for the Poiseuille flow (assuming that laminar flow can be maintained) using the density of , Re = 400 for the driven cavity flow with a density of and Rayleigh number Ra = 1 000 000 for the natural convection flow with a density of . Copyright © 2001 John Wiley & Sons, Ltd.     

改进的小损伤结构动力学有限元建模方法

在遗传算法或神经网络方法识别结构损伤位置和程度时,都是基于少量的在线测量的损伤结构振动响应数据和大量的模型仿真数据来实现的,因而建立高效和精确的损伤结构动力学有限元模型,以便仿真获得损伤结构的大量动力学响应数据是十分重要的基础前提工作。本文针对ANSYS结构分析软件在建立结构小损伤有限元动力学模型存在两个关键问题,结构损伤处直接网格划分的计算结果误差和网格节省问题,以结构损伤振动检测的实际需要为出发点,提出了建立含小损伤结构的ANSYS动力学建模技术,研究了结构局部小损伤及其位置与所在处单元刚度矩阵变化的数量关系。     

Polarizable coarse‐grained models for molecular dynamics simulation of liquid cyclohexane

Force field parameters for polarizable coarse‐grained (CG) supra‐atomic models of liquid cyclohexane are proposed. Two different bead sizes were investigated, one representing two fine‐grained (FG) CH₂r united atoms of the cyclohexane ring, and one representing three FG CH₂r united atoms. Electronic polarizability is represented by a massless charge‐on‐spring particle connected to each CG bead. The model parameters were calibrated against the experimental density and heat of vaporization of liquid cyclohexane, and the free energy of cyclohexane hydration. Both models show good agreement with thermodynamic properties of cyclohexane, yet overestimate the self‐diffusion. The dielectric properties of the polarizable models agree very well with experiment. © 2015 Wiley Periodicals, Inc.