SMA长纤维铝基复合材料的热力学性能

从作者建立的增量型的SMA本构关系出发 ,借助于细观力学的方法 ,推导出了新的长纤维SMA复合材料的增量型细观本构模型 ;应用此模型分析了该复合材料的在循环热载作用下的力学性能 ,尤其是计算了复合材料在不同条件下残余应力的变化 ,这对智能复合材料的设计提供了很大帮助。     

反应、扩散化学动力学方程的有效解法

对扩散、化学反应或瞬态温度场问题，给出了具有4阶精度、自起步的隐式时间积分算法．算例显示，其精度和稳定性都好于四阶Runge-Kutta法，并且保留了原系数矩阵的稀疏存储方式和稀疏矩阵的运算规则，使紧缩存储技术和减少计算时间有效的结合．以旋转填充床内的竞争串联反应为算例，表明该算法是有效的．     

弹性混合板的振动和稳定问题

通过将非线性应变位移关系引入Hellinger-Reissner变分原理,推导出了各向异性板基于弹性理论下的振动和屈曲控制方程.用精细积分法研究了四边简支混合矩形板.精细积分法与传统的有限差分法相比,可以给出计算机精度允许的很精确的数值结果.所以,给出的混合板的振动和稳定的结果可以看作是近似解析的.这些结果可以作为衡量各种板理论准确性的一个标准.而且,非对称层合板中出现的各种耦合影响,比如弯扭耦合,拉弯耦合等在同一组控制方程里被考虑了.     

THE CURVED BEAM ELEMENT AND ITS CONVERGENCE RATE

The quasi-conforming element of the curved beam and shallow curved beam is given inthis paper.Numerical examples illustrate that the quasi-conforming elements of the curvedbeam and shallow curved beam Which is used to aooroximate the curved beam have betteraccuracy than the straight beam element.The curved beam element constructed bydisplacement method can not satisly rigid body motion condition and the verv fine gridshave to be used in order to satisfy rigid body motion condition approximately.In this paper it is proved that the straight beam element and the quasi-conformingelement of the curved beam and shallow curved beam.when element size is reducedinfinitely,have convergence rate with the same order O(l~2)and when regulur elements areused,I is the element length.     

非线性动力学方程的一种级数解

本文针对n维未知向量v的一阶微分议程v=Hv f(v,t)进行求解,其中Hv和f(v,t)分别是右端项的线性剂次部分和非线性部分,首先,将非线性部分f(v,t)在所论时刻tk处展成t-tk=τ的泰勒级数,并通过求原函数的方法直接给出每一项的积分,从而获得了待求微分方程在级数形式下的闭合争,它的具有不同精度的各次静似解可表示成τ的分段解析函数,便于研究非线性动力学行为与其物理参数的依赖关系。本文还用算例验证了各次近似解之间的数值关系,并和解析解等作了比较。     

The curved beam element and its convergence rate

The quasi-conforming element of the curved beam and shallow curved beam is given in this paper. Numerical examples illustrate that the quasi-conforming elements of the curved beam and shallow curved beam which is used to approximate the curved beam have better accuracy than the straight beam element. The curved beam element constructed by displacement method can not satisfy rigid body motion condition and the very fine grids have to be used in order to satisfy rigid body motion condition approximately.In this paper it is proved that the straight beam element and the quasi-conforming element of the curved beam and shallow curved beam, when element size is reduced infinitely, have convergence rate with the same order O(l²) and when regular elements are used l is the element length.The Project Supported by National Natural Science Foundation of China.     

Vibration and stability of hybrid plate based on elasticity theory

The governing equations of elasticity theory for natural vibration and buck- ling of anisotropic plate are derived from Hellinger-Reissner＇s variational principle with nonlinear strain-displacement relations. Simply supported rectangular hybrid plates are studied with a precise integration method. This method, in contrast to the traditional finite difference approximation, gives highly precise numerical results that approach the full computer precision. So the results for natural vibration and stability of hybrid plates presented in the paper can be riewed as approximate analytical solutions. Furthermore, several types of coupling effects such as coupling between bending and twisting, and coupling between extension and bending, when the layer stacking sequence is asymmetric, are considered by only one set of governing equations.     

An analytical model for nanowire junctionless SOI Fin FETs with considering three-dimensional coupling effect

In this paper, the three-dimensional(3D) coupling effect is discussed for nanowire junctionless silicon-on-insulator(SOI) Fin FETs. With fin width decreasing from 100 nm to 7 nm, the electric field induced by the lateral gates increases and therefore the influence of back gate on the threshold voltage weakens. For a narrow and tall fin, the lateral gates mainly control the channel and therefore the effect of back gate decreases. A simple two-dimensional(2D) potential model is proposed for the subthreshold region of junctionless SOI Fin FET. TCAD simulations validate our model. It can be used to extract the threshold voltage and doping concentration. In addition, the tuning of back gate on the threshold voltage can be predicted.     

一种弹性粘塑性统一本构模型

在深入研究分析材料变形过程的基础上,对材料变形与选定描述材料变形内变量的问题进行探讨,在唯象法的基础上提出一种金属材料变形的粘塑性统一本构模型.用该模型对304不锈钢的变形过程进行模拟,其计算结果较Miller模型更接近实验结果.     

不可压缩体在给定位移边界条件下的一种解法

1、引言有些材料在变形时,尤其在大变形时,体积变形甚微,以致于可以忽略,这个特点,在数学上就抽象为不可压缩材料.不可压缩材料应力的特点是它的应力不能由应变唯一地确定,而必须考虑静水压力р.对于全部给定位移的边界条件(满足整体不可压缩条件)问题,正如所指出的,应力是不唯一的,反映在有限元计算中,如定理二指出的,