具有一个无外力圆弧边含转动自由度的杂交应力元

根据一种修正的余能原理，建立了一类具有一个无外力圆弧边，且结点含转动自由度的4结点杂交应力膜元。该元内假定应力场满足以柱坐标表示的平衡方程，及圆弧边的无外力边界条件；边界位移与相邻元协调。数值算例表明，这类特殊杂交应力元，可有效地分析具有圆形槽孔及倒圆角槽孔板的应力分布。     

非协调轴对称杂交应力元单元刚度矩阵的准确建立

给出新型三类用理性杂交模式、根据一种修正的Ｈｅｌｌｉｎｇｅｒ－Ｒｅｉｓｓｎｅｒ原理、建立高精度非协调轴对称实体旋转有限元时，其单元刚度矩阵的准确计算式。     

具有V型槽孔板的应力集中分析

根据杂交应力理性模式，基于一种修正的Hellinger－Reissuer原理，建立了具有一个无外力斜边的杂交应力元，其应力场由无边界面力在非协调位移上所作虚功之和为零的约束条件导出，将这种特殊元与具有一个无外力圆弧边的杂交应力元联合，可有效地分析具有倒圆角V型槽孔板的应力集中，并可提供远较一般假定位移及一般假定应力元准确的孔边应力分布。     

具有一个无外力自由圆柱表面的杂交实体元

应用假设应力杂交元的方法,导出了一个八节点的实体元。此元具有二个平行的表面及一个无外力自由的园柱表面。引用园柱坐标、以使所假设的应力场满足平衡方程及固柱边界面无外力的条件。当退化至平面应力状态时,此应力场也满足协调方程。一些算例证实这种特殊元在分析具有固孔实体时的优越性。     

对三维特殊杂交应力元的进一步研究

应用杂交应力模式导出新的特殊实体元,这种元具有两个平行表面及一个无外力圆柱面.以圆孔矩形板、圆孔方块等作为算例,评价了不同的元,并选出一种相对最佳的应力场.将以上结果与8节点实体杂交应力特殊元、一般杂交应力元及假设位移元等结果对比,明显看出现在的元.给出远较以上各类元准确的应力集中系数及应力分布.     

脆体破裂过程中应力场的边界元计算

本文利用边界元的数值计算方法(BEM),计算了在不同外部应力作用下材料内部具有不同形态的微裂纹尖端区域的应力场情况和应力集中因子,得出了在不同应力作用条件下微裂纹尖端区域的最大主应力场分布和应力集中因子,并给出了不同应力条件和裂纹形态与应力集中因子的关系。在裂纹尖端这些高应力区内一些与结构畸变有关的效应如原子外层电子能量增加与逃逸现象等是能够发生的。     

水泥土损伤模型的试验研究

假定应力主轴与材料主轴重合，并在加载过程中保持不变，在此基础上，推导出水泥土的损伤模型，提出了针对水泥土的损伤演化方程；对水泥土进行无侧限压缩加－卸荷试验，确定了水泥土损伤演化方程中的参数，对其进行了试验，证明了模型的合理性。     

对掘进工作面超前支护方式的探索

前言。根据物体受力平衡的原理，物体在任何时刻，都处于平衡状态，但平衡状态却有动态平衡和静态平衡之分，在理想的状态下物体的受力是六面的相对平衡的，而地下岩石的受力结构在受到外力破坏时就更为复杂了。在这里我们只是肤浅的就普掘工作面的原岩石应力受破坏后而对其立即给予一个初撑力并使之保持平衡方法的探索。     

利用边界远法实现对生物体皮下温度的重构及血液灌注率和代谢率的无…

将经典生物传热方程Ｐｅｎｎｅｓ方程中的两项血液灌注率Ｗｂ与代谢热产率Ｑｍ关联了起来并用于物性测定，利用边界条件及生物传热折特点，并采用边界元技术，实现了在已知热源温度条件下同时对生物体皮下温度及随空间变化的Ｗｂ和Ｑｍ的无损检测，重构结果与实验数据及文献结论吻合较好。     

稠油油藏考虑启动压力梯度下的动边界和压降漏斗研究

<正>考虑启动压力梯度的稠油不稳定渗流数学模型解法十分繁琐,主要原因是控制方程具有强烈的非线性[1,2]。本文根据不稳定渗流方程的半解析解,在考虑启动压力梯度条件下,求出压力分布情况,再结合物质平衡原理,求得定产量生产时的不同时刻的供给边界[3,4],得出不同启动压力梯度下的激动边界随时间的变化,得到启动压力梯度对于"压降漏斗"的影响,以及不同时刻下的"压力漏斗"[5,6],并且定量确定启动压力梯度对地层能量和流体流动的损耗。     

BEPCII对撞点束流轨道反馈系统设计(英文)

介绍了BEPCII(北京正负电子对撞机二期工程)对撞点束流轨道反馈系统的设计.由于BEPCII将采用双环、多束团、交叉角对撞,并且多种原因会使束流处于非最佳对撞状态甚至无法对撞,因此一套基于束—束偏转技术的对撞点束流反馈系统的建立,以使得对撞机保持在最佳对撞状态是非常必要的.此外,为了同时测量对撞点处正、负电子束的位置,两套带有8电极的特殊束流位置探测器(BPM)将安装在对撞点两侧.8电极BPM的工作原理以及采用有限元法进行模拟计算的结果在文章中也进行了介绍     

Nonlinear thermo-inertial stability of thin circular FGM plates

In this research, linear and non-linear stability behaviour of a thin circular FGM plate subjected to the uniform temperature rise and the constant angular velocity loadings is analyzed. Properties of the FGM media are distributed across the thickness based on a power law form. Each property of the metal or ceramic constituents is considered to be the function of temperature based on the Touloukian model. General equilibrium equations for such conditions are obtained based on the classical plate theory. At first, the non-linear governing equations are established in a complete asymmetrical form. After that, two different analytical methods are presented to study the bifurcation behaviour. Existence of bifurcation phenomenon is examined. Pre-buckling analysis is performed for a plate with the immovable clamped edge. Stability equations are obtained based on the adjacent equilibrium criterion. The resulted equations are solved via the two distinct methodologies, i.e. the exact solution in terms of Coulomb wave functions and the power series method. A non-linear solution is also presented to detect the equilibrium path of the heated rotating FGM plate. It is found that the angular speed may stabilize the homogeneous circular plate which buckles during uniform heating. Furthermore, snapping may occur for FGM plates under the simultaneous action of heating and uniform rotation.     

BEPCⅡ对撞点束流轨道反馈系统设计

介绍了BEPCⅡ(北京正负电子对撞机二期工程)对撞点束流轨道反馈系统的设计.由于BEPCⅡ将采用双环、多束团、交叉角对撞,并且多种原因会使束流处于非最佳对撞状态甚至无法对撞,因此一套基于束-束偏转技术的对撞点束流反馈系统的建立,以使得对撞机保持在最佳对撞状态是非常必要的.此外,为了同时测量对撞点处正、负电子束的位置,两套带有8电极的特殊束流位置探测器(BPM)将安装在对撞点两侧.8电极BPM的工作原理以及采用有限元法进行模拟计算的结果在文章中也进行了介绍.     

Iterative algorithms for optimal design of columns subject to a stress constraint

Two algorithms based on an integral equation formulation of the buckling optimization problem are formulated and implemented. The objective of the optimization is to maximize the buckling load of an elastically restrained column by optimally designing the cross-sectional area subject to a minimum cross-section or maximum stress constraint. The first approach involves solving the resulting integral equations iteratively taking into account the boundary conditions, the optimality criterion and the imposed constraints. In the second approach an iterative finite difference approximation scheme is developed.The column is elastically restrained at both ends which produce the simple support and clamped end conditions for the limiting cases leading to the optimal design of columns under general boundary conditions. The above problems do not have analytical solutions due to the complexity of the boundary conditions, constraints and the optimality conditions necessitating the formulation of computational schemes for their solution. Several numerical results are given and compared with available results in the literature. Moreover the accuracy of the methods is studied by comparing the iterative solutions with finite element ones and with exact results when available.     

偶应力问题的非协调元分析

从偶应力弹性体势能泛函的驻值条件出发,得到了偶应力理论中非协调元体系的能量相容原理。基于其常应力(常偶应力)分片检验条件的强形式,对平面四结点单元的非协调试探内函数进行了优化,提出了一种稳定有效的非协调元方法。有限元列式中,微转动和宏观转动相等的约束条件通过罚因子的形式引入。分析了含中心圆孔的无限平板,在单轴拉伸以及纯剪状态时,偶应力的存在对孔周应力集中的影响。算例表明,该单元计算效率高,精度好,即使在材料本征长度很小时,仍然能够得到相当理想的结果     

褶皱变形应力场对断裂控制作用的有限元模拟

有限元法作为一种求解连体力学问题的有效方法，已经广泛应用于地质领域，本文对软硬夹层的紧闭褶皱的变形应力场进行了二维有限元数值模拟。数值模拟结果表明，在本文的模拟条件下，裂隙的发育位置受破裂指标Fn大于3．0的高值点控制．高值点的密度决定了断裂发育的多少：裂隙的延伸方向与模拟的剪切应力方向一致：裂隙的前端具有代表应力集中的Fn指标值的高值点，断裂沿此生长；当断裂延伸至褶皱核部发生分又与合并时，应力梯度下降，应力对断裂的控制能力减弱。研究结果对于有限元法应用于实际地质问题具有重要意义。     

A quantitative evaluation of the influence of the lithosphere on the anomalies of gravity

A quantitative investigation is made of the influence of a strong elastic lithosphere on departures from isostasy. Isostasy is shown to be a special case of a more general principle that may be called the principle of isobaric equilibrium. This principle which expresses the condition for vertical equilibrium is formulated quantitatively both in terms of the resultant vertical stresses in the lithosphere and in terms of measurable gravity anomalies. Employing the principle, a stress function may be determined that permits an estimate of the fraction of the uniform superposed load carried by the lithosphere. By applying this method, it is found that for the central region of a block to be in substantial isostatic adjustment (96 per cent.), the linear dimension of the load must approximate characterizing the elastic deformations of the lithosphere is determined by appeal to geological data from deltas and regions near a thrust fault. The values so obtained suggest a value of 50 ± 15 Km. for the effective thickness of the lithosphere. The deformed figures of the lithosphere for certain special types of load have been worked out together with the stress function that measures both the gravity anomaly and the resultant vertical stress.