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1.
小山水电站厂房高边坡岩体稳定性研究   总被引:1,自引:0,他引:1  
刘汉东 《力学学报》1997,5(3):218-223
本文采用块体极限平衡Sarma法和非线有限单元分析法对小山水电站厂房边坡岩体稳定性进行了分析研究。综合两种方法的计算成果分析, 厂房边坡岩体在自然状态下是基本稳定的, 整体安全系数均大于1.30, 但在边坡岩体内存在部分张应力区和塑性区。若考虑Ⅵ度地震, 厂房边坡岩体Sarma法和有限元计算的安全系数分别为1.18和1.16, 处于极限平衡状态。考虑到长期稳定边坡安全系数大于1.30的规范要求, 需进行一定的加固处理, 保障厂房安全运行。  相似文献   

2.
通过吸收有限元与无网格法的优点,提出了一种新的数值方法------自由单元法.此方法在离散方面,采用有限元法中的等参单元,表征几何形状和进行物理量的插值;在算法方面,采用单元配点技术,逐点产生系统方程.主要特点是,在每个配置点只需要一个和周围自由选择的节点而形成的一个独立的等参单元,因而不需要考虑物理量在单元之间的相互连接关系与导数连续性问题. 本文介绍强形式与弱形式两种自由单元法,前者直接由控制方程和边界条件直接产生系统方程,后者通过在自由单元上建立控制方程的加权余量式产生弱形式积分式,并通过像传统有限元法中的积分过程建立系统方程组.本文提出的方法是一种单元配点法,对于域内点为了获得较高的导数精度,需要采用至少具有一个内部点的等参单元,为此除了可使用各阶次的拉格朗日四边形单元外, 还 给出了七节点三角形等参单元,用于模拟较为复杂的几何形状问题.   相似文献   

3.
4.
确定疲劳极限的外推法   总被引:3,自引:0,他引:3  
提出了利用成组法的结果代替升降法确定疲劳极限的外推法。首先给出以疲劳极限为参量的S-N曲线的数学表达式。然后将四组成组法的试验结果代入上式,得到四个等式。从这四个等式中消去其它的材质参量,即可得到求解疲劳极限的超越方程。在求得疲劳极限后,再根据上述试验结果以最小二乘法拟合上述其它材质参量。利用该方法可进一步做出完整的中值S-N曲线,这就大大地节约了疲劳试验的机时与疲劳试验费用。  相似文献   

5.
用动态焦散线方法研究圆环在冲击载荷作用下的破坏机理   总被引:1,自引:0,他引:1  
本文用动态焦散线实验方法并结合理论分析,深入地研究了圆环在冲击载荷作用下的破坏问题。考察了试件的几何尺寸和支承材料对破坏模态及破坏过程的影响。用应力波传播的几何理论(rays-theory)分析了应力波在圆环内部的传播过程,着重分析了圆环中应力波聚焦的现象。理论分析和实验结果在破坏时刻和破坏位置上吻合的很好。  相似文献   

6.
本文将计算力学的边界元法和实验力学的激光散斑法相结合用于求解受力物体的应力应变场。即用实验提供变形物体的真实边界条件,用数值方法进行求解。文中定义了虚边界的概念,并进一步提出了子域杂交法。同单纯数值计算和实验分析相比较,本文提出的方法无需构造力学模型,因而具有简单、可靠的特点,并可以更好地应用于实际问题。  相似文献   

7.
根据水泥浆液的Navier-Stokes方程及连续性方程,采用特征线法建立了灌浆管道非定常流动的动态流体力学模型.其中包括划分网格,单管混合问题的特征线差分法等,将整个灌浆管路简化为一系列描述管道、设备、灌浆孔、调节阀的非线性代数方程组,并采用 Newton-Raphson法进行了求解.基于该模型的 GYPC 控制系统可将波动的灌浆压力在短时间内调节控制在±0.02MPa范围内,表明该流体力学模型是合理与实用的.  相似文献   

8.
提出了一种基于滑移界面耦合技术的旋转电机磁场仿真方法。首先,对旋转电机问题建立等效弱形式,用Lagrange乘子法施加Coulomb规范条件和滑移界面处的磁矢势连续性条件;然后,采用混合单元方法离散整个求解域中的未知量,采用棱边单元法离散滑移界面处的Lagrange矢量乘子,并采用多点约束法耦合滑移界面处的Lagrange标量乘子自由度,该方法无须在旋转电机模型的非匹配网格中构建生成树,即可自动保证磁矢势解的唯一性;最后,采用旋转线圈案例和简化的永磁同步电机案例验证了本文方法的有效性。  相似文献   

9.
赵大华  李华锋 《实验力学》2006,21(4):513-518
工程结构裂纹尖端应力强度因子(SIF)由于形状、荷载的复杂性及边界条件的不确定性,难以用解析法得到,数值计算也有困难,而光弹性法弥补了上述方法的不足。本文用环氧树脂制作圆轴模型,采用机加工的方法制作圆轴模型裂纹,然后将加载模型进行应力冻结,通过光弹性实验研究分析了圆轴裂纹尖端应力分布。由于带环形裂纹的圆轴在弯扭组合变形时,离中性轴最远的裂纹尖端处于复合裂纹状态,而三维光弹性应力冻结法是测定复杂三维问题复合裂纹的有效方法。本文用双参数法测定I型应力强度因子,用切片逐次削去法测定Ⅲ型应力强度因子,实验误差较小。  相似文献   

10.
黄羽  计欣华  秦玉文 《力学季刊》2002,23(1):131-135
由Pindera等提出了等达因法导出了平面问题的三个应力分量,可以非破坏性测取受力物体内部的应力状态,是一种有效的光测技术,应力分量与等达因条纹级次的导数相关,为得到具有高测试精度的应力分量在等达因条纹测试中引入了双折射相移技术,文中提出了一种在散光激光入射光路中用加入一可调偏振片和一可调1/4波片实现散光图象双折射相移的方法,该方法设备简单,能保证总体光强的一致性。  相似文献   

11.
In this study, a unified nonlinear dynamic buckling analysis for Euler–Bernoulli beam–columns subjected to constant loading rates is proposed with the incorporation of mercurial damping effects under thermal environment. Two generalized methods are developed which are competent to incorporate various beam geometries, material properties, boundary conditions, compression rates, and especially, the damping and thermal effects. The Galerkin–Force method is developed by implementing Galerkin method into force equilibrium equations. Then for solving differential equations, different buckled shape functions were introduced into force equilibrium equations in nonlinear dynamic buckling analysis. On the other hand, regarding the developed energy method, the governing partial differential equation for dynamic buckling of beams is also derived by meticulously implementing Hamilton’s principles into Lagrange’s equations. Consequently, the dynamic buckling analysis with damping effects under thermal environment can be adequately formulated as ordinary differential equations. The validity and accuracy of the results obtained by the two proposed methods are rigorously verified by the finite element method. Furthermore, comprehensive investigations on the structural dynamic buckling behavior in the presence of damping effects under thermal environment are conducted.  相似文献   

12.
Computations of wall distances by solving a transport equation   总被引:1,自引:0,他引:1  
Computations of wall distances still play a key role in modern turbulence modeling. Motivated by the expense involved in the computation, an approach solving partial differential equations is considered. An Euler-like transport equation is proposed based on the Eikonal equation. Thus, the efficient algorithms and code components developed for solving transport equations such as Euler and Navier-Stokes equations can be reused. This article provides a detailed implementation of the transport equation in the Cartesian coordinates based on the code of computational fluid dynamics for missiles (MICFD) of Beihang University. The transport equation is robust and rapidly convergent by the implicit lower-upper symmetric Gauss-Seidel (LUSGS) time advancement and upwind spatial discretization. Geometric derivatives must also be upwind determined to ensure accuracy. Special treatments on initial and boundary conditions are discussed. This distance solving approach is successfully applied on several complex geometries with 1–1 blocking or overset grids.  相似文献   

13.
Computations of wall distances still play a key role in modern turbulence modeling. Motivated by the expense involved in the computation, an approach solving partial differential equations is considered. An Euler-like transport equation is proposed based on the Eikonal equation. Thus, the efficient algorithms and code components developed for solving transport equations such as Euler and Navier-Stokes equations can be reused. This article provides a detailed implementation of the transport equation in the Cartesian coordinates based on the code of computational fluid dynamics for missiles (MICFD) of Beihang University. The transport equation is robust and rapidly convergent by the implicit lower-upper symmetric Gauss-Seidel (LUSGS) time advancement and upwind spatial discretization. Geometric derivatives must also be upwind determined to ensure accuracy. Special treatments on initial and boundary conditions are discussed. This distance solving approach is successfully applied on several complex geometries with 1-1 blocking or overset grids.  相似文献   

14.
由于直接配点法在求解边值问题时边界上的求解精度较低,本文提出了Hermite梯度重构核近似配点法(HGCM)来改进边界求解精度。重构核近似是无网格法中一种常用的近似函数,但是其在求解高阶导数时格式复杂且非常耗时。HGCM采用梯度重构核近似构建形函数的任意高阶导数,提高了计算效率;通过Hermite配点法构建离散方程,提高了边界求解精度。这种方法在求解对应变系数四阶偏微分方程的功能梯度材料板的静力问题时精度高,计算效率高,并可进一步推广应用于高阶偏微分方程描述的边值问题。  相似文献   

15.
Helmholtz方程的微分容积解法   总被引:1,自引:0,他引:1  
用一种新型的数值技术--微分容积法(Differential Cubature Method)求解二维Helmholtz方程的边值问题,几个数值算例表明,该方法稳定收敛,并具有较好的数值精度,本文方法适用于求解具有较小波数的Helmholtz方程。  相似文献   

16.
The purpose of this research is to analyze the application of neural networks and specific features of training radial basis functions for solving 2‐dimensional Navier‐Stokes equations. The authors developed an algorithm for solving hydrodynamic equations with representation of their solution by the method of weighted residuals upon the general neural network approximation throughout the entire computational domain. The article deals with testing of the developed algorithm through solving the 2‐dimensional Navier‐Stokes equations. Artificial neural networks are widely used for solving problems of mathematical physics; however, their use for modeling of hydrodynamic problems is very limited. At the same time, the problem of hydrodynamic modeling can be solved through neural network modeling, and our study demonstrates an example of its solution. The choice of neural networks based on radial basis functions is due to the ease of implementation and organization of the training process, the accuracy of the approximations, and smoothness of solutions. Radial basis neural networks in the solution of differential equations in partial derivatives allow obtaining a sufficiently accurate solution with a relatively small size of the neural network model. The authors propose to consider the neural network as an approximation of the unknown solution of the equation. The Gaussian distribution is used as the activation function.  相似文献   

17.
General exact solutions in terms of wavelet expansion are obtained for multi- term time-fractional diffusion-wave equations with Robin type boundary conditions. By proposing a new method of integral transform for solving boundary value problems, such fractional partial differential equations are converted into time-fractional ordinary differ- ential equations, which are further reduced to algebraic equations by using the Laplace transform. Then, with a wavelet-based exact formula of Laplace inversion, the resulting exact solutions in the Laplace transform domain are reversed to the time-space domain. Three examples of wave-diffusion problems are given to validate the proposed analytical method.  相似文献   

18.
The group theoretic method is applied for solving the problem of the combined influence of the thermal diffusion and diffusion thermoeffect on magnetohydrodynamic free convective heat and mass transfer over a porous stretching surface in the presence of thermophoresis particle deposition with variable stream conditions. The application of one-parameter groups reduces the number of independent variables by one; consequently, the system of governing partial differential equations with boundary conditions reduces to a system of ordinary differential equations with appropriate boundary conditions. The equations along with the boundary conditions are solved numerically by using the Runge-Kutta-Gill integration scheme with the shooting technique. The impact of the Soret and Dufour effects in the presence of thermophoresis particle deposition with a chemical reaction plays an important role on the flow field.  相似文献   

19.
A semi-analytical approach for the geometrically non-linear analysis of rectangular laminated plates with general inplane and out-of-plane boundary conditions under a general distribution of out-of-plane loads is developed. The analysis is based on the elastic thin plate theory with geometrically non-linear von Kármán strains. The solution of the non-linear partial differential equations is reduced to an iterative sequential solution of non-linear ordinary differential equations using the multi-term extended Kantorovich method. The efficiency, accuracy, and convergence of the proposed method are examined through a comparison with other semi-analytical methods and with finite element analyses. The capabilities of the approach and its applicability to the non-linear large deflection analysis of plate structures are demonstrated through various numerical examples. Emphasis is placed on combinations of lamination, boundary, and loading conditions that cannot be analyzed using alternative semi-analytical methods.  相似文献   

20.
由于流场参数重构中, 用于重构的基网格单元的物理参数波动量相对于均值较小, 径向基函数(RBF) 直接插值方法重构会产生较大的数值振荡, 论文提出了一种增量RBF 插值方法, 并用于有限体积的流场重构步, 明显改善了插值格式的收敛性和稳定性. 算例首先通过简单的一维模型说明该方法的有效性, 当目标函数波动量相对于均值为小量时, 增量RBF 插值能够抑制数值振荡; 进一步通过二维亚音速、跨音速定常无黏算例、静止圆柱绕流非定常算例以及超音速前台阶算例来说明该方法在典型流场数值求解中的通用性和有效性. 研究表明增量RBF 重构方法可陡峭地捕捉激波间断, 可有效改善流场求解的收敛性和稳定性, 数值耗散小, 计算效率高.  相似文献   

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