无网格法在几何非线性力学中的应用

利用无网格法分析几何非线性力学问题,建立拉格朗日坐标系下基于移动最小二乘法的无网格静力学和动力学模型,并采用载荷增量和修正牛顿迭代法相结合的混合法对静力学模型进行方程求解,采用Wilson-θ法求解动力学模型方程.最后计算直杆和悬臂梁在载荷作用下的变形结果与动力响应,并将计算结果与有限元方法的相比较,结果表明,本文方法是可行的.     

点插值无网格法在弹性力学中的应用

点插值法是一种新型的无网格法,它改善了其他无网格方法中形函数计算复杂、本质边界条件处理困难等问题.文中分析点插值法的计算原理,给出其在弹性问题中的应用,并与有限元法以及移动最小二乘法进行比较.结果表明,点插值法具有计算速度较快、精度较高以及本质边界处理相对简单等优点.     

基于MLS无网格思想的数值流形方法

介绍了一种基于无网格思想的数值流形方法.用移动最小二乘法(MLS)构造插值函数,罚函数法处理位移边界条件,根据变分原理导出整体离散方程,最后用算例验证本文方法是可行的.     

无网格法在金属成形塑性分析中的应用

比较了有限元法与无网格法在金属成形应用中的优缺点,分析描述了无网格法在金属弹塑性变形、金属体积成形、板料成形等金属成形加工方面的应用现状,并阐述了无网格法的不足、亟待继续深入解决的问题以及未来的展望.     

弹塑性力学问题的无网格法分析

提出弹塑性力学问题的无网格局部Petrov—Galerkin(meshless local Petrov—Galerkin,MLPG)方法,这是一种真正的无网格方法。这种方法采用移动最小二乘近似函数作为试函数,并且采用移动最小二乘近似函数的权函数作为加权残值法的权函数,本质边界条件用罚因子法施加。文中采用Newton—Raphson法进行计算。计算实例表明．局部Petrov—Galerkin方法是一种很有效的求解弹塑性力学问题的方法。     

平面问题无网格局部边界元方法研究

推导了弹性力学平面问题的无网格局部边界元积分方程 ,实现了该法离散过程 ,应用两个典型算例验证了该法的有效性。研究中 ,发现局部域半径的大小对计算精度有一定影响 ,其值大小会造成很大的误差     

无网格方法的研究应用与进展

无网格方法是一种比较新的数值方法,是有限元等传统的数值分析方法的重要补充和发展.它的优点就是节点离散.目前,无网格方法得到了迅速的发展,是科学和工程计算方法研究的热点和发展趋势.文章阐述了无网格方法及其发展,并对其目前的应用领域予以探讨和发展前景给予展望.     

计算应力强度因子的无网格-直接位移法

目前计算裂纹尖端应力强度因子的无网格法一般均采用。积分方法,但由于该方法为间接求解,降低了求解精度与求解效率。文中采用无网格—伽辽金方法,选取带有扩展基的奇异基函数,以精确计算裂纹尖端位移场,并借鉴有限元法中计算应力强度因子的直接位移法,提出一种计算含裂结构裂纹尖端应力强度因子的新方法,即无网格—直接位移法。数值计算结果表明,该方法具有简捷、高效的特点,可以准确计算裂纹尖端应力强度因子。     

几何非线性问题的无网格法分析

用局部Petrov-Galerkin方法求解几何非线性问题,这是一种真正的无网格方法。这种方法采用移动最小二乘近似函数作为试函数;只包含巾心在所考虑点处的规则局部区域上以及局部边界上的积分;所得系统矩阵是一个带状稀疏矩阵。该方法可以容易推广到求解非线性问题以及非均匀介质力学问题。在涉及几何非线性问题的数值方法中,通常都采用增量和迭代分析的方法。本文从虚功原理出发,用移动最小二乘近似函数的权函数替代虚位移,并在整个分析过程中所有变量的表达格式都是采用全拉格朗日格式。数值算例表明,无网格局部Petrov-Galerkin方法在求解几何非线性问题时仍具有很好的精度。     

基于FEM与SPH耦合算法的单颗磨粒切削玻璃的动态过程仿真

采用有限元法(FEM)与光滑质点流体动力学法（SPH）耦合算法,假设以圆锥作为磨粒的形状,以玻璃为工件材料,进行了单颗金刚石磨粒的三维磨削仿真。仿真结果表明：磨粒的挤压使工件材料向前方及两侧流动而产生隆起,且磨屑发生粉末化现象;沟槽的实际宽度远大于磨粒的切削宽度,断裂裂纹向沟槽两侧扩张,裂纹扩展一段后就停止不前而残留下来,成为残留裂纹。该方法可以较好地解决传统有限元法进行脆性材料磨削仿真时容易发生单元畸变的问题,验证了FEM与SPH耦合算法应用于脆性材料磨削仿真研究的可行性。     

基于 SPH／FEM 方法的机器人脚在土壤中的沉陷特性研究

基于SPH／FEM方法,将数值模拟方法与贝克经验公式进行了比较;建立了机器人脚与土壤的相互作用模型,进行了机器人脚在土壤中的沉陷研究。结果表明,当机器人脚底部圆弧曲率半径R为16cm时,机器人脚的几何形状更为理想。     

基于有限元的模块化振动料斗动态分析

对振动料斗进行模块划分和有限元建模,运用有限元分析软件ANSYS对该模型进行动态分析,计算出振动料斗的固有频率和振型,以及对正弦激振的响应曲线。实际应用效果表明,该方法可有效地指导振动料斗的设计和调试。     

基于参数化模型特征的有限元网格划分方法研究

基于开孔实体的参数化特征模型思想，本文提出了一种非自由边界分割有限元网格划分方法，可以针对开孔实体的几何特征和力学特征，对多种类型的开孔构件进行全六面体网格划分，生成的网格质量均匀、局部加密方便且疏密过渡合理。经买例应用表明，此种网格划分方法具有通用性强、简单、实用、高效等特点。     

SPH方法在冲击破坏中的爆炸现象分析

由于SPH方法已被广泛应用到工程模拟的各个方面,虽然已有很大成功,但是还有很多的方面不成熟,其中之一就是爆炸现象,笔者对这种现象产生的原因进行了分析。     

Abrasive waterjet machining simulation by SPH method

Abrasive waterjet machining (AWJM) is a non-conventional process. The mechanism of material removing in AWJM for ductile materials and existing erosion models are reviewed in this paper. To overcome the difficulties of fluid–solid interaction and extra-large deformation problem using finite element method (FEM), the SPH-coupled FEM modeling for abrasive waterjet machining simulation is presented, in which the abrasive waterjet is modeled by SPH particles and the target material is modeled by FE. The two parts interact through contact algorithm. The creativity of this model is multi-materials SPH particles, which contain abrasive and water and mix together uniformly. To build the model, a randomized algorithm is proposed. The material model for the abrasive is first presented. Utilizing this model, abrasive waterjet penetrating the target materials with high velocity is simulated and the mechanism of erosion is depicted. The relationship between the depth of penetration and jet parameters, including water pressure and traverse speed, etc., are analyzed based on the simulation. The results agree with the experimental data well. It will be a benefit to understand the abrasive waterjet cutting mechanism and optimize the operating parameters.     

Shot peening simulation based on SPH method

Shot peening is a complex surface-treating process which is usually employed to improve the fatigue strength of metallic part or members. In dealing with shot peening simulation, existing literatures apply finite element method (FEM) to establish only a single shot or several shots models, thus the effect of a mass of shots impacting repeatedly and the interaction among adjacent shots are ignored. To overcome these defects of FEM models, smoothed particle hydrodynamics (SPH) coupled FEM modeling is presented, in which the shots are modeled by SPH particles and the target material is modeled by finite elements. Contact algorithm is used to simulate the interaction between shots and target. Utilizing this model, material model for shots is established, the relationships between compressive residual stress and peening frequencies, coverage, and velocities are analyzed. Steady compressive residual stress can be gotten by multiple peening; higher coverage can improve the compressive residual stress; faster velocities can induce greater and deeper maximum residual stress in target subsurface. The simulation results agree well with the existing experimental data. The study will not only provide a new powerful tool for the simulation of shot peening process, but also be benefit to optimize the operating parameters.     

基于参数化模型特征的有限元网格划分方法研究

基于开孔实体的参数化特征模型思想,本文提出了一种非自由边界分割有限元网格划分方法,可以针对开孔实体的几何特征和力学特征,对多种类型的开孔构件进行全6面体网格划分,生成的网格质量均匀、局部加密方便且疏密过渡合理.经实例应用表明,此种网格划分方法具有通用性强、简单、实用、高效等特点.     

Numerical simulation of single particle acceleration process by SPH coupled FEM for abrasive waterjet cutting

The existing numerical simulations of hydrodynamic characteristics of abrasive waterjet in a cutting head were mainly based on Eulerian grid or arbitrary Lagrange–Eulerian grid method to establish computational fluid dynamics models. However, using these two methods, the abrasive and water were premixed and given an identical initial velocity, which were different from the mixing and acceleration processes of abrasive in the cutting head. This paper presents a more suitable numerical model that the abrasive particle enters into the mixing chamber in a low velocity and is accelerated in the focus tube by a high-speed waterjet from the orifice. In order to model this mixing-and-acceleration process of abrasive and high-speed waterjet, the smooth particle hydrodynamics (SPH) coupled finite element method (FEM) is adopted, in which SPH particles are used to model the high-speed waterjet to adapt its extremely large deformation and FEM is applied to model the discrete abrasive particle, cutting head, and workpiece. As a result, evolution of abrasive and waterjet velocities along focus tube is analyzed; trajectory of single abrasive particle in focus tube is sighted; the relationships between abrasive particle velocities and different water pressures are described; the rule of outlet velocities of abrasive particle vs. dimensionless ratio of diameter is conducted; depth of penetration caused by single abrasive particle impact is obtained. The current model is validated by the existing theoretical and experimental data.     

大型卫星天线系统固有模态的有限元分析

通过对卫星—天线系统的物理模型进行分析,提出了卫星—大型天线系统固有模态的有限元分析模型,并在此基础上进行了系统若干低阶模态的分析。研究工作不仅为天线结构设计提供了固有频率与振型的分析结果,而且进一步为天线结构的优化设计和弹簧力的优选提供了理论基础。