RTM充模分析控制体积法的求解方法

RTM充模分析在控制体积法对于某些单元会产生不对称的矩阵，为了充分利用现有的对称矩阵高效求解方法，本文提出了一种处理方法。由千方程矩阵的不对称性足比较弱且充模过程是一个渐变的过程，因此把不对称部分移到方程右边，在求解过程中只有在充满节点发生变化时更新方程的右边。采用预处理共轭梯度求解法计箅了两个实例，结果表明这样计算效果非常有效，尤其适于求解三维网格模型的充模分析。     

边界形状的红外识别算法

基于表面测温的边界形状识别是导热反问题的重要研究内容,同时也是红外无损检测技术从定性到定量发展的重要理论基础。对于边界识别类导热反问题,由于需要在迭代过程中不断改变不规则的求解区域的形状,所以其计算复杂性较大,计算时间也相对比较长,直接影响到实际算法的应用。本文基于试件整体对传热的宏观影响规律提出了基于有效热导率评估的边界识别方法。该方法将不规则求解区域上的边界识别问题转化为一个规则求解区域上的有效热导率的识别问题,从而大大降低了边界形状迭代求解的复杂性和计算所需时间。数值算例证明了算法的有效性。边界的初始假设可以忽略。算法没有明显放大温度测量的误差。     

三维比例边界有限元法与八叉树网格剖分相结合求结构响应

比例边界有限元法是一种线性偏微分方程的半解析的数值求解方法,它结合了有限元法和边界元法的优点。比例边界有限元法与边界元法一样,只需要对(环向)边界进行离散,使计算维度降低一维,但比例边界有限元法不需要事先给出研究域的可行解,同时在环向(边界)的离散化与有限元法类似且具有有限元法的精度,在径向是解析的,相比常规有限元法更有优势。本文将八叉树网格剖分算法与三维比例边界有限元相结合求结构的响应。八叉树网格算法基于层次树的算法思想,从根单元格开始,按照2:1的平衡分割原则递归地进行等分,可以快速地实现粗网格到细网格的过渡。为适应复杂结构的边界几何形状,给出了空间多面体裁剪及网格生成技术,根据带符号的距离函数数值判断被裁剪的结点与多面体的位置关系。论文给出了三维比例边界有限元的有关列式,并对边界单元的裁剪方法进行了讨论。最后首先采用八叉树网格剖分单元,运用三维比例边界有限元法对结构静力荷载作用下的响应进行分析。结果表明,三维比例边界有限元与八叉树网格相结合计算具有良好的精确性,并且收敛较快,能够在不损失精度的前提下大大提高计算效率,节约计算成本。     

旋转液滴法测界面张力的模型分析与应用

在进行旋转液滴法测界面张力的实验过程中,在液滴体积小或者界面张力值大的情况下,提高转速不能达到仪器测试的条件要求。对旋转液滴法测界面张力的模型进行分析,首先给出了旋转液滴椭圆形态计算界面张力的求解模型,对参数的敏感性进行了分析的同时刻画了椭圆边界的形态特征;其次根据建立的模型求解过程形成的数据库,建立了求解旋转液滴椭圆形态计算界面张力值的图版方法和迭代算法;再次列举出了一个新的求解方法,最后对以上各种计算方法进行了实例应用。研究认为各种方法下,推荐对液滴长度和直径都进行测量。     

面向方程技术中选择输出变量的一种新方法

寻找输出变量是过程模拟、动态仿真和换热网络中面向方程求解时的一个重要步骤。已报道的结合“Ｓｔｅｗａｒｄ通路”的匈牙利算法及一些其它的算法运算量很大，很难推广应用；“禁点法”是比较快速、有效的算法，但出现“平凡解（ＴｒｉｖｉａｌＳｏｌｕｔｉｏｎ，ＴＳ）”情况时，它有时会失败。本文在禁点概念的基础上，提出了一种处理ＴＳ的新算法，证明了ＴＳ矩阵产生的充分必要条件。本文用矩阵随机发生器产生０－１矩阵对新算法进行了考核，结果表明：本算法对处理ＴＳ问题是高效的并具有较好的鲁棒性。     

气体辅助注射成型气道网格算法

根据气体辅助注射成型的特点,在塑件表面三角形网格的基础上,提出了手工拟合气道路径和自动求解气道节点相结合的方法生成气道网格,并给出了求解多边形最大内切圆的气道网格算法和优化气道网格的算法,通过软件应用和实例分析,证明所提出的算法是行之有效的。该算法为气体辅助注射成型模拟分析的数值计算提供了依据。     

负氧平衡发射药膛口燃烧流场的数值模拟

采用多组分ALE( Arbitrary Lagrangian-Eulerian)方程组对含有高速运动弹丸的负氧平衡发射药膛口射流燃烧流场进行了数值模拟.分别用HLLC格式和基元反应模型处理对流项和化学反应项,用网格局部重构的动网格技术处理因弹丸大位移动边界造成的网格变形,并基于非结构动网格和分区算法开发了并行程序,对膛...     

基于格子Boltzmann方法的地下矿巷道系统突水与蔓延数字模拟

采用格子Boltzmann方法建立了巷道突水蔓延二维仿真模型.将物理巷道划分为网格模型,确定每个网格节点的基本物理量,对水粒子在网格模型内碰撞和迁移过程做了定义,巷道边界使用修正反弹格式,针对复杂巷道,使用分块耦合算法,将巷道分块处理,各块只在边界处进行数据交换,实现了不同块之间流场的耦合,简化计算,提高了程序效率.仿...     

边界单元法在聚合物加工研究中的应用

将边界单元法引入聚合物加工过程粘性流场的数值计算中，并与其它数值计算方法进行了比较。结果表明边界单元具有计算量少，计算精度高等优点，便于推广应用，以挤出机排气段熔体输送流场求解为例，说明了边界单元法的实际应用。     

网格最优化信息反馈模型研究

针对网格计算中信息反馈机制或者信息传递机制因网格结点多、弧数量及考虑重点变化大、反馈路径和信息传递路径选择难度大的问题,提出一种基于优势比及路径期望的方法,对网格下的信息反馈问题进行建模,利用求解算法解出最优值。实验表明,该模型及求解算法在大规模网格信息反馈或者信息传递过程中能求得最优解,而且迭代次数与时间开销将趋于最优。     

Numerical simulation of the resin transfer mold filling process using the boundary element method

A numerical simulation of the mold filling process during resin transfer molding with a heated die was performed using the boundary element method. The governing differential equation with a variable coefficient was rearranged into a system of Poisson equations using the perturbation technique. The boundary element method was employed to solve the resulting equations. The resin viscosity was calculated by introducing markers at the resin inlet and tracing them. As the calculation domain changes because of the proceeding resin front, numerical calculation nodes on the boundary were rearranged for each time step and integration was performed only for the meshes in the calculation domain among the fixed meshes over the mold. Sample calculations were performed for two molds with different shapes. To check the validity of the numerical scheme, the calculated mass flow rate at the resin front was compared with the mass flux at the inlet. Close agreement was observed.     

注塑冷却快速边界元算法

在用边界元方法进行注塑冷却分析时,形成的矩阵方程为满阵,当单元数目超过一定值时,计算机则变得无能为力.针对这一问题,本文介绍一种新的计算方法,首先将单元分组,求出组内单元的平均温度,再利用得到的结果进一步计算组内每一个单元上的温度.采用这种方法,能够有效缩短计算时间,使计算时间仅为常规方法的1/4甚至更少.另外,通过单元合并减少了计算的数据量,改善了因计算机截断误差积累导致计算结果异常的情况,使得冷却分析能处理的单元数目较常规方法提高1倍以上.     

注塑模典型截面温度场的数值分析

通过二维典型截面简化模具的三维结构,建立了注塑模典型截面温度场的边界积分方程,并进行数值求解。将模具温度分为稳态和波动两部分,稳态部分是采用循环平均假设,推导出求解模具典型截面二维稳态温度场的边界积分方程。然后利用边界元法,分别对动模和定模进行传热分析,根据分型面边界相容性条件进行耦合;波动部分是在给出温度波动的微分方程后,利用有限差分法结合传热学对型腔表面温度波动进行数值求解。最后通过实例验证了文中算法的正确性与有效性。     

Fast Calculating Method and In-Mold Labeling Model for Cooling Analysis in Injection Molding

Cooling analysis with the boundary element method (BEM) forms full-matrix equations in injection molding. Computers have no ability to handle it when the element number is more than its acceptance. This paper adopts the elements incorporation method. It changes the original model from one large matrix equation to one small union matrix equation and several small block matrix equations. In this way, the calculation time is shortened considerably and the treatable number of element in cooling analysis is enhanced dramatically. In-mold labeling processing, which adds a label on part surface in the mold is a new technology, and it is becoming more and more popular. It affords the mold designer far greater latitude in the design of graphics, part shape, and the use of multiple molded components in a single molded unit. Its simulation is a new task in computer aided engineering (CAE). This paper is based on the feature that the cavity surface is always meshed into planar triangular elements, Supposing that the label and part are two plates with perfect contact, establishes a one dimensional unsteady heat transfer model under the first dissymmetry boundary for each element. Using this heat transfer model, the cooling analysis model of in-mold labeling is established.     

Coupled Part and Mold Temperature Simulation for Injection Molding Based on Solid Geometry

This paper presents a coupled method that determines the interface temperatures by filling and cooling analyses simultaneously to simulate the mold and part temperature distributions for injection molding. The mold temperature is assumed to be changing and is calculated with melt together at the filling stage instead of keeping constants as is usually done in conventional methods. The mold temperature is first determined with a 3-D finite element method by specifying the heat-flow rate at the interface between mold and part. Then the finite difference approach is employed to solve the melt thermal problem to get melt temperature distributions inside the cavity and the heat-flow rate at the interface. The under-relax scheme is used to correct the boundary condition and to resolve both mold and melt thermal problems until the solutions are convergent. This method can simulate transient and multicycle problems with more complex process conditions. The simulated results agree with experimental data.     

A study on the mold filling process in resin transfer molding

A numerical simulation of the mold filling process during resin transfer molding (RTM) was performed using the boundary element method (BEM). Experimental verification was also done. Darcy's law for anisotropic porous media was employed along with mass conservation to construct the governing differential equation. The resulting potential problem was solved with the boundary element technique. As the calculation domain changed due to the proceeding resin front, boundary nodes were rearranged for each time step. The node which goes out of the calculation domain as time progresses was relocated at the intersection between the solid boundary and the line drawn between the node at previous and at current time steps. Results showed good agreement with data for a rectangular mold. To evaluate further the validity of the model, the area velocity of the resin-impregnated region during mold filling was calculated. The area velocity thus calculated was compared with the corresponding resin inlet velocity to check the mass conservation. A close agreement was observed, which renders confidence in the resin front proceeding algorithm. Numerical calculations were also performed for complicated geometries to illustrate the effectiveness of the current method.     

注塑模典型截面温度场的数值分析及影响因素

通过二维典型截面简化模具的三维结构，建立了注塑模典型截面温度场的边界积分方程，并利用边界元法通过分别对动模和定模进行传热分析，根据分型面边界相容性条件进行耦合，最终求出型腔表面温度场的数值解。最后通过实例分析了影响型腔温度的各种因素，也验证了文中算法的正确性与有效性。     

RIM充模过程数值模拟

用有限元法对RIM充模过程进行数值模拟．采取任意拉格朗日－欧拉法（ALE）处理流动前缘.并以边充模边划分网格的方法,使前缘边界条件得到较充分的满足．对不同操作参数下的RIM充模模拟结果进行了讨论、分析,得出选用薄腔、较快的充模速度以及适当较高的物料初始温度对RIM充模有利的结论,这对工业实践有重要的指导意义．     

变系数各向异性热传导问题边界元解法

提出了一种用边界元法求解一般变系数各向异性热传导问题时建立基本解的方法,并导出了求解一般二维和三维各向异性稳态热传导问题的纯边界积分方程。所建立的基本解考虑了热导率是空间坐标的函数,因此所导出的积分方程可用于求解非均质材料传热问题。由热源项引起的域积分,运用径向积分法将其转换成边界积分,形成不需要内部点的纯边界元算法。给出了二维和三维问题3个分析算例,并通过将边界元法结果与有限元法结果进行对比,证明了方法的正确性和有效性。