注塑模充模过程动态分析

注塑成型是利用型腔模制造理想制品主要的成型加工方式 ,塑料熔体的流动行为将直接影响着最终塑件的质量 ,塑料熔体在三维薄壁型腔内的流动属于带有运动边界的粘性不可压缩流体的流动 ,本文针对塑料注塑成型特点 ,经过量纲分析和引入合理而必要的假设 ,得到了适合于充模分析的数学模型。控制方程的求解主要包括三个阶段 :压力场、温度场和流动前沿位置的确定。数值求解采用有限元法求解压力场、有限差分法求解温度场、并利用控制体积法跟踪熔体前沿 ,实现了充模过程的动态模拟     

磁场对液态金属流的制动效应

研究在静磁场作用下；连铸坯中液态金属的流动，建立了二维数学模型并考虑了湍流的影响．采用数值分析方法分析了磁场对液态金属流股的制动效应．计算结果说明静磁场可以有效地减小流股速度并使其分散，同时使上升到液态金属液面的反转流减弱．随着哈特曼数增高和雷诺数的减小，磁场的制动效应增强．     

注塑模冷却系统灵敏度分析方法及应用

本文提出了利用灵敏度数值计算方法进行设计参数选择和修改的注塑模冷却系统设计方法和理论分析数学模型,并开发出了一个处于CAD环境中的冷却系统分析软件,为设计人员优化冷却管道布置、保证模具型腔表面温度分布均匀、减少塑件翘曲变形提供了科学依据和分析手段。     

多孔氧化铝陶瓷储油材料的摩擦学性能研究

用石墨作为造孔剂,利用模压成型高温烧结方法制备了分布均匀的多孔氧化铝陶瓷,将多孔氧化铝陶瓷浸渍甲基硅油得到多孔氧化铝储油材料,在THT07-135型高温摩擦磨损试验机上考察了其同Si3N4陶瓷球对摩时的摩擦磨损性能,用扫描电子显微镜观察分析了磨损表面形貌.结果表明,浸渍甲基硅油后多孔氧化铝陶瓷的减摩抗磨性能显著改善,这是由于储存在多孔氧化铝陶瓷中的润滑剂起到润滑作用并抑制偶件的氧化磨损所致.     

环模修复机模孔定位关键技术研究

环模在饲料加工机械中是一个易阻塞的核心部件。国内外常见清理手段是人工手动逐孔清理。针对现有技术存在清理效率低、易产生误操作及毁坏环模等瓶颈,提出了一套有效的环模模孔定位方法。首先运用磁敏元件检测漏磁原理,分析了模孔定位方法的可行性;然后根据电磁屏蔽对屏蔽材料的选择角度,制作关键探测探头;最后根据捕获模孔的信号特征,基于高效的黄金分割优化搜索的设计思想,构建了环模模孔定位算法模型,分析了模孔定位方案的有效性。结果表明研制的修复机系统模孔定位精度在mm级以下,模孔刮伤率大大降低,进而环模的使用寿命得到延长。     

Parallel three‐dimensional simulation of the injection molding process

This paper describes the development of a parallel three‐dimensional unstructured non‐isothermal flow solver for the simulation of the injection molding process. The numerical model accounts for multiphase flow in which the melt and air regions are considered to be a continuous incompressible fluid with distinct physical properties. This aspect avoids the complex reconstruction of the interface. A collocated finite volume method is employed, which can switch between first‐ and second‐order accuracy in both space and time. The pressure implicit with splitting of operators algorithm is used to compute the transient flow variables and couple velocity and pressure. The temperature equation is solved using a transport equation with convection and diffusion terms. An upwind differencing scheme is used for the discretization of the convection term to enforce a bounded solution. In order to capture the sharp interface, a bounded compressive high‐resolution scheme is employed. Parallelization of the code is achieved using the PETSc framework and a single program multiple data message passing model. Predicted numerical solutions for several example problems are considered. The first case validates the solution algorithm for moderate Reynolds number flows using a structured mesh. The second case employs an unstructured hybrid mesh showing the capability of the solver to describe highly viscous flows closer to realistic injection molding conditions. The final case presents the non‐isothermal filling of a thick cavity using three mesh sizes and up to 80 processors to assess parallel performance. The proposed algorithm is shown to have good accuracy and scalability. Copyright © 2008 John Wiley & Sons, Ltd.     

实正规阵乘幂法的改进

本文对实正规阵乘幂法予以改进，给出了一个容易求复特征值的收敛格式     

驻波实验中"二分频"现象的探讨

在大学物理实验教材中常用音叉弦振动形成共振驻波来测量音叉的振动频率,但对其中的"二分频"现象无相关的理论解释,本文在建立与‘‘二分频"现象相似的模型中,用数值计算的方法演示了这一结果.     

A study on the micro‐injection molding of multi‐cavity ultra‐thin parts

In this study, we report the micro‐injection molding of ultra‐thin parts (100, 250, and 500 µm). The results show that the flow resistance increases as the cavity becomes thinner. The melt front is not symmetric when filling a four‐cavity ultra‐thin part and filling the eight‐cavity mold under a low temperature. If we increase the mold temperature or cavity thickness, the melt front becomes symmetric. Finally, we construct the operation windows of molding for three kinds of plastics (PS, PMMA, PC) and provide a molding range based on mold temperature and injections speed. Meanwhile, the relationship between the thickness and the operation windows are also investigated. The thinner the cavity is, the smaller the operation window is. We need to increase the injection speed significantly for molding the ultra‐thin parts with micro‐features on both surfaces which are 60 µm in thickness. Furthermore, we succeed in molding 30 µm ultra‐thin parts in this experiment. Copyright © 2009 John Wiley & Sons, Ltd.     

The Use of a Coulter Counter to Quantitatively Determine Mold in Carbonated Soft Drinks

Abstract

A method for the rapid, quantitative screening of carbonated soft drinks for mold at levels well below what is normally detected by candling and which is quantitatively more reliable than counting mold clumps is proposed. It involves the use of a Coulter Counter and can detect as few as 10 mold filaments per milliliter of the original soft drink. Soft drinks containing pulp pose a problem that is only partially solved. Dead mold getting into the soft drink is almost completely separated by a density gradient salt solution but live mold uses the pulp as a growth base and is not separated.