基于MPI技术的注射成型流动数值模拟研究

以塑料注射成型流动分析软件MPI为工具,对注塑过程中流动数值模拟技术进行了深入研究,建立了塑料熔体流动过程的数学模型。对注射成型模型进行了简化数值计算,以更清楚的认识各物理变量对成型过程的影响,并通过实例说明MPI技术在注射成型流动数值模拟技术的合理应用,用软件预测了温度、压力分布,注射充填型腔计算机模拟,以指导模具设计工作。     

低压铸造铝合金车轮充型过程数值模拟的研究

利用数值模拟技术,对低压铸造铝合金车轮的流动、充型过程进行了分析。应用表明,流动场数值模拟技术可以跟踪液态金属的充型形貌,分析各部位的压力分布,为优化铸造工艺、改进模具设计提供了有效的手段。     

低压铸铝合金车轮充型过程数值模拟的研究

利用数值模拟技术，对低压铸造铝合金车轮的流动，流型过程进行了分析，应用表明，流动场数值模拟技术可以跟踪液态金属的充型形貌，分析各部位的压力分布，为优化铸造工艺、改进模具设计提供了有效的手段。     

小管径涡流管三维数值模拟及热力学过程分析

为了探究小管径涡流管的工作机制,建立了其内流场的三维数值计算模型,并采用Standard k-ε湍流模型进行了数值模拟。根据数值计算所得结果,结合工质的流动特点,将其内部流动过程分为三个特征区域,分析各区域所得相关物理量的分布情况,给出了小管径涡流管工作过程中工质的热力学变化过程,同时通过对比实验和模拟所得的出入口数据,验证了所用数值模拟方法的可行性。以此对小管径涡流管工质及温度的分离现象做出一定解释。     

汽车缸套离心铸造凝固数值模拟研究

建立汽车缸套离心铸造凝固过程的数学及物理模型,对汽车缸套离心铸造的凝固过程进行数值模拟,得到汽车缸套离心铸造过程中的温度场、液固相分布及缩孔缩松状况。结果表明:采用数值模拟分析能够使汽车缸套的高速、高温、复杂的卧式离心铸造过程可视化,并可方便地通过改变铸造参数来分析对铸造效果的影响;合适的铸型转速会对充型产生较大的影响,过小则会产生雨淋现象,过大则会使充型不连续;为减少铸件外表面及端面与内表面中心部分凝固速度的差距,可以适当提高铸型的预热温度。     

基于近似因子分解法的铸造充型过程数值模拟研究

目前求解流动过程中速度场、压力场最常用的方法是SOLA法,在求解过程中由于需要在连续性方程、动量方程间反复迭代,所以计算效率不高。采用近似因子分解法进行速度场、压力场求解,由于在求解过程中每一步均可采用托马斯算法求解三对角方程,所以计算简单,可有效提高计算效率。最终建立了基于有限差分法的流动场数值模拟程序,并针对Benchmark件进行了充型过程流动场数值模拟,通过对比模拟结果与实验结果,验证了计算模型的正确性。     

温度和摩擦条件对不锈钢管材挤压过程的影响

以316LN不锈钢管材挤压件为例,采用3种温度状态和4种摩擦因子的不同组合共进行12组挤压过程的数值模拟,得到了不同参数下坯料温变、模具载荷及材料流动情况,掌握了温度和摩擦条件对挤压力和材料流动的影响规律,为管材挤压工艺优化提供了理论依据。     

铸铁件铸造缺陷的有限元分析

采用有限元法建立了铸件凝固过程的数学模型，考虑材料随温度变化的非线性因素和相变中结晶潜热问题，对铸造凝固过程进行了数值模拟，得到了铸件在凝固过程的瞬态温度场、温度梯度场的分布和变化规律。预测出了铸件可能出现缩孔、缩松等铸造缺陷的位置，结果表明模拟预测与生产验证结果基本一致。     

一种铸造成形过程影响因素模拟与优化分析方法

针对目前钢锭铸造成形时常用的"瞬时充型、温度均匀"假设条件,提出一种基于正交试验设计、数值模拟及响应面法的铸造成形过程影响因素模拟与优化分析方法。以材料Cr5钢的6t钢锭铸造过程为研究对象,采用试验设计和数值模拟方法获取试验样本数据,运用极差分析得到各因素对响应指标的主次顺序。基于双三次插值算法的响应面建模方法,建立换热系数及预热温度与响应指标的回归响应面模型。基于响应面函数建立了一种对参数进行局部敏感性分析的方法,以修正试验结果。结果表明:为保证铸造成形过程影响因素模拟的精度和可靠性,提高钢锭的铸造质量,应考虑充型过程温度场变化对凝固过程的影响。     

废旧轮胎裂解炉结构及裂解盘表面温度数值模拟研究

热裂解炉是废旧轮胎热裂解的核心部分,同时裂解温度的控制是影响裂解过程及产物质量的主要因素之一。以热解炉内热解盘为研究对象,建立了空心热解盘内高温烟气流动与表面不锈钢板热交换的物理与数学模型。提出了数值模拟仿真的方法,利用Fluent软件,采用标准湍流模型,对两种结构的空心热解盘温度场进行了数值模拟,得到了裂解炉内热解盘表面的温度分布,并计算了每层表面x轴线方向上的温度分布方差。通过比较两种热解盘结构方案选出了其中较优方案,并进一步对裂解炉的结构和工艺参数优化提供指导。     

消失模铸造充型与凝固过程的计算机仿真

根据消失模铸造液态金属充型及液态金属—模样界面的推进机制,提出了充型过程界面推移位置的人工神经网络算法。根据计算得出的界面位置,用SOLA算法计算了充型过程中液态金属的流场,并耦合计算了充型过程中的温度场。根据计算得到的充型结束时铸件及铸型温度场,求解三维导热微分方程,计算了铸件凝固过程的温度场。结合消失模铸造型壁移动的规律,预测了球墨铸铁件消失模铸造的收缩缺陷。计算模拟结果与充型过程实际测试结果及铸件解剖结果一致。     

Vibration-assisted filling capability in thin wall investment casting

Understanding the mechanism of the vibration needed to fill thin section and clarifying the dominant control parameters of the vibration in thin wall investment casting are the keys to producing sound casting. The filling capability in thin wall investment casting method can be assessed by the metal head. It was found that the effect of the vibration on the metal head is markedly dependent on acceleration of applied vibration. Two potential mechanisms were observed from the experimental results during the filling process in thin wall casting: discontinuous propagation flow in vibration conditions and continuous propagation flow without vibration. These mechanisms can modify the contact angles between liquid metal and a wall of the mold. Experiments also showed that two features of the transition can be observed from the front of the morphology: coherent liquid metal front, this occurs in thin wall investment casting when the acceleration due to vibration is less than (1?g) and jetting at the free surface, this occurs in thin wall investment casting when the acceleration due to vibration exceeds 1?g.     

铝合金消失模充型过程的流场及温度场的数值模似

将ＳＯＬＡ－ＶＯＦ法应用于消失模充型过程中，并与传热过程耦合起来，综合考虑了消失模气化分解对充型速度的影响，得到了一维、二维流动的流场和温度场分布，预测了铝合金在消失模铸造中的流动性，揭示了铝合金消失模铸造充型过程与普通砂型铸造充型过程充填模式的差异。     

型腔充填过程三维自由表面的数值模拟

开发了铸件充型过程三维数值模拟软件 ,采用了一种改进的 VOF方法处理三维自由表面 ,包括自由表面网格中流体方位的确定、自由表面的推进及边界条件施加等 ,并利用一个方形板腔的压铸水模拟实验结果对程序进行了验证 ,表明了程序具有处理复杂自由表面的能力。     

Optimal gating system design for investment casting of sterling silver by computer-assisted simulation

The first requirement of all casting processes is complete filling without any defects after solidification. However, casting defects often occur in casting processes, especially incomplete filling. The causes of incomplete filling are related to poor gating system, incorrect pouring, and molding temperature. A suitable shape and dimension of gating system will increase the melt flow while it is feeding into mold cavity by eliminating excessive pouring and molding temperature. The objective of this study is to develop a new design of gating system for eliminating incomplete filling. The new shape and dimension of pouring cup, main sprue, and sprue base are proposed and investigated. The computational flow model is solved with the aid of computer simulation. The targets of an optimum solution are increasing the efficiency of metal flow and reducing turbulence. The experiments are conducted to validate the simulation data. The results of this study will aid in the elimination of casting defects and increase the productivity.     

A new shell casting process based on expendable pattern with vacuum and low-pressure casting for aluminum and magnesium alloys

A new shell casting process, with the adoption of the foam pattern of lost foam casting (LFC) as prototype and the combination of the thin shell fabrication technology of investment casting and vacuum and low-pressure casting process, was proposed for manufacturing complicated and thin-walled aluminum and magnesium alloy precision castings. Loose-sand uniting vacuum was used in the new process to further reinforce the thin shell, and the new process proves to be a process with simple process, low cost, and high thin shell strength. Because the molten metal filling and solidification are completed under air pressure and vacuum level, the filling capability and feeding capacity of the molten metal are greatly improved, and the castings become denser. This paper mainly investigated the fabrication technology of thin shell based on foam pattern prototype, the removing foam and roasting shell process and vacuum and low-pressure casting process. The few-layer compound thin shell of silica sol–sodium silicate was adopted for the new process. Removing foam pattern was carried out at 250°C for 30 min, and the shell was roasted at 800°C for 1 h. Combined with the vacuum and low-pressure casting process, this new shell casting process has successfully produced thin wall and complex aluminum and magnesium alloy parts with high quality. In addition, comparisons in terms of filling ability, microstructure, mechanical properties, porosity, and surface roughness among this new shell casting, gravity casting, and LFC were also made to show the characterization of this new shell casting process.     

Thermal analysis of casting dies with local temperature controller

In high pressure die casting processes, a die plays a critical role in removing heat from the molten metal during the cavity filling and solidification stages. Proper control of die temperature is essential for producing superior quality components and yielding high production rates. In this paper, a computerized intelligent real-time monitoring and control system (IRMCS) is developed for die casting processes involving cooling of a die with multiple channels. A local temperature controller is designed to monitor temperature signals from the die insert and flow rate signals from the cooling lines. The performance of the controller is evaluated, and the effect of the controller on local temperature and heat transfer of casting dies is analyzed. The experimental results obtained from a laboratory die casting process simulator indicate that the developed control system is capable of adjusting the desired supply of cooling water into multiple cooling lines, which effectively controls the local temperature of the die insert within a given range. Hence, the desired thermal pattern of the die becomes achievable.     

充型过程流场数值模拟研究

对充型过程进行分析,确立了充型过程数值模拟的数学模型。利用计算机数值模拟技术对充型阶段的流动过程进行了计算。在此基础上开发了流场模拟软件,并对铸件进行了模拟,结果证明所建立的数学模型及开发的程序是正确的。