铸件凝固过程温度场数值模拟研究进展

作者概述了国内外铸件凝固过程中温度场数值模拟进展，介绍了傅立叶方程及其相应初始条件、边界条件、潜热处理以及多种计算方法，提出了凝固过程温度场模拟需解决的问题和发展趋势。     

铸件凝固过程微观数值模拟方法进展

分析了铸件凝固过程微观数值模拟的两种方法：即晶粒动力学方法和相场合,分别介绍了其原理及其应用,并指出了各自的优缺点。在文章的最后,总结了微观模拟研究的现状及其发展方向。     

增量变刚度法在铸件凝固过程数值模拟中的应用

目的开发铸件凝固过程位移场数值模拟程序。方法 采用有限元增量变刚度法计算位移场。结果 对实际铸件进行模拟。结果与理论分析一致。结论 本研究工作是进一步模拟应力场和进行热裂预测的基础。     

铸件凝固组织微观模拟的研究进展

综述了铸件凝固过程微观组织模拟的研究进展，详细介绍了确定性方法、随机性方法、相场方法的发展过程．论述了共晶合金和枝晶合金凝固组织的数值模拟进展．最后，预测了凝固组织数值模拟研究的未来发展方向。     

铸件凝固模拟软件的可视化

介绍了在自行开发的凝固模拟软件中对目标数据的处理．针对模拟计算使用的正交网格单元设计了适合于处理目标数据的独特的处理流程和算法，将目标数据转化为计算机图形，为分析目标数据提供了直观方便的手段．采用VC 6．0编写的可视化程序，利用对话框等交互手段实现对图形处理过程的全面控制．可以对模拟获得的温度场图形进行一般显示或剖切、旋转、透视等实时操作，并可动态演示凝固温度场的变化过程．     

对铸件凝固过程数值模拟中异步计算的改进

在铸件凝固过程数值模拟中，采用虚拟的界面换热系数来代替原界面换热系数，并以此协调不同单元用不同的时间步长进行计算所带来的不协调性和误差。并且，计算速度较快，精度较高。     

厚大断面球铁铸件凝固过程的数值模拟

应用计算机对厚大断面球铁铸件的凝固过程进行了温度场的数值模拟，提出了铸型受热辐 铁水浸泡的初始温度分布函数，并考虑了结晶潜热和强制冷却工艺等因素，使模拟精度高，误差在５％以内，为研究厚大断面球铁铸件的凝固规律提供了较可靠的参考依据。     

铸件凝固过程微观组织模拟技术的研究

目的 揭示国内外对微观组织模拟研究的重要方法。方法 利用确定性模型和随机性模型相结合的方法，建立晶粒形核和生长的物理、数学模型。结果 通过计算机已能初步模拟出微观组织形态，并能预测铸件的机械性能。结论 发展微观模拟广阔前景，有待在理论和实践中进一步完善。     

凝固组织计算机模拟技术评述

用计算机模拟的方法研究组织形成过程对于改善材料性能、优化材料成型工艺等有重要意义,概述了近年来国内外凝固组织计算机模拟技术的进展,评述了当前使用的数学模型,即蒙特－卡洛模型、相场模型和基于界面稳定性理论的晶体生长模型的特点及局限性,展望了凝固组织计算机模拟技术的发展方向。     

Simulation of stray grain formation during unidirectional solidification of IN738LC superalloy

The influence of casting parameters on stray grain formation of a unidirectionally solidified superalloy IN738LC casting with three platforms was investigated by using a 3D cellular automaton-finite element (CAFE) model in CALCOSOFT package. The model was first validated by comparison of the reported grain structure of Al-7%Si (mass fraction) alloy. Then, the influence of pouring temperature, heat flux of the lateral surface, convection heat coefficient of the cooled chill and mean undercooling of the bulk nucleation on the stray grain formation was studied during the unidirectional solidification. The predictions show that the stray grain formation is obviously sensitive to the pouring temperature, heat flux and mean undercooling of the bulk nucleation. However, increasing the heat convection coefficient has little influence on the stray grain formation.     

Microsegregation and Rayleigh number variation during the solidification of superalloy Inconel 718

The microstructure and composition of the residual liquid at different temperatures were investigated by scanning electron microscopy （SEM） and energy dispersive X-ray spectrometer （EDX） associated with the Thermo-calc software calculation of the equilibrium phase diagrams of Inconel 718 and segregated liquid. The liquid density difference and Rayleigh number variation during solidification were estimated as well. It is found that the heavy segregation of Nb in liquid prompts the precipitation of δ and Laves phase directly from liquid and the resultant quenched liquid microstructure consists of pro-eutectic γ＋eutectic,or complete eutectic according to the content of Nb from low to high. The liquid density increases with decreasing temperature during the solidification of Inconel 718 and the liquid density difference is positive. The largest relative Rayleigh number occurs at 1320°C when the liquid fraction is about 40vol%.     

高温合金定向凝固枝晶间距与冷却速率的关系

利用高梯度快速定向凝固设备,对ＤＺ２２高温合金定向凝固组织进行了研究．研究结果表明,一次和二次枝晶组织随冷却速率的增长,都有明显细化,横向分枝的生长受到抑制．一次和二次枝晶间距与冷却速率之间都符合指数关系．在冷却速率达到５４℃／ｓ时,一次枝晶间距为２８８μｍ,二次枝晶间距８４μｍ．     

GPU-accelerated phase field simulation of directional solidification

The phase field simulation has been actively studied as a powerful method to investigate the microstructural evolution during the solidification.However,it is a great challenge to perform the phase field simulation in large length and time scale.The developed graphics processing unit(GPU)calculation is used in the phase filed simulation,greatly accelerating the calculation efficiency.The results show that the computation with GPU is about 36 times faster than that with a single Central Processing Unit(CPU)core.It provides the feasibility of the GPU-accelerated phase field simulation on a desktop computer.The GPU-accelerated strategy will bring a new opportunity to the application of phase field simulation.     

刀具螺旋槽生成的直接方法及计算机仿真

螺旋槽的生成是通用刀具设计和加工的基本问题。虽然已经积累大量研究经验和资料，需要探索和开发的领域还很广阔。螺旋槽生成方法历来广泛应用的是已知槽型求其加工砂轮或刀具的轮廓，通常称为逆方法。另一种方法是已知砂轮轮廓求槽型，所谓正方法(或直接方法)。这两种方法各有其特点和局限性。直接方法虽然比较容易实现，但尚未引起足够重视，在原理和应用上还有许多问题待研究。本文论述直接方法的数学建模及其应用，并通过实际加工比较计算结果与成品的误差，证实按直接方法编制的程序可以成为仿真软件。     

刀具螺旋槽生成的直接方法及计算机仿真

螺旋槽的生成是通用刀具设计和加工的基本问题。虽然已经积累大量研究经验和资料,需要探索和开发的领域还很广阔。螺旋槽生成方法历来广泛应用的是已知槽型求其加工砂轮或刀具的轮廓,通常称为逆方法。另一种方法是已知砂轮轮廓求槽型,所谓正方法(或直接方法)。这两种方法各有其特点和局限性。直接方法虽然比较容易实现,但尚未引起足够重视,在原理和应用上还有许多问题待研究。本文论述直接方法的数学建模及其应用,并通过实际加工比较计算结果与成品的误差,证实按直接方法编制的程序可以成为仿真软件。     

包钢大方坯连铸机结晶器凝固传热的数值模拟

根据包钢的现场条件,建立了大方坯连铸机结晶器内二维非稳态凝固传热数学模型,采用有限差分法对数学模型求解,得出结晶器中铸坯的温度分布规律和凝固坯壳生成规律,同时研究了拉坯速度对坯壳生成厚度的影响。     

Numerical analysis on solidification process and heat transfer of FGH95 superalloy droplets during PREP

In order to understand the relation between microstructure of superalloy powders and its solidification progress, the processing parameters are optimized during plasma rotating electrode processing (PREP). It was predicted from the results that the droplet velocities, droplet temperature, and fractional solidification with flight time about FGH95 superalloy droplet have been carried out based on Newtonian heat transfer formulation coupled with the classical heterogeneous nucleation and the specific solidification process. It has been found that the droplet dynamic and thermal behavior is strongly affected by the distribution of droplet diameters, the proportion of cooling atmosphere, but is relatively unaffected by the droplet superheat.