基于多计算模型耦合的铸造充型过程三相流多尺度数值模拟研究

Simulation of mold filling process of castings is necessary to optimize technological parameters before its practical implementation and thus overcomes the long-term problems in the production such as long trial period and difficulties in quality control. Multi-scale simulation of the filling process is of great scientific value and wide application prospect. Grid-based calculation methods such as FEM (Finite Element Method) and FDM (Finite Difference Method) have been widely used for the macro numerical simulation of casting filling process. However, they have their own problems when dealing with extreme grid deformation and moving interface tracking. It is of great difficulties to obtain all thermal physical parameters through experiments. On the other hand, results from the AIMD (Ab Initio Molecular Dynamics) theory agree well with experimental results but are only applicable for small systems. Investigations on the calculation of phase flow between liquid, gas and solid phases are rare. Based on SPH (Smoothed Particle Hydrodynamics), this project establishes a G-SPH mathematical model of three-phase flow for macro flow computation of filling processes. The proposed approach is able to solve the problems of extreme-scale deformation and moving interface tracking. This capability is achieved by a combination of AIMD and CMD (Classical Molecular Dynamics). The AIMD is first used to fit the potential function in CMD and a coupled AIMD-CMD method is applied to determine the thermal parameters of solid-liquid flow for a reasonable prediction of its macro performance and a coupled macro simulation.

铸造充型模拟可在工艺实施前优化工艺参数，克服生产中长期存在的试制周期长、质量控制难等缺点，进行充型过程多尺度模拟研究具有十分重要的科学价值和应用前景。铸造充型过程宏观数值模拟目前多采用FEM或FDM等基于网格的计算方法，难以处理极大网格变形和运动交界面跟踪等问题，且少见有关铸造充型过程三相流动计算的文献；通过实验获取完整热物性参数的难度较大；AIMD是计算材料性质的重要方法，但无法进行固液两相流热物性参数的计算。本项目拟基于无网格方法，建立G-SPH三相流数学模型，进行充型过程宏观三相流的流动计算，解决网格计算方法中极大尺度变形和运动交界面追踪的问题；拟采用AIMD进行熔体和晶体热物性参数计算，但由于AIMD所能处理的体系较小，拟利用AIMD的计算结果拟合CMD所需的势函数，采用CMD进行固液两相流热物性参数的计算，克服传统实验获取参数过程中难度大、费用较高的问题，实现了与宏观模拟的耦合。

铸造充型模拟可在工艺实施前优化工艺参数，克服生产中长期存在的试制周期长、质量控制难等缺点，进行充型过程多尺度模拟研究具有十分重要的科学价值和应用前景。.铸造充型过程宏观数值模拟目前多采用FEM或FDM等基于网格的计算方法，难以处理极大网格变形和运动交界面跟踪等问题，且少见有关铸造充型过程三相流动计算的文献；本项目拟基于SPH方法，建立三相流数学模型，进行充型过程宏观三相流的流动计算，解决网格计算方法中极大尺度变形和运动交界面追踪的问题。基于第一性原理研究了压力对合金的晶胞结构、力学性质、热力学性质和电子结构等的影响；以及压力和温度对合金的力学性能、热力学性能和电子结构等的影响。.在完成既定目标的同时，基于SPH方法，还进行了拓展研究，运用Cleary的接触理论法实现了SPH方法的热传导模型的建立，并提取平壁件温度分布趋于稳定后数值解与解析解进行拟合，验证了所建立的SPH方法热传导模拟的准确性。基于SPH法，建立含损伤预测的3D模拟数学模型，应用OpenMP技术编写并行SPH法程序，并应用于镁及镁合金ECAP过程3D数值模拟。