铸件凝固过程中温度场的数值模拟

为了掌握铸件凝固过程中温度场的变化规律以提高铸件质量，采用有限元和有限差分相结合的方法离散铸件凝固过程非稳态热传导方程的空间和时间变量，得到了关于金属铸件和铸型温度的代数方程．用二部法模拟铸件与铸模问的耦合，用迭代法求解离散后的代数方程组，并利用变时间步长技术提高计算效率；用热传递系数模拟铸件与铸型间的热传递，铸件冒口及铸型与冒口接触部分节点都当作内部节点，铸型与外界的换热按热对流和热辐射2种方式处理，忽略充型对凝固过程的影响，铸件材料潜热释放采用线性模型．算例结果表明，所用方法能有效地模拟铸件凝固过程中温度场的变化规律．

Numerical Simulation of Temperature Field in Process of Casting Solidification

In order to obtain the variation law of temperature during casting solidification to improve casting quality, a finite element method combining with a finite difference method was used to discretize time and space cariables in the governing equations of astable heat-conduction in the process of casting solidification so as to obtain the algebraic equations for casting and mold temperature. In order to solve the coupled problem of the equations governing temperature in the casting and the mold, alternative method of two-domain and an iterative method were used. In addition, varying time steps were automatically controlled in the light of the grade of change in temperature in order to save calculation time. For simplicity, some assumptions about boundary conditions were made, i. e. , the distributions of temperature in the casting and the mold are uniform at the beginning. The linear models expressing the release of latent heat of the casting were used for the revised coefficient of specific heat. The calculational results show that with this method the distribution of temperature in castings can be simulated.