Sand casting process simulation technology introduction in the process of national economic development, sand casting industry, as an important part of manufacturing industry, plays an irreplaceable role. In the new century, the precision, lightweight, toughness and greening of sand casting production have become the main development direction. In addition, the relationship between computer information technology and traditional sand casting industry is becoming closer and closer.
Computer simulation technology of sand casting process (casting CAE), which mainly involves the numerical simulation of liquid metal filling and solidification process. Through the simulation of the filling and solidification process of liquid metal, we can clearly reveal the internal law that determines the quality of sand casting, predict the size, location and time of various sand casting defects, help the sand casting process designers to verify the process in advance, and take improvement measures for the problems in advance, so as to continuously optimize the sand casting process scheme, avoid repeated waste, shorten the development cycle and improve the design and production efficiency, Ensure the effect of casting quality. Therefore, the computer simulation technology of sand mold casting process has become a new frontier field of the scientific development of sand mold casting. More and more scientific researchers have invested in the development of sand mold casting process simulation software and the establishment and improvement of material database.
The simulation technology of sand mold casting process takes numerical calculation as the basic method, combined with the research results of heat transfer, hydrodynamics, elastoplastic mechanics, rheology, crystallography and physical chemistry, simulates the flow field, temperature field, stress field and microstructure morphology of sand mold casting in the filling process, solidification process. At present, the development trend of sand mold casting process simulation technology is as follows:
1) The simulation scale changes from macro to micro. On the basis of predicting the shape, size and location of macro defects in sand mold casting by using flow field, temperature field and stress field, it focuses on the simulation and prediction of microstructure and structure with crystallization, segregation, diffusion, gas precipitation and phase transformation as the research objects;
2) The overall optimization design of multi physical field and multi-scale simulation. Based on the simulation of single flow field, temperature field, stress field and tissue field, explore the coupling simulation of multi physical field, including the coupling between temperature / stress field, temperature / tissue field and stress / tissue field, so as to truly simulate the sand mold casting process;
3) Parallelization, agility, digitization and networking are mainly reflected in the cross application with parallelization, agile engineering, virtual manufacturing and other fields, so as to effectively serve the networked remote design and manufacturing.
The numerical simulation methods in sand mold casting process mainly include finite element method (FEM), finite difference method (FDM), finite volume method (FVM), boundary element method (BDM), etc. Among them, finite element method and finite difference method are widely used in engineering practice. The finite difference method replaces the differential form of the governing equation with the difference method to calculate various numerical equations. The method is direct and convenient, and the calculation is fast. As the numerical calculation method of the explicit format, the finite difference method has advantages in memory occupation and calculation time. However, due to the inherent divergence possibility of the difference format, in order to ensure the convergence and stability of the calculation, It is required that there are restrictions on the selection of time step and distance step of difference calculation in the process of discretization. At the same time, because the typical finite difference calculation requires the regular hexahedron as the minimum three-dimensional difference grid, the division of the actual object is often distorted in its grid division, which affects the calculation accuracy of simulating objects with complex and irregular boundary geometry. The finite element method is mathematically more profound than the finite difference method, which is based on the classical variational method. In mesh generation, because its minimum element shape has great variability, it can retain the uniqueness of mesh generation of irregular objects to the greatest extent, and can accurately reproduce the boundary shape of complex objects. Therefore, it is the first choice for many popular and successful commercial numerical calculation software, such as ANSYS, anuqus and so on. As an implicit numerical method, the calculation process of finite element method is very complex, which consumes more memory and time.