In the 1980s, j.t. berry, a professor of Georgia Institute of technology and R.D. pehlkc, a professor of Michigan IL University, formed a joint research group with the research goal of finally realizing computer-aided design of casting process with the support of the National Science Foundation. In order to make the simulation results more consistent with the measured results, they first re established the mathematical model and various criteria to further mature the numerical simulation technology of casting solidification process. At the same time, using the new achievements made in the basic theoretical research of casting solidification, they organically combined the macro simulation calculation of computer with the micro crystallization process. Finally, they put forward the concept of casting process CAD, and organically combined numerical simulation, geometric simulation and database to establish the geometric technology model of computer-aided design of casting process.
Compared with the numerical simulation of temperature field, the numerical simulation of flow field is much more complex, so the computer simulation of casting filling process starts much later.
The filling process is the most important stage in the casting forming process. The defects such as insufficient pouring, air entrainment and cold shut in the later stage are caused by the long filling time of liquid metal, the unstable filling process and the unreasonable filling sequence. The filling process of liquid metal will also affect the initial temperature field of the later solidification process. There is heat exchange between the liquid metal and the mold wall during the filling process, and then an unsteady temperature field is formed. Therefore, the numerical simulation of the casting filling process can not only analyze the flow pattern of liquid metal in the filling process and predict the possible defects in the later stage, so as to provide a reasonable basis for the optimization of the casting process, but also provide the initial temperature field for the heat transfer calculation of the subsequent solidification process and further improve the accuracy of the simulation of solidification temperature field.
The numerical simulation of casting filling process began in the early 1980s. In 1983, Taiwan scholar W.S. Hwang and Professor R.A. stoehr at the University of Pittsburgh in the United States simulated the filling process of liquid metal flowing into stepped vertical cavity and rectangular horizontal cavity respectively. They used the two-dimensional fluid flow Software Mac to study the numerical simulation of casting filling process. For the first time, they applied the research results of hydrodynamics in the numerical simulation of casting filling process, opening up a new way to study the numerical simulation of casting filling process. A few years later, they used Mac and Smac methods to simulate the mold filling process of thin plate castings. At the same time, they also carried out hydraulic simulation of thin plate castings. In addition, they also recorded the mold filling process of thin plate castings by using high-speed photography and X-ray fluorescence photography. It was found that the calculation results were consistent with hydraulic simulation, high-speed photography The results of X-ray fluorescence photography were similar. W. S. Hwang and R. A. stoehr believed that MAC and Smac were effective methods to study the numerical simulation of mold filling process. Then they successfully used the combination of MAC method and SOLA-VOF method to simulate the flow field of casting mold filling process.
In 1984, the American scholar P.V. Desai studied the temperature distribution in the sprue under the condition of forced convection, and combined the simulation of flow field and heat transfer calculation during mold filling for the first time.
In 1985, C.M. Wang improved SOLA-VOF software and used it to calculate the two-dimensional filling process of a three spoke pulley. At the same time, he used high-speed photography technology to record the actual filling process of the three spoke pulley. It was found that the results calculated by the improved SOLA-VOF software were in good agreement with the results of high-speed photography test.
In 1986, researchers from Germany’s Aachen University led by P.R. Sahm and H. walte also numerically simulated the filling process of the above three spoke pulley. Different from C.M. Wang, they changed the inlet orientation of the fluid. In the same year, researchers from Argonne National Laboratory led by H.M. domanus studied the flow field and heat transfer process of a simple shape casting. The software used in the research is three-dimensional software commix, and the calculation part of this software draws lessons from Patankar’s method and VOF method.
In 1988, professors h.j.lin and R.A. stoehr of the University of Pittsburgh in the United States added heat transfer calculation to the two-dimensional SOLA-VOF calculation program, and used the improved program to predict the cold lap caused by uneven filling of flat castings. In the same year, the researchers of Tohoku University, led by hiroichi asari, used the pseudo three-dimensional SMAC calculation method to simulate the mold filling process of aluminum alloy die castings and predict the cold shut defects of castings. At the same time, they also conducted hydraulic simulation experiments on castings. The results showed that the calculation results were basically consistent with the hydraulic simulation results.