Macro-Micro Simulation Of Shrinkage Defects In Casting Solidification Process

The foundry industry has always been one of the most important parts of the modern machinery manufacturing industry.With the progress of the times and the proposal of the sustainable development,to obtain the best quality castings with minimum cost has gradually become the inevitable development goal of the foundry industry.Numerical simulation technology of casting process can provide effective technical support for casting production.It plays an important role in analyzing defects,predicting product quality,improving technical scheme and so on.In the actual production process,the castings which need to be simulated and analyzed are often large and complex.Due to the limitation of computer configuration,the simulation period might take a long time.How to improve the calculation accuracy and efficiency of the simulation process has been the focus of the experts and scholars.In this paper,the macro shrinkage degree model,macro-micro porosity degree model and dynamic grid technology model are put forward.Traditional numerical simulation model of the casting solidification process is improved,which improves the efficiency and precision of the simulation calculation process.On the basis of the original algorithm,the macro shrinkage degree model consumes the shrinkage of the current step in real time through each time step,and gives each of the top molten pool units on average.So each of the top molten pool units has a certain shrinkage degree.This degree is continuously superimposed,and the mesh sign is modified to shrink when it reaches 100%.Part of grids,which are judged to be completely filled due to solidification,will have a certain degree of shrinkage.The morphology of the shrinkage hole can be fitted by the shrinkage degree which will be more accuracy and realistic.In this way,prediction and display of shrinkage defects can get rid of the pace of grid space and improve the calculation precision of shrinkage defect prediction effectively.An algorithm model of macro-micro porosity degree is established.The numerical simulation of macro solidification process is coupled with the cellular automata algorithm of microstructure simulation and calculated in parallel according to a certain order of operation.On the one hand,real time temperature curve can be provided by the calculation of the macro temperature field to obtain accurate results of microstructural simulation.On the other hand,micromorphology of the porosity region can be provided by microscopic model to improve the calculation precision of porosity defect prediction.The dynamic grid technology is an algorithm model aiming at the sudden increase in computation time when the space step is reduced.A larger space step is adopted in the calculation of temperature field and the solid-liquid interface where shrinkage defects may occur will be locally refined.After that,the temperature and physical parameters for small grids will be redistributed and.Next,shrinkage defects are predicted and displayed by using small grids.Finally,the grid without defect will be coarsened.Dynamic grid technology can greatly improve the computational efficiency of numerical simulation of solidification process.The computation efficiency can be increased by tens of times under the same simulation accuracy.This program is based on Microsoft Visual Studio 2015 compiler platform.A three-dimensional macro numerical simulation program for solidification process of cast iron and a two-dimensional macro-micro coupling program of cast aluminum are developed by using Visual C++ programming language.Through these two programs,the macroscopic temperature field change,the prediction of the shrinkage defect and the coupling calculation of the macroscopic temperature field and the micro cellular automaton method can be realized.Through experimental verification and simulation comparison,it is proved that the software calculation model is accurate,fast and practical.