Visualization Of Post Processing Area And Prediction Of Air Entrapment Defect Location In Numerical Simulation Of High Pressure Die Casting

Casting numerical simulation is of great significance for optimizing casting production process.The post-processing module with complete functions allows users to observe the simulation results more comprehensively,but the current post-processing module is still not complete for the display of casting defects.Models of fluid flow in high pressure die casting process are emerging one after another,but the research on air defect that are closely related to flow often cannot meet the needs of actual production.Such defect greatly affect the shape size,mechanics properties and physical properties,even make castings scrap.This thesis first completes the development of the threedimensional visualization of the casting process to provide a more accurate and intuitive display for the subsequent air entrapment prediction;then two prediction models of air entrapment position are established;finally,the development of the solver and the example verification are completed.The main contents of this thesis include:(1)Building a post-processing system framework and labeling bubble connected domain.This thesis performs three dimensional modeling of each field data in the calculation result and labels each bubble to distinguish different connected regions by using the connected domain filling algorithm based on parallel computing.For the simulation process of double riser,the post-processing module displays the threedimensional data to verify the correctness of the program,and labels the gas connection domain to verify the accuracy of the connected domain filling algorithm.(2)Established a prediction model for the location of the air entrapment defect based on the gas phase tracking and fracture criterion.On the basis of single phase flow,this thesis adds the exploration of the changing process of the bubble's properties.The force field of the gas-liquid two phase changes dynamically with the filling process.At a certain moment,the force field is unbalanced and the bubble bursts and diffuses.This thesis calculates whether the bubble has a force field imbalance in each time step to determine whether the bubble bursts,and marks the remaining bubble as the possible entrainment position in the result.Examples are used to verify the correctness of the model.(3)Established a prediction model for the location of the entrapment defect based on the numerical calculation of the gas-liquid-solid three phase filling flow process.The prediction model for the location of the air entrapment defect based on the gas phase tracking and fracture criterion is established on the basis of single phase flow and is not applicable when the gas-liquid two phase has a strong interaction.This thesis takes into account the influence of temperature changes on the viscosity and solid phase rate during the filling process,modifies the flow equation and solves the temperature diffusion equation.After the filling is completed,the position where the bubble is labeled is the predicted air position.Examples are used to verify the correctness of the model.This thesis proposes a connected domain filling algorithm based on parallel computing,establishes a prediction model for the location of the air-entraining defect based on the gas phase tracking and fracture criterion and establishes a prediction model for the location of the entrapment defect based on the numerical calculation of the gasliquid-solid three phase filling flow process.This prediction program provides effective guidance for designing the casting process and improving the quality of product parts,and is of great value.