Key Technology Research Of LBM In Injection Molding Simulation

Injection filling process is a very complex non-Newtonian plastic melt flow process.Lattice Boltzmann Method(LBM),as a new numerical simulation method,has the advantages of simple boundary treatment,good parallelism and high computational efficiency,and is widely used in fluid numerical simulation.Based on the multi-phase flow LBM model HCZ-LBM(He-Chen-Zhang LBM),a two-phase flow HCZ-LBM program in C++ language was developed to simulate the plastic melt filling cavity,gas penetration in gas-assisted injection molding and water penetration in water-assisted injection molding,which laid the foundation for the wide application of LBM in injection molding simulation in the future.The main research work of this paper includes:(1)The HCZ-LBM program is used to simulate the classical flow problems such as droplet contact angle and Rayleigh-Taylor instability.The simulation results are basically consistent with those in the literature.It shows that HCZ-LBM can accurately describe these typical fluid phenomena.The developed HCZ-LBM program is used to simulate Poiseuille flow at different Reynolds numbers,the maximum error between the simulation results and theoretical understanding is less than 1%.By simulating these classical flow problems,the correctness and accuracy of the developed HCZ-LBM program are verified.(2)Introducing Cross-WLF viscosity model characterizing non-Newtonian characteristics of plastic melt into LBM,HCZ-LBM multi-relaxation scheme program was developed to simulate the Poiseuille flow of plastic melt between plates.The simulation results show the distribution of pressure,velocity,viscosity and shear strain rate of melt flow between plates.The simulated velocity and shear strain rate are basically consistent with their analytical solutions.The developed HCZ-LBM program can accurately simulate the flow of non-Newtonian plastic melt.(3)HCZ-LBM program was developed to simulate melt filling process in injection moulding,and the effects of different boundary treatments on simulation results were compared.At the same time,the HCZ-LBM program is used to simulate the gas penetration process of gas-assisted molding and the water penetration process of water-assisted molding.The simulation results reveal the evolution process of airway and waterway and the pressure and velocity distribution in the cavity.The effects of gas injection pressure or water injection pressure on the thickness and uniformity of airway and waterway are studied.The larger the gas injection pressure is,the smaller the airway thickness is,and the more uneven the distribution of airway thickness is in the direction of penetration.The smaller the water injection pressure is,the more evenly the channel thickness is distributed in the penetrating direction.