Multi-objective Optimization Of Injection Process Parameters And Stiffness Analysis For Vehicle Hood

The combination of numerical simulation and intelligent optimization algorithm for the optimization of process parameters of plastic parts is one of the research hot spots in the field of injection molding.And considering the fiber orientation and residual stress in the glass-containing plastic parts,it is important to simulate the mechanical properties of the plastic parts after the optimization of the process parameters.Based on a vehicle hood project of a car company,this paper establishes the panel hood inner mold-flow analysis model by injection molding CAE(Computer Aided Engineering)technology.The primary and secondary factor analysis of the panel hood inner injection molding was carried out based on the optimal Latin hypercube test.And then,an EBFNN(Ellipsoid-Based Neural Network)approximation model is established,and the NSGA-Ⅱ(Non-dominated Sorting Genetic Algorithm Ⅱ)is used to optimize the multi-objective process parameters.At the same time,the co-simulation method of mold-flow-structure is used to predict the static stiffness of the hood assembly after the optimization of the process para;meters,and the corresponding results are compared with traditional finite element methods and experiments.The specific work contents and conclusions are as follows:(1)Two casting system solutions are established for the automobile panel hood inner,and the simulated flow and warpage deformation results are compared under the recommended injection molding process parameters.And a cooling system of the best casting solution is established for flow analysis,cooling analysis and warpage deformation analysis.The results show that the flow and cooling results are better,but the maximum warpage of the panel hood inner is 5.175mm,which does not meet the design and process requirements,and the uneven shrinkage is the main factor that causes the warpage of the plastic parts.(2)According to the influence of process parameters on the injection quality of the panel hood inner,the surface temperature,melt temperature,injection time.packing pressure,packing time and cooling time of the mold are selected as the test factors.Based on the optimal Latin hypercube test,the volume shrinkage at ejection time and warpage deformation results were numerically simulated by injection molding.Through the analysis of variance,Pareto graph analysis,interaction effect and main effect analysis,the primary and secondary factors affecting the optimization index were determined,the main factors are mold surface temperature,melt temperature,injection time and packing time,respectively.(3)By constructing the EBFNN approximation model combined with the multi-objective optimization algorithm NSGA-Ⅱ,the injection molding process parameters of the panel hood inner are optimized,and the Pareto solution set of volume shrinkage at the time of ejection and warpage is obtained,and the injection molding numerical simulation results of four groups of relatively optimal Pareto solutions are compared to obtain the optimal combination of process parameters.The optimized volume shrinkage and warpage were reduced by 50.518%and 39.845%,respectively.The reliability and practicability of this method are verified,which has certain practical value for the process optimization of other plastic parts.(4)For predicting whether the static stiffness of the inner and outer panels of the hood in the actual loading process satisfies the design requirements after the optimization of the injection molding process parameters,the co-simulation method of mold-flow-structure is used to analysis the stiffness of the structure and the corresponding results are compared with traditional finite element methods and experiments.The results indicate that the static stiffness performance of the hood meets the target requirements,and the simulation results of the co-simulation method of mold-flow-structure are closer to the experimental values than the traditional simulation results,with a minimum error of 6.2%and a maximum error of 12.6%.Furthermore,the co-simulation method of mold-flow-structure could provide reference value for structural analysis of similar plastic parts.