| Plastic contains the characteristics of easy formability,high stability,high strength and good insulation,which can effectively reduce wear,shock and noise.With the introduction of concepts such as lightweight and energy saving,the concept of "plastics instead of steel" has gradually covered various fields,and plastics have played a good role in replacing metals,wood,and inorganic materials.In the field of automobile manufacturing,the proportion of plastic parts in automobiles has gradually increased.Among them,bumpers have been converted into plastic products earlier,and there has been a lot of research in injection molding.But bumpers are the most important car protection parts.The strength of polypropylene(pp)bumpers can no longer fully meet the standards that bumpers should meet.Carbon fiber composite bumpers have become a popular research direction.Therefore,this article conducts research on injection molding of carbon fiber composite bumpers,and explores the best parameter combination for injection molding.The front bumper of a certain model of automobile is used as a prototype in this paper,the mold of the bumper is designed using UG three-dimensional software and Moldflow simulation software to design the gating system and cooling system of the bumper,and analyzes these systems,and obtains a reasonable gating system and cooling system.Then,warpage,shrinkage,and volume shrinkage during ejection were used as the quality targets of injection molded products,and melt temperature,mold temperature,holding pressure,holding time,and fiber content were selected as influencing factors.Based on the Taguchi experiment method,related experiments were designed,and the results of the designed experiment were analyzed by the analysis of variance method and the signal-to-noise ratio analysis method,and the influence degree of each parameter on the quality target was obtained.The results show that melt temperature and fiber parameters have the most significant impact on the three quality indicators,while the impact of injection pressure is very low,and the optimal combination of parameters is obtained as follows: fiber content 27%,melt temperature 227°C,mold temperature 47 ℃,the injection pressure is 103 MPa,and the pressure holding time is 30s;but the result corresponding to the optimal parameter combination does not achieve a very ideal optimization effect.Then,in order to find a better parameter combination,based on the Taguchi experiment method,the response surface model method and the NSGA-II multi-objective genetic algorithm are combined,and the most significant melt temperature and fiber content are selected as the design parameters.The article further seeks the optimal combination.According to the equal diameter method experiment table,the corresponding response surface model function relationship is established,and then the MATLAB toolbox is used to obtain the best parameter combination under this method:fiber content 24%,melt temperature 227.6°C,mold temperature 47°C,The holding pressure is 103 Mpa,and the holding time is 30 s.Finally,the parameter combination is simulated and verified,and the error between the quality target result obtained and the predicted value obtained by the model-algorithm combination is very small;and compared with the result obtained by the Taguchi experimental method,the combined method has a more significant optimization effect.It is shown that the combination of response surface model method and NSGA-II multi-objective genetic algorithm can provide better theoretical guidance and basis for research on the improvement of related product quality and the selection of influencing parameters.Finally,whether the composite bumper corresponding to the optimal fiber content meets the stress,strain and deformation displacement under various working conditions is verified by finite element simulation,which proves that the bumper with the fiber content meets the standard. |
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