Simulation Of Reducing Residual Stress Process For Lens Of Automotive Lamp And Measurement Of The Residual Stress

For its light weigh,easy processing and assembling,good wear resistance,vibration resistance,self-lubricating,electrical insulation,corrosion resistance,chemical stability and high intensity,plastic has begun instead of metal,inorganic glass,ceramics and other traditional materials in application fields.Today,Automobile made of plastic is the general trend of international automotive industry,meanwhile,the requirements of the surface quality and mechanical performance of plastic products become more sophisticated,the residual stress generated by injection molding process is the key factor leading to the quality problems.Therefore,how to reduce the residual stress in injection molding products should be focus on.In this paper,by taking the lens of automotive lamp made in PC as an example,reducing residual stress methods of injection molding products are studied by using the means of theoretical analysis,numerical simulation and experimental verification.The process contains reducing the in-cavity residual stress in injection molding products and the annealing process after the product demoulded from the cavity.The main work and results are as follows:(1)According to the actual structure of the mold,a reasonable analytical model is built in Moldflow,the injection molding process is simulated in the fusion model.Based on the previous research results and the practical experience of trial engineers,the injection molding process parameters are optimized which is aimed at reducing the in-cavity residual stress.The results show that increasing the mold temperature,decrease the packing pressure and time properly can reduce the in-cavity residual stress effectively.(2)Different grid types of the lampshade model are simulated.Compared the warpage of simulations with the actual warpage of the lens,the 3D model is more suitable for the next simulation of annealing process.(3)By using the interface for Moldflow to ANSYS,the results of the injection molding analysis are converted for further analysis.The annealing process is simulated by using the modified time harden model.The results show that the modified time harden model can be used to simulate the creep and stress relaxation characteristics of polymer in annealing process.And the stress relaxation effect by rising the annealing temperature is more effective than by extending the annealing time.(4)The residual stresses before and after annealing are measured and calculated by using the loading measurement method.Compared with the simulation results,the numerical simulation of annealing process is verified.At last,works in this paper are summarized,and further research direction in the future is prospected.