Research On Cold Extrusion Process And Mechanism Of Automobile Cup Rod Parts

As a kind of cup rod parts,there are many processing methods for the joint bolt.The traditional processing methods are mainly cutting and hot forming.The forming quality and mechanical properties of the parts are poor,and the production efficiency is low,so it is difficult to meet the competitiveness of enterprises in the market.The working environment of the joint bolt is harsh,and it needs to withstand the constant impact and vibration of reciprocating motion,and the force condition is more complicated,so the mechanical performance of the parts is relatively high.Parts manufactured by cold extrusion process have advantages in terms of forming quality,dimensional accuracy,production efficiency,and economy.Based on the cold extrusion forming mechanism of cup and rod parts,the feasibility of cold extrusion forming process of joint bolt is analyzed by using the combination of numerical simulation and experimental verification.The main research contents are as follows:(1)According to the structural characteristics of the joint bolt parts,combined with the law of metal flow during cold extrusion forming,the causes of defects are analyzed.This paper introduces the key theory of cold extrusion forming of cup and rod parts,the influence of stress and strain on deformation,the relationship between equivalent stress and equivalent strain,the relationship between displacement and strain component,yield criterion,friction model theory in numerical simulation,which provides a theoretical basis for subsequent numerical simulation of cold extrusion forming process.(2)The selection of cold extrusion material,heat treatment process and lubrication method of blank are introduced.According to the part structure,the cold extrusion process diagram of joint bolt is designed,and the blank size and volume are calculated by using the volume invariance criterion.Through the calculation of height diameter ratio,deformation degree,extrusion ratio and cold extrusion pressure of cold extrusion process,the cold extrusion process scheme of joint bolt is determined.(3)The stress-strain and velocity distribution of each station are analyzed by numerical simulation of each station of the process scheme by using form-3d software,and the stress concentration position of each station is obtained.The second-order response model was established by response surface method and box Behnken design test.The multiple quadratic regression equation was used to fit the functional relationship between the influencing factors and the response objective.The stamping speed,the friction coefficient,the slant angle of punch boss and the length of punch boss sidewall were selected as the design variables,and the forming load was taken as the optimization objective.The second-order response model was established to obtain the optimal parameter combination.Through regression analysis,the optimal parameters are as follows: the outer bevel angle of the boss is 10.57°,the side wall length of the boss is 1.7mm,the stamping speed is 3.64mm/s,and the friction coefficient is 0.13.After optimizing the process parameters,the forming load of the final forging process is reduced by 12.8%,and the reliability of cold forming is improved.(4)Combined with the force analysis of punch and die in the process of cold extrusion,through theoretical calculation,the structure of punch and die and the overall die assembly drawing are designed.The multi-station cold heading machine was used for the trial production of parts,and the feasibility of the process plan was verified through physical and chemical experiments.