| Connecting rod is an important part of automobile engine, and it can bear largerimpact load and dynamic stress. So it must ensure that the excellent strength, stiffnessand fatigue performance. A large part of the engine vibration from the connecting rod,so the size, weight and surface quality must be accurate assurance. With thedevelopment of society, automation of the production mode is gradually introducingconnecting rod production fields in response to the rapid increase of labor costs, and topursuit of higher production efficiency. In this context, CWR+electric hydraulichammer automatic production line was developed, and become the most advancedconnecting rod production system. In this automatic production line, bending of theCWR billet is the biggest threat for automatic running.In this paper, the research object is the connecting rod active automatic productionline, and the core problems that affect the normal operation of production line areanalyzed. Using numerical simulation method to analyze the factory’s actual productionconditions, and all the active energy parameters and3D field variable information areachieved. On this basis, a connecting rod forging automatic production line activesystem is established, and the defects include necking、bending and internal voids wasanalyzed. The idea and methods was obtained to solve the defects, and the influence lawof the die parameters on those defects was analyzed. Paper main research work is thefollowing:①The bending of workpiece is analyzed, and the stress and temperature change ofworkpiece are studied during CWR process. The characteristics of each bending stagehas been definitely classifies, and the mechanism of bending is obtained, the basic ideasfor solve the bending be found.②The necking of workpiece is analyzed during CWR process. The distributioncoefficient of area reduction is presented to analyze the laws of necking in first andsecond stage. The effect of area reduction on the field variables has been investigated,including the effective strain, displacement and damage. The tendency of the CWRprocess, as related to necking, were ascertained and discussed. The optimal state wasachieved when the distribution coefficient of area reduction is close to1.③The stacking of workpiece is analyzed during CWR process. The mechanism ofstacking is obtained, the basic ideas for solve the bending be found. Main process parameters affecting stacking defects is inclined the friction coefficient and the formingangle. In order to prevent the stacking when design the CWR die, the friction coefficientmust should take small value, and forming angle close to28°.④The internal void of rod-part and small-end is analyzed during CWR process,and the mechanism is obtained. According to the stress-strain state of internal voids, itcan be divided to extended pattern and constraint pattern. The production mechanism ofextended pattern is that the center and surface deformation are severe, high frequencyfluctuating stress act on this part due to the mold for a long period of time rolling, sothis part generate internal void. The production mechanism of constraint pattern is thatwedge hindered the normal flow of metal, and make the surface of the workpiecedeformation is severe when the centre of workpiece is not deformation. The cyclictensile stress be generated by this extreme uneven deformation” island effect”. Whenthe stress reaches the yield limit, the internal voids will be generated.⑤The connecting rod forging automatic production line active system isestablished, the flow of energy and materials in the system be cleared. According to theprocess, connecting rod forging process is divided into input layer, processing layer andoutput layer, the processing layer includes two sub layers (the cross wedge rolling anddie forging forming). For each layer, the influence of element on the forging process isanalyzed. The system helps make more explicit the fact that the cross wedge rolling isthe key factors to impact production line automatic operation.⑥The new idea about predicting internal voids is presented during two stageCWR process. The idea is that different stress-strain state of internal voids should adoptdifferent methods to study and predict. When predict extended pattern internal voids,porous material is introduced into the numerical simulation model, through the changesof relative density measure this pattern internal void. When predict constraint patterninternal voids, dig a hole in the blank in advance, and then according to the change ofhole diameter to predict this pattern internal void.⑦The results of study is applied in the connecting rod forging automaticproduction line system, puts forward a new die structure, and empty and density methodbe used to analyze the internal void of rod-part and small-end. Research results showthat the internal hole located in small-end is not expansion, and diameter of hole is4.7522mm. The relative density of rod-part is0.631.Based on the research results, the die and process of optimization be validated.Production results show that the external defects such as stacking, bending and necking is not be found in the process of cross wedge rolling, and the internal voids cannot befound on the profile of rod-part and small-end. Die forgings quality is good, fill in full,without the external and internal defects. |
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