The Research On Automobile Body Covering Parts Die Wear Mechanism And The Life Prediction

China has been becoming the world's first vehicle production and sale country for10 years,and the annual output value of auto-die market is more than 200 billion RMB.As the automobile industry is experiencing even tougher competition,automobiles with high appearance and quality are more welcomed by customers.The vehicle perceptual quality mainly depends on three aspects of DTS consistency,feature line clarity and surface highlight.To ensure the quality of the covering part,the quality and precision of die must be guaranteed.Once the die involved by wear and tear,the perceptual quality of covering part will be directly affected.The detailed content is as follows:(1)This paper established a automobile perceptual quality evaluation mathematical model and found out the direction of the body covering part die technology promotion.Die design principle and three machining methods of zero rounded corners were systematically carried out.It was found that the first and the third methods could realize zero rounded corners processing,which must be finally machined after heat treatment and the laster treatment was the best one.The outer covering part defect evaluation method(GSQE)was set up to quantitatively evaluate the surface quality.In order to achieve the unification of the design and manufacture,the data design quality and processing technic of outer part were improved and verified.By analyzing the promotion process of outer covering part quality,the necessity of the covering part die wear simulation and life prediction must be concerned.(2)This paper proposed a dynamic die wear simulation algorithm based on the Archard model,and this algorithm was established on the analysis of common covering part's wear mechanism and the simulation models.In order to overcome the four major difficulties of die wear simulation,this paper transformed the impact factors of Archard model to the real dynamic wear coefficient K_d,consequently realized the combine of stamping forming simulation and die wear simulation.(3)This paper established a perceptional quality evaluation method based on the characteristic of outer covering part feature line clarity(FLS).After a detailed test,the influence of die wear on feature line was analyzed to set up the die wear failure evaluation index of feature line clarity.According to the relationship between GSQE evaluation and actual measuring result,this paper assigned surface variation Devi as A surface defect evaluating index and the die wear failure evaluating index of A surface highlight.Finally this paper established the covering part die wear life prediction evaluation criterion including the die wear on the feature line clarity failure evaluation criterion and A surface highlight failure evaluation criterion.(4)This paper developed a new stamping friction wear testing equipment and its control system,which took into account the friction sheet interface real-time update and pre-stressing of testing sheet.In terms of the analysis of error sources existing in the process of testing and the assembly relationship between vector ring description,the error analysis model of this testing equipment was established using direct linearization method.The important factors which affected measuring precision were found out by the sensitivity analysis,then three groups of experiments were implemented to get the testing equipment's real precision.It was confirmed that the testing precision was+/-0.005 mm along a single direction,which met to the design requirement;With this equipment,the outer covering part common friction pairs'(GM246-DC04)real dynamic wear coefficient K_d was obtained.Meanwhile,the correctness of the dynamic simulation algorithm was validated again by the analysis of the wear trace on the microstructure and 3d morphology(5)This paper developed a set of stamping tool wear prediction software,which put optimized Arhard wear model into Abaqus stamping simulation process then realized automatic calculate the node wear volume in stamping simulation.In the process of wear calculation,the wear coefficient could be updated in real time according to the actual working condition.Die wear simulation was realized by calling the software Hypermesh to move node along the outward normal direction,meanwhile the new updated grid could be achieved stamping and wear process simulation again.The cycle would be stopped automatically reaching the established failure criteria.A Hooder OTR die wear validation showed that the new software could better forecast covering parts die wear life prediction because of the precision increasing 16.3%.In order to evaluate the different production conditions influence on the die wear prediction,the wear prediction correction coefficient was established.At the same time,this paper compared the five aspects of a company's three bases in human,machine,material,process and environment,then found out that the wear prediction correction coefficient was directly affected by the die using environment,consequently the wear prediction correction coefficient of base C with high temperature and high humidity was the biggest one.To sum up,this paper has studied the wear mechanism of covering part die and wear influence on perceptional quality,solved the covering part preventing die wear influence on vehicle perceptional quality and wear simulation of life prediction problem.This research achievemens have been applied to the actual production die wear monitoring to obtain good results.It points out a promotion direction for the domestic automobile makers starting total vehicle perceptional quality promotion and die supplier improving manufacture technique.