Analysis And Optimization Of Flanging Cracks In Automotive Ultra High Strength Steel Structures

As the automotive industry’s requirements for light weighting become higher and higher,the application of ultra-high strength steel materials in automotive panels will become more and more widespread,such as B-pillar internal stiffeners and front longitudinal beam internal panels.Currently,The auto manufacturers prefer to use ultra-high-strength steel materials to achieve lightweight,ultra-high-strength steel can not only ensure the requirements of the rigidity and strength of the parts,but also can meet the manufacturing requirements of light weight and safety,but the super high-strength steel has poor forming performance during the forming process.It is more prone to forming defects such as cracking,wrinkling,and spring back.Due to the influence of components such as part structure,processing technology,material properties,and section quality,the forming ability of the edge of the sheet mater ial often fails to reach the forming limit predicted by the conventional FLD,and cracking or failure occurs.Therefore,it is of great significance and practical value to study the cracking of ultrahigh-strength steel panels.This paper starts with the basic theory of flange forming of super high-strength steel panels,and classifies the flanging process,defines the geometric parameters of the flanging parts,the flanging cracking mechanism,the flanging forming finite element theory,experimental design,and data processing methods.Systematic theoretical analysis.According to the structural features of the front longitudinal beam and the characteristics of the high-strength steel,the analysis of the forming process is completed,and the forming scheme is determined as follows: blanking and punching forming one flange and one edge flanging one edge trimming,punching and side punching Side trimming,side punching,and side cuffing of the hole.By analyzing the part forming process and summing up certain rules,it provides guidance for the finite element analysis of the parts and has certain guiding significance.Based on the basic theory and the process analysis of the front longitudinal beam inner panel,the local dangerous area of the previous stringer inner panel is the entry point,a concave curved flange forming scheme is designed,and a numerical simulation method is used to systematically study the structural parameters of a single part.Flanged cracking effect.Based on the grey correlation theory method,the correlation of each structural feature to the cracking of the flange is analyzed.The analysis shows that the influence of the cracking of the high-strength steel autoclave on the flange forming is the center angle of the curved surface,the he ight of the flange,and the turn.Edge radius,upper bend radius,lower bend radius,and curved surface radius.By analyzing the impact of the flanging features on the cracking of the flanging,and summing up certain rules,it provides guidance for the des ign of the parts.This paper also takes a front longitudinal beam inner panel as the research object,and the design test uses the maximum thinning rate and the maximum failure as the optimization judgment index of the flange cracking.The above bending ra dius,lower bending radius,flanging angle,radius of flanging and The five parameters of the central angle of the flanging are optimization objects,and the Kriging approximation model is established.The NSGA-II algorithm is used to optimize the paramete rs of the front side member inner panel by multi-objective optimization.The optimal structural parameter combination is obtained to guide the product design and process design,and the test is performed verification.