Influence Of The Weld Line On Numerical Simulation Of Tailor-welded Blank Forming Process And Experimental Study

The tailor-welded blank(TWB)technology is a main method to achieve the lightweight of auto body.But because the difference of the thickness and properties of base materials and existence of the weld line,the forming characteristic of tailor-welded blanks is different from base materials,and the forming characteristic of tailor welded blanks declines greatly.With the development of the computer technology and finite element method(FEM),FEM is more and more adopted during the design and manufacture procedure of production to improve the structure and forming process. However,because tailor-welded blanks are comprised of two or more sheets of metal with dissimilar strength and/or thickness that are welded into a single blank,compared to the base material,one or more weld lines whose geometry and properties are different from the base materials bring about more difficulties on the creation of finite element model of the tailor-welded blanks.This thesis studies the relationship among the finite element model,structure of the tailor-welded blanks and the results of the numerical simulation,thus it gives the direction on how to select the best finite element model of the tailor-welded blanks during the forming simulation of the tailor-welded blanks.Firstly the tensile test of the weld-tailored blanks and the base material was conducted,and the mechanical properties of them were analyzed to find the influence of the weld line on the forming characteristic of tailor-welded blanks.Then finite element analyses of standard tensile test of tailor-welded blanks were performed to determine the effects of weld modeling techniques on the simulation. Finite element models of TWBs were created either included a simple representation of the weld properties and geometry or included only the weld properties,or excluded both weld geometry or materials properties.In all models,shell elements were used to present base materials.The models including weld properties and geometry used solid elements for weld materials,and shell elements were coupled to the solid elements by a novel method.The models including material properties of weld line used shell elements for material properties of weld line.Hereafter the results including the movement of weld line,tensile critical displacement,location of the critical point were analyzed,and find the effect of the finite element model of TWBs on the numerical simulation results with the variation of the structure of the TWBs including thickness ratio,area ration,width of the weld line and the material properties.Finally through the numerical simulation of drawing process of tailor-welded blank box and the results of movement of weld line,max thinning ratio,max thickness ratio and compute time were analyzed to discuss the effect of the finite element model of TWBs on the simulation results in the FEA of the frequently used parts.The simulation results were compared to the experimental results,and it showed that the results of the model using the solid elements to represent the weld line were most close to the experimental results,and results of the model using shell elements to represent weld line were similar to that of the model ignoring the weld ling.