Study On The Welded-line Movement Of Square Cup Using TWBs In Hydro-forming Deep Drawing

The tailor-welded blanks(TWBs) become more and more important in the automobile industry and its applications can accelerate the development of the automobile industry,for their advantages such as low manufacturing cost,vehicle weight reduction,environmental protection and safety improvement,etc.Despite of these advantages of TWBs,there are great differences including mechanical properties and thickness between the two sides of TWBs which makes the stress and strain in the forming more complex compared with the traditional blank,so it cause problems mor easily,such as cracking,wrinkling,weld line movement and springback.In the actual production,how to control the weld-line movement and the decline of formability is the two main technical problems puzzling engineers in the different thickness TWBs forming.At present,national researchers have done a great works in traditional TWBs forming problems such as cracking,wrinkling and weld-line movement,but little work has been done in the hydro-forming of TWBs which includes not only drawing,but also bulging. Therefore,this thesis tries to find out the rules of different parameters influencing square cup with TWBs to supply theoretical foundation for directing and controlling weld-line movement.In this thesis,the effects of blank holder force and liquid pressure on the weld-line movement of square cup with different thickness TWBs have been researched.1.Theoretical analysis.The principle and characteristics of hydro-forming of different thickness TWBs were analyzed theoretically.Owing to the complex shaped mechanism of square cup,the effects of flange,wall and the free transfiguration between punch and blank holder on weld-line movement are separately analyzed at the mechanical point.2.The modelling of square car with TWBs.Considering the effects of the blank shape, welding line,material properties on formability,the finite element analyse model is built on the base of analysing these factors' effects.3.Control the weld-line movement in the hydro-forming.By analysing blank holder force's effects on weld-line movement in different forming process,the results show that hydro-forming has great advantage in decrease the weld-line movement,especially at the bottom of square cup;at the same time,by simulating these parameters' effects in hydro-forming,such as blank holder force and its distribution,liquid pressure and its load path,friction coefficient between mould and blank and mould clearance,the results show that weld-line movement can be controlled by adjusting these parameters.4.Control the limit drawing depth of hydro-forming.The simulation results show that hydro-forming process can improve limit drawing depth compared with traditional forming process in the same conditions,however,in hydro-forming,change liquid pressure and its load path don't have much effect on the limit drawing depth,while increase the mould clearance can improve the limit drawing depth greatly.