Research On The Upsetting Process Oriented To Tapped Plate With Variable Wall Thickness Using The Forming Method Based On Controllable Deformation Zone

Under the background of rapid development of automobile lightweight and parts integration,the application of tapped plates with variable wall thickness is becoming more and more widespread.In order to ensure the rigidity and connection strength requirements of parts,the plastic forming process has become an important way to achieve the overall forming of such parts.At present,the commonly used methods are stamping-forging composite process and shovel spinning process.However,these processes are also limited.With the development of sheet bulk forming technology,a method of upsetting with a controllable deformation zone(U-CDZ)has appeared.At present,this process is mainly used to achieve thickening at any position on the outer wall of the pipe.Based on this,a new idea is proposed to apply the U-CDZ process method to the inner wall thickening of tapped plates with variable wall thickness.Based on finite element numerical simulation and experimental verification,a systematic study was carried out.The thickening ratio limits of the inner wall thickening and outer wall thickening of tubes with different diameter-to-thickness ratios were compared with the evaluation index of folding,and the differences in process applicability of inner wall thickening and outer wall thickening were obtained.The extrusion process of the tube billet during the initial entry stage in the thickening of the inner and outer walls was studied.The difference was analyzed from two aspects of material stress state and damage distribution.The mechanism of the limit difference of the thickening ratio in the thickening processes of the inner and outer wall was described.A method for preparing inner annular right-angle boss billet was proposed for the inner thickening forming process.The mechanism of the thinning of the sidewall in the thinning and shaping process was studied,and the critical gap value in the shaping process with ironing was obtained based on numerical simulations.For the billet with rounded corner,a right-angle is formed using the shaping process with ironing,and the thickness of the side wall of the boss is kept uniform by controlling the gap value between the punch and the die to be smaller than the critical gap value.The influence of the shaping rate on the minimum thinning rate of the side wall was studied,and the prediction formula of the minimum thinning rate of the side wall was obtained by fitting the relationship curve.The thickening forming experiment of the prestrained billets with inner annular right-angled boss was carried out on the self-developed experimental platform,and compared with the machined billet.The difference of forming quality between the two kinds of billets under the same counterforce and different thickening ratio was compared.As a result,the changing rule of the thickness ratio limit of the prestrained billet of tapped plate was obtained.In addition,the minimum counterforce for thickening the inner wall of the prestrained billet under different thickening ratio was studied.The deviation of the minimum counterforce for the prestrained billet compared to the machined billet was obtained.It has certain guiding significance to the actual production process.