大直径超薄筒形件减薄旋压过程鼓形失稳分析

为解决超薄筒形件旋压过程中因鼓形易失稳引起旋压失稳问题，采取以鼓形产生及失稳机理分析出发，研究并确定影响其稳定性的关键因素及规律，以实现超薄壁筒稳定性旋压。结合薄壁筒在旋压时出现的鼓形失稳特征，展开对旋压接触区的边界约束、金属流变及应力场分析，得到旋压过程中鼓形与锁模环的形成机理；结合多组参数下的数值仿真结果，以鼓形比及鼓形刚度为体现鼓形状态参数，分析工模间隙、减薄率、进给率及径厚比对鼓形比与鼓形刚度的影响规律，确定相应参数选择区间；选择三旋轮旋压机床，进行壁厚2.00 mm、外径398 mm薄壁筒的旋压参数适应性及长程旋压实验。在3道次模式下，成功实现了薄壁筒壁厚由2.00 mm减薄到0.53 mm，长度由1 030 mm 伸长至大于3 800 mm的稳定性旋压。通过对鼓形形成及影响因素的研究，为大直径超薄壁筒形件旋压参数制定及长程稳定性旋压提供了理论和实验基础。

Analysis of Drum-shaped Instability of Spinning in Thinning of Thin-walled Cylindrical Part with Large Diameter-to-thicknessRatio

In order to eleminate the spinning instability caused by drum-shaped instability in the spinning process of ultra-thin cylindrical parts, the key factors and laws affecting the stability are studied and determined on the basis of the analysis of the mechanism of drum type formation and instability. Combining with the characteristics of drum-shaped instability during the spinning of thin-walled cylinder, the boundary constraint, metal rheology and stress field in spinning contact area are analyzed to obtain the forming mechanisms of drum and mode-locked ring during spinning process. Based on the numerically simulated results of multiple sets of parameters, the influences of clearance between workpiece and mould, thinning rate, feed rate and diameter-to-thickness ratio on drum shape ratio and drum stiffness are analyzed, and the selection range of the corresponding parameters is determined by using the drum shape ratio and drum stiffness as the parameters of drum shape state. The spinning parameter adaptability and long-stroke spinning experiments of thin-walled cylinder with 2.00 mm in thickness and 398 mm in outer diameter were carried out on a three-roller spinning machine. After 3 passes of spinning, the wall thickness of the thin-walled cylinder was reduced from 2.00 mm to 0.53 mm, and its length was extended from 1 030 mm to more than 3 800 mm. Through the study of drum formation and influencing factors, it provides theoretical and experimental basis for the development of spinning parameters and long-range stability spinning of large-diameter ultra-thin cylindrical parts.