薄壁管轴压精密成形过程中的无模约束自由变形特征

Characteristics of Free Deformation Zone in Thin Walled Tube Axial Compressing Forming

以实验研究和有限元数值模拟相结合的方法 ,对管轴压成形无模约束自由变形规律进行了研究。发现无模约束自由变形区的形状主要受管坯直径和模具圆角半径的影响 ;自由变形区的形状与模具圆角的形状差别较大 ,并且在成形达到稳定状态之前的过程中仍不断变化 ;模具的圆角半径r对自由变形区形状的影响较大 ,存在一个临界模具圆角半径 r0 。当 r <r0 时 ,相对间隙Δ/2 r >1 ,自由变形区的卷曲半径大于模具圆角半径 ;当 r>r0 时 ,Δ/2 r <1 。

The shape of the free deformation zone, which is without die control, determines the shape and the dimensions of part formed. We investigated by experiment and by FEM (Finite Element Method) numerical simulation the free deformation laws without die control. The results show that: (1) Tube blank diameter and fillet die radius have a great effect on the shape of the free deformation zone; before reaching steady forming stage, the shape of the free deformation zone is continuously changing and is different from that of fillet die. (2) There is a critical die radius r 0 ; when r<r 0 , the relative gap Δ/2r >1, and the radius of the free deformation zone is larger than that of fillet die; when r>r 0, Δ/2r <1, and the radius of the free deformation zone is smaller than that of fillet die.