Flow forming is a promising technique to manufacture thin-walled tubular parts with cross inner ribs (longitudinal and transverse inner ribs, LTIRs) which are highly demanded in aerospace field. However, the nature of local loading results in complicated material flow and consequently affects the formation of inner ribs by die filling. Therefore, flow forming experiment along with finite element (FE) simulation was carried out to study the material flowing behavior in the flow forming of stiffened parts, thus to reveal the die filling mechanism. The results showed that varied rib height occurred after flow forming on account of the different die filling mechanisms of longitudinal inner ribs (LIRs) and transverse inner ribs (TIRs). Namely, the axial tensile strain results in a low LIR, while it is a nearly plane strain state for TIR and the radial tensile strain in the inner layer of TIR is in charge of the larger TIR height. In order to improve the rib height, large wall thickness reduction and feed ratio should be used. The law of die filling in flow forming of thin-walled tubular parts with LTIRs will provide guidance for the integrated manufacture of stiffened thin-walled tubular parts in a high quality.

流动成型是一种制造具有交叉内肋（纵向和横向内肋，LTIR）的薄壁管状零件的有前途的技术，在航空航天领域中，这种交叉内肋（纵向和横向内肋，LTIR）非常需要。然而，局部载荷的性质导致复杂的材料流动，并因此影响通过模具填充形成内肋。因此，进行了有限元模拟的流动成型实验，研究了加硬零件的流动成型中的材料流动行为，从而揭示了模具填充机理。结果表明，由于纵向内部肋（LIR）和横向内部肋（TIR）的模具填充机制不同，流成形后出现了不同的肋高。即，轴向拉伸应变导致低的LIR，TIR几乎处于平面应变状态，而TIR内层的径向拉伸应变则负责更大的TIR高度。为了提高肋骨高度，应使用较大的壁厚减小量和进给比。利用LTIR在薄壁管状零件的流动成型中的模头填充法则将为高品质薄壁管状零件的集成制造提供指导。