开缝衬套孔挤压残余应力场数值计算研究

本文基于有限元技术模拟了开缝衬套挤压和直接芯棒挤压两种孔挤压工艺，对比研究了两种不同工艺导致的孔壁材料轴向流动和孔壁残余应力场。结果表明：开缝衬套挤压可有效抑制材料向挤出端流动，这在飞机夹层孔结构挤压中可减小夹层间隙尺寸；衬套开缝对应孔壁区域残余应力有突变，但仍然是对抗疲劳有利的压应力，而非拉应力；开缝衬套挤压挤入端孔边是压应力，而直接芯棒挤压是拉应力；相同干涉量条件下两种工艺引入的残余压应力峰值近似，但开缝衬套挤压残余压应力场域较直接芯棒挤压增大了约1 mm.

Numerical study on the residual stress field produced by split sleeve hole cold expansion

Both split sleeve cold expansion (SsCX) and direct cold expansion (CX) were simulated based on the finite element method (FEM), and the residual stress field and material movement induced by different cold expansion techniques were compared in this study. Results show that SsCX could effectively suppress the material movement toward exit surface, which is good for minimizing the intercalation gap for sandwich hole cold expansion. The residual stress in the zone near the sleeve split changed suddenly, but it was still residual compressive stress rather than residual tensile stress. The residual stress around hole edge in entrance face was compressive by SsCX, while it was tensile by CX. With the same interference value, the peak values of residual compressive stress imparted by the two techniques were almost the same, but the residual compressive stress field scale generated by SsCX was 1 mm larger than that by CX in the direction of radius of hole.