Abstract:

A 3D finite element simulation was used to study the stress distribution and effects of expansion degrees around the cold expanded hole in TC4 plate. Tangential residual stress distribution under different expansion degrees were obtained in the smallest cross section. The relation of expansion degree to residual stress and fatigue life was discussed. In order to get the fatigue life of different expanded degrees, the experiments of split sleeve cold expansion were carried out. It is found that residual stress can reduce stress concentration and optimize the stress distribution in the smallest cross section under tensile loading, also remarkably retard the crack propagation rate for cold expanded holes. The results show that 4% expansion degree is the optimal cold expanded degrees for TC4 plate in simulation and experiments.

Key words: Titanium alloy TC4, hole cold expansion, fatigue life, residual stress, finite element analysis(FEA)

摘要：

开展了不同挤压量下TC4钛合金板孔冷挤压强化有限元仿真研究，得到了挤压强化后最小截面的切向残余应力分布规律，分析了挤压量对受载试样孔边应力分布的影响，探讨了挤压量、残余应力和疲劳增益三者之间的内在关系。采用开缝衬套冷挤压强化工艺对TC4带孔板件进行冷挤压和疲劳验证试验。研究结果表明，挤压强化后的孔边切向压缩残余应力可以有效降低孔周应力集中程度，优化受拉试样最小截面应力分布，改变裂纹源的位置并延长疲劳裂纹的萌生和扩展寿命，有效提高试样疲劳寿命。综合仿真和疲劳试验得到TC4板孔最优挤压量为4%。

关键词: TC4钛合金, 孔冷挤压, 疲劳寿命, 残余应力, 有限元分析