孔用衬套冷挤压强化的残余应力分布对实现优异的挤压效果起到重要的作用,而被挤压件材料和挤压量对挤压残余应力分布的影响显著.根据非线性接触摩擦理论,建立了基于压合衬套冷挤压强化的三维有限元模型,模拟获得了 TB6钛合金、7050铝合金及TC4钛合金材料耳片孔强化的切向残余应力分布情况,并通过残余应力检测实验验证了有限元模拟的有效性;同时,研究了挤压量对耳片孔冷挤压强化残余应力状态的影响,揭示了切向残余应力沿着挤入面、中间面、挤出面以及衬套厚度方向的分布规律.研究结果表明:冷挤压孔强化后的残余应力在沿孔壁厚度方向上分布不均匀,切向残余压应力在中间面的分布区域最广;增大挤压量可以在一定程度上扩大压应力的分布范围,且能够提高区域压应力数值,但是也会引入部分拉应力,易产生褶皱现象;在相同的挤压条件下,TB6钛合金耳片冷挤压后所产生的切向残余压应力在应力数值和分布区域上都具有明显的优势.
The residual stress distribution strengthened by cold expansion of hole bushing plays an important role in achieving excellent extrusion effect,while the material of compressed part and the interference value have a significant impact on the distribution of extrusion residual stress.Ac-cording to the theory of non-linear contact friction,a three-dimensional finite element model based on cold expansion strengthening of compres-sion bushing was established.The tangential residual stress distribution of lug was obtained with the simulation model in terms of various mate-rials,TB6 titanium alloy,7050 aluminum alloy and TC4 titanium alloy.The model and simulation results were validated with the experiments of re-sidual stress testing.Moreover,the influence of interference value on the residual stress state in cold extrusion strengthening was also explored.Results also revealed the distribution of tangential residual stress of the squeezed surface,the middle surface,the expansion surface and the bushing thickness direction.It is shown from the research results that the residual stress is unevenly distributed along the thickness of the hole wall after cold expansion and the tangential residual compressive stress has the widest distribution area in the middle surface.The increase of the interference value can expand the distribution range of compressive stress to some extent and increase the value of regional compressive stress.However,the increase of the interference value can also produce partial tension stress,leading to wrinkle effect.Under the same extrusion condi-tions,the tangential residual compressive stress produced by cold extrusion of TB6 titanium alloy lug has obvious advantages in stress value and distribution area.