初始应力状态对薄壁件双侧滚压影响规律

Influence of initial stress state on bilateral rolling process of thin⁃walled part

双侧滚压工艺是航空结构件生产过程中常采用的校正方式,然而由于滚压校正过程中工件原有应力场与滚压应力场的耦合作用等材料内部物理力学性能变化机制不明确,限制了滚压校正工艺稳定性的提升。为此建立了无初始应力、仅毛坯应力、毛坯应力与加工应力耦合3种初始应力状态下的7050-T7451铝合金T型件双侧滚压有限元模型,获得了工件的滚压变形及残余应力分布规律。结果显示3种初始应力状态下滚压导致的工件最大弯曲变形量分别为2.56×10^(−1)、2.76×10^(−1)、2.49×10^(−1) mm。毛坯应力对滚压变形的影响程度约为7.8%,在此基础上加工应力的影响约为9.8%,且毛坯应力与加工应力的作用方向相反。滚压区域残余应力主要集中在滚压方向和垂直滚压方向,在工件表面均为压应力,在次表面达最大值。初始应力会导致工件沿滚压方向全厚度范围内的应力值增大;而在垂直滚压方向,初始应力主要造成表面应力的改变。对滚压过程中的应变-应力场演变过程进行了分析,揭示了毛坯应力与加工应力对滚压作用的影响机制。研究成果对于进一步提高滚压校正精度具有重要意义。

The bilateral rolling process as a correction method is widely used in the production of aerospace structural parts.However,because the evolution mechanism of the internal physical and mechanical properties of the material is unclear,such as the coupling effect of the original stress field and the rolling stress field,the improvement of the stabil⁃ity of the rolling correction process is limited.So,a verified bilateral rolling finite element model of T-shaped part with 7050-T7451 aluminum alloy under three initial stress states,i.e.,no initial stress,only blank stress,coupling blank stress and machining stress,was established,and the rolling deformation and residual stress distribution of the part are obtained.The results show that the maximum bending deformation caused by rolling is 2.56×10^(−1),2.76×10^(−1),2.49×10^(−1) mm respectively under the three initial stress states.The influence degree of blank stress on rolling defor⁃mation is about 7.8%.On this basis,the influence of machining stress is about 9.8%,and the action direction is op⁃posite.The residual stress in the rolling area is mainly concentrated in the rolling direction and vertical rolling direction,and the surface is usually compressive stress,which reaches the maximum value on the subsurface.In addition,the initial stress could cause the stress value increase within the full thickness in rolling direction,while,the initial stress mainly causes the change of the surface stress in vertical rolling direction.Finally,the evolution of the strain-stress field during the rolling process was analyzed,and the mechanism of the blank stress and the machining stress effect on the rolling process were revealed.The results have important significance for further improving the rolling correction accuracy.