中厚板变形过程中的弯曲和反弯曲效应影响其拉深变形能力.本工作以航空航天常用的5A06铝合金筒形件为研究对象,采用厚度为4.5mm的中厚板进行反拉深数值模拟和实验研究,分析了变形过程中应力、应变分布特点,讨论了3种凹模截面结构形式下的变形方式,以及应变路径随着凹模圆角变化规律.结果表明:凹模内圆角与直壁区过渡区在壁厚方向上存在应力和应变梯度,并在该处外侧产生最大径向拉应力,导致了拉深破裂的发生.采用半圆形凹模截面结构时,极限拉深深度达到203mm,相对于平面凹模结构增加了40%.半圆形凹模结构能减小弯曲效应,有效降低过渡区的应力梯度和最大应力数值,有利于提高5A06铝合金中厚板拉深变形能力.%The limit drawing ratio is influenced by the bending and unbending effect during reverse deep drawing of plate.The 5A06 aluminum alloy plate widely applied in aerospace industry was used, and the reverse deep drawing of the 4.5mm thick plate was investigated experimentally and numerically.The stress and strain distributions of plate were analyzed, the deformation behaviour was discussed for three types of cross section of die during the reverse deep drawing process;moreover, the changing rule of strain paths with the die profile was also discussed.Results show that a maximum radial stress is induced by the bending effect at the transient region between the inside die radius and straight wall, where a radial stress and strain gradient along the thickness direction appears and the fracture is easy to occur.For the semi-circle profiled die structure, the limited punch stroke is 203mm which is increased by 40% than that for the die with a planar profile section.The semi-circle profiled die structure can reduce the bending effect, effectively reduce the stress gradient and the maximum stress value in the transient region, and is helpful to improve the limit drawing ratio of the 5A06 aluminum alloy plate.
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