Influence of tempers on the hole-expansion formability of an AA7075 aluminum sheet is investigated for -T6 (as-received) and -W tempers (super saturated by the solution heat treatment followed by water quenching). The hole is prepared by end-milling, to limit the effects of hole preparation on the results and instead highlight the effects of material behavior. A flat-headed punch is used to expand the hole, and digital image correlation captures the strain fields throughout the experiment. The results present that the hole can expand by 70 % more in -W compared to -T6 temper with the lower forming force. In contrast, thickness strain distribution around the hole shows a similar pattern in both tempers except the observation of Portevin-Le Chatelier (PLC) effect in -W temper, which causing the inhomogeneous deformation. In parallel, the numerical simulation of the hole-expansion is performed using a user material subroutine implemented for the elasto-plastic material behavior, including plastic anisotropy, of both tempers. The predictions on the thickness strain variation and average level show good agreement with the experiment for -T6 temper, but less so for -W temper. This is shown to be the effect of PLC bands on the deformation: the material in -T6 temper is mainly governed by plastic anisotropy, but -W temper shows combined effect of plastic anisotropy and PLC bands. Nevertheless, the reasonable predictions of both tempers verify that the numerical framework established in this study can be used for preliminary, computationally-efficient virtual process design with a practical purpose, despite omitting the explicit physics of the PLC effect.

研究了-T6（按原样）和-W（通过固溶热处理后水淬处理过饱和）回火对AA7075铝板扩孔可成形性的影响。孔是通过端铣加工制备的，以限制孔制备对结果的影响，而是突出材料行为的影响。平头冲头用于扩大孔，数字图像相关性可捕获整个实验过程中的应变场。结果表明，与-T6回火相比，在较低的成形力下，孔的-W膨胀能力可增加70％。相反，除了在-W回火中观察到Portevin-Le Chatelier（PLC）效应（导致不均匀变形）外，孔周围的厚度应变分布在两种回火中均显示出相似的模式。在平行下，孔扩展的数值模拟是使用用户材料子例程执行的，该子例程针对两种回火的弹塑性材料行为（包括塑性各向异性）而实现。厚度应变变化和平均水平的预测与-T6回火的实验吻合得很好，而-W回火的预测则不太好。这表明是PLC带对形变的影响：-T6回火中的材料主要受塑性各向异性控制，而-W回火则显示了塑性各向异性和PLC带的综合影响。尽管如此，对两种回火的合理预测证明，尽管省略了PLC效应的明确物理原理，但本研究中建立的数值框架可用于具有实际目的的初步计算效率高的虚拟过程设计。