Optimization on Cruciform Specimen Geometries of AA5052 Under Equi-Biaxial Loading: Acquisition of Ultimate Fracture Strain
Optimization on Cruciform Specimen Geometries of AA5052 Under Equi-Biaxial Loading: Acquisition of Ultimate Fracture Strain
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DOI：
10.1007/s11340-023-01003-3
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发表时间：
2023-10
影响因子：
2.4
通讯作者：
S. S. Chen-S.;D. Cai;J. J. Cui-J.;G. Y. Li;H. Jiang
中科院分区：
文献类型：
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作者：
S. S. Chen-S.;D. Cai;J. J. Cui-J.;G. Y. Li;H. Jiang
研究背景复杂载荷条件下铝合金的成形性能评价尤为重要.十字形试件由于其可方便地获得多个应变路径状态的特点，在成形性评价试验中得到了广泛的应用。为了获得AA 5052铝合金板材在等轴拉伸下的等比例应变路径历史，并探索其极限断裂应变，本文首先提出了两种适用于1.2mm板材的十字形试件设计方案。通过模拟计算，估计了应变局部化特性，确定了中心区域的减薄临界值。随后，通过三维数字图像相关（DIC）测试系统，获得了初始断裂点的应变路径历史。结果两种设计（直型设计和扩口型设计）的初始断裂点均位于试件中心。带狭缝试样的中心区域应变梯度较小。结论两种设计方法均能优化成形极限值，实现中心断裂点等比例应变路径历史。设计直型和设计扩口型分别更适合于AA 5052-O和AA 5052-H材料。这与材料的局部应力集中效应有关。
BackgroundThe evaluation of the formability for aluminum alloy under complex loading conditions is particularly significant. Based on the characteristics of conveniently achieving multiple strain path states, the cruciform specimen has been widely used in the experiment of evaluating formability. But there is no general specimen design scheme to realize proportional strain path history in initial fracture point.ObjectiveThis paper was aiming at obtaining the equi-proportional strain path history and exploring the ultimate fracture strain of AA5052 aluminum alloy sheets under the equi-biaxial tension.MethodsFirstly, two cruciform specimen schemes suitable for 1.2 mm sheet materials were proposed. The strain localization characteristics were estimated and thinning critical value in the central region was determined by simulations. Subsequently, through the 3D digital image correlation (DIC) test system, the strain path history of the initial fracture point was obtained. Finally, the fracture morphology characteristics were observed through SEM.ResultsThe results showed that the initial fracture point could be located in the center of the specimen in both designs (Design-straight and Design-flaring). The specimens with slits showed a smaller strain gradient existed in the central region. Meanwhile, the initial point of fracture was closer to the equi-biaxial tensile strain path, and the strain limit was larger.ConclusionsThe two design methods could optimize forming limit value and realize the equi-proportional strain path history in central fracture point. The Design-straight and Design-flaring was more suitable for the AA5052-O and AA5052-H material respectively. It was related to the local stress concentration effect of the material.