Void coalescence and ductile fracture in automotive aluminum alloys

近年来，汽车业一直在寻求通过减轻车辆重量来提高车队的整体燃油效率。铝合金已经成为汽车面板和结构部件中替代钢的一种可行的轻质材料。然而，最近的研究表明，空洞损伤在成形过程中会导致延性断裂，从而限制了铝合金的成形性能。塑性断裂的数值模拟为改善这些合金的微观组织以满足汽车工业的需要提供了一种工具，可以将微观组织特征和成形行为联系起来。然而，尽管它在技术上很重要，但对铝合金中的空洞合并和延性断裂缺乏基本的了解。因此，对孔洞合并和韧性断裂进行系统的研究具有重要意义。 该项目是先前关于汽车铝板合金中空洞形核的发现拨款的延续。在拟议的项目中，我们将专注于延性断裂的整个过程，并试图描述各种成形操作中的延性断裂的特征。特别是，我们将集中在两个问题上：(1)预测局部空洞合并的开始；(2)基于微观结构的不同成形操作中不同延性断裂模式的模拟。我们将建立一个有限元/损伤渗流联合模型来模拟实际成形过程中的空洞损伤发展。在组合模型中，基于损伤的有限元模型描述了材料的软化，而损伤渗流模型则描述了被测微结构中的局部空穴形核和聚集。我们将使用组合模型来模拟目标材料的金属成形操作。这将导致汽车铝合金微观组织设计的重大技术进步，并促进其在汽车工业中的应用。

In recent years, the automotive industry has sought to increase overall fleet fuel efficiency through vehicle weight reduction. Aluminum alloys have gained prominence as a viable lightweight alternative to steel for automotive panels and structural components. However, recent research has revealed that void-damage induces ductile fracture during the forming processes, and therefore, limits the formability of aluminum alloys. Numerical simulations of ductile fracture provide a tool to bridge the microstructural features and forming behaviour in order to improve the microstructures of these alloys to meet the need in the automotive industry. However, despite its technological importance, a fundamental understanding of void coalescence and ductile fracture in aluminum alloys is lacking. Therefore, a systematic investigation of void coalescence and ductile fracture is of great interest. This project is a continuation of the previous discovery grant on void nucleation in automotive aluminum sheet alloys. In the proposed project, we will focus on the entire process of ductile fracture and attempt to characterize ductile fracture in various forming operations. In particular, we will focus on two issues: (1) predicting the onset of localized void coalescence; and (2) microstructure-based modelling of different ductile fracture modes in various forming operations. We will construct a combined finite element/damage percolation model to simulate void damage development in actual forming processes. In the combined model, the damage-based finite element model characterizes the material softening, while the damage percolation model captures the localized void nucleation and coalescence in the measured microstructures. We will use the combined model to simulate metal forming operations of the targeted materials. This will lead to important technological advancements in design of automotive aluminum alloy microstructures and promoting their use in the automotive industry.