Void coalescence and ductile fracture in automotive aluminum alloys

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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.