Towards a Micromechanical Damage Model for Lightweight Materials in Vehicle Crash

2012年美国企业平均燃油经济性（CAFÉ）目标要求到2025年将燃油消耗减少50%，这推动了汽车行业的研究和创新。为了在不影响乘员安全的情况下达到这些目标，超高强度钢、高强度铝和镁合金等新一代材料正在迅速开发，并应用于轻量化的多材料汽车架构中。尽管这些材料在轻量化方面具有巨大的潜力，但由于其复杂的材料性能和断裂敏感性，它们也带来了不断缩小的工艺设计窗口。因此，需要在高温下进行高级成形操作，以避免这些材料在室温下的低延展性。为了在大批量、低成本的汽车制造环境中保持竞争力，需要计算机辅助工程（CAE）来设计零部件、模具、成形工艺并预测其在汽车碰撞中的性能。这些轻质合金复杂的机械性能，加上对先进成形操作的需求，远远超出了当今数值模型的能力。拟议的研究将解决CAE断裂模型的这一严重不足，以利用这些新兴材料系统的轻量化潜力。

The 2012 U.S. Corporate Average Fuel Economy (CAFÉ) targets mandating a 50% cut in fuel consumption by 2025 have supercharged research and innovation within the automotive industry. To reach these targets without compromising occupant safety, next generation materials such as ultra high strength steels, high strength aluminum and magnesium alloys are being rapidly developed and implemented into a lightweight multi-material vehicle architecture. Although these materials offer tremendous potential for lightweighting, they also bring ever shrinking process design windows due to their complex material behaviour and fracture sensitivity. Consequently, advanced forming operations at elevated temperatures are required to avoid the low ductility of these materials at room temperature. To stay competitive in the high volume, low cost environment of automotive manufacturing, computer assisted engineering (CAE) is required to design the component, tooling, forming process and predict its performance in a vehicle crash. The complicated mechanical behaviour of these lightweight alloys coupled with the need for advanced forming operations far exceeds the capabilities of today's numerical models. The proposed research will address this critical shortfall in the CAE fracture models to capitalize on the potential of these emerging material systems for lightweighting. The long term goal of this research is the development of a comprehensive modeling platform for the simulation of product history, from manufacturing to in-service performance, to enable the design and commercialization of multi-material lightweight vehicle architectures. In the short term, the research program will develop innovative experimental and numerical methodologies to predict the behavior of anisotropic lightweight alloys in complex non-proportional loading conditions found in forming and crash events. Central to the research is the development of micromechanical void damage models that can replace the phenomenological damage models used by industry that have a limited physical basis. To optimize structural components and develop new alloys, it is imperative the material models can account for how a microstructure evolves across the process chain. The ability to design forming processes and components using advanced materials and manufacturing processes is critical for the innovation and global competitiveness of the automotive and manufacturing sectors in Canada. This research program is in direct alignment with Canada's 2014 Science and Technology Strategy for “Lightweight Materials and Technologies” to be a Research Focus within the new “Advanced Manufacturing” Research Priority. This research will provide Canadian automakers with a cutting edge research and design tool that can be used to design a component from its conception to crash and from the micro-to-macro-scale.