Modelling the deformation and failure of sheet metal in high-strain rate forming

轻型和耐碰撞客车的制造越来越需要使用难以成形的板材。轻质材料，例如先进的高强度钢、铝和镁合金，在使用常规成形工艺成形时固有地具有有限的可成形性。然而，已经开发了高应变率成形技术，例如电磁和电液成形，因为在特定条件下，板材可以实现至少100%的可成形性增加。这种增强的可成形性为汽车零件设计者提供了显著减轻重量的机会。 为了优化这些高应变率金属成形工艺并使其尽可能具有成本效益以用于工业实施，有必要能够以高度的置信度对其结果进行数值预测。申请人先前的研究集中于开发能够模拟电液成形操作的计算机模型。然而，为了提高模拟的准确性，仍然需要做大量的工作。 该研究计划旨在改进现有的模拟模型，以便更准确地预测在高应变率下变形的板材的变形行为和断裂发生。建议在0.001至1000 s-1的应变率范围内对薄板试样进行一系列机械试验。在测试过程中使用高速、高分辨率的数码相机将有助于获取实验数据，从而深入了解材料行为，并有助于开发更准确的模拟模型。这项工作的新颖之处之一将是确定在高应变率的片材的断裂极限。 还建议在显微镜下以不同的放大率观察试样，以确定其微观机械变形和损伤行为直至断裂发生。同样，将开发能够根据观察到的变形和失效的微观机制预测断裂发生的模拟模型。 该研究计划将为四名高素质人员（两名硕士生和两名博士生）提供高级培训，并将开发更精确的数值工具，用于模拟高应变率金属板材成形过程。这些模型在预测车辆的耐撞性方面也将是非常有用的。这也将有助于加速高应变率成形工艺在工业实践中的应用，并增加汽车中轻质板材的使用。此外，由于该研究计划的学员被加拿大汽车制造商雇用，他们将开发的专业知识将有助于保持加拿大在先进制造业的竞争优势。

The manufacture of lightweight and crash-resistant passenger vehicles increasingly requires the use of difficult-to-form sheet materials. Lightweight materials such as advanced high strength steels, aluminum and magnesium alloys inherently have limited formability when shaped using conventional forming processes. However, high-strain rate forming technologies, such as electromagnetic and electrohydraulic forming have been developed because under specific conditions, sheet materials can achieve at least 100% increase in formability. This enhanced formability offers significant weight reduction opportunities to automotive part designers. In order to optimize these high-strain rate metal forming processes and render them as cost-effective as possible for industrial implementation, it is necessary to be able to numerically predict their outcome with a high degree of confidence. The applicant's prior research focused on developing computer models that can simulate electrohydraulic forming operations. However, significant work is still required in order to improve the accuracy of the simulations. This research program aims to improve the existing simulation models in such a way as to more accurately predict the deformation behaviour and the onset of fracture of sheet materials deformed at high-strain rates. It is proposed to conduct a series of mechanical tests on sheet specimens across a range of strain rates from 0.001 to 1000 s-1. The use of high-speed, high-resolution digital cameras during testing will facilitate the acquisition of experimental data that gives insights into material behaviour and help to develop more accurate simulation models. One of the novelties of this work will be to determine the fracture limits of sheet materials at high strain rate. It is also proposed that specimens be observed at different magnifications under the microscope in order to determine their micro-mechanical deformation and damage behaviour up to the onset of fracture. Again, simulation models will be developed that are able to predict the onset of fracture based on observed micro-mechanisms of deformation and failure. This research program will provide advanced training for four highly qualified personnel (two Master's degree students and two PhD students) and will lead to the development of more accurate numerical tools for the simulation of high-strain rate sheet metal forming processes. These models will also be very useful in predicting the crashworthiness of vehicles. This will also help to accelerate the adoption of high-strain rate forming processes into industrial practice and increase the use of lightweight sheet materials in automobiles. Furthermore, as the trainees in this research program are hired by Canadian automotive manufacturers, the expertise they will develop will contribute toward maintaining Canada's competitive edge in advanced manufacturing.