Dynamic Failure of Light Weight Materials and Structures

这项拟议的研究解决了开发仿真平台的迫切需要，以预测与碰撞事件和弹道冲击相关的高应变率条件下轻型汽车、航空航天和国防车辆结构的失效。采用这些非常高强度、低密度或更薄的材料的一个关键挑战是它们的延展性较低，因此准确预测碰撞和弹道冲击条件下的故障发生至关重要。在失效过程中，塑性功产生的大量热量加剧了这个问题；因此，在预测失效时，除了本构应变速率敏感性和微结构损伤外，还必须考虑热软化和绝热剪切局部化过程。 为了满足这一需求，探索研究的拟议计划将： 1.表征和模拟高应变率加载过程中的损伤演化，重点是先进和超高强度钢； 2.表征高应变率破坏过程的热条件，特别是剪切局部化，并建立绝热剪切局部化模型； 3.在行业使用的有限元代码中实施先进的高应变率失效准则，从而确保研究成果的传播和采用。 这项研究将利用滑铁卢现有的一套广泛的高应变率本构和断裂表征基础设施，该实验室无疑是北美学术环境中最大的此类实验室，配备了由CFI资助的新型超高速光学相机(1000万fps)和高速热相机(9万fps)。新的成像基础设施将能够在高应变率下对断裂过程进行高保真测量。这些现场测量将得到基于光学显微镜的测量和对回收的测试样品的断层扫描测量的补充。目前的拉伸分离式霍普金森杆内的动量捕捉夹具允许在断裂前对样品进行软恢复，从而能够表征作为变形和加载条件函数的损伤。最先进的实验将为高应变率加载下的损伤和断裂提供新的模型。这些将应用于未来轻型、耐碰撞车辆的开发，提高乘员安全，并增强加拿大汽车、航空和国防部门的竞争力。 在这个探索研究项目的课程中，共有8名研究生将接受培训。这些研究人员将在材料对总塑性变形和冲击的响应领域内熟练掌握最先进的实验和分析技术。他们在加拿大工业界和学术界的招聘将进一步提高加拿大未来的竞争力。

The proposed research addresses the critical need to develop a simulation platform to predict failure of light weight automotive, aerospace and defence vehicle structures under the high strain rate conditions associated with crash events and ballistic impact. A key challenge in the adoption of these very high strength, low density or thinner materials is their lower ductility, making it critical to accurately predict the onset of failure under crash and ballistic impact conditions. This issue is exacerbated by significant levels of heat generation through plastic work during failure; thus thermal softening and adiabatic shear localization processes must be considered in predicting failure, in addition to constitutive strain rate sensitivity and microstructural damage. To address this need, the proposed program of Discovery Research will: 1. Characterize and model damage evolution during high strain rate loading, focusing on advanced- and ultra-high strength steels; 2. Characterize the thermal conditions associated with high strain rate failure processes, in particular shear localization, and develop models of adiabatic shear localization; 3. Implement advanced high strain rate failure criteria within finite element codes used by industry, thereby ensuring dissemination and adoption of the research outcomes. This research will utilize the extensive suite of high strain rate constitutive and fracture characterization infrastructure already in place at Waterloo, easily the largest such laboratory in an academic setting in North America, featuring new CFI-funded ultra-fast optical cameras (10 million fps) and high speed thermal cameras (90,000 fps). The new imaging infrastructure will enable high fidelity measurements of fracture processes at high rates of strain. These in situ measurements will be complemented by optical microscopy-based and tomography measurements of damage in recovered as-tested samples. Momentum-trapping fixtures within the current tensile split-Hopkinson bar allow soft recovery of samples prior to fracture, enabling characterization of damage as a function of deformation and loading conditions. State-of-art experiments will inform new models of damage and fracture under high strain rate loading. These will see application in the development of future lightweight, crashworthy vehicles, increasing occupant safety and enhancing the competitiveness of the Canadian auto, aero and defense sectors. A total of eight graduate students will be trained over the course of this Discovery Research program. These researchers will become skilled in state-of-the-art experimental and analytical techniques within the field of material response to gross plastic deformation and impact. Their recruitment within Canadian industry and academe will further enhance Canada's future competitiveness.