Investigation of local features and mechanisms that lead to global failure in heterogeneous materials

拟议的研究计划旨在更好地理解材料是如何失效的。许多材料的内部结构是不均匀的。非均质，这意味着失效很可能在结构和/或材料性能较弱的一个位置（或几个位置）开始。当前研究背后的基本前提是使用女王大学独特的微计算机断层扫描（microCT）设备来获取异质材料变形时内部结构的一系列三维图像。这些图像将为内部结构在引发材料失效中的作用提供宝贵的见解。两种不同类型的异质材料将被检查：金属合金和松质（或小梁）骨。在金属合金中，微ct图像中感兴趣的关键特征是随着材料变形而产生和生长的小空隙；它们最终连在一起导致灾难性的失败。在松质骨中，内部结构由支柱（小梁）和钢板组成的三维网络组成，其中的破坏首先由单个小梁的屈曲和/或断裂触发。这项研究的最终目标将是表征这些失效起始部位的物理特征，看看是否可以在所研究的两种材料的局部结构中找到共同的弱点。此外，从一个或多个局部包含区域到更全局范围的破坏进程也对预测材料破坏非常感兴趣。

The proposed research program seeks to provide a better understanding of how materials fail. The internal structure of many materials is non-uniform, ie. heteregeneous, which means that failure is likely to initiate at a location (or several locations) where the structure and/or material properties are weaker. The basic premise behind the current study is to use a unique micro-computed tomography (microCT) facility at Queen's University to acquire a sequence of three-dimensional images of the internal structure of hetergeneous materials as they are being deformed. These images will provide invaluable insight into the role of internal structure in initiating material failure. Two distinctly different types of heterogenous materials will be examined: metal alloys and cancellous (or trabecular) bone. In metal alloys, the key features of interest in the microCT images are small voids that initiate and grow as the material is deformed; they eventually link together to cause catastrophic failure. In cancellous bone, the internal structure is made up of a three-dimensional network of struts (trabeculae) and plates, where failure is first triggered by the buckling and/or fracture of individual trabeculae. The ultimate goal of this research will be to characterize the physical characteristics of these failure initiation sites to see if a common weakness in the local structure can be found for each of the two materials under study. Furthermore, the progression of failure from one or more locally contained regions to a more global scale is also of great interest in predicting material failure.