Deformation of Engineering Materials Across length and time Scales (DEMAS)

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The proposed program aims to study deformation of engineering materials across length and time scales. The long term objective of this research program is to be able to assess and enhance structural integrity and performance of the metallic and non-metallic composites used in three strategic industries: nuclear, aerospace, and transportation. The materials that are used in these industries are very often exposed to hostile environments while carrying mechanical loads. In such environments, materials deform reversibly (elastically) or irreversibly (plastically). Plastic deformation can potentially localize at particular points in engineering components and subsequently lead to crack nucleation and catastrophic failure. ***Finite element is a powerful numerical technique that can be used for simulating elastic and plastic deformation of materials. Crystal plasticity, as a constitutive model for materials' deformation, can further enhance the power of finite element to study mechanisms of deformation localization. Numerical studies often require experimental observations for both development and validation. For instance, electron or X-ray microscopy can be used to study localized deformation at nano and meso scales. ******The aim of this program is to characterize, formulate, and simulate localized plastic deformation; the applicant proposes to develop three numerical and experimental toolboxes that can significantly improve our fundamental understanding of deformation:******I) Developing a temperature dependent non-local crystal plasticity finite element code for modelling plastic deformation caused by formation of slip bands and twins. The code will be able to simulate interaction between point defects and line defects. This is a unique and novel capability as through such formulation, void formation resulting from diffusion of defects or climb of line defects can be studied; hence, the model can be used to study and simulate creep, fatigue, and eventually fracture of polycrystals. ******II) Developing a world leading capability for running temperature dependent in-situ High Resolution Electron BackScatter Diffraction and High Resolution Digital Image Correlation techniques. Both techniques are based on the use of scanning electron microscopes; they can be used for measuring localized deformation at nano, meso, and macro scales and hence validate the code that will be developed in (I).******The immediate application of (I) and (II) is in the Canadian nuclear industry. With the aging of CANDU reactors, irradiation enhanced creep has become a major concern. This mode of deformation is a time dependent plastic deformation the modelling of which is the primarily goal of (I). Another application of this research is in the aerospace industry. Creep and fatigue resistance of titanium and nickel alloys are the two main factors in manufacturing jet engines components.