Deformation, Strength, Fatigue and Fracture of Gradient Nanostructured Metals

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Non-technical Abstract:Metals play essential roles in infrastructural and overall economic developments of our society, as reflected by the fact that the annual global market value of metals is close to a trillion US dollars. During the last five years, a new class of nano materials called gradient nanostructured metals have emerged as a material class which exhibits an unusual combination of ultrahigh strength, good tensile ductility, enhanced strain hardening, superior fracture toughness and fatigue resistance. However, the current lack of understanding of the underlying mechanisms that control the properties of these materials severely limits our ability to tailor or optimize their properties for specific applications. On the other hand, recent advances in computational modeling and simulation capabilities are providing unprecedented opportunities to advance the knowledge frontier in our understanding of mechanical properties of materials at micro- and nano-scales. The proposed research will take advantage of the cutting-edge multiscale modeling and simulation methods to address the fundamental issues with regard to the mechanical properties and behavior of gradient nanostructured metals. The project will train graduate and undergraduate students in state of the art computational techniques. Technical AbstractThe proposed research will address the following questions: What are the deformation mechanisms that control the mechanical properties of gradient nanostructured metals? How to design the gradient micro- and nanostructures to optimize the mechanical responses of gradient nanostructured metals? The problems under study will be tackled via a multiscale modeling approach that combines finite element method, strain gradient plasticity, cohesive modeling, crystal plasticity, dislocation dynamics and molecular dynamics simulations will be used to investigate the deformation and failure mechanisms of gradient nanostructured metals. The technical approach will be based on the experience and theoretical/simulation capabilities developed by the PI. The proposed work will clarify the controlling deformation mechanisms through ultra-large-scale and high-resolution atomistic and dislocation dynamics simulations, interpret the experimental data and phenomena through continuum strain gradient plasticity and cohesive modeling of fatigue and fracture behavior, and guide further research in structural optimization and processing. The ultra-large scale simulations in the proposed work will be performed on the National Institute for Computational Sciences, and the rest of the proposed computational work will be performed at the Center for Computing and Visualization at Brown University. The project will train graduate and undergraduate students in state of the art computational techniques.