Development of Hierarchical Multiscale Method and Its Applications to the Characterization of Microstructure Effect

The mechanical properties of materials are inherently multiscale, depending on phenomena at all length scales. Hence, multiscale modeling is a huge scientific challenge as well as a critical necessity for successful manipulation of material properties. This proposed research aims to investigate the microstructure (i.e., grain and inclusion) effect on the material properties especially for the system which involve two characteristic microstructure features at distinct length scales using hierarchical multiscale method. The fundamental understanding of multiscale behavior is the key to the utilization of nano-materials and to the design of material systems contained nano-materials. In polycrystalline nanofilm, two distinct characteristic sizes, i.e. grain size of micrometers and film thickness of nanometers, are involved. The typical size of inclusion would vary significantly due to manufacturing process. The hierarchical multiscale simulation method, which integrates atomistic and continuum methods sequentially, offer the possibility to characterize the size dependence of both elastic and plastic properties. The proposed innovative algorithm adopts the representative volume element concept to link atomistic and continuum models through the parameters of the finite element method, which permits a reduction of the full set of atomistic degrees of freedom. This research gives a description of the proposed innovative method with special reference to the ways in which the method may be used to model crystals with more than a single grain or inclusion. In the project, we utilized the proposed innovative multiscale method to study the microstructure effect on the material properties. A multiscale method is developed to bridge the gap between nano-scale and macro-scale and study the multiscale behavior of materials. Ultimately, we developed a systematic approach to gain physical insight of the multiscale behavior of nano-materials for the design and fabrication of nano-devices.