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M. Asle Zaeem,H. El Kadiri,M.F. Horstemeyer,M. Khafizov,Z. Utegulov 한국물리학회 2012 Current Applied Physics Vol.12 No.2
Phase stability, topology and size evolution of precipitates are important factors in determining the mechanical properties of crystalline materials. In this article, the CahneHilliard type of phase-field model was coupled to elasticity equations within a mixed-order Galerkin finite element framework to study the coarsening morphology of coherent precipitates. The effects of capillarity, particle size and fraction,compositional strain, and inhomogeneous elasticity on the kinetics and kinematics of coherent precipitates in a binary dual phase crystal admitting a third intermediate stable/meta-stable phase were investigated. The results demonstrated the ability of the model to simulate coarsening under the concomitant action of Ostwald ripening and mismatch elastic strain mechanisms. Using a phenomenological coarsening power law, coarsening rates were determined to depend on precipitate size and volume fraction, compositional strain, and strain mismatch between precipitates and the matrix. Results also showed that the necking incubation time between two neighboring precipitates depends inversely on the precipitate’s initial sizes; however, under fixed volume fraction of precipitates, any increase in the initial sizes of the precipitates mitigates the coarsening. Meanwhile, the compositional strain and the growth of the intermediate stable/meta-stable phase leads to substantial enhancements of precipitate coarsening.
Investigation on Sintering Mechanism of Nanoscale Tungsten Powder Based on Atomistic Simulation
Amitava Moitra,Sungho Kim,Seong-Gon Kim,Seong Jin Park,Randall M. German,Mark F. Horstemeyer 한국소성가공학회 2010 기타자료 Vol.2010 No.6
Atomistic simulations focusing on sintering of crystalline tungsten powders at the submicroscopic level are performed to shed light on the processing on the nanoscale powders. The neck growth and shrinkage were calculated during these sintering simulations, so it is possible to extend these results to the global physical property evolution via sintering. The densification and grain growth during sintering were calculated with variations in temperature, pressure, particle configuration, additives, and crystalline misalignment between particles. These findings lay a foundation for a virtual approach to setting the processing cycles and materials design applicable to nanoscale powders.
Complexity science of multiscale materials via stochastic computations
Liu, Wing Kam,Siad, Larbi,Tian, Rong,Lee, Sanghoon,Lee, Dockjin,Yin, Xiaolei,Chen, Wei,Chan, Stephanie,Olson, Gregory B.,Lindgen, Lars-Erik,Horstemeyer, Mark F.,Chang, Yoon-Suk,Choi, Jae-Boong,Kim, Yo John Wiley Sons, Ltd. 2009 International Journal for Numerical Methods in Eng Vol.80 No.6
<P>New technological advances today allow for a range of advanced composite materials, including multilayer materials and nanofiber-matrix composites. In this context, the key to developing advanced materials is the understanding of the interplay between the various physical scales present, from the atomic level interactions to the microstructural composition and the macroscale behavior. Using the developing ‘multiresolution data sets mechanics’, the ‘predictive science-based governing laws of the materials microstructure evolutions’ are derived and melted into a ‘stochastic multiresolution design framework.’ Under such a framework, the governing laws of the materials microstructure evolution will be essential to assess, across multiple scales, the impact of multiscale material design, geometry design of a structure, and the manufacturing process conditions, by following the cause–effect relationships from structure to property and then to performance.</P><P>The future integrated multiscale analysis system will be constructed based on a probabilistic complexity science-based mathematical framework. Its verification, validation and uncertainty quantification are done through carefully designed experiments, and the life-cycled materials design for products design and manufacturing is performed through the use of petascale computing. The various techniques of microstructure reconstruction result in the generation of model microstructures that, at some level, has the same statistical properties as the real heterogeneous media. Having reconstructed the heterogeneous medium, one can then evaluate its effective properties via direct numerical simulation and compare these values with experimentally measured properties of the actual medium. The proposed analysis will be dynamic in nature to capture the multi-stage historical evolvement of material/structure performance over the life span of a product. In addition to providing more accurate assessment of structure performance with stochastic multiscale analysis, our development will provide the capability of predicting structure failures and system reliability to enable more reliable design and manufacturing decisions in product development. Copyright © 2009 John Wiley & Sons, Ltd.</P>