Dr. Shahriyar Keshavarz

For many practical problems, full representation or solution of the fine-scale problem is simply impossible for the predictable future because of the overwhelming costs. Therefore, we must seek alternative approaches that are more efficient. Recently, Multi-scale modeling is employed as a powerful approach to overcome this matter. Multi-scale modeling in materials science combines existing and emerging methods from diverse disciplines to bridge the wide range of time and length scales. A significant advantage of these models is their high efficiency enables them to be effectively incorporated in higher scale simulations, while retaining the accuracy of detailed lower scale models. In this work, a multi-scale approach is developed to bridge different scales in Nickel-based superalloys. Nickel based superalloys are used extensively in the aero-engine industry for turbine blades and disks in the form of single crystals and polycrystals. There has been significant investment to improve the efficiency of turbine engines, which has consistently led to increase demands on the materials used in the hot sections. The trend has been towards higher melting points and better service duties including better creep behaviors and longer fatigue lives. Therefore, there are several generations of these alloys with minor computational changes between them. The aim of this study is to develop a general framework for Nickel-based superalloys not only to simulate the existing generations but also design and predict for next generations. A hierarchical crystal plasticity finite element model (CPFEM) for Nickel-based superalloys is developed for three scales to address this demand.

Shahriyar Keshavarz is a research associate at the National Institute of Standards and Technology (NIST). He received all of his educational degrees from Sharif University of Technology in Iran. After his graduation, he joined to Johns Hopkins University as a Postdoc in 2011. In 2014, he joined to the Materials Science Division of NIST as a research associate. Shahriyar has been engaged in Computational solid Mechanics since his PhD program where he mainly focused on simulating and optimizing cold and hot powder compaction processes, which is one of the most applicable methods in metallurgy to make metal components. He started to conduct his research in the multi-scale context since his post-doctoral program. The major focus of his work was Multi-scale problems in nickel-based superalloys for aerospace applications. This research involves innovation of novel approaches in theoretical, computational and experimental methods for Nickel-based superalloys, which is one of the advanced metallic alloys used in extreme environments. Shahriyar is an author/co-author of over 20 published/accepted journal papers/book chapters/books. His research has been funded by NIST twice in last two years. Currently, Shahriyar is involved in multiple researches including implementing a crystal Plasticity framework for Object Oriented Finite element (OOF) software developed at NIST, Coupling discrete dislocation dynamics with Finite element, studying cobalt- based superalloys, and investigation of grain boundaries in polycrystalline materials.