Seminarium - dr hab. Stefanos Papanikolaou: „Nano/micro-mechanical deformation of metals and metallic alloys”

Miejsce: Sala Rady Wydziału (215), ul. Wołoska 141, Warszawa


Nano- and micro- scale testings of materials have been a key tool for understanding the different mechanical properties of materials at small scale with respect to bulk ones. Experimental techniques such as nanoindentation, digital image correlation, and uniaxial pillar compression have provided a great wealth of information and insights on the investigation of size effects in mechanical behavior of materials, dislocation mechanisms, and a comparison to multiscale modeling approaches. However, a precise comparison to experiments, especially for advanced materials towards extreme conditions' applications, pose stringent requirements on accuracy of both experimental procedures and modeling predictions. When the extreme case of irradiation is concerned, the key problems that need to be addressed are mainly: i) the ``invisibility" of irradiation defects, and ii) the non-destructive, continuous ability to develop structure-property relationships that can be used in multi-scale models, to be used as digital twins in the future.

In this presentation, I will show how the combination of machine learning and physics intuition can be utilized for the multiscale modeling approaches of crystalline systems. I will discuss density functional theory, molecular dynamics and continuum plasticity approaches to model these materials, with a focus on experimental comparisons. I will discuss machine learning methods, in relation to strain deformation signatures in digital image correlation, and dislocation dynamics mechanisms in pure metals and also, several multicomponent alloys.



Stefanos Papanikolaou acts as a Habilitated Professor and Research Group Leader of the Materials Structure, Informatics and Function (MASIF) Group, in the NOMATEN Center of Excellence for Multifunctional Materials in the National Center for Nuclear Research in Poland. His BSc is in Physics from the National University of Athens. His MS and PhD degrees are in Physics from the University of Illinois, Urbana-Champaign. He performed his postdoctoral work in the Department of Physics at Cornell University, and then he held positions at Yale University, Johns Hopkins University and West Virginia University. Papanikolaou won the internationally competitive 5-year VIDI excellence grant by the Netherlands research council in 2013 and a research excellence award in 2018. His research interest is in materials informatics and machine learning. Prof. Papanikolaou has received his habilitation in Poland since 2022. He actively works on fusion-related materials science, simulations and machine learning. Papanikolaou has been at the forefront of the international research community in the field of materials science and micromechanics of advanced alloys and specifically, crystal plasticity, especially in the context of stochastic aspects and non-linear dynamical phenomena. Having a strong background in theoretical condensed matter physics, statistical mechanics and strongly correlated electron phenomena, he represents an ideal upcoming world leader of the ever emerging Materials Informatics field in materials science. An example of such leadership has been the organization of the 1st Materials Informatics conference in Warsaw, Poland, in 2022, at the NCBJ premises, first of its kind in Poland. He has also published numerous manuscripts in machine learning aspects of crystal plasticity. Papanikolaou  leads the MAterials Structure, Informatics and Function (MASIF) group at the NOMATEN CoE, and leads the materials informatics research at NCBJ and in Poland. He has 80+ peer-reviewed publications, including more than 20 in machine learning aspects, with 2000+ total citations, and publications in high impact journals such as Nature, Nature Physics, Materials&Design, npj Comput. Materials, Scripta Materialia etc.. The MASIF group has 5 doctoral students, 3 postdoctoral associates and 2 machine learning experts. Papanikolaou received his Bachelors from Athens, Greece, and then his Physics Masters and Doctoral degrees at the University of Illinois in USA, and then developed a materials science and engineering career in USA, with the focus on statistical and stochastic aspects in mechanical deformation of advanced alloys. The MASIF group has been funded by multiple funding agencies, including NSF (Materials) (2017-2020), DOE (Basic Energy Sciences, 2016-2019) and AFOSR (2015-2017) in USA, as well as NWO in Netherlands (Vidi grant, 2013-2018). He received the 2018 WVU award for excellence in tenure-track research. Papanikolaou is currently writing a book on Materials Informatics Methods and Applications, towards future graduate students in Materials Science and Engineering programs. Finally, professional service and recognition has been evidenced through chairing and organizing the first materials informatics conference in Poland last summer (2022), has organized more than 20 symposia in major conferences, has been involved in the leadership of major regional (ASEE-NCS) and national (MRS) societies, and being on the editorial board of three peer-reviewed journals (Mat.Theory, J. Mechanics, Frontiers in Physics). He is currently one of four selected Associate Editors of Materials Theory at Springer/Nature, and one of six Associate Editors of Frontiers in Physics -- Condensed Matter Physics at Frontiers.

Prof. Papanikolaou and the MASIF group present a combination of expertise in two clear domains: First, he is an expert in materials informatics and versatile applications of machine learning for materials science. He has been utilizing DFT methods and multiscale modeling routinely to perform machine learning tasks, such as unsupervised clustering and neural network development, in more than 10 projects to date, co-authoring more than 10 manuscripts in machine learning aspects. He has been developing novel methods in designing alloys for optimal performance and in particular, strength optimization, by using mechanical digital image correlation effects, or/and microstructural correlation effects. Second, he has a strong understanding of mechanical effects in material properties, especially in the case of multi-component alloys. This kind of connections has been a major theme of Papanikolaou's research since his doctoral studies, starting from lattice distortions in topological materials and high-temperature superconductors, to grain boundaries in graphene and topoiogical band insulators, and then, strain and dislocation dynamics phenomena in a variety of micro/nano-mechanical contexts. In addition, Prof. Papanikolaou has strong experience as the lead coordinator of 5 past research projects, funded by highly competitive calls of USA funding (DOE, DOC, NSF, WV) and Netherlands (NWO) programs. This experience ensures a strong partnership towards the successful accomplishment of the objectives of a project.