Biography
Dr. Sergei Alexandrov
Dr. Sergei Alexandrov
Beihang University, China
Title: Plastic Flow of Polymers Near Rough Walls
Abstract: 
The main objective of the present paper is to investigate, by means of a boundary value problem permitting a semi-analytic solution, qualitative behaviour of solutions for two pressure-dependent yield criteria used for plastically incompressible polymers. The study mainly focuses on the regime of friction (sticking and sliding). It is shown that the existence of the solution satisfying the regime of sticking depends on other boundary conditions. In particular, there is such a class of boundary conditions depending on the yield criterion adopted that the regime of sliding is required for the existence of the solution independently of the friction law.
The boundary value problem considered consists of a planar deformation comprising the simultaneous shearing and expansion/contraction of a hollow cylindrical specimen of material. This problem is an ideal benchmark problem for understanding qualitative features of solution behaviour in the vicinity of frictional interfaces.
Therefore, in the present paper this boundary value problem is used in conjunction with two yield criteria proposed for polymers elsewhere.
It is shown that:
1. In the case of expansion of the cylinder, the solution satisfying the regime of sticking at the inner radius exists independently of the other boundary conditions for both yield criteria considered in the present paper. 
2. In the case of contraction of the cylinder obeying both yield criteria, the solution satisfying the regime of sticking does not exist if the ratio of the circumferential velocity at the outer radius to the radial velocity of the inner radius is large enough. However, there are qualitative differences in the conditions that controls the non-existence of solution.
The qualitative features of solutions found can be used to develop a new approach for predicting the generation of skin layers.
Biography: 
Sergei Alexandrov is a Visiting Professor at Beihang University (Beijing, China) under the program “Recruitment Program for Global Experts” (“1000 Talent Plan”) and a Research Professor at the Laboratory for Technological Processes of the Institute for Problems in Mechanics of the Russian Academy of Sciences. He received his Ph.D. in Physics and Mathematics in 1990 and D.Sc. in Physics and Mathematics in 1994. He worked as a Professor at Moscow Aviation Technology Technical University (Russia), a Visiting Scientist at ALCOA Technical Center (USA), GKSS Research Centre (Germany) and Seoul National University (South Korea), and was a Visiting Professor at Aveiro University (Portugal), University of Besancon (France) and Technical University of Malaysia (Malaysia). He is a member of the Russian National Committee on Theoretical and Applied Mechanics. Sergei Alexandrov has published more than 400 papers in journals, books and conference proceedings, including three monographs and around 200 papers in journals indexed in the Web of Science. He has participated in the scientific committee of several international conferences and served as a reviewer in a wide range of international journals. He is on the editorial board of several journals including Continuum Mechanics and Thermodynamics (Springer) and Structural Engineering and Mechanics (Technopress). His research areas are plasticity theory, fracture mechanics, and their applications to metal forming and structural mechanics.