| Biography | |
|---|---|
 Prof. Sergei Alexandrov Beihang University, China |
|
| Title: Prediction of the thickness of fine-grain layers in axisymmetric extrusion processes | |
| Abstract: Friction is responsible for the evolution of material properties near frictional interfaces in metal forming processes. Experimental data show that the gradient of many material properties is very high in a thin layer near these interfaces. Therefore, constitutive equations in this layer should differ from those in bulk. A novel approach for predicting the evolution of material properties near frictional interfaces is based on the strain rate intensity factor. This factor is the coefficient of the leading singular term in a series expansion of the equivalent strain rate in the vicinity of maximum friction surfaces. The layer where the gradient of material properties is very high is usually named the fine-grain layer. An empirical equation that connects the integrated strain rate intensity factor and the thickness of fine-grain layers has been recently established for Aluminum 6061. The present paper uses this equation to predict the thickness of fine-grain layers in axisymmetric extrusion processes. Since determining the strain rate intensity factor requires a solution to a singular boundary value problem, the standard finite element method cannot calculate the strain rate intensity factor. The present paper employs two methods for calculating this factor. One of these methods is the upper bound method. The kinematically admissible velocity field chosen accounts for the singular behavior of the real velocity field near the friction surface, which allows for the strain rate intensity factor to be calculated. The other method employs an exact analytic solution for the flow of material through an infinite channel. If the maximum friction law is adopted, this solution produces the singular velocity field. The second method is appropriate for long dies. | |
| 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. | |
