General imperfect interfaces with application to computational multi-physics multi-scale problems
Dr. Ali Javili, TU Dortmund
Date: Thursday, May 5, 2016
Place: EA 409
The objective of this presentation is firstly, to develop a thermodynamically consistent theory for general imperfect interfaces and to establish a unified computational framework to model all classes of such interfaces using the finite element method. Secondly, the influence of the interface on the overall response of material is examined through an enhanced computational homogenization framework.
In the context of a thermal problem, the interface is termed general imperfect in the sense that it allows for a jump of the temperature as well as for a jump of the normal heat flux across the interface. Conventionally, imperfect interfaces with respect to their thermal behavior are restricted to being either highly-conducting (HC) or lowly conducting (LC) also known as Kapitza. While HC and LC interfaces are generally accepted and well established today, the general imperfect interfaces remain poorly understood. Here we propose a thermodynamically consistent theory of general imperfect interfaces. Furthermore, we show how all classes of interfaces are derived from a general imperfect interface model and that allows us to establish a unified finite element framework to model all types of interfaces. The interface effect is particularly important at the micro-structure level and often becomes the dominant mechanism for the nano-sized structures due to the increasing area to volume ratio at small scales. Nevertheless, standard computational homogenization cannot capture the size-effect. Motivated by this rather controversial issue, an enhanced computational homogenization is developed by introducing the interfaces at the microscale into the picture. Unlike several other attempts to introduce a virtual length-scale, this framework is physically motivated by the fact that the lower dimensional energetic are no longer negligible at small scales. It is shown how elegantly the issue of size-effect is rectified in this enhanced framework. In particular, we elaborate on the influence of the interface on the overall response of materials and compare our results with atomistic simulations.
Dr. Ali Javili studied Mechanical Engineering at Sharif University of Technology in Tehran, Iran and then moved to Germany for his graduate studies. He received his M.Sc. degree in Computational Engineering at Bochum University in 2007 followed by his PhD in Mechanical Engineering at the University of Erlangen-Nuremberg in 2012. Dr. Javili worked as a post-doctoral research fellow on magneto-mechanical modeling of materials at the University of Erlangen-Nuremberg for 18 months. From September 2014 until the end of 2015 he was a post doctoral research fellow in Computational Micromechanics of Materials Lab at Stanford University. Since January 2016, he is a senior researcher in the institute of mechanics at TU-Dortmund. His current research revolves around computational multiphysics multi-scale understanding of complex materials behavior where lower-dimensional energetics such as surfaces and interfaces play a crucial role.