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报告内容摘要：
A multiscale method that couples the space-time finite element method with the molecular dynamics is developed for the simulation of dynamic lattice fracture problems. The initiation of the fracture in the lattice system is viewed equivalently as a debonding process. Correspondingly, a detailed atomistic description is employed in the region immediately surrounding the crack tip to capture the initiation and propagation of the fracture. In the remaining region, a coarse scale description with an enrichment function that describes the fracture path is established. The enrichment function is incorporated by exploiting the concept of partition of unity. The space-time framework further enables flexible choice of time steps in different regions of interest. Coupling between the fine and coarse scale simulation is achieved with the introduction of a projection operator and bridging scale treatment [1-3]. The main feature of the work is that the evolution of the crack is dynamically tracked and the enrichment in the coarse scale simulation evolves along with it. As a result, we have a moving atomistic region, resulting in a moving boundary problem. The robustness of the method is illustrated using examples for different lattice structures for straight cracks, inclined cracks, branching and multiple cracks.

报告人简介：
Dr. Dong Qian is an associate professor and the director of the graduate studies in the school of dynamic systems at the University of Cincinnati. He received his B.S. degree in Bridge Engineering from Tongji University in Shanghai, China in 1994, his M.S. degree in Civil Engineering from the University of Missouri in 1998 and Ph.D. degree in Mechanical Engineering from Northwestern University in 2002. Shortly after his graduation, He was hired as an assistant professor of mechanical engineering in the University of Cincinnati and promoted to the rank of associate professor with tenure in 2008. He has conducted research in the general areas of computational mechanics of materials and is an author /co-author of over 40 published/accepted journal papers and book chapters with over 1000 citations. He has been a PI or Co-PI of funded research projects worth over $7 M funded by NSF, AFOSR, AFRL, State of Ohio and industries such as P&G and General Electric. He has been a guest editor for three journal special issues and the co-organizer of the 10-th US congress on Computational Mechanics. Dr. Qian is the recipient of the Young Investigator Award by ICACM in 2011, the Distinguished Researcher award in 2010 and the Junior Faculty Research Award in 2008 by the college of Engineering at UC. He is a member of ASME and USACM.