Topic: Ductile vs Brittle Fracture Behaviors and Related Deformation Mechanisms in Nanostructured Materials

Speaker: Prof. Huajian Gao

　　　　 School of Engineering, Brown University, USA

ABSTRACT

The rapid development of synthesis and characterization of materials with feature sizes at nanoscale as well as unprecedented computational power have brought forth a new era of materials research in which experiments, modeling and simulations are performed side by side to probe the unique mechanical properties of nanostructured materials. Here we report a number of recent studies on ductile vs brittle fracture behaviors and related deformation mechanisms in nanostructure of materials, including a twin-spacing-induced ductile-brittle transition in nanotwinned nanopillars [1], crack bridging by nanoscale twins in thin films [2], and fluctuation induced ductile-brittle fracture transition in metallic glasses [3]. In each study, there has been a strong synergy between theory and experiment, with new experimental findings driving advances in modeling and simulations, and new theoretical insights suggesting new experimental studies. The discussions will be organized around the current understandings based on existing experimental and theoretical efforts, as well as the outstanding questions that require further studies in the future.

REFERENCES

1. D.C. Jang, X.Y. Li, H.J. Gao and J.R. Greer, “Deformation Mechanisms in Nanotwinned Metal Nanopillars,” 2012, Nature Nanotechnology, Vol. 7, 594–601.

2. S.W. Kim, X.Y. Li, H.J. Gao and S. Kumar, “In situ Observations of Crack Arrest and Bridging by Nanoscale Twins in Copper Thin Films,” 2012, Acta Materialia, Vol. 60, 2959–2972.

3. P. Murali, T.F. Guo, Y.W. Zhang, R. Narasimhan, Y. Li and H.J. Gao, “Atomic Scale Fluctuations Govern Brittle Fracture and Cavitation Behavior in Metallic Glasses,” 2011, Physical Review Letters, Vol. 107(21), Art. No. 215501.

About Prof. Huajian Gao

Huajian Gao received his B.S. degree from Xian Jiaotong University of China in 1982, and his M.S. and Ph.D. degrees in Engineering Science from Harvard University in 1984 and 1988, respectively. He served on the faculty of Stanford University between 1988 and 2002, where he was promoted to Associate Professor with tenure in 1994 and to Full Professor in 2000. He served as a Director at the Max Planck Institute for Metals Research between 2001 and 2006 before joining the Faculty of Brown University in 2006. At present, he is the Walter H. Annenberg Professor of Engineering at Brown.

Professor Gao’s research is focused on the understanding of basic principles that control mechanical properties and behaviors of materials in both engineering and biology. He is an author/co-author of more than 300 scientific papers with total citations exceeding 12K and an h-index of 58. He is a Member of the National Academy of Engineering of USA and a co-editor-in-chief of the Journal of the Mechanics and Physics of Solids, the flagship journal of his field. He is also the recipient of numerous academic honors, from a John Simon Guggenheim Fellowship in 1995 to recent honors including the Alexander von Humboldt Prize from Germany and Rodney Hill Prize in Solid Mechanics from the International Union of Theoretical and Applied Mechanics in 2012.