<span styletimes="" new="" roman';="" mso-ansi-language:="" en-us;="" mso-fareast-language:="" zh-cn;="" mso-bidi-language:="" ar-sa"="">湍流与复杂系统国家重点实验室，力学与空天技术系

<span styletimes="" new="" roman';="" mso-ansi-language:="" en-us;="" mso-fareast-language:="" zh-cn;="" mso-bidi-language:="" ar-sa"=""> 

 

 

 

 

 

 

In this talk, I will discuss some recent studies on the mechanics of plastic deformation in nanocrystalline materials as well as mechanics of focal adhesions in cell-substrate interactions. One study attempts to explain recent experiments that plastic strains in nanocrystalline aluminum and gold films with grain sizes on the order of 50 nm are partially recoverable. To reveal the mechanisms behind such strain recovery, we perform large scale molecular dynamics simulations of plastic deformation in nanocrystalline aluminum with mean grain sizes of 10, 20, and 30 nm. Our results indicate that the inhomogeneous deformation in a polycrystalline environment results in significant residual stresses in the nanocrystals. Upon unloading, these internal residual stresses cause strain recovery via competitive deformation mechanisms including dislocation reverse motion/annihilation and grain-boundary sliding/diffusion. Our analysis shows that, even under strain rates as high as those in molecular dynamics simulations, grain boundary-mediated processes play important roles in the deformation of nanocrystalline aluminum. The second topic attempts to explain recent experiments that cells can strongly sense mechanical properties of their surroundings. We consider clusters of specific receptor-ligand bonds that link an animal cell to an extracellular matrix. To understand the mechanical responses of cell adhesions, we develop a stochastic-elasticity model of a periodic array of adhesion clusters between two elastic media subjected to inclined loads, in which stochastic descriptions of molecular bonds and elastic descriptions of interfacial traction are unified in a single modeling framework. The results show that elasticity can play a key role in cell-substrate adhesion by modulating the lifetime of focal adhesions across many orders of magnitude. The predictions of our model provide feasible explanations for a wide range of experimental observations.

 

Prof. 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.He has more than 20 years of research experience with more than 200 publications. He has broad collaborations with scientists in the United States, Europe and China.

Professor Gao is a receipient of numerous academic awards including the ASME Robert Henry Thurston Lecture Award, the ASME Best Achievement Award for Young Investigators in Applied Mechanics, the SES Young Investigator Award, the Humboldt Research Fellowship Award, the NSF Young Investigator Award, the Guggenheim Memorial Fellowship Award, the IBM Faculty Development Award, and the Alcoa Science Award. He is a fellow of the American Society of Mechanical Engineers and fellow of the Institute of Physics (UK).