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Eshelby Dislocation and Twisting of Nanowires

In 1953 Eshelby predicted that a cylinder containing a screw dislocation will induce a twist to a cylinder, stabilizing the dislocation in its center.  Such a dislocation is later termed the Eshelby dislocation. Using atomistic and mesoscale simulations, we show that Eshelby dislocations can nucleate in a pristine metal nanowire under torsion, and give rise to strong orientation dependence of nanowire plasticity in torsion.  When Eshelby dislocations nucleate, the plastic twist is homogeneous along the nanowire, in contrast to heterogeneous twist when grain boundaries nucleate.  The Eshelby dislocations can also give rise to pseudoelastic or shape memory effect, depending on the stability of Eshelby dislocations.  The stability of Eshelby dislocation in a metal nanowire against thermal fluctuation is also studied.  The Eshelby dislocation prefers to escape from the nanowire ends but asymmetry exists -- escape from one end is easier than from the other end.


Biosketch: 

Wei Cai obtained his B.S. degree in Optoelectronic Engineering from Huazhong University of Science and Technology, P. R. China in 1995 and his PhD in Nuclear Engineering from MIT in 2001. He was a Lawrence Postdoctoral Fellow at the Lawrence Livermore National Laboratory from 2001 to 2004 before he joined the faculty at the Mechanical Engineering Department at Stanford University.  He received the Presidential Early Career Award for Scientists and Engineers in 2004and the ASEE Beer and Johnston Outstanding New Mechanics Educator Award in 2009.  He serves on the editorial board on Modelling and Simulation in Materials Science and Engineering (MSMSE).  His research interests are in dislocation dynamics, nanoscale deformation and synthesis mechanisms.

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