Surface Stress and Configurational Effects on Dislocations by Prof Anandh Subramaniam

Location and Date: 
Tuesday, June 12, 2018, 4:00 PM, LT 202

The surface is a ubiquitous defect in crystals and others like
dislocations are nearly so, at leas in metals. The effect of surface
stress is accentuated in nanostructures and so can be the effect of the
Poisson's ratio. Hollow metal nanoshells (MNS) are an interesting in that,
there is interplay between the surface stress existing in the inner and
outer surfaces; which can lead to an anomalous lattice expansion in very
thin walled MNS.
The proximity of interfaces gives prominence to
image forces experienced by dislocations. The presence of surface stress
alters the traction-free boundary conditions existing on free-surfaces and
hence is expected to alter the magnitude of the image force. If the extra
half-plane of the edge dislocation is parallel to the surface, the image
force (glide) is not altered due to surface stress; however, the
dislocation experiences a torque. The surface stress breaks the 'climb
image force' symmetry, thus leading to non-equivalence between positive
and negative climb. An equilibrium position exists for the edge
dislocation in the positive 'climb geometry', arising due to a competition
between the interaction of the dislocation stress fields with the surface
stress and the image dislocation.


Anandh Subramaniam did his
B.Tech from IIT Madras, followed by a M.E and Ph.D from
Bangalore. Then he was a scientist in CSIR followed by the position of a
Scientist at Max Planck Institute for Metals Research at
Stuttgart (as a Max Planck Fellow and
as an Alexander von Humboldt
Fellow). After being a faculty in the department of Applied
at IIT Delhi he joined IIT Kanpur in the department of Materials Science
Engineering. Selected awards received by him include: The Shri
Ram Arora International
Award for Materials Science and Engineering
Education (TMS, USA) and Young Research
Award (IUMRS). His areas of
interest are: Physical Materials Science, Nanomaterials,
Quasicrystals, Amorphous Materials, Metastable Materials, Epitaxial
Systems, Defects &
Interfaces in Materials, Symmetry,
Crystallography, Transmission Electron Microscopy, Finite
Method. Using theory, computational theory, computer simulation and
experiments hehas published papers on Metals, Semiconductors and
Insulators (Ceramics). He has authored two video courses and an e-book
('Materials Science and Engineering'), which has a wide global
circulation. He has two NPTEL video courses to his credit.