Page 35 - ASME IMECE 2017 Program

TRACK PLENARY
Track 11: Materials: Genetics To Structures
11-19-1: MATERIALS: GENETICS TO STRUCTURES
PLENARY
Wednesday, November 8, 8:00am–9:45am
Room 4, Tampa Convention Center
Biological Cell-Matrix Interactions in Fibrous Extracellular
Materials
(IMECE2017-73546)
Gurswami Ravichandran
California Institute of Technology
Abstract: Biological cells are complex living systems that can
be viewed as micromachines, which derive many of their
mechanical functions from the molecular motors within the cell.
The force that cells apply to their surrounding extracellular
matrix through focal adhesions control processes such as
growth, adhesion, development and migration. A new experi-
mental approach to quantify three dimensional full-field
displacements and tractions due to cells embedded in a
fibrous matrix is presented. Cells and their surrounding matrix
are imaged in three dimensions using laser scanning confocal
microscopy. Cell-induced matrix displacements are computed
using digital volume correlation. The full-field tractions are
computed directly from the displacement data. The simul-
taneous imaging of the cell and the labeled matrix enables the
study of cell-matrix interactions and the consequences of
matrix remodeling due to cell-induced forces. The three
dimensional traction force microscopy technique is used to
investigate how cells employ physical forces during cell
division, spreading and sensing. In a three-dimensional fibrous
matrix, dividing cells apply tensile force to the matrix through
thin, persistent extensions that in turn direct the orientation and discrete carriers of plasticity will be discussed. Both
location of the daughter cells. During spreading, cells extend
thin protrusions into the matrix and apply forces using these
protrusions. These forces lead to the formation of localized
intercellular bands of tensile deformations. A constitutive
model for a fibrous materiall to simulate deformations induced
by cells is presented. It is shown that cells in a fibrous matrix
induce deformation fields that propagate over a longer range
than predicted by linear elasticity. The model captures
measured cell induced matrix displacements from experiments
and identifies loss of compression stiffness due to micro-
buckling of fibers as an important mechanism for long-range
cell mechanosensing.
Biography: Guruswami (Ravi) Ravichandran is
the John E. Goode, Jr. Professor of Aerospace mentioned.
and Mechanical Engineering and Otis Booth
Leadership Chair of the Division of Engineer-
ing and Applied Science at the California
Institute of Technology. He received his B.E.
(Honors) in Mechanical Engineering from the University of
Madras, Sc.M. in Engineering and Applied Mathematics, and
Ph.D. in Engineering (Solid Mechanics and Structures) from
Brown University. He has held visiting scholar appointments at
Ecole Polytechnique, France (CNRS Senior Scientist), Tokyo
Institute of Technology (Chair in International Cooperation) and
Indian Institute of Science (Aditya Birla Chair). He is a member
of the National Academy of Engineering, International Academy
of Engineering, and European Academy of Sciences and Arts.
He is a Fellow of the American Society of Mechanical
Engineers (ASME), Society for Experimental Mechanics (SEM)
and American Academy of Mechanics (AAM). He received a
Doctor honoris causa from Paul Verlaine University. He was
named Chevalier de l’ordre des Palmes Academiques by the
Republic of France. His awards include A.C. Eringen Medal
from the Society of Engineering Science, Warner T. Koiter
Medal from ASME, Charles Russ Richards Medal from Pi Tau
Sigma and ASME, and William M. Murray Lecture Award from
SEM. His research interests are in mechanics of materials
including deformation, damage and failure, micro/nano
mechanics, wave propagation, composites, active materials,
biomaterials and cell mechanics, and experimental methods.
Track 11: Materials: Genetics To Structures
11-19-1: MATERIALS: GENETICS TO STRUCTURES
PLENARY
Wednesday, November 8, 8:00am- 9:45am
Room 4, Tampa Convention Center
Modeling Mesoscale Heterogeneous Plastic Deformation
(IMECE2017-73547)
Alan Needleman
Texas A&M University
Abstract: Plastic deformation generally occurs by a series of
discrete events, including, for example, glide of dislocations
between obstacles, deformation twinning or the atomic
rearrangements known as shear transformation zones (STZs).
A method for solving plasticity problems with plastic
deformation arising from the evolution of a collection of
dislocation plasticity and STZ plasticity will be considered, but
a main focus will be on STZ plasticity, in particular for metallic
glasses. At each instant, superposition is used to represent the
boundary value problem solution in terms of a collection of
discrete entities, which are given in terms of analytical
solutions for an infinite elastic medium, and an image solution
that enforces the prescribed boundary conditions on the finite
solid of interest. The image problem corresponds to a
standard linear elastic boundary value problem. Constitutive
relations are specified for the kinetics of the dislocation motion
or for the STZ transformation. Solutions to a variety of
boundary value problems will be presented to illustrate the
capabilities and potential of the framework. Needs and
opportunities for extending the framework will also be
Biography: Alan Needleman completed his xxxiii
Ph.D. in Engineering at Harvard University in
1970. He then spent five years in Applied
Mathematics at MIT before moving to Brown
University where he became Florence Pirce
Grant University Professor in 1996. He retired
from Brown in June 2009 and moved to the Materials Science
and Engineering Department at the University of North Texas
(UNT). In January 2015 he left UNT and is now a University