Page 36 - ASME_AM3DIDETC_2016_Program

Keynote and Plenary Lectures

IDETC/CIE/AM3D

integration of comprehensive multibody codes with the accurate evalua- VIB KEYNOTES
tion of three-dimensional stress fields.
Wednesday, August 24
10:20am–12:00pm
In the simulation of rigid multibody systems (RMS), the core difficulty lies in
Location: 208A
the representation of the kinematics of the system rather than the
simulation of its dynamic behavior. The traditional approach has been to
decompose motion into displacement and rotation, using the rotation
B. Balachandran
tensor to represent the latter. Due to the complexity of manipulating
rotations, which do not form a linear space, the last three decades have
Minta Martin Professor
witnessed the development of many rotation-free formulations.
Department of Mechanical Engineering
As systems with increasingly complex geometries and materials become
prevalent, the finite element method (FEM) has become an integral part of University of Maryland, College Park, MD
the simulation process. Cosserat solids, such as beams, plates, and shells
are the basic structural components in flexible multibody systems (FMS) Nonlinear Oscillations With Noise
and the description of their kinematics calls for both displacement and
Abstract: Nonlinearity influenced dynamics occur in a variety of mechani-
rotation fields in one or two dimensions. Screw theory, first introduced by
cal and structural systems. In many of these system operations, noise is
Ball in 1900, is a fundamental tool in the fields of kinematics and robotics.
often viewed as being undesirable. However, the interplay between noise
Its central finding is that the displacement and rotation fields of a rigid
and nonlinearity in a system can result in significant response changes
body should not be described independently. Yet all textbooks in
that can be beneficial to a system’s performance. In this spirit, the work
multibody systems dynamics represent the motion of rigid bodies using
carried out to further our understanding on the constructive use of noise
independent displacement and rotation fields. The same contradiction is
in a nonlinear system to realize noise-enhanced responses, noise-enabled
found in the formulation of Cosserat solids (beams, plates, and shells) and
stabilization, and noise-assisted response steering will be discussed.
mechanical joints that form FMS.
Representative physical systems that will be considered include coupled
The second part of the talk reviews screw theory and its applications to oscillator arrays at the micro- and macroscale, flexible rotor systems, and
both RMS and FMS. The fundamental quantity of this formalism is the pendulum systems. The findings of these studies are expected to be
motion tensor, which is suitable for the description of both FMS and FEM relevant to a variety of different nonlinear, mechanical, and structural
kinematics, thereby bridging the gap between the two formulations systems. Some thoughts on future directions in the realm of applied
naturally. This assertion hides a fundamental theoretical hurdle. Motion nonlinear dynamics will be presented to close the talk.
does not form a linear space but rather a Lie group and the linear
interpolation process inherent to the FEM does not respect Lie group
properties. While rooted in a new kinematic description of FMS, the
Biography: Dr. Balachandran received his B. Tech (naval architecture) from
proposed motion formalism results in a novel Eulerian formulation of
the Indian Institute of Technology, Madras, India, MS (aerospace engineer-
dynamics. Theoretical advantages follow: the equations of motion are cast
ing) from Virginia Tech, Blacksburg, VA and PhD (engineering mechanics)
in a flux preserving form and the preservation of invariants such as energy
from Virginia Tech. Currently, he is a Minta Martin Professor of Engineering
and momentum is underlined. Numerical advantages include robust time
at the University of Maryland, where he has been since 1993. His research
integration schemes, exact preservation of invariants, and new shape
interests include nonlinear phenomena, dynamics and vibrations, and
functions that will improve finite element performance dramatically.
control. The publications that he has authored/co-authored include nearly
85 journal publications, a Wiley textbook entitled Applied Nonlinear
Dynamics: Analytical, Computational, and Experimental Methods (1995,
Biography: Dr. Bauchau is the Igor Sikorsky Professor of Rotorcraft at the 2006), a Thomson/Cengage textbook entitled Vibrations (2004, 2009),
Department of Aerospace Engineering of the University of Maryland, and a co-edited Springer book entitled Delay Differential Equations:
College Park. His fields of expertise include finite element methods for Recent Advances and New Directions (2009). He holds four U.S. patents
structural and multibody dynamics, rotorcraft comprehensive analysis, and and one Japan patent, three related to fiber optic sensors and two related
experimental mechanics and dynamics. He is a Fellow of the American to atomic force microscopy. He serves on the editorial boards of the
Society of Mechanical Engineers and the American Helicopter Society, International Journal of Dynamics and Control and Acta Mechanica Sinica,
and a senior member of the American Institute of Aeronautics and is a contributing editor of the International Journal of Non-Linear Mechan-
Astronautics. He has authored a book entitled Flexible Multibody ics, and serves as an associate editor of Nonlinear Theory and its
Dynamics, which has won the 2012 Textbook Excellence Award from the Applications, IEICE. He became the editor of the ASME Journal of
Text and Academic Authors Association. Computational and Nonlinear Dynamics in January 2016. He is a Fellow of
ASME and AIAA, a senior member of IEEE, and a member of ASA, AAM,
and SPIE.

36