Analyzed the instabilities associated with an isolated blade
of a hingeless rotor helicopter. The research centered around determination of
the influence of geometrical nonlinearities and of key design parameters on the
stability of the system. A patent was granted for identification of significant
stabilizing parameters. (1970 - 1976)

Participated in official investigation of mast-bumping
phenomenon for AH/UH Army helicopters. (1974)

Developed an analysis and a successful computer program
(FLAIR) used by the major helicopter manufacturers for predicting
aeromechanical stability of bearingless rotor helicopters. (1977)

Participated in the NASA Ames UH helicopter accident
investigation. (1978)

Developed an accurate variable order finite element scheme
for analyzing vibration and response of nonuniform rotating beams with
discontinuities. (1978)

Member of the Technical Advisory Group for the Second
Generation Comprehensive Helicopter Analysis System, a computer software system
under development by the U.S. Army. (1979 - 1986)

Developed a variable-order finite element scheme for
aeroelastic stability analysis of nonuniform rotating blades. This inherently
nonlinear problem requires solution of the equilibrium
deformed shape of the blade under the influence of aerodynamic and inertial
loads prior to the actual stability analysis. (1980)

Developed a new definition of strain in a beam for which
strain and rotation are rigorously uncoupled. The deformation-induced rotations
of the beam reference axis can assume arbitrarily large values, whereas the
strain components are linear in elongations and shears. (1984 - 1986)

Served as project manager, chief analyst, and co-developer
of the General Rotorcraft Aeromechanical Stability Program (GRASP), a hybrid
multi-body/variable-order finite element program. GRASP has the capability of
modeling the complex behavior of bearingless rotor helicopters. GRASP treats a
helicopter as an arbitrary collection of beam elements and rigid bodies
connected together in an arbitrary fashion, allowing large displacements and
rotations, and relative motion between elements. Rotor aerodynamics for the
axial flight and ground contact conditions, including dynamic inflow, are
treated. This powerful program has over 170,000 lines of FORTRAN 77 code. (1980
- 1986)

Developed mixed variational formulation for geometrically
exact behavior of initially curved and twisted, anisotropic beams. (1988)

Participated in developing a mixed finite element method
based on geometrically-exact intrinsic equations for
rigid-body dynamics and elastodynamics of beams which allows for the use of
extremely crude shape functions. The method yields very accurate results for
time marching, two-point boundary value problems in space or time, and
space-time behavior of beams. (1989 - 1994)

Participated in developing a finite element formulation for
optimal control problems based on a weak Hamiltonian form of the necessary
conditions, providing a robust, self-starting method for solving variational
optimization problems with inequality constraints. (1990 - 1996)

Participated in developing theory and computational
algorithms that determine asymptotically correct elastic constants for
anisotropic beams by means of the finite element method. The computer program VABS contains an implementation of
most of these algorithms. (1990 - present)

Participated in developing computational algorithms that
determine asymptotically correct elastic constants for anisotropic plates and
shells. The computer program VAPAS
contains an implementation of most of these algorithms. (1991 - present)

Participated in developing a dynamics/control formulation
for a robust missile guidance algorithm based on a finite element formulation
of weak Hamiltonian (patented). (1993 - 1995)

Participated in developing an *h-p* adaptive finite element scheme for solution of dynamics and
optimal control problems. (1992 - 1998)

Participated in the development of computational algorithms
to transfer data accurately from meshes for computational fluid dynamics to
those for computational structural dynamics. (1994 - 1996)

Participated in development of computational algorithms for
nonlinear aeroservoelasticity of high-aspect-ratio-winged HALE aircraft,
including flying wing configurations, and in parametric studies of such
aircraft. Participated in development of the computer program NATASHA -
Nonlinear Aeroelastic Trim and Stability of HALE Aircraft. (1997 - present)

Participated in development of computational algorithms for
nonlinear structural dynamics and aeroelasticity of wind turbines. (1998 -
2003)

Participated in development of computational algorithms for
nonlinear structural dynamics and aeroelasticity of missiles. (2000 - 2004)

Developed geometrically exact, fully intrinsic equations of
motion and space-time compatibility for twisted and curved anisotropic beams.
These equations have no displacement or rotation variables. (2002 – 2003)

Developed geometrically-exact
composite beam element (GCB) for the Rotorcraft Comprehensive Analysis System
(RCAS). (2004)

Participated in development of geometrically exact, fully
intrinsic equations of motion and space-time compatibility equations for
anisotropic plates. These equations have no displacement or rotation variables.
(2006)

Last Updated 10/6/2008