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Seminar Series - 1996-1997
Solutions of Navier's Equations in Polar Coordinate
System
Development of Laminated Composites
with Nanoreinforced Interfaces
Stress Fields Due to Dislocation Walls in Infinite
Body
Date: Tuesday, April 15, 1997
Time: 3:30 p.m.
Place: 306 Bancroft Hall
Solutions of Navier's Equations in Polar Coordinate
System
J. Guo
Department of Engineering Mechanics
University of Nebraska
Lincoln, NE 68588-0526
M.S. Advisor: Dr. Mao S. Wu
Navier's equations, or equations of equilibrium in terms of displacement,
have been well solved in Cartesian coordinate. As to crack problem, however,
it may be more convenient to express them in polar coordinate, especially
for cracks on the boundary of two materials with different properties.
The current purpose of my research is to express strains and stresses in
terms of r and q with the help of Hooke's law in polar coordinate, and
finally, to find the stress field around such a crack.
Development of Laminated Composites with
Nanoreinforced Interfaces
S. Sergiyenko
Department of Engineering Mechanics
University of Nebraska
Lincoln, NE 68588-0526
M.S. Advisor: Dr. Yuris Dzenis
Delamination is considered to be the most prevalent life-limiting phenomenon
in advanced composites. Interlaminar cracking due to interlaminar stresses
tends to intensify near localities where there is an abrupt change in material
properties or in geometry. In this presentation, methods of experimental
evaluation of delamination and recent approaches to improve delamination
fracture resistance are briefly reviewed. A new method of delamination
suppression by small fiber reinforcement of interfaces is discussed. Laminates
with and without small fiber reinforcement of interfaces are manufactured.
Several types of microfibers are utilized. Mode I, Mode II, and mixed mode
delamination is studied by the Arcan test method. Preliminary results indicate
improvement in delamination fracture resistance.
Stress Fields Due to Dislocation Walls in Infinite
Body
Y. Yu
Department of Engineering Mechanics
University of Nebraska
Lincoln, NE 68588-0526
M.S. Advisor: Dr. Mao S. Wu
Stress fields due to dislocation walls in infinite body are derived.
Finite, infinite and semi-infinite walls of identical edge dislocations
with uniform spacing are considered. The result corresponding to wall with
discreet dislocation distributions are compared to those of the walls with
continuous distribution of infinitesimal dislocations. It is shown that
the long range stresses are exerted by bounded walls. The stress divergence
or its absence is discussed for various wall configurations.
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