Brown University --
Joint Solid Mechanics/Materials Seminar Series
Interim Dean College of Engineering University of Rhode Island, Kingston, RI 02881, USA | |
Abstract: An analytical and experimental study has been conducted to investigate the static and dynamic fracture in functionally graded materials (FGMs). Both layered as well as continuously graded materials have been investigated. First, the dynamic fracture in FGMs graded in layers was studied using the technique of dynamic photoelasticity combined with high-speed photography. FGMs suitable for photoelastic studies were prepared using polyester resin and plasticizer. Next, analytical solutions for crack tip stress fields in continuously graded materials were developed for static and dynamic problems. Quasi-static stress fields for a straight as well as a crack inclined to the direction of property gradation in FGMs were obtained through an asymptotic analysis coupled with Westergaard's stress function approach. Asymptotic expansion of the stress field around a crack propagating at constant velocity in FGMs was then developed. The analysis revealed that the crack-tip stress fields retain the inverse square root singularity and only the higher order terms in the expansion are influenced by the material nonhomogeneity.
A technique for preparing continuously graded model FGMs
using polyester resin and cenospheres was also developed.
The physical, elastic and fracture properties of the
prepared FGMs were evaluated as a function of location
to generate the property profiles.
The seminar will also briefly discuss other areas of research currently underway in our dynamic photomechanics laboratory.
Brown University Center for Statistical Sciences Seminar
Center for Health Studies, Group Health Cooperative | |
A Study of Direct Cortical Electrical Interference | |
1st Floor Conference Room *Sponsored by The Charles K. Colver Lectureships Fund |
Abstract: In this talk, I will discuss a hierarchical approach for combining information across multiple images called Template Mixture Modeling. Our work was motivated by a functional brain mapping technique called direct cortical electrical interference (DCEI) that gives binary observations of an underlying "true" region at multiple sites throughout the brain. To model region shapes that may vary widely across individuals, we use mixtures of simple templates (e.g.,circles). These subject-specific templates are treated as random effects, governed by a set of population templates that make up a population region. The numbers of subject-specific and population templates are treated as unknown variables to be estimated from the data, and inference is made using reversible jump Markov chain Monte Carlo. The approach will be illustrated with two examples using DCEI data collected at the Johns Hopkins Medical Institutions on motor and language functions.
* Coffee and donuts will be served.
Brown University Graduate School Dissertation Defense
Brown Mathematics Department Analysis Seminar
Special Scientific Computing Seminar
Abstract: Scientists, engineers and mathematicians have successfully devised numerical techniques for partial differential equations in order to simulate a variety of physical phenomena for many years. These techniques have been adapted, augmented and used in conjunction with a variety of other newly developed ideas in order to address problems in other areas such as the simulation of natural phenomena for the feature film special effects industry. This talk will cover some interesting techniques such the Level Set Method for tracking interfaces and discontinuities, the Ghost Fluid Method for accurate modeling of boundary conditions at these interfaces and discontinuities, and Vorticity Confinement as a method of removing excess numerical dissipation on coarse grids. Examples will include smoke, fire, water and cloth. Emphasis will be given to the synergistic effect that computational physics and visual computing have on each other in the area of numerical algorithm design. Time permitting, we will also discuss some new mesh generation techniques for deformable objects and a new algorithm for simulating rigid bodies.
PDE Seminar
Department of Mathematics Colloquium
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