Title:
PDE Dynamics of Dislocations
Abstract:
The talk will describe a PDE framework to deal with the dynamics of dislocations leading to plasticity in solids. Dislocations are defects of deformation compatibility/integrability in elastic response. The presented framework will be shown to be capable of representing discrete defect dynamics as well as present a natural setting for asking questions related to macroscopic plasticity arising from the underlying dislocation dynamics.
About the Speaker:
Amit Acharya is a Professor in the Mechanics, Materials, and Computing group in the Department of Civil & Environmental Engineering at Carnegie Mellon University (CMU). He received a PhD degree in Theoretical & Applied Mechanics from the University of Illinois at Urbana-Champaign (UIUC) in 1994. Subsequently, he did post-doctoral work for a year at the University of Pennsylvania and then worked for HKS, Inc. in Providence, RI (now Simulia, Dassualt Systemes) from 1995-1998, spending most of his time as a senior research engineer in the ABAQUS Std Development group. There, he was the lead developer of the *Hysteresis nonlinear viscoelastic material model and the S4, fully-integrated finite strain shell element, that are still in use in the ABAQUS general-purpose FE code. From 1998-2000, he was a Research scientist at the DOE-ASCI funded Center for Simulation of Advanced Rockets at UIUC, before joining CMU in 2000.
His broad research interests are in Continuum Mechanics, Mathematical Materials Science, and Applied Mathematics with special emphasis on theoretical and computational continuum dislocation mechanics and plasticity and its coupling to solid-solid phase transformations, liquid crystal mechanics, damage, coarse-graining of nonlinear time-dependent systems, nonlinear shell theory and fluid-structure interaction including mass transfer.
Faculty Host:Prof. Somnath Ghosh, 203 Latrobe, 410-516-7833, [email protected]
For more information, please contact Jae Hong, 410-516-5033, [email protected]
Title
Dental Enamel- a Multi-Scale Modelling Challenge
Abstract
The tooth is a unique functionally graded composite structure at several levels providing a hard and apparently self-healing enamel external shell bonded to a dynamic and resilient dentin core both supported by a vascular and neural network in the tooth pulp. Tooth enamel is nature’s cell derived method for production of a high elastic modulus (~ 90 GPa), hard, wear, and fatigue resistant structure. This presentation will review the micro and meso structure of human teeth as well as studies on their Hertzian contact and Vickers indentation response. The fracture toughness measurements of enamel and dentin by several groups and the need to further explore mechanical response with enamel location and orientation are discussed. Emphasis well be on the role of decussation on enamel properties and likely mechanisms for enamel self-repair of microcracks when teeth are fatigued
About the Speaker
Van P. Thompson, DDS, PhD, is currently, Professor of Biomaterials, Biomimetics and Biophotonics at King’s College London Dental Institute and was previously Chair, Biomaterials and Biomimetics, NYU College of Dentistry. Known for his work on adhesion and bonded bridges at the University of Maryland he has published many articles and made numerous presentations on dental biomaterials in the U.S. and internationally. His current research areas include dentin caries activity, all-ceramic crown fatigue and fracture, modifications of dentin for bonding, engineering tissue response via scaffold architecture and practice based research (PEARL Network).
Faculty Host: Prof. Somnath Ghosh, 203 Latrobe, 410-516-7833, [email protected]
Khairul Bariah Abd Majid: 410-516-5033 or [email protected]
Title:
MECHANICS OF MULTIFUNCTIONAL MATERIALS & MICROSYSTEMS
Abstract:
The area of multifunctional structures has become prominent in the last few years with a number of definitions and concepts being put forth. The most popular definition is a structure that has the ability to perform multiple tasks through judicious combinations of structural integrity with specific functional properties dictated by the system requirements. Some researchers take a rather pragmatic view of multifunctional design by starting with a conventional composite and incorporating the additional layers with specific functionality. Others try to emulate biological systems, in which jointed frameworks and complex materials impart active functionality at multiple length scales. It is hoped that individual material elements are concurrently participating in distinct, beneficial physical processes thereby delivering truly dramatic improvements in system-level efficiency instead of incremental improvements. Among various visionary contexts for developing a new generation of multifunctional structures, the most revolutionary one appears to be “autonomic” systems that can sense, diagnose and respond to external stimuli with minimal intervention. One prominent example has been “self-healing” polymers and composites that mimic the autonomic repair process of biological systems in response to damage. Ever since this novel concept was demonstrated barely thirteen years ago, the worldwide support has allowed focusing extensive research efforts to the subject of autonomic structures in ever-expanding scope. These efforts have established the concepts of “micro-vascular composites for self-cooling,” “neurological system inspired network for self-sensing and actuation,” “self-sustaining structures with integrated power sources,” etc. Such structures would be able to attain each of specific functionalities, adapt to new situations, and perhaps reconfigure them to respond to a perceived threat or change of environment. Each of the cited examples points the values of a truly autonomic system capable of multiple functions to survive its operating condition and environment for longer periods of time than the traditional structures can endure.
About the Speaker:
Dr. Lee is a Program Manager for Mechanics of Multifunctional Materials & Microsystems at the US AFOSR in Arlington, Va. His primary responsibilities include the establishment of science base for integration of emerging materials and micro-devices into future aerospace systems requiring multi-functionality. Dr. Lee joined AFOSR in 2001, following12 years on the faculty of Dept. of Engineering Science & Mechanics at the Pennsylvania State University. He has presided over a number of multi-disciplinary research initiatives, covering a broad range of topics such as “self-healing materials,” “neurological system-inspired sensory network,” “self-sustaining structures with integrated power sources,” “load-bearing antenna systems,” and “biomolecular autonomic materials.” At Penn State, he taught the engineering mechanics courses and performed the sponsored research in the areas of: nanocomposites, penetration failure mechanics, fatigue behavior, and manufacturing science of composites. Prior to his academic career, he had 10 years’ industrial research experience and 3 years’ government research experience.
Faculty Host:Prof. Somnath Ghosh, 203 Latrobe, 410-516-7833, [email protected]
For more information, please contact Khairul Bariah Abd Majid PhD, 410-516-5033, [email protected]