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A new superposition framework for di...

O'Day, Michael P.

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A new superposition framework for discrete dislocation plasticity: Methodology and application to inhomogeneous boundary value problems.

Record Type:	Electronic resources : Monograph/item
Title/Author:	A new superposition framework for discrete dislocation plasticity: Methodology and application to inhomogeneous boundary value problems./
Author:	O'Day, Michael P.
Description:	164 p.
Notes:	Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2667.
Contained By:	Dissertation Abstracts International66-05B.
Subject:	Applied Mechanics. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=3174654
ISBN:	0542128144

A new superposition framework for discrete dislocation plasticity: Methodology and application to inhomogeneous boundary value problems.
O'Day, Michael P.

A new superposition framework for discrete dislocation plasticity: Methodology and application to inhomogeneous boundary value problems. - 164 p.

Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2667.

Thesis (Ph.D.)--Brown University, 2005.

We develop a new formulation of discrete dislocation (DD) plasticity to provide a robust framework for efficiently solving elastically inhomogeneous boundary value problems. The DD methodology is truly a mechanism-based plasticity theory; flow arises directly from the motion of large numbers of dislocations. The method is well-suited for modelling microscale deformation in metals; geometrically-necessary dislocations and size-dependent plasticity emerge naturally from this framework. However, the DD literature has largely focused on elastically homogeneous systems, due to features of the standard formulation that become cumbersome for inhomogeneous systems. To address this limitation and allow a broader application of the DD method, a new formulation is proposed. Once verified, we apply the new methodology to the quantitative analysis of: (i) mixed mode micro-crack growth along a metal/ceramic bimaterial interface, and (ii) crack nucleation during thin film micro-indentation; interfaces are modeled with cohesive zones so that crack growth, or nucleation, is an outcome of the model solution. These problems illustrate how interface properties (e.g. peak strength and intrinsic work of fracture) influence separation in the presence of microscale plastic deformation. Together, the two problems represent distinctly different fracture mechanisms. The growth of a pre-existing crack is an energy driven process, where brittle fracture is occurs when the applied stress intensity factor reaches a critical value determined by the surface energy and background plasticity. Conversely, nucleation is a stress driven mechanism where the work of fracture is often of secondary importance. We quantify the interplay between various material and interface parameters, their effect on microstructural deformation and influence on macroscopically measurable quantities. In both cases, comparison to classical continuum and size-dependent (e.g. strain gradient) plasticity theories are made; the former providing crucial insight into regimes where small-scale effects are important and demand treatment with a size-dependent plasticity theory.

ISBN: 0542128144Subjects--Topical Terms:

1018410
Applied Mechanics.

A new superposition framework for discrete dislocation plasticity: Methodology and application to inhomogeneous boundary value problems.
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245 1 2 $a A new superposition framework for discrete dislocation plasticity: Methodology and application to inhomogeneous boundary value problems.
300 $a 164 p.
500 $a Source: Dissertation Abstracts International, Volume: 66-05, Section: B, page: 2667.
500 $a Adviser: William A. Curtin.
502 $a Thesis (Ph.D.)--Brown University, 2005.
520 $a We develop a new formulation of discrete dislocation (DD) plasticity to provide a robust framework for efficiently solving elastically inhomogeneous boundary value problems. The DD methodology is truly a mechanism-based plasticity theory; flow arises directly from the motion of large numbers of dislocations. The method is well-suited for modelling microscale deformation in metals; geometrically-necessary dislocations and size-dependent plasticity emerge naturally from this framework. However, the DD literature has largely focused on elastically homogeneous systems, due to features of the standard formulation that become cumbersome for inhomogeneous systems. To address this limitation and allow a broader application of the DD method, a new formulation is proposed. Once verified, we apply the new methodology to the quantitative analysis of: (i) mixed mode micro-crack growth along a metal/ceramic bimaterial interface, and (ii) crack nucleation during thin film micro-indentation; interfaces are modeled with cohesive zones so that crack growth, or nucleation, is an outcome of the model solution. These problems illustrate how interface properties (e.g. peak strength and intrinsic work of fracture) influence separation in the presence of microscale plastic deformation. Together, the two problems represent distinctly different fracture mechanisms. The growth of a pre-existing crack is an energy driven process, where brittle fracture is occurs when the applied stress intensity factor reaches a critical value determined by the surface energy and background plasticity. Conversely, nucleation is a stress driven mechanism where the work of fracture is often of secondary importance. We quantify the interplay between various material and interface parameters, their effect on microstructural deformation and influence on macroscopically measurable quantities. In both cases, comparison to classical continuum and size-dependent (e.g. strain gradient) plasticity theories are made; the former providing crucial insight into regimes where small-scale effects are important and demand treatment with a size-dependent plasticity theory.
590 $a School code: 0024.
650 4 $a Applied Mechanics. $3 1018410
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710 2 0 $a Brown University. $3 766761
773 0 $t Dissertation Abstracts International $g 66-05B.
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791 $a Ph.D.
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