Mohammed Zikry - Academia.edu (original) (raw)

Papers by Mohammed Zikry

Research paper thumbnail of Demonstration of failure identification methodology incorporating sensor degradation

Proceedings of SPIE, Jul 29, 2004

... Pearson, Kara Peters, Mohammed Zikry. Abstract. The long-term goal of this project is the dev... more ... Pearson, Kara Peters, Mohammed Zikry. Abstract. The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling ...

Research paper thumbnail of The onset of spallation in nanocrystalline copper: An atomic scale study

Bulletin of the American Physical Society, Jun 30, 2009

Research paper thumbnail of Tunneling Effects and Electrical Conductivity of CNT Polymer Composites

MRS Proceedings, 2011

ABSTRACTA three-dimensional (3D) carbon nanotube (CNT) network computational model was developed ... more ABSTRACTA three-dimensional (3D) carbon nanotube (CNT) network computational model was developed to investigate the electrical conductivity and current flow in polymer composites with randomly dispersed CNTs. A search algorithm was developed to determine conductive paths for 3D CNT arrangements and to account for electron tunneling effects. Tunneled currents were obtained as a function of tunneling distance and matrix material. Several possible CNT conductive paths were obtained and finite-element representative volume elements (RVEs) were then used to predict current densities in different CNT arrangements. The predictions indicate that random CNT arrangements can be optimized for current transport.

Research paper thumbnail of Radiation and cladding modes as independent measurements of Bragg grating sensor integrity

Proceedings of SPIE, May 16, 2005

ABSTRACT

Research paper thumbnail of Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors

Proceedings of SPIE, Apr 11, 2013

In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the ... more In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the adhesive layer of a single composite lap joint subjected to harmonic excitation after fatigue loading. After a fully-reversed cyclic fatigue loading is applied to the composite lap joint, the full spectral response of the sensor is interrogated in reflection at 100 kHz during two states: with and without an added harmonic excitation. The dynamic response of the FBG sensor indicates strong nonlinearities as damage progresses. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. Pulse-phase thermography indicates a progression in defect size at the adhesive layer that strongly suggests non-uniform loading of the FBG sensor.

Research paper thumbnail of Optimization of fiber Bragg sensor configurations for in situ failure identification in woven composites throughout impact

Proceedings of SPIE, Apr 6, 2007

In this study, the development and optimization of embedded fiber Bragg grating (FBG) sensor netw... more In this study, the development and optimization of embedded fiber Bragg grating (FBG) sensor networks within composite materials was investigated. Various densities of optical fibers were embedded within composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Embedded fibers were interrogated with light to determine the degree to which light could pass through them for each density and arrangement. Cross sectional optical micrographs of the specimens were used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Currently FBG sensors are being calibrated and prepared for embedment in specifically chosen configurations within the composite. They will be serially multiplexed together to create a single fiber sensing network capable of monitoring damage over a large area. Real time strain information will be gathered as future embedded laminates are subjected to impact events, and the resulting data will be used to better monitor and predict damage in the composite system.

Research paper thumbnail of High-speed full-spectrum fiber Bragg gratings interrogator system and testing

Proceedings of SPIE, May 15, 2011

ABSTRACT

Research paper thumbnail of High-speed full-spectrum interrogation of fiber Bragg gratings for composite impact sensing

Proceedings of SPIE, Mar 25, 2010

This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (F... more This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (FBG's). The new system highlights a method that allows a tradeoff between the full spectrum capture rate and the wavelength range and/or the spectral resolution of the technique. Rapid capture of the entire reflection spectrum at high interrogation rates shows important features that are missed

Research paper thumbnail of In situ failure identification in woven composites throughout impact using fiber Bragg grating sensors

Smart Structures and Materials 2006: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, Mar 16, 2006

Research paper thumbnail of Microwave Excitation of Crystalline Energetic Composites

Research paper thumbnail of Reliable Local Strain Characterization on Si/SiGe Structures in Biaxial Tension

Research paper thumbnail of Computational Modeling and Design of Adaptive Thin-Film Composite Coatings

MRS Proceedings, 2006

The tailoring of thin film coatings comprised of high strength constituents, such as diamond like... more The tailoring of thin film coatings comprised of high strength constituents, such as diamond like carbon and partially stabilized zirconia and ductile constituents, such as gold and molybdenum is investigated by new microstructurally-based finite-element techniques for applications related to the wear, durability, and performance of these coatings over a broad range of temperatures and loading conditions. The effects of contact transfer films, grain-shape sizes and distributions, grain-boundary structure and sliding, texture, and strength are used to determine the optimal thin film coating compositions. Comparisons are made with experimental measurements and observations, and guidelines for optimal thin film composite coatings are proposed.

Research paper thumbnail of Inelastic microstructural failure mechanisms in crystalline materials with high angle grain boundaries

Journal of The Mechanics and Physics of Solids, Nov 1, 1996

Research paper thumbnail of Dislocation-density evolution and pileups in bicrystalline systems

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Apr 1, 2023

Research paper thumbnail of Large-scale crystal plasticity computations of microstructural failure modes

Computing Systems in Engineering, Jun 1, 1995

ABSTRACT

Research paper thumbnail of The Challenges of Modeling Defect Behavior and Plasticity across Spatial and Temporal Scales: A Case Study of Metal Bilayer Impact

Research paper thumbnail of Local Strain Measurement with Convergent Beam Electron Diffraction and Finite Element Simulation

Meeting abstracts, 2006

not Available.

Research paper thumbnail of Local Strain Characterization on Strained-Si/SiGe Heterostructures with Convergent Beam Electron Diffraction and Finite Element Simulation

ECS transactions, Dec 21, 2019

We introduce a novel and reliable method to quantify local strain variation in microelectronic de... more We introduce a novel and reliable method to quantify local strain variation in microelectronic device structures based on convergent beam electron diffraction (CBED) and finite element (FE) calculation. The match of the finite element calculation results with the experimental data not only validated the parameters used for the finite element simulations, but also gives us insights into the origin of high order Laue zone (HOLZ) line splitting in a lattice-mismatched heterostructure. The 2D and 3D calculations showed that the residual strain measured from clean and sharp CBED patterns deviate from the initial strain. The effect of a SiO2 layer on the strain in a TEM sample was also investigated by FE simulation and we found that a SiO2 layer can suppress some of the elastic deformation making it possible to obtain clean and sharp CBED patterns. The here proposed novel method uses the elastic deformation to determine the initial strain in microelectronic devices structures by combining FE simulations and CBED patterns.

Research paper thumbnail of The Mechanics and Stability of Gold Nanoparticle-Oligo-Ligand-DNA Systems

MRS Proceedings, 2013

ABSTRACTSystems in which DNA is adsorbed onto gold nanoparticles have the potential for applicati... more ABSTRACTSystems in which DNA is adsorbed onto gold nanoparticles have the potential for applications in gene regulation therapies, drug delivery, sensing, and DNA scaffolding. However, the mechanical stability of gold nanoparticles (AuNPs) and interfacial behavior between the gold nanoparticles and thiol ligands are not well understood or quantified. The stability of DNA-AuNP) systems is, therefore, examined using a large-scale specialized finite-element approach with a dislocation-density based crystalline plasticity framework to model the AuNPs and an elastic description to model thiol ligands, DNA, and the ionic solution. For compressive loading conditions, the system exhibited morphological instabilities in the nanoparticles, as well as high stress and dislocation-density gradients at the thiol-nanoparticle attachment sites, which can affect system stability and attachment strength.

Research paper thumbnail of High strain-rate localization and failure of crystalline materials

Mechanics of Materials, Dec 1, 1990

ABSTRACT A theoretical and a computational model are introduced to study the micromechanical high... more ABSTRACT A theoretical and a computational model are introduced to study the micromechanical high strain-rate failure mechanisms of shear-strain localization in monocrystalline fcc structures. A theoretical framework for a constitutive model for the dynamic finite plastic deformation of rate-dependent single fcc crystals is developed. The micromechanics of plastic flow are based on a high strain-rate single crystal plasticity model and a visco-plastic power law. The single crystal is subjected to far-field dynamic tensile strain-rates ranging from 100/s to 2000/s. An explicit finite-element model is introduced for the integration of the numerically stiff visco-plastic constitutive relations. The total deformation rate tensor is obtained by the central difference explicit integration of the equations of motion. The plastic deformation rate tensor is obtained from the solution of an initial-value nonlinear problem for the resolved shear stresses. In time intervals when the differential equations for the resolved shear stresses are not numerically stiff, the initial-value problem is integrated by the explicit fifth-order Runge-Kutta adaptive time-step method. In time domains where the propagated error grows and the time-step must be restricted due to stability requirements, which is an indication of numerical stiffness, the initial-value problem is integrated by an ALPHA-stable method. To correctly differentiate time-step reductions due to stability, from time-step reductions due to accuracy, a stiffness ratio is defined. The present analysis corroborates experimental observations that high strain-rate shear-strain localization, in rate-dependent crystals, is a function of thermal and geometrical softening, overall strain-rates, strain hardening, strain-rate hardening, and strain-rate sensitivity.

Research paper thumbnail of Demonstration of failure identification methodology incorporating sensor degradation

Proceedings of SPIE, Jul 29, 2004

... Pearson, Kara Peters, Mohammed Zikry. Abstract. The long-term goal of this project is the dev... more ... Pearson, Kara Peters, Mohammed Zikry. Abstract. The long-term goal of this project is the development of embedded, optimally distributed, multi-scale sensing methodologies that can be integrated into material systems for failure identification in structural systems. The coupling ...

Research paper thumbnail of The onset of spallation in nanocrystalline copper: An atomic scale study

Bulletin of the American Physical Society, Jun 30, 2009

Research paper thumbnail of Tunneling Effects and Electrical Conductivity of CNT Polymer Composites

MRS Proceedings, 2011

ABSTRACTA three-dimensional (3D) carbon nanotube (CNT) network computational model was developed ... more ABSTRACTA three-dimensional (3D) carbon nanotube (CNT) network computational model was developed to investigate the electrical conductivity and current flow in polymer composites with randomly dispersed CNTs. A search algorithm was developed to determine conductive paths for 3D CNT arrangements and to account for electron tunneling effects. Tunneled currents were obtained as a function of tunneling distance and matrix material. Several possible CNT conductive paths were obtained and finite-element representative volume elements (RVEs) were then used to predict current densities in different CNT arrangements. The predictions indicate that random CNT arrangements can be optimized for current transport.

Research paper thumbnail of Radiation and cladding modes as independent measurements of Bragg grating sensor integrity

Proceedings of SPIE, May 16, 2005

ABSTRACT

Research paper thumbnail of Characterization of fatigue damage in adhesively bonded lap joints through dynamic, full-spectral interrogation of fiber Bragg grating sensors

Proceedings of SPIE, Apr 11, 2013

In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the ... more In this study we evaluate the measurements of a fiber Bragg grating (FBG) sensor embedded at the adhesive layer of a single composite lap joint subjected to harmonic excitation after fatigue loading. After a fully-reversed cyclic fatigue loading is applied to the composite lap joint, the full spectral response of the sensor is interrogated in reflection at 100 kHz during two states: with and without an added harmonic excitation. The dynamic response of the FBG sensor indicates strong nonlinearities as damage progresses. The short-time Fourier transform (STFT) is computed for the extracted peak wavelength information to reveal time-dependent frequencies and amplitudes of the dynamic FBG sensor response. Pulse-phase thermography indicates a progression in defect size at the adhesive layer that strongly suggests non-uniform loading of the FBG sensor.

Research paper thumbnail of Optimization of fiber Bragg sensor configurations for in situ failure identification in woven composites throughout impact

Proceedings of SPIE, Apr 6, 2007

In this study, the development and optimization of embedded fiber Bragg grating (FBG) sensor netw... more In this study, the development and optimization of embedded fiber Bragg grating (FBG) sensor networks within composite materials was investigated. Various densities of optical fibers were embedded within composite laminates, and low-velocity impact damage responses were evaluated to determine the effects on the mechanical behavior of the laminates. The woven composites were subjected to multiple strikes at 2 m/s until perforation occurred, and the impactor position and acceleration were monitored throughout each event. From these measurements, we obtained dissipated energies and contact forces for specimens with and without embedded optical fibers. Embedded fibers were interrogated with light to determine the degree to which light could pass through them for each density and arrangement. Cross sectional optical micrographs of the specimens were used to determine the local effects of the embedded fibers on neighboring fibers and the surrounding matrix material, both before and after impact events. Currently FBG sensors are being calibrated and prepared for embedment in specifically chosen configurations within the composite. They will be serially multiplexed together to create a single fiber sensing network capable of monitoring damage over a large area. Real time strain information will be gathered as future embedded laminates are subjected to impact events, and the resulting data will be used to better monitor and predict damage in the composite system.

Research paper thumbnail of High-speed full-spectrum fiber Bragg gratings interrogator system and testing

Proceedings of SPIE, May 15, 2011

ABSTRACT

Research paper thumbnail of High-speed full-spectrum interrogation of fiber Bragg gratings for composite impact sensing

Proceedings of SPIE, Mar 25, 2010

This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (F... more This paper presents a means for the high repetition rate interrogation of fiber Bragg gratings (FBG's). The new system highlights a method that allows a tradeoff between the full spectrum capture rate and the wavelength range and/or the spectral resolution of the technique. Rapid capture of the entire reflection spectrum at high interrogation rates shows important features that are missed

Research paper thumbnail of In situ failure identification in woven composites throughout impact using fiber Bragg grating sensors

Smart Structures and Materials 2006: Sensors and Smart Structures Technologies for Civil, Mechanical, and Aerospace Systems, Mar 16, 2006

Research paper thumbnail of Microwave Excitation of Crystalline Energetic Composites

Research paper thumbnail of Reliable Local Strain Characterization on Si/SiGe Structures in Biaxial Tension

Research paper thumbnail of Computational Modeling and Design of Adaptive Thin-Film Composite Coatings

MRS Proceedings, 2006

The tailoring of thin film coatings comprised of high strength constituents, such as diamond like... more The tailoring of thin film coatings comprised of high strength constituents, such as diamond like carbon and partially stabilized zirconia and ductile constituents, such as gold and molybdenum is investigated by new microstructurally-based finite-element techniques for applications related to the wear, durability, and performance of these coatings over a broad range of temperatures and loading conditions. The effects of contact transfer films, grain-shape sizes and distributions, grain-boundary structure and sliding, texture, and strength are used to determine the optimal thin film coating compositions. Comparisons are made with experimental measurements and observations, and guidelines for optimal thin film composite coatings are proposed.

Research paper thumbnail of Inelastic microstructural failure mechanisms in crystalline materials with high angle grain boundaries

Journal of The Mechanics and Physics of Solids, Nov 1, 1996

Research paper thumbnail of Dislocation-density evolution and pileups in bicrystalline systems

Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, Apr 1, 2023

Research paper thumbnail of Large-scale crystal plasticity computations of microstructural failure modes

Computing Systems in Engineering, Jun 1, 1995

ABSTRACT

Research paper thumbnail of The Challenges of Modeling Defect Behavior and Plasticity across Spatial and Temporal Scales: A Case Study of Metal Bilayer Impact

Research paper thumbnail of Local Strain Measurement with Convergent Beam Electron Diffraction and Finite Element Simulation

Meeting abstracts, 2006

not Available.

Research paper thumbnail of Local Strain Characterization on Strained-Si/SiGe Heterostructures with Convergent Beam Electron Diffraction and Finite Element Simulation

ECS transactions, Dec 21, 2019

We introduce a novel and reliable method to quantify local strain variation in microelectronic de... more We introduce a novel and reliable method to quantify local strain variation in microelectronic device structures based on convergent beam electron diffraction (CBED) and finite element (FE) calculation. The match of the finite element calculation results with the experimental data not only validated the parameters used for the finite element simulations, but also gives us insights into the origin of high order Laue zone (HOLZ) line splitting in a lattice-mismatched heterostructure. The 2D and 3D calculations showed that the residual strain measured from clean and sharp CBED patterns deviate from the initial strain. The effect of a SiO2 layer on the strain in a TEM sample was also investigated by FE simulation and we found that a SiO2 layer can suppress some of the elastic deformation making it possible to obtain clean and sharp CBED patterns. The here proposed novel method uses the elastic deformation to determine the initial strain in microelectronic devices structures by combining FE simulations and CBED patterns.

Research paper thumbnail of The Mechanics and Stability of Gold Nanoparticle-Oligo-Ligand-DNA Systems

MRS Proceedings, 2013

ABSTRACTSystems in which DNA is adsorbed onto gold nanoparticles have the potential for applicati... more ABSTRACTSystems in which DNA is adsorbed onto gold nanoparticles have the potential for applications in gene regulation therapies, drug delivery, sensing, and DNA scaffolding. However, the mechanical stability of gold nanoparticles (AuNPs) and interfacial behavior between the gold nanoparticles and thiol ligands are not well understood or quantified. The stability of DNA-AuNP) systems is, therefore, examined using a large-scale specialized finite-element approach with a dislocation-density based crystalline plasticity framework to model the AuNPs and an elastic description to model thiol ligands, DNA, and the ionic solution. For compressive loading conditions, the system exhibited morphological instabilities in the nanoparticles, as well as high stress and dislocation-density gradients at the thiol-nanoparticle attachment sites, which can affect system stability and attachment strength.

Research paper thumbnail of High strain-rate localization and failure of crystalline materials

Mechanics of Materials, Dec 1, 1990

ABSTRACT A theoretical and a computational model are introduced to study the micromechanical high... more ABSTRACT A theoretical and a computational model are introduced to study the micromechanical high strain-rate failure mechanisms of shear-strain localization in monocrystalline fcc structures. A theoretical framework for a constitutive model for the dynamic finite plastic deformation of rate-dependent single fcc crystals is developed. The micromechanics of plastic flow are based on a high strain-rate single crystal plasticity model and a visco-plastic power law. The single crystal is subjected to far-field dynamic tensile strain-rates ranging from 100/s to 2000/s. An explicit finite-element model is introduced for the integration of the numerically stiff visco-plastic constitutive relations. The total deformation rate tensor is obtained by the central difference explicit integration of the equations of motion. The plastic deformation rate tensor is obtained from the solution of an initial-value nonlinear problem for the resolved shear stresses. In time intervals when the differential equations for the resolved shear stresses are not numerically stiff, the initial-value problem is integrated by the explicit fifth-order Runge-Kutta adaptive time-step method. In time domains where the propagated error grows and the time-step must be restricted due to stability requirements, which is an indication of numerical stiffness, the initial-value problem is integrated by an ALPHA-stable method. To correctly differentiate time-step reductions due to stability, from time-step reductions due to accuracy, a stiffness ratio is defined. The present analysis corroborates experimental observations that high strain-rate shear-strain localization, in rate-dependent crystals, is a function of thermal and geometrical softening, overall strain-rates, strain hardening, strain-rate hardening, and strain-rate sensitivity.