You searched for +publisher:"Georgia Tech" +contributor:("McDowell, David L.").
Showing records 1 – 30 of
67 total matches.
◁ [1] [2] [3] ▶
Georgia Tech
1.
Fernandez-Zelaia, Patxi.
Thermomechanical fatigue crack formation in nickel-base superalloys at notches.
Degree: MS, Mechanical Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/48991 
► Hot sections of gas engine turbines require specialized materials to withstand extreme conditions present during engine operation. Nickel-base superalloys are typically used as blades and…
(more)
▼ Hot sections of gas engine turbines require specialized materials to withstand extreme conditions present during engine operation. Nickel-base superalloys are typically used as blades and disks in the high pressure turbine section because they possess excellent fatigue strength, creep strength and corrosion resistance at elevated temperatures. Components undergo thermomechanical fatigue conditions as a result of transient engine operation. Sharp geometric features, such as cooling holes in blades or fir-tree connections in disks, act as local stress raisers. The material surrounding these features are potential sites of localized inelastic deformation and crack formation. To reduce customer costs associated with unnecessary overhauls or engine down-time, gas turbine manufacturers require accurate prediction methods to determine component endurances. The influence of stress concentration severity on thermomechanical fatigue crack formation is of particular importance as cracks often initiate in these hot spots. Circumferentially notched specimens were utilized to perform thermomechanical fatigue experiments on blade material CM247LC DS and disk material PM IN100. A parametric study on CM247LC DS was performed utilizing four notched specimens. Experimental results were coupled with finite element simulations utilizing continuum based constitutive models. The effects of applied boundary conditions on crack initiation life was studied in both alloys by performing experiments under remotely applied force and displacement boundary conditions. Finite element results were utilized to develop a life prediction method for notched components under thermomechanical fatigue conditions.
Advisors/Committee Members: Neu, Richard W. (advisor), McDowell, David L. (committee member), Antolovich, Stephen D. (committee member).
Subjects/Keywords: Crack formation; Thermomechanical fatigue; Fatigue; Thermomechanical; Notches; Notch; Superalloys; Nickel-base; Alloys; Heat resistant alloys Thermomechanical properties; Heat resistant alloys Fatigue; Heat resistant alloys; Heat resistant materials; Metals Thermomechanical properties
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Fernandez-Zelaia, P. (2012). Thermomechanical fatigue crack formation in nickel-base superalloys at notches. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/48991
Chicago Manual of Style (16th Edition):
Fernandez-Zelaia, Patxi. “Thermomechanical fatigue crack formation in nickel-base superalloys at notches.” 2012. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/48991.
MLA Handbook (7th Edition):
Fernandez-Zelaia, Patxi. “Thermomechanical fatigue crack formation in nickel-base superalloys at notches.” 2012. Web. 17 Feb 2019.
Vancouver:
Fernandez-Zelaia P. Thermomechanical fatigue crack formation in nickel-base superalloys at notches. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/48991.
Council of Science Editors:
Fernandez-Zelaia P. Thermomechanical fatigue crack formation in nickel-base superalloys at notches. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/48991
Georgia Tech
2.
Kern, Paul Calvin.
Improvements to the computational pipeline in crystal plasticity estimates of high cycle fatigue of microstructures.
Degree: MS, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/55070
► The objective of this work is to provide various improvements to the modeling and uncertainty quantification of fatigue lives of materials as understood via simulation…
(more)
▼ The objective of this work is to provide various improvements to the modeling and uncertainty quantification of fatigue lives of materials as understood via simulation of crystal plasticity models applied to synthetically reconstructed microstructures.
A computational framework has been developed to automate standardized analysis of crystal plasticity models in the high cycle fatigue regime. This framework incorporates synthetic microstructure generation, simulation preparation, execution and post-processing to analysis statistical distributions related to fatigue properties. Additionally, an improved crack nucleation and propagation approach has been applied to Al 7075-T6 to improve predictive capabilities of the crystal plasticity model for fatigue in various loading regimes. Finally, sensitivities of fatigue response to simulation and synthetic microstructure properties have been explored to provide future guidance for the study of fatigue quantification based on crystal plasticity models.
Advisors/Committee Members: McDowell, David L. (advisor), Capolungo, Laurent (committee member), Neu, Richard W. (committee member).
Subjects/Keywords: Fatigue; Extreme value; Crystal plasticity; Crack; Model; Aluminum
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Kern, P. C. (2016). Improvements to the computational pipeline in crystal plasticity estimates of high cycle fatigue of microstructures. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55070
Chicago Manual of Style (16th Edition):
Kern, Paul Calvin. “Improvements to the computational pipeline in crystal plasticity estimates of high cycle fatigue of microstructures.” 2016. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/55070.
MLA Handbook (7th Edition):
Kern, Paul Calvin. “Improvements to the computational pipeline in crystal plasticity estimates of high cycle fatigue of microstructures.” 2016. Web. 17 Feb 2019.
Vancouver:
Kern PC. Improvements to the computational pipeline in crystal plasticity estimates of high cycle fatigue of microstructures. [Internet] [Masters thesis]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/55070.
Council of Science Editors:
Kern PC. Improvements to the computational pipeline in crystal plasticity estimates of high cycle fatigue of microstructures. [Masters Thesis]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/55070
Georgia Tech
3.
Hennessey, Conor Daniel.
Modeling microstructurally small crack growth in Al 7075-T6.
Degree: MS, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53947
► Fatigue of metals is a problem that affects almost all sectors of industry, from energy to transportation, and failures to account for fatigue or incorrect…
(more)
▼ Fatigue of metals is a problem that affects almost all sectors of industry, from energy to transportation, and failures to account for fatigue or incorrect estimations of service life have cost many lives. To mitigate such fatigue failures, engineers must be able to reliably predict the fatigue life of components under service conditions. Great progress has been made in this regard in the past 40 years; however one aspect of fatigue that is still being actively researched is the behavior of microstructurally small cracks (MSCs), which can diverge significantly from that of long cracks. The portion of life spent nucleating and growing a MSC over the first few grains/phases can consume over 90% of the total fatigue life under High Cycle Fatigue (HCF) conditions and is the primary source of the scatter in fatigue lives. Therefore, the development of robust fatigue design methodologies requires that the MSC regime of crack growth can be adequately modeled. The growth of microstructurally small cracks is dominated by influence of the local heterogeneity of the microstructure and is a highly complex process. In order to successfully model the growth of these microstructurally small cracks (MSCs), two computational frameworks are necessary. First, the local behavior of the material must be modeled, necessitating a constitutive relation with resolution on the scale of grain size. Second, a physically based model for the nucleation and growth of microstructurally small fatigue cracks is needed. The overall objective of this thesis is best summarized as the introduction these two computational frameworks, a crystal plasticity constitutive model and fatigue model, specifically for aluminum alloy 7075-T6, a high-strength, low density, precipitation hardened alloy used extensively in aerospace applications. Results are presented from simulations conducted to study the predicted crack growth under a variety of loading conditions and applied strain ratios, including uniaxial tension-compression and simple shear at a range of applied strain amplitudes. Results from the model are compared to experimental results obtained by other researchers under similar loading conditions. A modified fatigue crack growth algorithm that captures the early transition to Stage II growth in this alloy will also be presented.
Advisors/Committee Members: McDowell, David L. (advisor), Neu, Richard (committee member), Xia, Shuman (committee member).
Subjects/Keywords: Fatigue; Microstructurally small cracks; 7075; Crystal plasticity
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hennessey, C. D. (2015). Modeling microstructurally small crack growth in Al 7075-T6. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53947
Chicago Manual of Style (16th Edition):
Hennessey, Conor Daniel. “Modeling microstructurally small crack growth in Al 7075-T6.” 2015. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/53947.
MLA Handbook (7th Edition):
Hennessey, Conor Daniel. “Modeling microstructurally small crack growth in Al 7075-T6.” 2015. Web. 17 Feb 2019.
Vancouver:
Hennessey CD. Modeling microstructurally small crack growth in Al 7075-T6. [Internet] [Masters thesis]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/53947.
Council of Science Editors:
Hennessey CD. Modeling microstructurally small crack growth in Al 7075-T6. [Masters Thesis]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53947
Georgia Tech
4.
Clark, Brian.
Microstructure-sensitive fatigue modeling of medical-grade fine wire.
Degree: MS, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/56362
► This work presents a model to assess the microstructure-sensitive high-cycle fatigue (HCF) performance of thin MP35N alloy wires used as conductors in cardiac leads. The…
(more)
▼ This work presents a model to assess the microstructure-sensitive high-cycle fatigue (HCF) performance of thin MP35N alloy wires used as conductors in cardiac leads. The major components of this model consist of a microstructure generator which constructs a statistically representative microstructure, a crystal plasticity finite-element analysis to determine the local response behavior of the microstructure, and a postscript employing fatigue indicating parameters (FIPs) to assess the fatigue crack incubation potency at fatigue hotspots. The crystal structure of the MP35N alloy, which contains major elements (wt %) 35Ni-35Co-20Cr-10Mo, is modeled as single-phase, face-centered cubic material, and the constitutive behavior is calibrated based on monotonic tensile and cyclic ratcheting stress-strain response data. Non-metallic inclusions (NMIs) have been shown to be detrimental in fatigue of MP35N wires by serving as fatigue crack nucleation sites. The detrimental effects of NMIs are modeled within a stochastic framework. By evaluating multiple statistical volume elements, the fatigue potency and inherent variability of inclusion-grain and grain-grain interactions at the NMI-matrix interface can be assessed. The extreme-value distributions of the Fatemi-Socie FIP were successfully correlated to rotating beam bending fatigue (RBBF) life data collected for MP35N fine wire. The correlation indicates that the fatigue potency in RBBF is strongly influenced by the NMI proximity to the wire surface with the most severe case occurring when the NMI intersects the surface. A significant drop in fatigue potency is observed when the NMI is fully embedded in the wire. Fatigue-life correlations to a second set of RBBF data were performed in order to identify a transition life value between crack incubation and microcrack growth fatigue mechanisms. The model has applications in numerous additional aspects of microstructure-sensitive HCF which can be explored in a future work.
Advisors/Committee Members: Neu, Richard W (advisor), McDowell, David L (committee member), Reiterer, Markus (committee member).
Subjects/Keywords: Microstructure-sensitive; high cycle fatigue; crystal plasticity; MP35N
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Clark, B. (2016). Microstructure-sensitive fatigue modeling of medical-grade fine wire. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56362
Chicago Manual of Style (16th Edition):
Clark, Brian. “Microstructure-sensitive fatigue modeling of medical-grade fine wire.” 2016. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/56362.
MLA Handbook (7th Edition):
Clark, Brian. “Microstructure-sensitive fatigue modeling of medical-grade fine wire.” 2016. Web. 17 Feb 2019.
Vancouver:
Clark B. Microstructure-sensitive fatigue modeling of medical-grade fine wire. [Internet] [Masters thesis]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/56362.
Council of Science Editors:
Clark B. Microstructure-sensitive fatigue modeling of medical-grade fine wire. [Masters Thesis]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/56362
Georgia Tech
5.
Radzicki, Andrew Thomas.
Characterization and modeling of the thermomechanical fatigue crack growth behavior of Inconel 718 superalloy.
Degree: PhD, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/58598
► Understanding the impact of the complex and harsh thermomechanical environment aircraft turbine engines subject their components to is critical for designers and operators to ensure…
(more)
▼ Understanding the impact of the complex and harsh thermomechanical environment aircraft turbine engines subject their components to is critical for designers and operators to ensure the safe and efficient operation of the systems they are responsible for. The combined effects of elevated temperatures and high loads on the components of these engines are not fully understood. The purpose of this project was to better understand this complex interaction. This effort consisted of the characterization and modeling of the performance of Nickel-base superalloys, specifically Inconel 718, used in turbine engine disk applications. Isothermal and thermomechanical tests up to and above the maximum usage temperature for Inconel 718 (650˚C) were executed to characterize the impact of time spent at elevated temperature on fatigue crack growth rate. Various spectra were designed to evaluate the impact of tensile and compressive holds at elevated temperature. This included evaluating the sequence within the spectrum where the holds occurred. Tensile holds executed at a spectrum's maximum load or immediately following an increase in load were shown to increase fatigue crack growth rate immediately follow the hold. Additionally, a robust series of tests were executed to evaluate the impact of the stress intensity, duration, and temperature of a tensile hold on fatigue crack growth rate. The concept of a thermally affected zone to describe an area ahead of the crack tip weakened by the tensile hold that allows for the crack to propagate faster than expected is discussed. As the stress intensity, duration, or temperature of a tensile hold increase, the temperature affected zone increases leading to an increase in fatigue crack growth rate for cycling following the hold. Observations made during the experimental investigation were used to develop a thermomechanical fatigue crack growth model that accommodates realistic spectra and accounts for the effects of time spent at elevated temperature. The model provides designers and operators with a more thorough representation of how their components will respond in actual application and allow them to make more informed decisions on the safe and efficient implementation of their systems.
Advisors/Committee Members: Johnson, William S. (advisor), Neu, Richard W. (advisor), McDowell, David L. (committee member), Pierron, Olivier (committee member), Muhlstein, Christopher (committee member).
Subjects/Keywords: IN 718; Ni-base superalloy; Fatigue crack growth; Thermomechanical fatigue; Hold time; Out-of-phase
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Radzicki, A. T. (2016). Characterization and modeling of the thermomechanical fatigue crack growth behavior of Inconel 718 superalloy. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58598
Chicago Manual of Style (16th Edition):
Radzicki, Andrew Thomas. “Characterization and modeling of the thermomechanical fatigue crack growth behavior of Inconel 718 superalloy.” 2016. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/58598.
MLA Handbook (7th Edition):
Radzicki, Andrew Thomas. “Characterization and modeling of the thermomechanical fatigue crack growth behavior of Inconel 718 superalloy.” 2016. Web. 17 Feb 2019.
Vancouver:
Radzicki AT. Characterization and modeling of the thermomechanical fatigue crack growth behavior of Inconel 718 superalloy. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/58598.
Council of Science Editors:
Radzicki AT. Characterization and modeling of the thermomechanical fatigue crack growth behavior of Inconel 718 superalloy. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/58598
Georgia Tech
6.
Evans, Nathan Timothy.
Processing-structure-property relationships of surface porous polymers for orthopaedic applications.
Degree: PhD, Materials Science and Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/55004
► The use of polymers in orthopaedics is steadily increasing. In some markets, such as spinal fusion and soft tissue anchors, the polymer polyetheretherketone (PEEK) is…
(more)
▼ The use of polymers in orthopaedics is steadily increasing. In some markets, such as spinal fusion and soft tissue anchors, the polymer polyetheretherketone (PEEK) is already the material of choice in the majority of implants. Despite PEEK’s widespread use, it is often associated with poor osseointegration, which can lead to implant loosening and ultimately failure of the device. Many attempts have been explored to improve the osseointegration of PEEK but none have had widespread clinical success. In this dissertation, a novel surface porous structure has been created, where limiting the porosity to the surface maintains adequate mechanical properties for load bearing applications while providing a surface for improved osseointegration. Careful control of the processing parameters resulted in tunable porous microstructures optimized for bone ingrowth: highly interconnected 200-500µm pores with porosity ranging from 60-85% and pore layers from 300-6000µm thick. Mechanical characterization, including monotonic tensile and compression, tensile fatigue, shear, and abrasion tests, were used to probe the effects of the surface porosity on the relevant mechanical properties of the material. In addition, the effect of surface porosity and surface roughness on the mechanical properties of a range of thermoplastics with varying chemistries and crystallinities was explored. This research showed that there is a great disparity in the notch sensitivity of polymers that correlates to the polymers fracture toughness as well as trends in the monotonic stress-strain curve. The results illustrate that care must be taken in the design of polymeric implants, especially when introducing topographical changes to promote osseointegration, in order to ensure they maintain adequate load-bearing capacity. Finally, preliminary in vitro and in vivo data demonstrated the ability of surface porous PEEK (PEEK-SP) to promote osseointegration. Cells grown on PEEK-SP demonstrated enhanced mineralization and differentiation, suggesting the ability of PEEK-SP to facilitate bone ingrowth. The potential of PEEK-SP was further demonstrated by implantation in a rat femoral segmental defect model which demonstrated bone ingrowth and reduced formation of a fibrous capsule.
Advisors/Committee Members: Gall, Ken (advisor), Guldberg, Robert E. (committee member), McDowell, David L. (committee member), Shofner, Meisha L. (committee member), Kumar, Satish (committee member).
Subjects/Keywords: Polyetheretherketone; Biomaterials; Polymers; Porosity; Osseointegration; Fatigue; Strength
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Evans, N. T. (2016). Processing-structure-property relationships of surface porous polymers for orthopaedic applications. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55004
Chicago Manual of Style (16th Edition):
Evans, Nathan Timothy. “Processing-structure-property relationships of surface porous polymers for orthopaedic applications.” 2016. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/55004.
MLA Handbook (7th Edition):
Evans, Nathan Timothy. “Processing-structure-property relationships of surface porous polymers for orthopaedic applications.” 2016. Web. 17 Feb 2019.
Vancouver:
Evans NT. Processing-structure-property relationships of surface porous polymers for orthopaedic applications. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/55004.
Council of Science Editors:
Evans NT. Processing-structure-property relationships of surface porous polymers for orthopaedic applications. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/55004
Georgia Tech
7.
Dong, Xin.
Dependence of mechanical properties of partially oriented polymeric systems on chemical structure and molecular architecture.
Degree: PhD, Materials Science and Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/55506
► Partially oriented polymeric structures such as semi-crystalline polymers and liquid crystalline polymers/elastomer cover a wide range of synthetic and natural polymeric materials. Owing to the…
(more)
▼ Partially oriented polymeric structures such as semi-crystalline polymers and liquid crystalline polymers/elastomer cover a wide range of synthetic and natural polymeric materials. Owing to the significant differences between the molecular structure and properties of ordered and amorphous regions, semi-crystalline polymers show complex patterns of behavior, although the molecular level mechanisms for deformation are still not well-understood. Molecular dynamics simulation based on a united atom method were performed, to study the crystallization behavior and molecular response of semi-crystalline polyethylene structures under external stresses in a time scale of nanoseconds to capture the molecular details. Using the data from molecular dynamics simulations, the effect of lamellae orientation on the stress-strain behavior was evaluated to understand the morphological evolution during deformation. The stress-induced morphological changes of free-standing and supported thin films with strong interacting surfaces were also investigated. Process-structure-property relationships are also investigated for liquid crystalline elastomers, with experimental approaches for validation. Structures and properties of a series of azobenzene containing liquid crystalline elastomeric films were characterized in detail.
Advisors/Committee Members: Jacob, Karl I. (advisor), McDowell, David L. (advisor), Griffin, Anselm C. (committee member), Yao, Donggang (committee member), Gokhale, Arun (committee member).
Subjects/Keywords: Semi-crystalline polymer; Liquid crystalline elastomer; Molecular dynamics; Azobenzene; Photoresponsive; Actuator
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dong, X. (2015). Dependence of mechanical properties of partially oriented polymeric systems on chemical structure and molecular architecture. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55506
Chicago Manual of Style (16th Edition):
Dong, Xin. “Dependence of mechanical properties of partially oriented polymeric systems on chemical structure and molecular architecture.” 2015. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/55506.
MLA Handbook (7th Edition):
Dong, Xin. “Dependence of mechanical properties of partially oriented polymeric systems on chemical structure and molecular architecture.” 2015. Web. 17 Feb 2019.
Vancouver:
Dong X. Dependence of mechanical properties of partially oriented polymeric systems on chemical structure and molecular architecture. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/55506.
Council of Science Editors:
Dong X. Dependence of mechanical properties of partially oriented polymeric systems on chemical structure and molecular architecture. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/55506
Georgia Tech
8.
Wu, Wenzhuo.
Piezotronic devices and integrated systems.
Degree: PhD, Materials Science and Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/51726
► Novel technology which can provide new solutions and enable augmented capabilities to CMOS based technology is highly desired. Piezotronic nanodevices and integrated systems exhibit potential…
(more)
▼ Novel technology which can provide new solutions and enable augmented capabilities to CMOS based technology is highly desired. Piezotronic nanodevices and integrated systems exhibit potential in achieving these application goals. By combining laser interference lithography and low temperature hydrothermal method, an effective approach for ordered growth of vertically aligned ZnO NWs array with high-throughput and low-cost at wafer-scale has been developed, without using catalyst and with a superior control over orientation, location/density and morphology of as-synthesized ZnO NWs. Beyond the materials synthesis, by utilizing the gating effect produced by the piezopotential in a ZnO NW under externally applied deformation, strain-gated transistors (SGTs) and universal logic operations such as NAND, NOR, XOR gates have been demonstrated for performing piezotronic logic operations for the first time. In addition, the first piezoelectrically-modulated resistive switching device based on piezotronic ZnO NWs has also been presented, through which the write/read access of the memory cell is programmed via electromechanical modulation and the logic levels of the strain applied on the memory cell can be recorded and read out for the first time. Furthermore, the first and by far the largest 3D array integration of vertical NW piezotronic transistors circuitry as active pixel-addressable pressure-sensor matrix for tactile imaging has been demonstrated, paving innovative routes towards industrial-scale integration of NW piezotronic devices for sensing, micro/nano-systems and human-electronics interfacing. The presented concepts and results in this thesis exhibit the potential for implementing novel nanoelectromechanical devices and integrating with MEMS/NEMS technology to achieve augmented functionalities to state-of-the-art CMOS technology such as active interfacing between machines and human/ambient as well as micro/nano-systems capable of intelligent and self-sufficient multi-dimensional operations.
Advisors/Committee Members: Wang, Zhong Lin (advisor), Deng, Yulin (committee member), Dupuis, Russell D. (committee member), McDowell, David L. (committee member), Singh, Preet (committee member).
Subjects/Keywords: Piezotronics; Piezopotential; Piezoelectricity; NEMS; Self-powered systems; Metal oxide semiconductors, Complementary; Nanoelectromechanical systems; Piezoelectric devices
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wu, W. (2012). Piezotronic devices and integrated systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51726
Chicago Manual of Style (16th Edition):
Wu, Wenzhuo. “Piezotronic devices and integrated systems.” 2012. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/51726.
MLA Handbook (7th Edition):
Wu, Wenzhuo. “Piezotronic devices and integrated systems.” 2012. Web. 17 Feb 2019.
Vancouver:
Wu W. Piezotronic devices and integrated systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2012. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/51726.
Council of Science Editors:
Wu W. Piezotronic devices and integrated systems. [Doctoral Dissertation]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/51726
Georgia Tech
9.
Liu, Ran.
Synthesis and mechanical properties of hierarchical nanoporous metals.
Degree: PhD, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53848
► Nanoporous (NP) metals are a unique class of materials that are characterized by extremely high surface-to-volume ratios and possess such desirable properties of metals as…
(more)
▼ Nanoporous (NP) metals are a unique class of materials that are characterized by extremely high surface-to-volume ratios and possess such desirable properties of metals as high electrical conductivity, catalytic activity, and mechanical strength. At the same time, understanding of their physical properties is often lacking, especially for hierarchical NP metals where individual struts and joints that make up open cell 3D network are nanocrystalline. The aim of this work is to employ a dedicated experimental campaign to understand the structure property relation of nanostructured nanoporous metals. Towards this goal, NP Pt and NP Cu have been synthesized for a range of strut sizes and their mechanical properties have been investigated via ex-situ and in-situ nanoindentation experiments. Both NP Pt and NP Cu exhibit relatively high hardness in the range of 0.2 to 1.3 GPa. The relative role of material effects arising from small dimensions of the struts/joints and the geometrical features of NP metals are discussed. Selected applications of the systems synthesized during this work in electrochemistry and catalysis are demonstrated. In the examined applications the NP metals exhibited catalytic activity comparable to or significantly exceeding the best available alternative systems, while offering superior stability.
Advisors/Committee Members: Antoniou, Antonia (advisor), McDowell, David L. (committee member), Mara, Nathan (committee member), Pierron, Olivier (committee member), Frazier, Bruno (committee member).
Subjects/Keywords: Modulus; Hardness; Experiments; Nanoindentation; Nanoporous metals; Mechanical properties
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Liu, R. (2015). Synthesis and mechanical properties of hierarchical nanoporous metals. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53848
Chicago Manual of Style (16th Edition):
Liu, Ran. “Synthesis and mechanical properties of hierarchical nanoporous metals.” 2015. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/53848.
MLA Handbook (7th Edition):
Liu, Ran. “Synthesis and mechanical properties of hierarchical nanoporous metals.” 2015. Web. 17 Feb 2019.
Vancouver:
Liu R. Synthesis and mechanical properties of hierarchical nanoporous metals. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/53848.
Council of Science Editors:
Liu R. Synthesis and mechanical properties of hierarchical nanoporous metals. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53848
Georgia Tech
10.
He, Lijuan.
Multiple phase transition path and saddle point search in computer aided nano design.
Degree: PhD, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53967
► Functional materials with controllable phase transitions have been widely used in devices for information storage (e.g. hard-disk, CD-ROM, memory) and energy storage (e.g. battery, shape…
(more)
▼ Functional materials with controllable phase transitions have been widely used in devices for information storage (e.g. hard-disk, CD-ROM, memory) and energy storage (e.g. battery, shape memory alloy). One of the important issues to design such materials is to realize the desirable phase transition processes, in which atomistic simulation can be used for the prediction of materials properties. The accuracy of the prediction is largely dependent on searching the true value of the transition rate, which is determined by the minimum energy barrier between stable states, i.e. the saddle point on a potential energy surface (PES). Although a number of methods that search for saddle points on a PES have been developed, they intend to locate only one saddle point with the maximum energy along the transition path at a time. In addition, they do not consider the input uncertainty associated with the calculation of potential energy. To overcome the limitations, in this dissertation, new saddle point search methods are developed to provide a global view of energy landscape with improved efficiency and robustness. First, a concurrent search algorithm for multiple phase transition pathways is developed. The algorithm is able to search multiple local minima and saddle points simultaneously without prior knowledge of initial and final stable configurations. A new representation of transition paths based on parametric Bézier curves is introduced. A curve subdivision scheme is developed to dynamically locate all the intermediate local minima and saddle points along the transition path. Second, a curve swarm search algorithm is developed to exhaustively locate the local minima and saddle points within a region concurrently. The algorithm is based on the flocking of multiple groups of curves. A collective potential model is built to simulate the communication activities among curves. Third, a hybrid saddle-point search method using stochastic kriging models is developed to improve the efficiency of the search algorithm as well as to incorporate model-form uncertainty and numerical errors associated with density functional theory calculation. These algorithms are demonstrated by predicting the hydrogen diffusion process in FeTiH and body-centered iron Fe8H systems.
Advisors/Committee Members: Wang, Yan (advisor), Henkelman, Graeme (committee member), Jang, Seung Soon (committee member), Zhu, Ting (committee member), McDowell, David L. (committee member).
Subjects/Keywords: Saddle point; Reaction path; Density functional theory; Uncertainty
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
He, L. (2015). Multiple phase transition path and saddle point search in computer aided nano design. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53967
Chicago Manual of Style (16th Edition):
He, Lijuan. “Multiple phase transition path and saddle point search in computer aided nano design.” 2015. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/53967.
MLA Handbook (7th Edition):
He, Lijuan. “Multiple phase transition path and saddle point search in computer aided nano design.” 2015. Web. 17 Feb 2019.
Vancouver:
He L. Multiple phase transition path and saddle point search in computer aided nano design. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/53967.
Council of Science Editors:
He L. Multiple phase transition path and saddle point search in computer aided nano design. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53967
11.
Bertin, Nicolas.
On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling.
Degree: PhD, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/54370
► This thesis focuses on the effects of slip-slip, slip-twin, and slip-precipitates interactions on strain hardening, with the intent of developing comprehensive modelling capabilities enabling to…
(more)
▼ This thesis focuses on the effects of slip-slip, slip-twin, and slip-precipitates interactions on strain hardening, with the intent of developing comprehensive modelling capabilities enabling to investigate unit processes and their collective effects up to the macroscopic response. To this end, the modelling strategy adopted in this work relies on a two-way exchange of information between predictions obtained by discrete dislocation dynamics (DDD) simulations and crystal plasticity laws informed by DDD. At the scale of lattice defects, a DDD tool enabling simulations on any crystalline structure is developed to model dislocation-dislocation, dislocation-twin and dislocation-particles interactions. The tool is first used to quantify the collective effect and strength of dislocation-dislocation interactions on latent-hardening, especially in the case of pure Mg. With regards to slip-twin interactions, a transmission mechanism is implemented in the DDD framework so as to investigate the collective effects of dislocation transmission across a twin-boundary. With respect to slip-particles interactions, an efficient novel DDD approach based on a Fast Fourier Transform (FFT) technique is developed to include the field fluctuations related to elastic heterogeneities giving rise to image forces on dislocation lines. In addition, the DDD-FFT approach allows for the efficient treatment of anisotropic elasticity, thereby paving the way towards performing DDD simulations in low-symmetry polycrystals. The information extracted from the collective dislocation interactions are then passed to a series of constitutive models, and later used to quantify their effects at the scale of the polycrystal. For such purpose, a constitutive framework capable of receiving information from lower scales and establishing a direct connection with DDD simulations is notably developed.
Advisors/Committee Members: Capolungo, Laurent (advisor), McDowell, David L. (committee member), Kalidindi, Surya R. (committee member), Garmestani, Hamid (committee member), Tomé, Carlos N. (committee member).
Subjects/Keywords: DDD; Dislocation dynamics; Anisotropic elasticity; Heterogeneous elasticity; Spectral method; Crystal plasticity; Scale transition
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Bertin, N. (2015). On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54370
Chicago Manual of Style (16th Edition):
Bertin, Nicolas. “On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling.” 2015. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/54370.
MLA Handbook (7th Edition):
Bertin, Nicolas. “On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling.” 2015. Web. 17 Feb 2019.
Vancouver:
Bertin N. On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/54370.
Council of Science Editors:
Bertin N. On the role of lattice defects interactions on strain hardening: A study from discrete dislocation dynamics to crystal plasticity modelling. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/54370
Georgia Tech
12.
Priddy, Matthew William.
Exploration of forward and inverse protocols for property optimization of Ti-6Al-4V.
Degree: PhD, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/55665
► The modeling and simulation of advanced engineering materials undergoing mechanical loading requires accurate treatment of relevant microstructure features, such as grain size and crystallographic texture,…
(more)
▼ The modeling and simulation of advanced engineering materials undergoing mechanical loading requires accurate treatment of relevant microstructure features, such as grain size and crystallographic texture, to determine the heterogeneous response to deformation. However, many models constructed for this purpose are not being fully realized in their predictive capability. Additionally, physics-based models can be combined with bottom-up deductive mappings and top-down inductive decision paths to increase their utility in materials selection and optimization. However, connecting these types of models or algorithms with experiments, rapid inverse property/response estimates, and design decision-making via integrated workflows has yet to become well-established for materials design and/or development. One material system primed for this type of concurrent advancement is alpha+beta titanium alloys, because its resultant microstructure and mechanical properties are highly dependent on material processing and composition. This dissertation seeks to advance a materials design process for fatigue resistance, strength, and elastic stiffness of Ti-6Al-4V through the advancement of various computational tools, as well as the integration of simulation-based tools and high-throughput experimental datasets. The microstructure-sensitive crystal plasticity finite element method (CPFEM) is utilized to explicitly account for the grain structure and crystallographic texture of Ti-6Al-4V. To improve the predictive capability of the CPFEM model, high throughput spherical indentation experimental datasets are used for model calibration because of their ability to extract elastic and plastic individual phase and grain properties from multiphase materials such as titanium alloys. The CPFEM can be used to capture the microstructure heterogeneity on fatigue crack driving forces, but these types of simulations are computationally expensive. Instead, an explicit integration of the relevant constitutive relations in the CPFEM model are combined with the materials knowledge system (MKS) approach for generating spatially local results of polycrystalline materials. These bottom-up simulation methods provide macroscopic properties from microstructure-level model inputs. For materials design, it is important to determine the inverse – microstructure-level information from the macroscopic response – which is referred to as top-down modeling. The Inductive Design Exploration Method (IDEM) offers a systematic approach to combining bottom-up simulations with top-down inductive design search. In this dissertation, a generalized framework of the IDEM is implemented to assess multi-objective design scenarios specific to the microstructure-sensitive datasets generated in this work.Th e general approach presented in this dissertation integrates CPFEM simulations with experimental spherical indentation for model refinement and also combines CPFEM with the MKS for computational-efficient generation of local quantities. These advancements are the…
Advisors/Committee Members: McDowell, David L. (advisor), Shih, Donald S. (advisor), Kalidindi, Surya R. (committee member), Neu, Rick W. (committee member), Garmestani, Hamid (committee member).
Subjects/Keywords: Finite element model; Crystal plasticity; Titanium alloys; High-throughput; Inverse design
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Priddy, M. W. (2016). Exploration of forward and inverse protocols for property optimization of Ti-6Al-4V. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55665
Chicago Manual of Style (16th Edition):
Priddy, Matthew William. “Exploration of forward and inverse protocols for property optimization of Ti-6Al-4V.” 2016. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/55665.
MLA Handbook (7th Edition):
Priddy, Matthew William. “Exploration of forward and inverse protocols for property optimization of Ti-6Al-4V.” 2016. Web. 17 Feb 2019.
Vancouver:
Priddy MW. Exploration of forward and inverse protocols for property optimization of Ti-6Al-4V. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/55665.
Council of Science Editors:
Priddy MW. Exploration of forward and inverse protocols for property optimization of Ti-6Al-4V. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/55665
Georgia Tech
13.
Turner, David M.
Construction of representative 3D microstructures from complete and partial statistics.
Degree: PhD, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/56337
► The principle concern of the material scientist is the connection between microstructure, properties, and processing. Microstructure is characterized via experimental measurements of geometry at the…
(more)
▼ The principle concern of the material scientist is the connection between microstructure, properties, and processing. Microstructure is characterized via experimental measurements of geometry at the appropriate length scale. This is usually followed by a quantification of microstructure via statistics for which there are a broad base of possibilities including classical stereological measures such as grain size and higher order descriptions like the N-point spatial correlations. Despite advances in 3D characterization of microstructures such as X-ray tomography and serial sectioned SEM, most techniques still capture measurements only in 2D sections. Even when 3D datasets are available they are typically measuring only small volumes leading to uncertainty about their statistical significance. Can we build statistically representative reconstructions of 3D microstructure from the partial information gathered on a collection of 2D cross sections? The proposed work introduces new approaches to these problems for two phase composites with complex anisotropic geometries. Efficient algorithms for the computation of "higher order" statistics, such as N-point correlations and chord length distributions, will be explored. These higher order metrics will form the basis for establishing structure based representative volume elements (RVEs) in both cases where microstructure geometry information is complete and incomplete.
Advisors/Committee Members: Kalidindi, Surya R (advisor), McDowell, David L (committee member), Garmestani, Hamid (committee member), Song, Le (committee member), Jacob, Karl I (committee member).
Subjects/Keywords: Microstructure; 2-point statistics; Reconstruction; Solid Texture Synthesis
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Turner, D. M. (2016). Construction of representative 3D microstructures from complete and partial statistics. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/56337
Chicago Manual of Style (16th Edition):
Turner, David M. “Construction of representative 3D microstructures from complete and partial statistics.” 2016. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/56337.
MLA Handbook (7th Edition):
Turner, David M. “Construction of representative 3D microstructures from complete and partial statistics.” 2016. Web. 17 Feb 2019.
Vancouver:
Turner DM. Construction of representative 3D microstructures from complete and partial statistics. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/56337.
Council of Science Editors:
Turner DM. Construction of representative 3D microstructures from complete and partial statistics. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/56337
Georgia Tech
14.
Wu, Zhibo.
Equation of state for polytetrafluoroethylene (PTFE) and mixtures with PTFE.
Degree: PhD, Aerospace Engineering, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/29696
► The objectives of this work are to discuss multiscale models that are used to characterize the constitutive relations of the granular composite materials with dual…
(more)
▼ The objectives of this work are to discuss multiscale models that are used to characterize the constitutive relations of the granular composite materials with dual functions. This is accomplished by the use of ab initio methods to obtain the constitutive relations of the structural energetic materials without conducting tests. First, it is necessary to study the quantum many body problem to quantitatively determine the internal energy of the material when subjected to different strain conditions. It is impossible to obtain an exact solution to the quantum many body problem that is modeled by the Schrödinger's equations with the current technology. It is possible to solve these equations approximately by the density functional theory which yields only energies at absolute 0ºK. Thus it becomes necessary to add both the lattice thermal contributions and electron thermal contribution. Then, resulting energy is used to bridge to the continuum level and obtain the constitutive equations. This is the procedure that is used in this work.
The issues of the constitutive equations form the focus of this thesis. More specifically, the scope of the thesis is further restricted to analyze the constitutive equations of specific mixtures of nickel, aluminum with PTFE or Teflon as the binder. It is to be noted that the equations of state forms only a part of the complete constitutive relationships. This thesis presents solutions to the following problems:
(1) Determination of the thermodynamically complete equation of state of the binder and the energetic material PTFE or Teflon, from ab initio methods based on the density functional theory.
(2) Determination of the equations of state of the granular composite or the mixture of nickel, aluminum and PTFE from ab initio methods.
(3) Determination of the complete constitutive equation of aluminum, from ab initio methods, under conditions of finite deformations, with principle of objectivity, material symmetry conditions and polyconvexity of the strain energy.
All results are compared to test results whenever they are available.
Advisors/Committee Members: Hanagud,Sathya (Committee Chair), Apetre, Nicoleta (Committee Member), Kardomateas, George (Committee Member), McDowell, David L. (Committee Member), Ruzzene, Massimo (Committee Member).
Subjects/Keywords: Finite deformation; Polymer; Constitutive equations; Mixture; Density function theory; Equation of state; Binders (Materials); Matter Properties; Polytef
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wu, Z. (2009). Equation of state for polytetrafluoroethylene (PTFE) and mixtures with PTFE. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/29696
Chicago Manual of Style (16th Edition):
Wu, Zhibo. “Equation of state for polytetrafluoroethylene (PTFE) and mixtures with PTFE.” 2009. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/29696.
MLA Handbook (7th Edition):
Wu, Zhibo. “Equation of state for polytetrafluoroethylene (PTFE) and mixtures with PTFE.” 2009. Web. 17 Feb 2019.
Vancouver:
Wu Z. Equation of state for polytetrafluoroethylene (PTFE) and mixtures with PTFE. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/29696.
Council of Science Editors:
Wu Z. Equation of state for polytetrafluoroethylene (PTFE) and mixtures with PTFE. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/29696
Georgia Tech
15.
Paulson, Noah H.
Structure-property linkages for polycrystalline materials using materials knowledge systems.
Degree: PhD, Mechanical Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/60113
► Computational tools that are capable of rapidly exploring candidate microstructures and their associated properties are required to accelerate the rate of development and deployment of…
(more)
▼ Computational tools that are capable of rapidly exploring candidate microstructures and their associated properties are required to accelerate the rate of development and deployment of novel materials. In this work, a suite of computationally efficient protocols, based on the materials knowledge system (MKS) framework, are developed to evaluate the properties and performance of polycrystalline microstructures. In the MKS approach, physics-capturing coefficients (calibrated with microstructures and their responses obtained via experiments or simulations) store the microstructure-sensitive response of the material system of interest. Once calibrated, the linkages may be employed to predict the local responses (through localization) or effective properties (through homogenization) of new microstructures at low computational expense. Specifically, protocols are developed to predict bulk properties (elastic stiffness and yield strength), local cyclic plastic strains and resistance to fatigue crack formation and early growth (in the high cycle fatigue and transition fatigue regimes). These protocols are demonstrated on a diverse set of α-titanium microstructures, which exhibit heterogeneous microstructure features, in addition to anisotropy on multiple length-scales.
Advisors/Committee Members: Kalidindi, Surya R. (advisor), McDowell, David L. (committee member), Shih, Donald S. (committee member), Neu, Richard W. (committee member), Garmestani, Hamid (committee member).
Subjects/Keywords: Microstructure; Structure-property relationship; Polycrystalline; Titanium alloys; High cycle fatigue; Transition fatigue; Yield strength; Elastic modulus; Data science; Materials informatics; High-throughput; 2-point correlations; Computational model; Crystal plasticity; Reduced-order model; Extreme value statistics
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Paulson, N. H. (2017). Structure-property linkages for polycrystalline materials using materials knowledge systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60113
Chicago Manual of Style (16th Edition):
Paulson, Noah H. “Structure-property linkages for polycrystalline materials using materials knowledge systems.” 2017. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/60113.
MLA Handbook (7th Edition):
Paulson, Noah H. “Structure-property linkages for polycrystalline materials using materials knowledge systems.” 2017. Web. 17 Feb 2019.
Vancouver:
Paulson NH. Structure-property linkages for polycrystalline materials using materials knowledge systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/60113.
Council of Science Editors:
Paulson NH. Structure-property linkages for polycrystalline materials using materials knowledge systems. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60113
Georgia Tech
16.
Lin, Long.
Nanogenerators for mechanical energy harvesting and self-powered sensor networks.
Degree: PhD, Materials Science and Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/55514
► Energy crisis and internet of things have attracted long term interests due to rapid development of modern society. In this regard, the invention of nanogenerators…
(more)
▼ Energy crisis and internet of things have attracted long term interests due to rapid development of modern society. In this regard, the invention of nanogenerators provide us new insights on scavenging wasted mechanical energy from the ambient environment, and convert kinetic agitations into electricity for powering electronic devices. Piezoelectric nanogenerators are based on the piezoelectric property of semiconductor nanowires. Vertical integration, proper selection of materials, and surface modifications have been applied to enhance its output performance. Triboelectric nanogenerators (TENG), on the other hand, work on the basis of contact electrification and electrostatic induction. Four fundamental working modes have been developed to accommodate different types of mechanical motions. A high output power density of 35.6 W/m2, an excellent energy conversion efficiency of up to 55%, and terrific output stability of over 300,000 cycles have been accomplished with the state-of-art TENG devices. The niche applications of the TENGs have been demonstrated for powering portable electronics toward the goal of fully-integrated self-powered system.
Since the nanogenerators are enabled to convert mechanical input into electrical output signals, the information of mechanical stimuli (amplitude and frequency) can be retrieved through analyzing the output performance of the nanogenerators. In this way, nanogenerators were employed as self-powered/active sensors without an external power supply, and multiple functions could be achieved including pressure detection and motion sensing. Both static and dynamic pressure sensing was realized using the open-circuit voltage and short-circuit current from the TENG, respectively. A high sensitivity of 0.31 kPa-1 and a low detection limit of 2.1 Pa were also fulfilled. The integration of pressure sensor array for tactile imaging was further demonstrated for its potential application in electronic skin, human-machine interface, and security monitoring.
Advisors/Committee Members: Wang, Zhong Lin (advisor), McDowell, David L (committee member), Singh, Preet (committee member), Dupuis, Russell D. (committee member), Deng, Yulin (committee member).
Subjects/Keywords: Nanogenerator; Energy harvesting; Self-powered system; Active sensor
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lin, L. (2015). Nanogenerators for mechanical energy harvesting and self-powered sensor networks. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/55514
Chicago Manual of Style (16th Edition):
Lin, Long. “Nanogenerators for mechanical energy harvesting and self-powered sensor networks.” 2015. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/55514.
MLA Handbook (7th Edition):
Lin, Long. “Nanogenerators for mechanical energy harvesting and self-powered sensor networks.” 2015. Web. 17 Feb 2019.
Vancouver:
Lin L. Nanogenerators for mechanical energy harvesting and self-powered sensor networks. [Internet] [Doctoral dissertation]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/55514.
Council of Science Editors:
Lin L. Nanogenerators for mechanical energy harvesting and self-powered sensor networks. [Doctoral Dissertation]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/55514
Georgia Tech
17.
Seitz, Benjamin.
Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys.
Degree: MS, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/60405
► In Additive Manufacturing (AM) of Inconel 718 the main focus lies on the primary solidification occurring in the build. The next critical processing step for…
(more)
▼ In Additive Manufacturing (AM) of Inconel 718 the main focus lies on the primary solidification occurring in the build. The next critical processing step for age-hardened alloys is the post-built heat treatment. Since diffusivity depends on the spatial distribution of the elements, the solution treatment and age parameter established for conventionally manufactured Inconel 718 components will likely not be optimal for Additive Manufactured components. This study specifically focuses on developing methods to rapidly establish the post-built heat treatment for age-hardened alloys. It will be showcased on Inconel 718 fabricated by Electron Beam Melting (EBM). The method incorporates as well as reveals challenges and considerations that go along with the unique processing route of AM. Based on a thorough literature review on Inconel 718, Processing-Structure-Property-Performance (PSPP) relations and Electron Beam Melting, a PSPP chart is outlined and used to detect further research goals. It is recognized that the work on systematically evaluating and improving the influence on mechanical properties is most efficiently conducted by utilizing post-processing parameter. After identifying promising post-processing parameter in solution treatment and aging, a material library is defined based on a selection of strain-rate jump tests which are found to be advantageous based on the demand of AM and efficiency considerations. An efficient test geometry enables evaluating strucutral and property features in the direct vicinity of each other. Design of Experiments has shown to be useful for establishing efficient test matrixes on post-built heat treatment parameter. Analyzing the data revealed major porosity concerns in the AM feedstock material which are found to detrimentally affect the material’s ductility.
Advisors/Committee Members: Neu, Richard W. (advisor), McDowell, David L. (committee member), Schmauder, Siegfried (committee member), Sawodny, Oliver (committee member).
Subjects/Keywords: Additive manufacturing; Inconel 718; Heat treatment
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Seitz, B. (2016). Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60405
Chicago Manual of Style (16th Edition):
Seitz, Benjamin. “Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys.” 2016. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/60405.
MLA Handbook (7th Edition):
Seitz, Benjamin. “Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys.” 2016. Web. 17 Feb 2019.
Vancouver:
Seitz B. Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys. [Internet] [Masters thesis]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/60405.
Council of Science Editors:
Seitz B. Methodology for efficiently establishing processing-structure-property relationships for additive-manufactured age-hardened alloys. [Masters Thesis]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/60405
Georgia Tech
18.
Gomberg, Joshua A.
Data-driven PSP linkages for atomistic datasets.
Degree: PhD, Materials Science and Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/60125
► For a variety of materials, atomic-scale modeling techniques are commonly employed as a means of investigating fundamental properties, including both structural and chemical responses. While…
(more)
▼ For a variety of materials, atomic-scale modeling techniques are commonly employed as a means of investigating fundamental properties, including both structural and chemical responses. While force-field based calculations are significantly less computationally expensive than their quantum-mechanical counterparts, the datasets often investigated are large in size (10
3 – 10
9 atoms) and high-dimensional, and thus cumbersome for use in multi-scale models. The development of quantitative “process-structure-property” (PSP) linkages for atomistic simulations presents a powerful route to convert atomistic simulation data into actionable knowledge. Here, a framework is presented for quantifying structure from these simulations in full- and reduced-dimensional form, and a series of protocols are developed for establishing regression models for process-structure and structure-property linkages.
Advisors/Committee Members: Kalidindi, Surya R. (advisor), McDowell, David L. (committee member), Li, Mo (committee member), Haaland, Benjamin (committee member), Garmestani, Hamid (committee member).
Subjects/Keywords: Grain boundaries; Materials informatics; Molecular dynamics; Pair correlation function; Principal component analysis; Process-structure-property linkage; Interatomic potentials; Multiscale modeling
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gomberg, J. A. (2017). Data-driven PSP linkages for atomistic datasets. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/60125
Chicago Manual of Style (16th Edition):
Gomberg, Joshua A. “Data-driven PSP linkages for atomistic datasets.” 2017. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/60125.
MLA Handbook (7th Edition):
Gomberg, Joshua A. “Data-driven PSP linkages for atomistic datasets.” 2017. Web. 17 Feb 2019.
Vancouver:
Gomberg JA. Data-driven PSP linkages for atomistic datasets. [Internet] [Doctoral dissertation]. Georgia Tech; 2017. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/60125.
Council of Science Editors:
Gomberg JA. Data-driven PSP linkages for atomistic datasets. [Doctoral Dissertation]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/60125
19.
Ferri, Brian Anthony.
Effect of mesoscale inhomogeneities on planar shock response of materials.
Degree: MS, Mechanical Engineering, 2017, Georgia Tech
URL: http://hdl.handle.net/1853/58333
► In all previous spall models, the source of spall failure in metals either comes from damage at the grain boundary or from void nucleation, growth,…
(more)
▼ In all previous spall models, the source of spall failure in metals either comes from damage at the grain boundary or from void nucleation, growth, and coalescence. However, it has been observed in experiments that both phenomena occur in Aluminum 6061-T6, which is termed “combined failure” for the purposes of this thesis. Thus, the challenge undertaken in this thesis is to use a computational study to determine the role that each source of spall plays separately, and then in tandem to determine the traditional failure parameters for each source. The results of determining each failure model’s ideal parameters, which are representative of that source’s role in combined failure, is compared with data gathered from plate-flyer experiments to determine the accuracy of the model in both 1D and in 2D simulations.
Sand is a heterogeneous granular material that has the capability of allowing a shock wave to propagate through it. The computational model and study presented in this thesis is phenomenologically similar, yet easier to conduct than a spall study on granular Aluminum. The study of sand using the same computational LS-DYNA method shows both an introduction to the process for completing the spall study on granular Aluminum, and it also yields interesting results in the wave phenomena as well as the effect of porosity on the average stress on the sand grains.
With the conclusion of the sand study, the same process of creating the grain structure is applied to create the Aluminum grain structure for spall simulations, which are carried out in LS-DYNA using 2D cohesive elements. The results of the LS-DYNA Aluminum simulation are compared to both the 1D spall results as well as to the experimental data to determine model accuracy.
The main findings from this thesis show that, first, a mutually exclusive combined failure linear relationship can be shown with the 1D simulation results, which gives insight into a method that could be used to choose a set of optimal failure parameters. Second, the 2D LS-DYNA homogeneous results had excellent agreement with the 1D homogeneous results, which gave confidence to the notion that the parametric studies in 1D simulations could be used to find parameter values that could be applied in the 2D models. Lastly, LS-DYNA was shown to be an effective way to simulate grain structure response to shock wave propagation and showed spall modeling was possible with 2D cohesive elements, which lays the groundwork for combined failure studies in 2D.
Advisors/Committee Members: Dwivedi, Sunil K (advisor), McDowell, David L (advisor), Neu, Richard W (committee member).
Subjects/Keywords: Shock physics; Shock response, Granular materials; LS-DYNA; Computational; Spall; Modeling; Cohesive elements
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Ferri, B. A. (2017). Effect of mesoscale inhomogeneities on planar shock response of materials. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/58333
Chicago Manual of Style (16th Edition):
Ferri, Brian Anthony. “Effect of mesoscale inhomogeneities on planar shock response of materials.” 2017. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/58333.
MLA Handbook (7th Edition):
Ferri, Brian Anthony. “Effect of mesoscale inhomogeneities on planar shock response of materials.” 2017. Web. 17 Feb 2019.
Vancouver:
Ferri BA. Effect of mesoscale inhomogeneities on planar shock response of materials. [Internet] [Masters thesis]. Georgia Tech; 2017. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/58333.
Council of Science Editors:
Ferri BA. Effect of mesoscale inhomogeneities on planar shock response of materials. [Masters Thesis]. Georgia Tech; 2017. Available from: http://hdl.handle.net/1853/58333
20.
Blumer, Joel David.
Cross-scale model validation with aleatory and epistemic uncertainty.
Degree: MS, Mechanical Engineering, 2015, Georgia Tech
URL: http://hdl.handle.net/1853/53571
► Nearly every decision must be made with a degree of uncertainty regarding the outcome. Decision making based on modeling and simulation predictions needs to incorporate…
(more)
▼ Nearly every decision must be made with a degree of uncertainty regarding the outcome. Decision making based on modeling and simulation predictions needs to incorporate and aggregate uncertain evidence. To validate multiscale simulation models, it may be necessary to consider evidence collected at a length scale that is different from the one at which a model predicts. In addition, traditional methods of uncertainty analysis do not distinguish between two types of uncertainty: uncertainty due to inherently random inputs, and uncertainty due to lack of information about the inputs. This thesis examines and applies a Bayesian approach for model parameter validation that uses generalized interval probability to separate these two types of uncertainty. A generalized interval Bayes’ rule (GIBR) is used to combine the evidence and update belief in the validity of parameters. The sensitivity of completeness and soundness for interval range estimation in GIBR is investigated. Several approaches to represent complete ignorance of probabilities’ values are tested. The result from the GIBR method is verified using Monte Carlo simulations. The method is first applied to validate the parameter set for a molecular dynamics simulation of defect formation due to radiation. Evidence is supplied by the comparison with physical experiments. Because the simulation includes variables whose effects are not directly observable, an expanded form of GIBR is implemented to incorporate the uncertainty associated with measurement in belief update. In a second example, the proposed method is applied to combining the evidence from two models of crystal plasticity at different length scales.
Advisors/Committee Members: Wang, Yan (advisor), McDowell, David L. (advisor), Swiler, Laura P. (committee member).
Subjects/Keywords: Aleatory uncertainty; Epistemic uncertainty; Uncertainty quantification; Generalized intervals; GIBR
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Blumer, J. D. (2015). Cross-scale model validation with aleatory and epistemic uncertainty. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53571
Chicago Manual of Style (16th Edition):
Blumer, Joel David. “Cross-scale model validation with aleatory and epistemic uncertainty.” 2015. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/53571.
MLA Handbook (7th Edition):
Blumer, Joel David. “Cross-scale model validation with aleatory and epistemic uncertainty.” 2015. Web. 17 Feb 2019.
Vancouver:
Blumer JD. Cross-scale model validation with aleatory and epistemic uncertainty. [Internet] [Masters thesis]. Georgia Tech; 2015. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/53571.
Council of Science Editors:
Blumer JD. Cross-scale model validation with aleatory and epistemic uncertainty. [Masters Thesis]. Georgia Tech; 2015. Available from: http://hdl.handle.net/1853/53571
21.
Neal, Sean Douglas.
Reduced order constitutive modeling of a directionally-solidified nickel-base superalloy.
Degree: MS, Mechanical Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/51735
► Hot section components of land-based gas turbines are subject to extremely harsh, high temperature environments and require the use of advanced materials. Directionally solidified Ni-base…
(more)
▼ Hot section components of land-based gas turbines are subject to extremely harsh, high temperature environments and require the use of advanced materials. Directionally solidified Ni-base superalloys are often chosen as materials for these hot section components due to their excellent creep resistance and fatigue properties at high temperatures. These blades undergo complex thermomechanical loading conditions throughout their service life, and the influences of blade geometry and variable operation can make life prediction difficult. Accurate predictions of material response under thermomechanical loading conditions is essential for life prediction of these components. Complex crystal viscoplasticity models are often used to capture the behavior of Ni-base superalloys. While accurate, these models are computationally expensive and are not suitable for all phases of design. This work involves the calibration of a previously developed reduced-order, macroscale transversely isotropic viscoplasticity model to a directionally solidified Ni-base superalloy. The unified model is capable of capturing isothermal and thermomechanical responses in addition to secondary creep behavior. An extreme reduced order microstructure-sensitive constitutive model is also developed using an artificial neural network to provide a rapid first-order approximation of material response under various temperatures, rates of loading, and material orientation from the axis of solidification.
Advisors/Committee Members: Neu, Richard (advisor), Antolovich, Stephen (committee member), McDowell, David L. (committee member).
Subjects/Keywords: Superalloy; Nickel base; Directionally solidified; Reduced order modeling; Heat resistant alloys; Nickel alloys; Viscoplasticity; Microstructure
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Neal, S. D. (2013). Reduced order constitutive modeling of a directionally-solidified nickel-base superalloy. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51735
Chicago Manual of Style (16th Edition):
Neal, Sean Douglas. “Reduced order constitutive modeling of a directionally-solidified nickel-base superalloy.” 2013. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/51735.
MLA Handbook (7th Edition):
Neal, Sean Douglas. “Reduced order constitutive modeling of a directionally-solidified nickel-base superalloy.” 2013. Web. 17 Feb 2019.
Vancouver:
Neal SD. Reduced order constitutive modeling of a directionally-solidified nickel-base superalloy. [Internet] [Masters thesis]. Georgia Tech; 2013. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/51735.
Council of Science Editors:
Neal SD. Reduced order constitutive modeling of a directionally-solidified nickel-base superalloy. [Masters Thesis]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/51735
22.
Brindley, Kyle A.
Thermomechanical fatigue of Mar-M247: extension of a unified constitutive and life model to higher temperatures.
Degree: MS, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/51852
► The goal of this work is to establish a life prediction methodology for thermomechanical loading of the Ni-base superalloy Mar-M247 over a larger temperature range…
(more)
▼ The goal of this work is to establish a life prediction methodology for thermomechanical loading of the Ni-base superalloy Mar-M247 over a larger temperature range than previous work. The work presented in this thesis extends the predictive capability of the Sehitoglu-Boismier unified thermo-viscoplasticity constitutive model and thermomechanical life model from a maximum temperature of 871C to a maximum temperature of 1038C. The constitutive model, which is suitable for predicting stress-strain history under thermomechanical loading, is adapted and calibrated using the response from isothermal cyclic experiments conducted at temperatures from 500C to 1038C at different strain rates with and without dwells. In the constitutive model, the flow rule function and parameters as well as the temperature dependence of the evolution equation for kinematic hardening are established. In the elevated temperature regime, creep and stress relaxation are critical behaviors captured by the constitutive model. The life model accounts for fatigue, creep, and environmental-fatigue damage under both isothermal and thermomechanical fatigue. At elevated temperatures, the damage terms must be calibrated to account for thermally activated damage mechanisms which change with increasing temperature. At lower temperatures and higher strain rates, fatigue damage dominates life prediction, while at higher temperatures and slower strain rates, environmental-fatigue and creep damage dominate life prediction. Under thermomechanical loading, both environmental-fatigue and creep damage depend strongly on the relative phasing of the thermal and mechanical strain rates, with environmental-fatigue damage dominating during out-of-phase thermomechanical loading and creep damage dominating in-phase thermomechanical loading. The coarse-grained polycrystalline microstructure of the alloy studied causes a significant variation in the elastic response, which can be linked to the crystallographic orientation of the large grains. This variation in the elastic response presents difficulties for both the constitutive and life models, which depend upon the assumption of an isotropic material. The extreme effects of a large grained microstructure on the life predictions is demonstrated, and a suitable modeling framework is proposed to account for these effects in future work.
Advisors/Committee Members: Neu, Richard W. (advisor), McDowell, David L. (advisor), Pierron, Olivier N. (advisor).
Subjects/Keywords: Ni-base superalloy; Thermomechanical fatigue; Creep-plasticity; Constitutive model; Heat resistant alloys; Nickel alloys Thermal properties; Nickel alloys Fatigue
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Brindley, K. A. (2014). Thermomechanical fatigue of Mar-M247: extension of a unified constitutive and life model to higher temperatures. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51852
Chicago Manual of Style (16th Edition):
Brindley, Kyle A. “Thermomechanical fatigue of Mar-M247: extension of a unified constitutive and life model to higher temperatures.” 2014. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/51852.
MLA Handbook (7th Edition):
Brindley, Kyle A. “Thermomechanical fatigue of Mar-M247: extension of a unified constitutive and life model to higher temperatures.” 2014. Web. 17 Feb 2019.
Vancouver:
Brindley KA. Thermomechanical fatigue of Mar-M247: extension of a unified constitutive and life model to higher temperatures. [Internet] [Masters thesis]. Georgia Tech; 2014. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/51852.
Council of Science Editors:
Brindley KA. Thermomechanical fatigue of Mar-M247: extension of a unified constitutive and life model to higher temperatures. [Masters Thesis]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/51852
23.
Narayanan, Sankar.
Atomistic and multiscale modeling of plasticity in irradiated metals.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/53004
► Irradiation induces a high concentration of defects in the structural materials of nuclear reactors, which are typically of body-centered cubic Iron (BCC Fe) and its…
(more)
▼ Irradiation induces a high concentration of defects in the structural materials of nuclear reactors, which are typically of body-centered cubic Iron (BCC Fe) and its alloys. The primary effect of irradiation is hardening which is caused by the blocking of dislocations with defects and defect clusters like point defects, self-interstitial loops, and voids. The dislocation-defect interactions are atomistic in nature due to the very small length and time scales involved, i.e., of the order of nanometers and picoseconds. To predict the effect of dislocation-defect interactions on the macroscopic mechanical and plastic behavior of the material, it is critically important to develop robust coupling schemes by which accurate atomic level physics of the rate-limiting kinetic processes can be informed into a coarse-grained model such as crystal plasticity. In this thesis we will develop an atomistically informed constitutive model. Relevant atomistic processes are identified from molecular dynamics simulations. The respective unit process studies are conducted using atomistic reaction pathway sampling methods like Nudged Elastic Band method. Stress-dependent activation energies and activation volumes are computed for various rate-liming unit processes like thermally activated dislocation motion via kinkpair nucleation, dislocation pinning due to self interstitial atom, etc. Constitutive laws are developed based on transition state theory, that informs the atomistically determined activation parameters into a coarse-grained crystal plasticity model. The macroscopic deformation behavior predicted by the crystal plasticity model is validated with experimental results and the characteristic features explained in the light of atomistic knowledge of the constituting kinetics. We also investigate on unique irradiation induced defects such as stacking fault tetrahedra, that are formed under non-irradiated condition. This thesis also includes our work on materials with internal interfaces that can resist irradiation induced damage. Overall, the research presented in this thesis involves the implementation and development of novel computational paradigm that encompasses computational approaches of various length and time scales towards robust predictions of the mechanical behavior of irradiated materials.
Advisors/Committee Members: Zhu, Ting (advisor), Deo, Chaitanya (committee member), Garmestani, Hamid (committee member), McDowell, David L. (committee member).
Subjects/Keywords: Metal plasticity; Multiscale modeling; Atomistic modeling; Molecular dynamics; Solid mechanics; Irradiation damage; Nudged elastic band method
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Narayanan, S. (2014). Atomistic and multiscale modeling of plasticity in irradiated metals. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53004
Chicago Manual of Style (16th Edition):
Narayanan, Sankar. “Atomistic and multiscale modeling of plasticity in irradiated metals.” 2014. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/53004.
MLA Handbook (7th Edition):
Narayanan, Sankar. “Atomistic and multiscale modeling of plasticity in irradiated metals.” 2014. Web. 17 Feb 2019.
Vancouver:
Narayanan S. Atomistic and multiscale modeling of plasticity in irradiated metals. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/53004.
Council of Science Editors:
Narayanan S. Atomistic and multiscale modeling of plasticity in irradiated metals. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/53004
24.
Fromm, Bradley S.
Linking phase field and finite element modeling for process-structure-property relations of a Ni-base superalloy.
Degree: MS, Materials Science and Engineering, 2012, Georgia Tech
URL: http://hdl.handle.net/1853/45789
► Establishing process-structure-property relationships is an important objective in the paradigm of materials design in order to reduce the time and cost needed to develop new…
(more)
▼ Establishing process-structure-property relationships is an important objective in the paradigm of materials design in order to reduce the time and cost needed to develop new materials. A method to link phase field (process-structure relations) and microstructure-sensitive finite element (structure-property relations) modeling is demonstrated for subsolvus polycrystalline IN100. A three-dimensional (3D) experimental dataset obtained by orientation imaging microscopy performed on serial sections is utilized to calibrate a phase field model and to calculate inputs for a finite element analysis. Simulated annealing of the dataset realized through phase field modeling results in a range of coarsened microstructures with varying grain size distributions that are each input into the finite element model. A rate dependent crystal plasticity constitutive model that captures the first order effects of grain size, precipitate size, and precipitate volume fraction on the mechanical response of IN100 at 650°C is used to simulate stress-strain behavior of the coarsened polycrystals. Model limitations and ideas for future work are discussed.
Advisors/Committee Members: Garmestani, Hamid (Committee Chair), McDowell, David L. (Committee Member), Neu, Richard W. (Committee Member).
Subjects/Keywords: Finite-element method; Crystal plasticity; Phase-field modeling; Process structure property relations; Microstructure-sensitive design; Microstructure; Finite element method; Materials science; Simulation methods
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Fromm, B. S. (2012). Linking phase field and finite element modeling for process-structure-property relations of a Ni-base superalloy. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/45789
Chicago Manual of Style (16th Edition):
Fromm, Bradley S. “Linking phase field and finite element modeling for process-structure-property relations of a Ni-base superalloy.” 2012. Masters Thesis, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/45789.
MLA Handbook (7th Edition):
Fromm, Bradley S. “Linking phase field and finite element modeling for process-structure-property relations of a Ni-base superalloy.” 2012. Web. 17 Feb 2019.
Vancouver:
Fromm BS. Linking phase field and finite element modeling for process-structure-property relations of a Ni-base superalloy. [Internet] [Masters thesis]. Georgia Tech; 2012. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/45789.
Council of Science Editors:
Fromm BS. Linking phase field and finite element modeling for process-structure-property relations of a Ni-base superalloy. [Masters Thesis]. Georgia Tech; 2012. Available from: http://hdl.handle.net/1853/45789
Georgia Tech
25.
Dunn, Aaron Yehudah.
Radiation damage accumulation and associated mechanical hardening in thin films and bulk materials.
Degree: PhD, Mechanical Engineering, 2016, Georgia Tech
URL: http://hdl.handle.net/1853/54959
► The overall purpose of this dissertation is to develop a multi-scale framework that can simulate radiation defect accumulation across a broad range of time and…
(more)
▼ The overall purpose of this dissertation is to develop a multi-scale framework that can simulate radiation defect accumulation across a broad range of time and length scales in metals.
In order to accurately describe defect accumulation in heterogeneous microstructures and under complex irradiation conditions, simulation methods are needed that can explicitly account for the effect of non-homogeneous microstructures on damage accumulation. In this dissertation, an advanced simulation tool called spatially resolved stochastic cluster dynamics (SRSCD) is developed for this purpose. The proposed approach relies on solving spatially resolved coupled rate equations of standard cluster dynamics methods in a kinetic Monte Carlo scheme. Large-scale simulations of radiation damage in polycrystalline materials are enabled through several improvements made to this method, including a pseudo-adaptive meshing scheme for cascade implantation and implementation of this method in a synchronous parallel kinetic Monte Carlo framework. The performance of the SRSCD framework developed in this dissertation is assessed by comparison to other simulation methods such as cluster dynamics and object kinetic Monte Carlo and experimental results including helium desorption from thin films and defect accumulation in neutron-irradiated bulk iron. The computational scaling of the parallel framework is also investigated for several test cases of irradiation conditions. SRSCD is next used to investigate radiation damage in three main types of microstructures, using α-iron as a test material: iron thin films, coarse-grained bulk iron, and nanocrystalline iron. SRSCD is used to investigate the mechanisms involved with defect accumulation in irradiated materials, such as effective diffusivity of helium in thin films and the effect of grain boundary sink strength on defect accumulation in nano-grained metals, and to predict defect populations in irradiated materials for comparison with experiments. Particular emphasis is placed on the role of microstructural features such as free surfaces and grain boundaries in influencing damage accumulation. Finally, the methodology developed in this dissertation is applied in the context of multiscale modeling and experimental design. To complete the multi-scale transition between defect-level behavior and macroscopic material property changes caused by irradiation, the relationship between mechanical loading and radiation damage is investigated. The impact of radiation damage on hardening of irradiated materials is investigated by using the results of SRSCD as inputs into polycrystalline crystal plasticity simulations. This is carried out in bulk iron by fitting hardening models to experimental data from neutron irradiation of iron and then used to predict hardening under irradiation conditions beyond what has already been accomplished in experimental studies. In addition, SRSCD is used to demonstrate the temperature shift required to achieve equivalent damage accumulation in irradiation conditions with…
Advisors/Committee Members: Capolungo, Laurent (advisor), McDowell, David L. (committee member), Thadhani, Naresh (committee member), Deo, Chaitanya (committee member), Dingreville, Rémi (committee member), Martínez-Saez, Enrique (committee member).
Subjects/Keywords: Radiation damage; Cluster dynamics; Stochastic cluster dynamics; Radiation hardening; Ion irradiation; Neutron irradiation
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Dunn, A. Y. (2016). Radiation damage accumulation and associated mechanical hardening in thin films and bulk materials. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/54959
Chicago Manual of Style (16th Edition):
Dunn, Aaron Yehudah. “Radiation damage accumulation and associated mechanical hardening in thin films and bulk materials.” 2016. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/54959.
MLA Handbook (7th Edition):
Dunn, Aaron Yehudah. “Radiation damage accumulation and associated mechanical hardening in thin films and bulk materials.” 2016. Web. 17 Feb 2019.
Vancouver:
Dunn AY. Radiation damage accumulation and associated mechanical hardening in thin films and bulk materials. [Internet] [Doctoral dissertation]. Georgia Tech; 2016. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/54959.
Council of Science Editors:
Dunn AY. Radiation damage accumulation and associated mechanical hardening in thin films and bulk materials. [Doctoral Dissertation]. Georgia Tech; 2016. Available from: http://hdl.handle.net/1853/54959
Georgia Tech
26.
Lloyd, Jeffrey T.
Microstructure-sensitive simulation of shock loading in metals.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/51853
► A constitutive model has been developed to model the shock response of single crystal aluminum from peak pressures ranging from 2-110 GPa. This model couples…
(more)
▼ A constitutive model has been developed to model the shock response of single crystal aluminum from peak pressures ranging from 2-110 GPa. This model couples a description of higher-order thermoelasticity with a dislocation-based viscoplastic formulation, both of which are formulated for single crystals. The constitutive model has been implemented using two numerical methods: a plane wave method that tracks the propagating wave front; and an extended one-dimensional, finite-difference method that can be used to model spatio-temporal evolution of wave propagation in anisotropic materials. The constitutive model, as well as these numerical methods, are used to simulate shock wave propagation in single crystals, polycrystals, and pre-textured polycrystals. Model predictions are compared with extensive existing experimental data and are then used to quantify the influence of the initial material state on the subsequent shock response. A coarse-grained model is then proposed to capture orientation-dependent deformation heterogeneity, and is shown to replicate salient features predicted by direct finite-difference simulation of polycrystals in the weak shock regime. The work in this thesis establishes a general framework that can be used to quantify the influence of initial material state on subsequent shock behavior not only for aluminum single crystals, but for other face-centered cubic and lower symmetry crystalline metals as well.
Advisors/Committee Members: McDowell, David L. (advisor), Clayton, John D. (committee member), Zhou, Min (committee member), Rimoli, Julian J. (committee member), Thadhani, Naresh N. (committee member), Xia, Shuman (committee member).
Subjects/Keywords: Continuum mechanics; Aluminum; High rate deformation; Dislocation dynamics; Crystal plasticity; Thermoelasticity; Viscoplasticity; Elasticity; Thermodynamics; Shock (Mechanics); Microstructure
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Lloyd, J. T. (2014). Microstructure-sensitive simulation of shock loading in metals. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51853
Chicago Manual of Style (16th Edition):
Lloyd, Jeffrey T. “Microstructure-sensitive simulation of shock loading in metals.” 2014. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/51853.
MLA Handbook (7th Edition):
Lloyd, Jeffrey T. “Microstructure-sensitive simulation of shock loading in metals.” 2014. Web. 17 Feb 2019.
Vancouver:
Lloyd JT. Microstructure-sensitive simulation of shock loading in metals. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/51853.
Council of Science Editors:
Lloyd JT. Microstructure-sensitive simulation of shock loading in metals. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/51853
Georgia Tech
27.
Matlack, Kathryn H.
Nonlinear ultrasound for radiation damage detection.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/51965
► Radiation damage occurs in reactor pressure vessel (RPV) steel, causing microstructural changes such as point defect clusters, interstitial loops, vacancy-solute clusters, and precipitates, that cause…
(more)
▼ Radiation damage occurs in reactor pressure vessel (RPV) steel, causing microstructural changes such as point defect clusters, interstitial loops, vacancy-solute clusters, and precipitates, that cause material embrittlement. Radiation damage is a crucial concern in the nuclear industry since many nuclear plants throughout the US are entering the first period of life extension and older plants are currently undergoing assessment of technical basis to operate beyond 60 years. The result of extended operation is that the RPV and other components will be exposed to higher levels of neutron radiation than they were originally designed to withstand. There is currently no nondestructive evaluation technique that can unambiguously assess the amount of radiation damage in RPV steels. Nonlinear ultrasound (NLU) is a nondestructive evaluation technique that is sensitive to microstructural features such as dislocations, precipitates, and their interactions in metallic materials. The physical effect monitored by NLU is the generation of higher harmonic frequencies in an initially monochromatic ultrasonic wave, arising from the interaction of the ultrasonic wave with microstructural features. This effect is quantified with the measurable acoustic nonlinearity parameter, beta. In this work, nonlinear ultrasound is used to characterize radiation damage in reactor pressure vessel steels over a range of fluence levels, irradiation temperatures, and material composition. Experimental results are presented and interpreted with newly developed analytical models that combine different irradiation-induced microstructural contributions to the acoustic nonlinearity parameter.
Advisors/Committee Members: Jacobs, Laurence J. (advisor), Qu, Jianmin (committee member), Kim, Jin-Yeon (committee member), McDowell, David L. (committee member), Deo, Chaitanya (committee member), Wall, James J. (committee member).
Subjects/Keywords: Nonlinear ultrasound; Second harmonic generation; Nondestructive evaluation; Radiation damage; Reactor pressure vessel steel; Structural health monitoring; Nondestructive testing; Nuclear pressure vessels
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Matlack, K. H. (2014). Nonlinear ultrasound for radiation damage detection. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/51965
Chicago Manual of Style (16th Edition):
Matlack, Kathryn H. “Nonlinear ultrasound for radiation damage detection.” 2014. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/51965.
MLA Handbook (7th Edition):
Matlack, Kathryn H. “Nonlinear ultrasound for radiation damage detection.” 2014. Web. 17 Feb 2019.
Vancouver:
Matlack KH. Nonlinear ultrasound for radiation damage detection. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/51965.
Council of Science Editors:
Matlack KH. Nonlinear ultrasound for radiation damage detection. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/51965
Georgia Tech
28.
Hirsch, Michael Robert.
Temperature dependent fretting damage modeling of AISI 301 stainless steel.
Degree: PhD, Mechanical Engineering, 2013, Georgia Tech
URL: http://hdl.handle.net/1853/52975
► Prediction of fatigue damage due to fretting is complex due to the number of influential factors and the competitive interaction between wear and fatigue. The…
(more)
▼ Prediction of fatigue damage due to fretting is complex due to the number of influential factors and the competitive interaction between wear and fatigue. The majority of current fretting damage modeling approaches are limited to narrow ranges of conditions where little competition between damage mechanisms occurs. Recent models which account for damage interaction are largely phenomenological in nature and are still limited to a narrow range of applicability. A method to characterize and model the level of fatigue damage due to fretting was developed in this work to address the shortcomings of the current methods available by extending the range of conditions captured and enhancing the physical basis of the damage model.
Baseline material properties for thin sheets of AISI 301 stainless steel in the full hard condition were determined as a function of temperature through tensile tests, fatigue tests, and metallography. Fretting experiments were performed for contact between 301 stainless steel and each ANSI A356 aluminum and AISI 52100 steel. Fretting experiments were performed over a range of material combinations, normal forces, displacement amplitudes, atmospheres, and temperatures. Subsequent characterization of the damage due to fretting was performed to determine the level of wear and fatigue damage incurred for each condition tested.
A finite element model of the experiment was created to determine the cyclic stress-strain behavior and local frictional energy dissipation for each condition. Fatigue damage metrics were evaluated to determine the effects of the contact conditions on the driver for fatigue damage. A new model for fatigue damage due to fretting was developed which incorporates the wear behavior to describe the effect of wear on the level of fatigue damage caused by fretting. The level of fatigue damage is influenced using a function of frictional energy dissipation and wear rate to account for differences in wear mechanisms and changes in the severity of wear caused by changes in oxidation behavior and mechanical properties which result from changes in temperature or contacting materials.
Advisors/Committee Members: Neu, Richard W. (advisor), Antolovich, Stephen D. (committee member), McDowell, David L. (committee member), Singh, Preet M. (committee member), Sitaraman, Suresh K. (committee member).
Subjects/Keywords: Fretting; Fatigue; Stainless steel; FEM
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Hirsch, M. R. (2013). Temperature dependent fretting damage modeling of AISI 301 stainless steel. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52975
Chicago Manual of Style (16th Edition):
Hirsch, Michael Robert. “Temperature dependent fretting damage modeling of AISI 301 stainless steel.” 2013. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/52975.
MLA Handbook (7th Edition):
Hirsch, Michael Robert. “Temperature dependent fretting damage modeling of AISI 301 stainless steel.” 2013. Web. 17 Feb 2019.
Vancouver:
Hirsch MR. Temperature dependent fretting damage modeling of AISI 301 stainless steel. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/52975.
Council of Science Editors:
Hirsch MR. Temperature dependent fretting damage modeling of AISI 301 stainless steel. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/52975
Georgia Tech
29.
Li, Yan.
Prediction of material fracture toughness as function of microstructure.
Degree: PhD, Mechanical Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/52999
► Microstructure determines fracture toughness of materials through the activation of different fracture mechanisms. To tailor the fracture toughness through microstructure design, it is important to…
(more)
▼ Microstructure determines fracture toughness of materials through the activation of different fracture mechanisms. To tailor the fracture toughness through microstructure design, it is important to establish relations between microstructure and fracture toughness. To this end, systematic characterization of microstructures, explicit tracking of crack propagation process and realistic representation of deformation and fracture at different length scales are required. A cohesive finite element method (CFEM) based multiscale framework is proposed for analyzing the effect of microstructural heterogeneity, phase morphology, texture, constituent behavior and interfacial bonding strength on fracture toughness. The approach uses the J-integral to calculate the initiation/propagation fracture toughness, allowing explicit representation of realistic microstructures and fundamental fracture mechanisms.
Both brittle and ductile materials can be analyzed using this framework. For two-phase Al₂O₃/TiB₂ ceramics, the propagation fracture toughness is improved through fine microstructure size scale, rounded reinforcement morphology and appropriately balanced interphase bonding strength and compliance. These microstructure characteristics can promote interface debonding and discourage particle cracking induced catastrophic failure. Based on the CFEM results, a semi-empirical model is developed to establish a quantitative relation between the propagation toughness and statistical measures of microstructure, fracture mechanisms, constituent and interfacial properties. The analytical model provides deeper insights into the fracture process as it quantitatively predicts the proportion of each fracture mechanism in the heterogeneous microstructure. Based on the study on brittle materials, the semi-analytical model is extended to ductile materials such as AZ31 Mg alloy and Ti-6Al-4V alloy. The fracture resistance in these materials not only depends on the crack surfaces formed during the failure process, but also largely determined by the bulk plastic energy dissipation. The CFEM simulation permits surface energy release rate to be quantified through explicit tracking of crack propagation in the microstructure. The plastic energy dissipation rate is evaluated as the difference between the predicted J value and the surface energy release rate. This method allows competition between material deformation and fracture as well as competition between transgranular and intergranular fracture to be quantified. The methodology developed in this thesis is potentially useful for both the selection of materials and tailoring of microstructure to improve fracture resistance.
Advisors/Committee Members: Zhou, Min (advisor), McDowell, David L. (committee member), Neu, Richard (committee member), Zhu, Ting (committee member), Xia, Shuman (committee member), Shih, Donald (committee member).
Subjects/Keywords: Fracture toughness; Microstructure; Multiscale modeling
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Li, Y. (2014). Prediction of material fracture toughness as function of microstructure. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/52999
Chicago Manual of Style (16th Edition):
Li, Yan. “Prediction of material fracture toughness as function of microstructure.” 2014. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/52999.
MLA Handbook (7th Edition):
Li, Yan. “Prediction of material fracture toughness as function of microstructure.” 2014. Web. 17 Feb 2019.
Vancouver:
Li Y. Prediction of material fracture toughness as function of microstructure. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/52999.
Council of Science Editors:
Li Y. Prediction of material fracture toughness as function of microstructure. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/52999
Georgia Tech
30.
Wang, Sihong.
Nanogenerator for mechanical energy harvesting and its hybridization with li-ion battery.
Degree: PhD, Materials Science and Engineering, 2014, Georgia Tech
URL: http://hdl.handle.net/1853/53437
► Energy harvesting and energy storage are two most important technologies in today's green and renewable energy science. As for energy harvesting, the fundamental science and…
(more)
▼ Energy harvesting and energy storage are two most important technologies in today's green and renewable energy science. As for energy harvesting, the fundamental science and practically applicable technologies are not only essential in realizing the self-powered electronic devices and systems, but also tremendously helpful in meeting the rapid-growing world-wide energy consumptions. Mechanical energy is one of the most universally-existing, diversely-presenting, but usually-wasted energies in the natural environment. Owing to the limitations of the traditional technologies for mechanical energy harvesting, it is highly desirable to develop new technology that can efficiently convert different types of mechanical energy into electricity. On the other hand, the electricity generated from environmental energy often needs to be stored before used to drive electronic devices. For the energy storage units such as Li-ion batteries as the power sources, the limited lifetime is the prominent problem. Hybridizing energy harvesting devices with energy storage units could not only provide new solution for this, but also lead to the realization of sustainable power sources.
In this dissertation, the research efforts have led to several critical advances in a new technology for mechanical energy harvesting—triboelectric nanogenerators (TENGs). Previous to the research of this dissertation, the TENG only has one basic mode—the contact mode. Through rational structural design, we largely improved the output performance of the contact-mode TENG and systematically studied their characteristics as a power source. Beyond this, we have also established the second basic mode for TENG—the lateral sliding mode, and demonstrated sliding-based disk TENGs for harvesting rotational energy and wind-cup-based TENGs for harvesting wind energy. In order to expand the application and versatility of TENG by avoid the connection of the electrode on the moving part, we further developed another basic mode—freestanding-layer mode, which is capable of working with supreme stability in non-contact mode and harvesting energy from any free-moving object. Both the grating structured and disk-structured TENGs based on this mode also display much improved long-term stability and very high energy conversion efficiency. For the further improvement of the TENG’s output performance from the material aspect, we introduced the ion-injection method to study the maximum surface charge density of the TENG, and for the first time unraveled its dependence on the structural parameter—the thickness of the dielectric film. The above researches have largely propelled the development of TENGs for mechanical energy harvesting and brought a big potential of impacting people’s everyday life.
Targeted at developing sustainable and independent power sources for electronic devices, efforts have been made in this dissertation to develop new fundamental science and new devices that hybridize the nanogenerator-based mechanical energy harvesting and the Li-ion-battery-based energy…
Advisors/Committee Members: Wang, Zhong Lin (advisor), Liu, Meilin (committee member), El-Sayed, Mostafa A. (committee member), Dupuis, Russell D. (committee member), Kohl, Paul A. (committee member), McDowell, David L. (committee member).
Subjects/Keywords: Energy harvesting; Energy storage; Nanogenerator; Mechanical energy; Li-ion battery; Self-powered systems; Self-charging power cell; Triboelectrification
Record Details
Similar Records
Cite
Share »
Record Details
Similar Records
Cite
« Share
❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wang, S. (2014). Nanogenerator for mechanical energy harvesting and its hybridization with li-ion battery. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/53437
Chicago Manual of Style (16th Edition):
Wang, Sihong. “Nanogenerator for mechanical energy harvesting and its hybridization with li-ion battery.” 2014. Doctoral Dissertation, Georgia Tech. Accessed February 17, 2019.
http://hdl.handle.net/1853/53437.
MLA Handbook (7th Edition):
Wang, Sihong. “Nanogenerator for mechanical energy harvesting and its hybridization with li-ion battery.” 2014. Web. 17 Feb 2019.
Vancouver:
Wang S. Nanogenerator for mechanical energy harvesting and its hybridization with li-ion battery. [Internet] [Doctoral dissertation]. Georgia Tech; 2014. [cited 2019 Feb 17].
Available from: http://hdl.handle.net/1853/53437.
Council of Science Editors:
Wang S. Nanogenerator for mechanical energy harvesting and its hybridization with li-ion battery. [Doctoral Dissertation]. Georgia Tech; 2014. Available from: http://hdl.handle.net/1853/53437
◁ [1] [2] [3] ▶
. 
Open Access Theses and Dissertations
