+publisher:"Cornell University" +contributor:("Ingraffea,Anthony R")

Cornell University

1. Bomarito, Geoffrey. A Computational Investigation Of Ductile Failure In Al5083-H116 And The Shear Strengths Of Pure Aluminum Grain Boundaries.

Degree: PhD, Civil and Environmental Engineering, 2015, Cornell University

URL: http://hdl.handle.net/1813/39335

► Computational models, besides their relatively low cost, offer the benefit of complete control over all testing variables (e.g., atmospheric conditions, loading rates, applied stress states),… (more)

▼ Computational models, besides their relatively low cost, offer the benefit of complete control over all testing variables (e.g., atmospheric conditions, loading rates, applied stress states), which can be difficult to control in experiments. This control can be used to identify key controlling parameters and improve our understanding of the deformation and failure processes. This dissertation investigates how modern computational resources can be leveraged to improve both the understanding and prediction of material deformation and failure. Because of its widespread use and variability of application, aluminum and its alloys are the focus of the investigation. Specifically, the applications of ductile failure and grain boundary shear strength were chosen for this dissertation. Though these phenomena are quite different, the same theme is present in the approach to both problems. In both cases, we were able to run numerous simple simulations of the phenomenon in concern. A large computational effort was required in all cases to run the sets of simulations, but the results of these simulations were synthesized into a simple model which can be used at larger scales. In the case of ductile failure, a unit cell was designed to simulate the microstructural evolution of an aluminum alloy. The population of second phase particles in the alloy was represented as a spherical void surrounded by an alu- minum matrix. Many different loadings were applied to the cell which were characterized by a stress state and orientation. The results of these tests were used to form a simple model for the dependence of ductile failure on applied stress state. By refining the model microstructure, it was found that increasing the fidelity of the model microstructure leads to increased predictive capability of the model. In the case of grain boundary shear strength, atomistic models of interface structures were subjected to shear in many directions in the boundary plane. The simulation of a large number of these interface structures showed that shear yield strengths were relatively independent of the macroscopic parameters describing each interface. Subsequently, it was shown that a statistical approach to predicting grain boundary shear strengths could be used. Advisors/Committee Members: Warner, Derek H. (chair), Ingraffea, Anthony R (committee member), Baker, Shefford P. (committee member).

Subjects/Keywords: Ductile Failure; Aluminum; Grain Boundary

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APA (6^th Edition):

Bomarito, G. (2015). A Computational Investigation Of Ductile Failure In Al5083-H116 And The Shear Strengths Of Pure Aluminum Grain Boundaries. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/39335

Chicago Manual of Style (16^th Edition):

Bomarito, Geoffrey. “A Computational Investigation Of Ductile Failure In Al5083-H116 And The Shear Strengths Of Pure Aluminum Grain Boundaries.” 2015. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/39335.

MLA Handbook (7^th Edition):

Bomarito, Geoffrey. “A Computational Investigation Of Ductile Failure In Al5083-H116 And The Shear Strengths Of Pure Aluminum Grain Boundaries.” 2015. Web. 14 Apr 2021.

Vancouver:

Bomarito G. A Computational Investigation Of Ductile Failure In Al5083-H116 And The Shear Strengths Of Pure Aluminum Grain Boundaries. [Internet] [Doctoral dissertation]. Cornell University; 2015. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/39335.

Council of Science Editors:

Bomarito G. A Computational Investigation Of Ductile Failure In Al5083-H116 And The Shear Strengths Of Pure Aluminum Grain Boundaries. [Doctoral Dissertation]. Cornell University; 2015. Available from: http://hdl.handle.net/1813/39335

Cornell University

2. Baker, Kristopher. Improving Atomistic Simulations To Predict Deformation And Fracture.

Degree: PhD, Civil and Environmental Engineering, 2012, Cornell University

URL: http://hdl.handle.net/1813/31080

► Atomistic simulations can illuminate detailed mechanisms of brittle and ductile fracture and plasticity. However, there are many limitations to these simulations like short timescales, small… (more)

▼ Atomistic simulations can illuminate detailed mechanisms of brittle and ductile fracture and plasticity. However, there are many limitations to these simulations like short timescales, small spatial scales, and limitations of the discretization. Using molecular dynamics (MD) and multiscale methods, adaptations can be made to allow MD to answer problems relevant to engineers. In the first of three examples, MD is adapted to simulate brittle fracture by changing the discretization and allowing permanent damage between particles. By changing the discretization, specific mechanisms inherent to MD can be suppressed to allow accurate, macroscopic simulations of dynamic fragmentation of brittle materials. Second, the timescale available to MD is extended in a concurrent multiscale method (CADD) combined with accelerated MD. This combined approach allows for microseconds of simulation time at experimentally achievable loading rates. The method is applied to crack opening in aluminum alloys, and the effect of the loading rate on crack growth mechanisms is observed. From the results, it is clear that crack growth mechanisms depend greatly on the rate of the far-field loading. Third, the effect of aging on fatigue crack growth is studied by varying the resistance to dislocation motion in the dislocation dynamics region of CADD. Only in a multiscale simulation like CADD, can dislocation pileups reaching microns into the material interact with the atomic-scale mechanisms at a crack tip. The results of the simulations indicated that increasing the friction force raises the fatigue crack threshold. Also, a transition from stage I fatigue crack growth to stage II fatigue crack growth occurs by dislocations shielding dislocation nucleation on the primary slip plane. These observations support the conclusion that the fatigue crack growth threshold is controlled by the spacing between obstacles to dislocation glide, which is consistent with experimental observations. Advisors/Committee Members: Warner, Derek H. (chair), Ingraffea, Anthony R (committee member), Hennig, Richard G. (committee member).

Subjects/Keywords: Multiscale; Fatigue; Molecular Dynamics

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APA (6^th Edition):

Baker, K. (2012). Improving Atomistic Simulations To Predict Deformation And Fracture. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/31080

Chicago Manual of Style (16^th Edition):

Baker, Kristopher. “Improving Atomistic Simulations To Predict Deformation And Fracture.” 2012. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/31080.

MLA Handbook (7^th Edition):

Baker, Kristopher. “Improving Atomistic Simulations To Predict Deformation And Fracture.” 2012. Web. 14 Apr 2021.

Vancouver:

Baker K. Improving Atomistic Simulations To Predict Deformation And Fracture. [Internet] [Doctoral dissertation]. Cornell University; 2012. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/31080.

Council of Science Editors:

Baker K. Improving Atomistic Simulations To Predict Deformation And Fracture. [Doctoral Dissertation]. Cornell University; 2012. Available from: http://hdl.handle.net/1813/31080

Cornell University

3. Aguilo, Miguel. Inverse Strategies For Characterization Of Material Properties.

Degree: PhD, Civil and Environmental Engineering, 2011, Cornell University

URL: http://hdl.handle.net/1813/33569

► The imaging of constitutive parameters is of interest in many science and engineering fields. Indeed, non-invasive and nondestructive techniques are used to characterize key properties… (more)

▼ The imaging of constitutive parameters is of interest in many science and engineering fields. Indeed, non-invasive and nondestructive techniques are used to characterize key properties of a system given its response due to an external excitation. Then, assuming a priori a given model of the system, the measured response and an inverse approach are used to identify material properties. This work was undertaken in the context of identification of spatially-varying elastic and viscoelastic parameters of solids using vibroacoustics based techniques. Two optimization approaches, nongradient and gradient-based optimization, were investigated in this work. Initially, nongradient-based algorithms were preferred over gradient-based algorithms because of there ability to find global minima irrespective of initial guesses. For instance, Gaussian radial basis functions were used to construct a finite-dimensional representation of the elastic moduli. Then, an inverse approach was used to approximate the spatiallyvarying elastic moduli through the system response induced by the radiation force of ultrasound. The inverse problem was cast as an optimization problem in which a least-square error functional that quantified the misfit between the experimental and finite element representation system response is minimized by searching over a space of admissible vectors that best describe the spatial distribution of the elastic moduli. Subsequently, gradient-based optimization was preferred over nongradient-based optimization as the number of design variables increased due to the increment in computational cost. Two inverse approaches, L2-adjoint and concept of error in constitutive equation, were investigated in the context of gradient-based optimization. First, the L2-adjoint inverse approach was used to characterize spatially-varying viscoelastic properties because of its advantage to efficiently calculate the gradient of the error functional with respect to the design variables by solving the corresponding adjoint equations. The inverse problem was cast as an optimization problem in which a least-square error functional that quantified the misfit between the experimental and the finite element representation system response is minimized by searching over a space of admissible functions that best describe the spatially-varying viscoelastic properties. Given that the least-square error functional is non-convex, an inverse approach based on the concept of error in constitutive equation was investigated. The convexity property of the error in constitutive equation functionals, shown extensively for elliptic boundary value problems, reduce the sensitivity of the inverse solution to parameter initialization. The inverse problem was cast as an optimization problem in which an error in constitutive equation functional that quantified the misfit between the kinematically and dynamically admissible stress fields is minimized by searching over a space of admissible functions that best describe the spatially-varying viscoelastic properties.… Advisors/Committee Members: Aquino, Wilkins (chair), Mukherjee, Subrata (committee member), Ingraffea, Anthony R (committee member), Bonassar, Lawrence (committee member).

Subjects/Keywords: viscoelasticity imaging; inverse problem; vibroacoustography

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APA (6^th Edition):

Aguilo, M. (2011). Inverse Strategies For Characterization Of Material Properties. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/33569

Chicago Manual of Style (16^th Edition):

Aguilo, Miguel. “Inverse Strategies For Characterization Of Material Properties.” 2011. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/33569.

MLA Handbook (7^th Edition):

Aguilo, Miguel. “Inverse Strategies For Characterization Of Material Properties.” 2011. Web. 14 Apr 2021.

Vancouver:

Aguilo M. Inverse Strategies For Characterization Of Material Properties. [Internet] [Doctoral dissertation]. Cornell University; 2011. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/33569.

Council of Science Editors:

Aguilo M. Inverse Strategies For Characterization Of Material Properties. [Doctoral Dissertation]. Cornell University; 2011. Available from: http://hdl.handle.net/1813/33569

Cornell University

4. Ning, Jing. Creep Damage And Fracture Mechanics Of High Temperature Materials.

Degree: PhD, Mechanical Engineering, 2013, Cornell University

URL: http://hdl.handle.net/1813/33875

► This dissertation studies the deformation behavior of high temperature alloys with an aim to understand creep damage and fracture mechanics of these materials. First, we… (more)

▼ This dissertation studies the deformation behavior of high temperature alloys with an aim to understand creep damage and fracture mechanics of these materials. First, we study the creep fatigue deformation of a unified viscoplastic material subjected to uniaxial cyclic loading using a dynamical system approach. We find oscillation of back stress significantly increases the inelastic strain accumulation in a cyclic test. The accumulated inelastic strain at long times are sensitive to the initial condition (e.g. whether one starts with tension or compression). We define a ratcheting ratio to quantify the interaction of creep and cyclic plasticity on the accumulated inelastic strain per cycle. The second part of the dissertation focuses on solving the asymptotic stress and strain field near the tip of a plane strain Mode I stationary crack in a viscoplastic material. For small scale creep where the region of inelasticity is small in comparison with typical specimen dimensions, our asymptotic and finite element analysis show that the near tip stress field has the same singularity as elastic power law creeping materials with a time dependent amplitude. This amplitude is found to vanish at long times and the elastic K field dominates. For the case of cyclic loading, we study the effect of stress ratio on inelastic strain and find that the strain accumulated per cycle decreases with stress ratio. iii The third part of the dissertation carries out finite element simulations on the planar deformation of random sized power law creeping grains with sliding and cavitating boundaries. Grain boundary sliding and grain boundary separation due to cavity nucleation and growth are incorporated into a cohesive zone model. Finite element simulation of a relaxation test shows that more grain boundary separation occurs in a microstructure with sliding resistant grain boundaries than in a microstructure with more freely sliding grain boundaries. The overall inelastic strain rate of the microstructure in uniaxial tension test is found to be greatly enhanced by grain boundary sliding and grain boundary cavitation. Finally, we extend the cohesive zone model in the third part of the dissertation to account for interface embrittlement caused by grain boundary impurities. Finite element simulation of an uniaxial creep test using a two dimensional random grain structure shows that grain boundary cavitation and interface embrittlement are two competing mechanisms for grain boundary separation. The occurrence of one grain boundary separation mode would slow down or even inhibit the other. iv Advisors/Committee Members: Hui, Chung-Yuen (chair), Ingraffea, Anthony R (committee member), Phoenix, Stuart Leigh (committee member).

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APA (6^th Edition):

Ning, J. (2013). Creep Damage And Fracture Mechanics Of High Temperature Materials. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/33875

Chicago Manual of Style (16^th Edition):

Ning, Jing. “Creep Damage And Fracture Mechanics Of High Temperature Materials.” 2013. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/33875.

MLA Handbook (7^th Edition):

Ning, Jing. “Creep Damage And Fracture Mechanics Of High Temperature Materials.” 2013. Web. 14 Apr 2021.

Vancouver:

Ning J. Creep Damage And Fracture Mechanics Of High Temperature Materials. [Internet] [Doctoral dissertation]. Cornell University; 2013. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/33875.

Council of Science Editors:

Ning J. Creep Damage And Fracture Mechanics Of High Temperature Materials. [Doctoral Dissertation]. Cornell University; 2013. Available from: http://hdl.handle.net/1813/33875

Cornell University

5. Veilleux, Michael. Geometrically Explicit Finite Element Modeling Of Aa7075-T651 Microstructure With Fatigue Cracks.

Degree: PhD, Civil and Environmental Engineering, 2011, Cornell University

URL: http://hdl.handle.net/1813/33578

► This dissertation is divided into three chapters, where each is an independent paper intended to be submitted as a refereed journal article. The main thrust… (more)

▼ This dissertation is divided into three chapters, where each is an independent paper intended to be submitted as a refereed journal article. The main thrust of the research project overarching all three papers is to develop a high fidelity, geometrically explicit approach to finite element modeling fatigue at the microstructural length scale. Each paper is a study within this thrust, and the following is a sweeping overview of each study. More detailed abstracts for each paper are given at the beginning of each chapter. The paper in the first chapter is the fourth in a series of papers focused on implementing, calibrating, and validating criteria for simulating microstructurally small fatigue crack (MSFC) evolution, with high strain conditions in aluminum alloy (AA)7075-T651 as the proof-test application. MSFC evolution is divided into three stages: incubation, nucleation, and propagation. The specific focus of this paper is on the last stage, MSFC propagation, which is microstructure-governed fatigue crack growth through grains and/or along grain boundaries. Three simulated field metrics, crack tip displacement, crack-induced plastic slip localization, and maximum tangential stress ahead of the crack, previously investigated for prediction of nucleation, are investigated in this paper to determine their dependence on microstructural heterogeneities after nucleation. A total of 21 simulations are performed on a simplified baseline model of an AA7075-T651 microstructural region containing an MSFC. All three metrics are determined to be significantly dependent on the local microstructure immediately subsequent to nucleation. The particle spawning the crack and the orientation(s) of the grain(s) immediately surrounding the nucleated MSFC most influence the MSFC metrics. The paper in the second chapter focuses on the implementation of a computational framework that accurately and probabilistically models fatigue crack propagation at the microstructural scale, once again with high strain conditions in AA7075-T651 as the proof-test application. Toolsets are presented that generate and discretize statistically accurate microstructure geometry models and explicitly simulate the evolution of microstructurally small fatigue cracks. The concept is demonstrated through two model simulations and feasibility of the approach is critically evaluated. The paper in the third chapter is the fifth in the same series of papers described above for the first chapter. The focus of this paper is again on the last MSFC evolution stage, MSFC propagation. High resolution, micro-scale images of three propagating MSFC's are analyzed to determine dependencies of MSFC propagation on microstructural heterogeneities. Additionally, the three MSFC metrics studied in the first chapter - maximum tangential stresses, plastic slip localization, and crack displacements local to the crack front - are simulated in a finite element model that replicates an observed MSFC and the surrounding microstructure. The detailed observations and simulation reveal that… Advisors/Committee Members: Ingraffea, Anthony R (chair), Zehnder, Alan Taylor (committee member), Earls, Christopher J (committee member).

Subjects/Keywords: fracture; fatigue; microstructure

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APA (6^th Edition):

Veilleux, M. (2011). Geometrically Explicit Finite Element Modeling Of Aa7075-T651 Microstructure With Fatigue Cracks. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/33578

Chicago Manual of Style (16^th Edition):

Veilleux, Michael. “Geometrically Explicit Finite Element Modeling Of Aa7075-T651 Microstructure With Fatigue Cracks.” 2011. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/33578.

MLA Handbook (7^th Edition):

Veilleux, Michael. “Geometrically Explicit Finite Element Modeling Of Aa7075-T651 Microstructure With Fatigue Cracks.” 2011. Web. 14 Apr 2021.

Vancouver:

Veilleux M. Geometrically Explicit Finite Element Modeling Of Aa7075-T651 Microstructure With Fatigue Cracks. [Internet] [Doctoral dissertation]. Cornell University; 2011. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/33578.

Council of Science Editors:

Veilleux M. Geometrically Explicit Finite Element Modeling Of Aa7075-T651 Microstructure With Fatigue Cracks. [Doctoral Dissertation]. Cornell University; 2011. Available from: http://hdl.handle.net/1813/33578

Cornell University

6. Aron Melo, Felipe Alejandro. Active And Long-Lived Permanent Forearc Deformation Driven By The Subduction Seismic Cycle.

Degree: PhD, Geological Sciences, 2014, Cornell University

URL: http://hdl.handle.net/1813/38981

► I have used geological, geophysical and engineering methods to explore mechanisms of upper plate, brittle deformation at active forearc regions. My dissertation particularly addresses the… (more)

▼ I have used geological, geophysical and engineering methods to explore mechanisms of upper plate, brittle deformation at active forearc regions. My dissertation particularly addresses the permanent deformation style experienced by the forearc following great subduction ruptures, such as the 2010 Mw8.8 Maule, Chile and 2011 Mw9.0 Tohoku, Japan earthquakes. These events triggered large, shallow seismicity on upper plate normal faults above the rupture reaching Mw7.0. First I present new structural data from the Chilean Coastal Cordillera over the rupture zone of the Maule earthquake. The study area contains the Pichilemu normal fault, which produced the large crustal aftershocks of the megathrust event. Normal faults are the major neotectonic structural elements but reverse faults also exist. Crustal seismicity and GPS surface displacements show that the forearc experiences pulses of rapid coseismic extension, parallel to the heave of the megathrust, and slow interseismic, convergence-parallel shortening. These cycles, over geologic time, build the forearc structural grain, reactivating structures properly-oriented respect to the deformation field of each stage of the interplate cycle. Great subduction events may play a fundamental role in constructing the crustal architecture of extensional forearc regions. Static mechanical models of coseismic and interseismic upper plate deformation are used to explore for distinct features that could result from brittle fracturing over the two stages of the interplate cycle. I show that the semi-elliptical outline of the first-order normal faults along the Coastal Cordillera may define the location of a characteristic, long-lived megathrust segment. Finally, using data from the Global CMT catalog I analyzed the seismic behavior through time of forearc regions that have experienced great subduction ruptures >Mw7.7 worldwide. Between 61% and 83% of the cases where upper plate earthquakes exhibited periods of increased seismicity above background levels occurred contemporaneous to megathrust ruptures. That correlation is stronger for normal fault events than reverse or strike-slip crustal earthquakes. More importantly, for any given megathrust the summation of the Mw accounted by the forearc normal fault aftershocks appears to have a positive linear correlation with the Mw of the subduction earthquake - the larger the megathrust the larger the energy released by forearc events. Advisors/Committee Members: Allmendinger, Richard Waldron (chair), Ingraffea, Anthony R (committee member), Pritchard, Matthew (committee member).

Subjects/Keywords: Subduction seismic cycle; Permanent forearc deformation; 2010 Maule earthquake

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APA (6^th Edition):

Aron Melo, F. A. (2014). Active And Long-Lived Permanent Forearc Deformation Driven By The Subduction Seismic Cycle. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/38981

Chicago Manual of Style (16^th Edition):

Aron Melo, Felipe Alejandro. “Active And Long-Lived Permanent Forearc Deformation Driven By The Subduction Seismic Cycle.” 2014. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/38981.

MLA Handbook (7^th Edition):

Aron Melo, Felipe Alejandro. “Active And Long-Lived Permanent Forearc Deformation Driven By The Subduction Seismic Cycle.” 2014. Web. 14 Apr 2021.

Vancouver:

Aron Melo FA. Active And Long-Lived Permanent Forearc Deformation Driven By The Subduction Seismic Cycle. [Internet] [Doctoral dissertation]. Cornell University; 2014. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/38981.

Council of Science Editors:

Aron Melo FA. Active And Long-Lived Permanent Forearc Deformation Driven By The Subduction Seismic Cycle. [Doctoral Dissertation]. Cornell University; 2014. Available from: http://hdl.handle.net/1813/38981

Cornell University

7. Zamora, Richard. Illuminating The Chemo-Mechanics Of Environment Assisted Fatigue In Aluminum.

Degree: PhD, Civil and Environmental Engineering, 2015, Cornell University

URL: http://hdl.handle.net/1813/39402

► This dissertation composes three papers detailing work intended to illuminate the atomistic-scale mechanisms governing environment assisted fatigue crack growth in aluminum. All studies focus on… (more)

▼ This dissertation composes three papers detailing work intended to illuminate the atomistic-scale mechanisms governing environment assisted fatigue crack growth in aluminum. All studies focus on the application of concurrent atomistic-continuum multiscale modeling, utilizing the coupled atomistic and discrete dislocation (CADD) methodology. First, an ab-initio prediction of environmental embrittlement in aluminum is demonstrated using a density functional theory (DFT) based multiscale framework to simulate the behavior of a loaded crack-tip in the presence of both elemental oxygen and hydrogen impurities. The multiscale simulations and subsequent analysis suggest that electronegative surface impurities can inhibit dislocation nucleation from a crack-tip, which is consistent with macroscopic brittle failure. Second, a series of ab-initio and multiscale simulations are performed, directly linking an atomistic mechanism of hydrogen-assisted cracking (HAC) to experimental fatigue data. The mechanism of enhanced surface deformation is demonstrated using an aluminum-only interatomic potential capable of reproducing ab-initio trends by strategically shielding critical surface bonds in accordance with the environmental exposure level. The strategic shielding approach is used within a CADD-based model to predict an embrittling effect of hydrogen on near threshold fatigue crack growth rates. Third, a CADD-based model is used to simulate the approximate effects of monolayer surface layer stiffening on near-threshold fatigue behavior in aluminum. Stiff surface layer effects are investigated by adding a Lennard-Jones overlay potential to exposed aluminum crack-face atoms. For the single crystal orientation studied, we find that deformation behavior generally begins with a short period of fast transient crack-tip propagation until a stable defect structure has accumulated ahead of the crack. Additionally, the approximate effects of stiff monolayer surface-film formation are found to inhibit crack growth by resisting typical slip-plane cracking behavior. For all studies, the results are discussed in terms of the current environment assisted fatigue literature. Advisors/Committee Members: Warner, Derek H. (chair), Hennig, Richard G. (committee member), Ingraffea, Anthony R (committee member).

Subjects/Keywords: Atomistic modeling; Fatigue; Environment Assisted Cracking

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APA (6^th Edition):

Zamora, R. (2015). Illuminating The Chemo-Mechanics Of Environment Assisted Fatigue In Aluminum. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/39402

Chicago Manual of Style (16^th Edition):

Zamora, Richard. “Illuminating The Chemo-Mechanics Of Environment Assisted Fatigue In Aluminum.” 2015. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/39402.

MLA Handbook (7^th Edition):

Zamora, Richard. “Illuminating The Chemo-Mechanics Of Environment Assisted Fatigue In Aluminum.” 2015. Web. 14 Apr 2021.

Vancouver:

Zamora R. Illuminating The Chemo-Mechanics Of Environment Assisted Fatigue In Aluminum. [Internet] [Doctoral dissertation]. Cornell University; 2015. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/39402.

Council of Science Editors:

Zamora R. Illuminating The Chemo-Mechanics Of Environment Assisted Fatigue In Aluminum. [Doctoral Dissertation]. Cornell University; 2015. Available from: http://hdl.handle.net/1813/39402

Cornell University

8. Wham, Brad. Jointed Pipeline Response To Large Ground Movements.

Degree: PhD, Civil and Environmental Engineering, 2016, Cornell University

URL: http://hdl.handle.net/1813/43567

► This thesis addresses the performance of jointed pipelines subject to ground deformations triggered at a large scale by earthquakes and a construction-related scale by tunneling.… (more)

▼ This thesis addresses the performance of jointed pipelines subject to ground deformations triggered at a large scale by earthquakes and a construction-related scale by tunneling. Understanding and quantifying jointed pipeline response at these scales allows for better design, operational management, and risk assessment of underground infrastructure, where cast iron (CI) and ductile iron (DI) pipelines in the U.S. account for approximately 75% of water distribution systems. The thesis covers the response of DI and molecularly oriented polyvinyl chloride (PVCO) pipelines to earthquaketriggered soil movement as well as CI and DI pipeline response to tunneling. A series of specially designed four-point bending experiments and 3D finite-element (FE) simulations were performed to characterize DI push-on joints commonly used in water distribution systems to develop a relationship between the rotation and axial pullout at both metal binding and first leakage. The results of uniaxial tension and onedimensional compression tests on the elastomeric gaskets in DI push-on joints were implemented in numerical models that show joint leakage to be independent of load path, with a unique pressure boundary that predicts leakage for many combinations of axial pullout and rotation. The increased circumferential strength, reduced pipe wall thickness, and enhanced cross-sectional flexibility of PVCO pipelines was evaluated through the characterization of PVCO material properties, axial joint tension and compression tests, four-point bending tests, and a full-scale fault rupture experiment. A nominal 150-mm (6-in.)diameter PVCO pipeline is able to accommodate significant fault movement through axial tensile and bending strains in the pipe in combination with modest levels of axial slip at the restrained joints. Relatively large levels of axial strain in the low modulus PVCO material, which varies between 1% and 2% at pipeline failure, are able to sustain substantial extension and compression from ground movements. Soil/pipeline interaction modeling was performed for vertical and horizontal ground movements caused by tunneling in jointed CI and DI pipelines perpendicular to the tunnel centerline that (1) extend beyond the width of the settlement profile and (2) connect through 90° tees with a pipeline parallel to the tunnel. The modeling incorporates the results of large-scale laboratory tests. Guidance is provided for design and the identification before tunneling of potential difficulties. In particular, CI tees are at high risk when subject to tunneling induced soil movement, whereas DI pipelines and tees have sufficient capacity to accommodate high levels of tunneling related ground deformation. iv Advisors/Committee Members: O'Rourke,Thomas Denis (chair), Stewart,Harry Eaton (committee member), Ingraffea,Anthony R (committee member).

Subjects/Keywords: pipelines, pipe joints; ductile iron pipe, PVCO pipe; tunneling ground deformation

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APA (6^th Edition):

Wham, B. (2016). Jointed Pipeline Response To Large Ground Movements. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/43567

Chicago Manual of Style (16^th Edition):

Wham, Brad. “Jointed Pipeline Response To Large Ground Movements.” 2016. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/43567.

MLA Handbook (7^th Edition):

Wham, Brad. “Jointed Pipeline Response To Large Ground Movements.” 2016. Web. 14 Apr 2021.

Vancouver:

Wham B. Jointed Pipeline Response To Large Ground Movements. [Internet] [Doctoral dissertation]. Cornell University; 2016. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/43567.

Council of Science Editors:

Wham B. Jointed Pipeline Response To Large Ground Movements. [Doctoral Dissertation]. Cornell University; 2016. Available from: http://hdl.handle.net/1813/43567

Cornell University

9. Kunitake, Miki. The Effects Of Structure And Composition On The Hardness Of Biogenic And Synthetic Single Crystal Calcite.

Degree: PhD, Materials Science and Engineering, 2015, Cornell University

URL: http://hdl.handle.net/1813/41130

► Biologically controlled minerals are often intimately associated with occluded organic components that regulate composition and morphology, and induce complex hierarchical structures. This integration of strong… (more)

Subjects/Keywords: Calcite; Mechanical Properties; Nanoindentation

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APA (6^th Edition):

Kunitake, M. (2015). The Effects Of Structure And Composition On The Hardness Of Biogenic And Synthetic Single Crystal Calcite. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/41130

Chicago Manual of Style (16^th Edition):

Kunitake, Miki. “The Effects Of Structure And Composition On The Hardness Of Biogenic And Synthetic Single Crystal Calcite.” 2015. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/41130.

MLA Handbook (7^th Edition):

Kunitake, Miki. “The Effects Of Structure And Composition On The Hardness Of Biogenic And Synthetic Single Crystal Calcite.” 2015. Web. 14 Apr 2021.

Vancouver:

Kunitake M. The Effects Of Structure And Composition On The Hardness Of Biogenic And Synthetic Single Crystal Calcite. [Internet] [Doctoral dissertation]. Cornell University; 2015. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/41130.

Council of Science Editors:

Kunitake M. The Effects Of Structure And Composition On The Hardness Of Biogenic And Synthetic Single Crystal Calcite. [Doctoral Dissertation]. Cornell University; 2015. Available from: http://hdl.handle.net/1813/41130

Cornell University

10. Davis, Brett. Three-Dimensional Simulation Of Arbitrary Crack Growth.

Degree: PhD, Civil and Environmental Engineering, 2014, Cornell University

URL: http://hdl.handle.net/1813/38762

► A finite-element-based simulation technique is developed in Chapter 1 to predict arbitrary shape evolution of 3-D, geometrically explicit cracks under stable growth conditions. Point-by-point extensions… (more)

▼ A finite-element-based simulation technique is developed in Chapter 1 to predict arbitrary shape evolution of 3-D, geometrically explicit cracks under stable growth conditions. Point-by-point extensions along a crack front are predicted using a new, energy-based growth formulation that relies on a first-order expansion of the energy release rate. The key term in this expansion is the variation of energy release rate, made readily available via the virtual crack extension (VCE) method. The variation of energy release rate acts as an influence function relating changes in applied load to geometry changes along the crack front. The crack-growth formulation is incorporated into an incremental-iterative solution procedure that continually updates the crack configuration by re-meshing. The numerical technique allows crack shapes to evolve according to energy-based mechanics, while reducing the effects of computational artifacts, e.g. mesh bias. Chapter 1 offers three simulations of mode I, planar crack growth as proof-of-concept of the new technique. To extend the simulation approach to more general crack growth situations, Chapter 2 presents a new implementation for decomposing 3-D mixed-mode energy release rates using the VCE method. The technique uses a symmetric/anti-symmetric approach to decompose local crack-front displacements that are substituted into the global VCE energy release rate form. The subsequent expansion leads to the mixedmode energy release rate expressions. As a result of the expansion, previously unaddressed modal-interaction coupling terms are found to impact the mixed-mode energy release rates. Five numerical examples are presented as verification of the implementation. This development expands the VCE method's advantages over similar procedures when simulating arbitrary crack growth. The energy-based growth formulation and accompanying simulation technique is generalized in Chapter 3 to predict arbitrary, mixed-mode, non-planar crack evolution. The implementation uses a novel basis-function approach to generate a crack extension expression, rather than relying on the local, point-by-point approach described in Chapter 1. The basis-function expression dampens the effect of numerical noise on crack growth predictions that could otherwise produce unstable simulation results. Two simulations are presented to demonstrate the technique's ability to capture both general non-planar behavior, as well as local mixed-mode phenomena, e.g. "factory-roof" formation, along the crack front. Advisors/Committee Members: Ingraffea, Anthony R. (chair), Zehnder, Alan Taylor (committee member), Earls, Christopher J. (committee member), Aquino, Wilkins (committee member).

Subjects/Keywords: Fracture mechanics; Crack growth simulation; Finite element method

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Davis, B. (2014). Three-Dimensional Simulation Of Arbitrary Crack Growth. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/38762

Chicago Manual of Style (16^th Edition):

Davis, Brett. “Three-Dimensional Simulation Of Arbitrary Crack Growth.” 2014. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/38762.

MLA Handbook (7^th Edition):

Davis, Brett. “Three-Dimensional Simulation Of Arbitrary Crack Growth.” 2014. Web. 14 Apr 2021.

Vancouver:

Davis B. Three-Dimensional Simulation Of Arbitrary Crack Growth. [Internet] [Doctoral dissertation]. Cornell University; 2014. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/38762.

Council of Science Editors:

Davis B. Three-Dimensional Simulation Of Arbitrary Crack Growth. [Doctoral Dissertation]. Cornell University; 2014. Available from: http://hdl.handle.net/1813/38762

Cornell University

11. De Frias Garcia, Gabriel. Multiscale Methods For Accelerating Explicit Dynamics Computations In Solid Mechanics.

Degree: PhD, Civil and Environmental Engineering, 2013, Cornell University

URL: http://hdl.handle.net/1813/34008

► In this work we tackle two novel approaches for the solution of multiscale solid mechanics problems. In the first one a selective mass scaling approach… (more)

▼ In this work we tackle two novel approaches for the solution of multiscale solid mechanics problems. In the first one a selective mass scaling approach is presented that can significantly reduce the computational cost in explicit dynamic simulations, while maintaining accuracy. One of the main computational issues with traditional explicit dynamics simulations is the significant reduction of the critical time step as the spatial resolution of the finite element mesh increases. The proposed method is based on a multiscale decomposition approach that separates the dynamics of the system into low (coarse scales) and high frequencies (fine scales). Here, the critical time step is increased by selectively applying mass scaling on the fine scale component only. In problems where the response is dominated by the coarse (low frequency) scales, significant increases in the stable time step can be realized. In this work, we use the Proper Orthogonal Decomposition (POD) method to build the coarse scale space. The main idea behind POD is to obtain an optimal low-dimensional orthogonal basis for representing an ensemble of high-dimensional data. In our proposed method, the POD space is generated with snapshots of the solution obtained from early times of the full-scale simulation. The example problems addressed in this work show significant improvements in computational time, without heavily compromising the accuracy of the results. The second approach uses POD in a similar manner, but adopts an equation-free central difference projective integration scheme to observe and advance dynamics of the coarse scales. This equationfree approach is adopted in order to circumvent some of the drawbacks of the Galerkin projection of the momentum equations on the coarse scales, for model reduction. Proven consistency and accuracy properties make this method attractive for tackling transient dynamics problems. Advisors/Committee Members: Ingraffea, Anthony R (chair), Healey, Timothy James (committee member), Aquino, Wilkins (committee member), Heinstein, Martin W (committee member).

Subjects/Keywords: Explicit Dyanmics; Multiscale; Proper Orthogonal Decomposition; Solid Mechanics; Equation-Free

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

De Frias Garcia, G. (2013). Multiscale Methods For Accelerating Explicit Dynamics Computations In Solid Mechanics. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/34008

Chicago Manual of Style (16^th Edition):

De Frias Garcia, Gabriel. “Multiscale Methods For Accelerating Explicit Dynamics Computations In Solid Mechanics.” 2013. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/34008.

MLA Handbook (7^th Edition):

De Frias Garcia, Gabriel. “Multiscale Methods For Accelerating Explicit Dynamics Computations In Solid Mechanics.” 2013. Web. 14 Apr 2021.

Vancouver:

De Frias Garcia G. Multiscale Methods For Accelerating Explicit Dynamics Computations In Solid Mechanics. [Internet] [Doctoral dissertation]. Cornell University; 2013. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/34008.

Council of Science Editors:

De Frias Garcia G. Multiscale Methods For Accelerating Explicit Dynamics Computations In Solid Mechanics. [Doctoral Dissertation]. Cornell University; 2013. Available from: http://hdl.handle.net/1813/34008

Cornell University

12. Cerrone, Albert. Investigation Of Multiscale Damage Initiation And Propagation Capabilities.

Degree: PhD, Civil and Environmental Engineering, 2014, Cornell University

URL: http://hdl.handle.net/1813/37021

► Fracture is largely a microstructure-based phenomenon, but for experimentalists, computational mechanicians, and fleet managers operating at the macroscale, this fact might seem inexplicable, inapplicable, or… (more)

▼ Fracture is largely a microstructure-based phenomenon, but for experimentalists, computational mechanicians, and fleet managers operating at the macroscale, this fact might seem inexplicable, inapplicable, or even inconsequential. The latter response is what the three chapters of this dissertation address. Together, they attempt to dispel the notion that microstructural effects do not translate in any useful way to the structural scale. They also present models which are verified and validated herein to ease this disconnect. These three chapters are individual papers submitted to refereed journals for publication. The paper in the first chapter appears in Engineering Fracture Mechanics (DOI: http://dx.doi.org/10.1016/j.engfracmech.2014.03.010). It generalizes the Park-PaulinoRoesler potential-based cohesive zone model to three-dimensions, a means to model fracture even under a high degree of mode-mixity at both the macro- and micro-scales. The generalization is validated against several material tests at the macroscale: T-Peel, MMB, ECT, and BDWT. Its ability to model intergranular fracture at the microscale is also explored. The paper in the second chapter fills a void in the Digital Twin community- it presents for the first time a straight-forward use case which both clarifies and motivates this new paradigm in fleet management. Specifically, ductile fracture is modeled in a non-standardized specimen which fails along one of two likely crack paths. This crack path ambiguity, the result of grain-size deviations in specimen geometry, underpins the importance of considering as-manufactured component geometry in the design, assessment, and certification of structural systems, a cornerstone of Digital Twin. It also highlights the limitations of a continuum plasticity damage model in resolving accurately this ambiguity particularly close to the bifurcation, on the order of a few grain sizes, and motivates the need to consider crack nucleation at the microscale. The paper in the third chapter demonstrates Digital Twin at the microscale. It details the implementation, verification, and validation of a microstructure-based, Digital Twin framework which accounts for the predominant microcrack nucleation mechanism in the nickel-based superalloy LSHR. Also included is an extensive grain boundary analysis, an investigation that would otherwise be impossible to conduct to any appreciable fidelity without the as-processed, Digital Twin microstructural model. Advisors/Committee Members: Ingraffea, Anthony R (chair), Zehnder, Alan Taylor (committee member), Warner, Derek H. (committee member), Rollett, Anthony (committee member).

Subjects/Keywords: cohesive zone modeling; Digital Twin; microscale modeling

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Cerrone, A. (2014). Investigation Of Multiscale Damage Initiation And Propagation Capabilities. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/37021

Chicago Manual of Style (16^th Edition):

Cerrone, Albert. “Investigation Of Multiscale Damage Initiation And Propagation Capabilities.” 2014. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/37021.

MLA Handbook (7^th Edition):

Cerrone, Albert. “Investigation Of Multiscale Damage Initiation And Propagation Capabilities.” 2014. Web. 14 Apr 2021.

Vancouver:

Cerrone A. Investigation Of Multiscale Damage Initiation And Propagation Capabilities. [Internet] [Doctoral dissertation]. Cornell University; 2014. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/37021.

Council of Science Editors:

Cerrone A. Investigation Of Multiscale Damage Initiation And Propagation Capabilities. [Doctoral Dissertation]. Cornell University; 2014. Available from: http://hdl.handle.net/1813/37021

Cornell University

13. Brock, Garry. Changes In Bone Tissue Properties With Osteoporosis Treatment.

Degree: PhD, Mechanical Engineering, 2015, Cornell University

URL: http://hdl.handle.net/1813/39339

► Osteoporosis is a disease characterized by low bone mass leading to an increased risk of fracture. Bisphosphonate therapies are commonly prescribed medications that reduce the… (more)

▼ Osteoporosis is a disease characterized by low bone mass leading to an increased risk of fracture. Bisphosphonate therapies are commonly prescribed medications that reduce the risk of osteoporotic fractures through reduced bone turnover. Recently, a rise in atypical femoral fractures (AFF) has occurred in patients taking long-term bisphosphonate treatments. These fractures have features similar to a fatigue failure; however, the mechanisms through which these fractures initiate are unknown. Knowledge of material property changes with bisphosphonates has been limited to monotonic tests and measures above the scale of bone structures. The purpose of this thesis was to examine the fatigue and nanoscale properties of bisphosphonatetreated cortical bone tissue. To examine these properties an osteoporosis model was used in sheep followed by osteoporosis treatment: bisphosphonate (alendronate or zoledronate), SERM (raloxifene), PTH (teriparatide) or vehicle. Beams of known geometry were created from the cortical bone tissue and tested in four-point bend fatigue to failure. Differences in fatigue life occurred including a loss of fatigue life with alendronate and a rise in fatigue life with PTH treatment when compared to the grand mean. The lack of fatigue life change with zoledronate treatment indicates that factors such as dosage, method of administration, or chemical structure are affecting material properties, and not solely the class of drug. Increased fatigue life with PTH may indicate effectiveness for AFF treatment. Fatigue loading induces microdamage in cortical bone tissue that is well characterized using microscale techniques. Bisphosphonate treatments are likely inducing changes to tissue properties at the nanoscale, below levels typically viewed with bone measure techniques. To examine nanoscale tissue damage, methods were developed and implemented using transmission-ray microscopy with synchrotron radiation to gain nanoscale imaging of fatigue damaged bone tissue. Heavy metal staining of microdamage was used, in conjunction with transmission x-ray tomography (TXM), to determine where damage initiates and forms at the nanoscale. Fatigue loaded samples had more staining present within the lacunar-canalicular network as compared to monotonic loaded samples. Damage may, therefore, be occurring within the bone structures themselves and not through surrounding tissue. The lacunar-canalicular network may be altered through bisphosphonate treatments, leading to development of novel imaging networks to examine these questions. Trabeculae were examined with TXM, and tomographies were created to compare nanoscale porosity. Results indicated porosity differences throughout trabeculae with the majority of the lacunar-canalicular network forming near the surface. The TXM methods are among the first studies to view bone at the nanoscale in three dimensions. Overall, results indicated differences in fatigue life of bone tissue given an osteoporosis treatment, with novel methods developed to help examine the origin of this… Advisors/Committee Members: van der Meulen, Marjolein (chair), Baker, Shefford P. (committee member), Hernandez, Christopher J. (committee member), Ingraffea, Anthony R (committee member).

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APA (6^th Edition):

Brock, G. (2015). Changes In Bone Tissue Properties With Osteoporosis Treatment. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/39339

Chicago Manual of Style (16^th Edition):

Brock, Garry. “Changes In Bone Tissue Properties With Osteoporosis Treatment.” 2015. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/39339.

MLA Handbook (7^th Edition):

Brock, Garry. “Changes In Bone Tissue Properties With Osteoporosis Treatment.” 2015. Web. 14 Apr 2021.

Vancouver:

Brock G. Changes In Bone Tissue Properties With Osteoporosis Treatment. [Internet] [Doctoral dissertation]. Cornell University; 2015. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/39339.

Council of Science Editors:

Brock G. Changes In Bone Tissue Properties With Osteoporosis Treatment. [Doctoral Dissertation]. Cornell University; 2015. Available from: http://hdl.handle.net/1813/39339

14. Womer, Russell. The Viability Of Black Locust And The Triakonta Connection System As Structural Components In Modular Framing Systems.

Degree: M.S., Design, Design, 2012, Cornell University

URL: http://hdl.handle.net/1813/29171

Subjects/Keywords: Black Locust; Structures; Modular; Connection; Design for Disassembly

…system designed by Professor Jack Elliott of Cornell University, known as the Triakonta…

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APA (6^th Edition):

Womer, R. (2012). The Viability Of Black Locust And The Triakonta Connection System As Structural Components In Modular Framing Systems. (Masters Thesis). Cornell University. Retrieved from http://hdl.handle.net/1813/29171

Chicago Manual of Style (16^th Edition):

Womer, Russell. “The Viability Of Black Locust And The Triakonta Connection System As Structural Components In Modular Framing Systems.” 2012. Masters Thesis, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/29171.

MLA Handbook (7^th Edition):

Womer, Russell. “The Viability Of Black Locust And The Triakonta Connection System As Structural Components In Modular Framing Systems.” 2012. Web. 14 Apr 2021.

Vancouver:

Womer R. The Viability Of Black Locust And The Triakonta Connection System As Structural Components In Modular Framing Systems. [Internet] [Masters thesis]. Cornell University; 2012. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/29171.

Council of Science Editors:

Womer R. The Viability Of Black Locust And The Triakonta Connection System As Structural Components In Modular Framing Systems. [Masters Thesis]. Cornell University; 2012. Available from: http://hdl.handle.net/1813/29171

15. Spear, Ashley. Numerical And Experimental Studies Of Three-Dimensional Crack Evolution In Aluminum Alloys: Macroscale To Microscale.

Degree: PhD, Civil and Environmental Engineering, 2014, Cornell University

URL: http://hdl.handle.net/1813/37154

► In a broad sense, the work described herein addresses either extreme of a traditional da/dN vs. dK plot. The first chapter addresses the uppermost limit… (more)

▼ In a broad sense, the work described herein addresses either extreme of a traditional da/dN vs. dK plot. The first chapter addresses the uppermost limit of such plot, where tearing represents the limit state of structural failure. Subsequent chapters address the lower limit, where emphasis is placed on nucleation and early propagation of microstructurally small fatigue cracks (MSFCs). A common theme throughout the dissertation is the development of new tools and techniques (be they experimental or numerical) to enable unprecedented interrogation of crack evolution in 3D, with applications to various aluminum-alloy structures. Each chapter represents a separate body of work providing novel contributions in one or more areas involving fracture mechanics (viz. structural prognosis, corrosion science and engineering, and materials characterization). A brief overview of each chapter is described next. In Chapter 1, a methodology is described for predicting in real time the residual strength of structures with discrete-source damage. An artificial neural network (ANN) is trained using linear-elastic fracture mechanics (LEFM)-based data from numerical models; the ANN predicts residual strength given a set of damage parameters. Section 1.3 focuses on augmenting the existing LEFMbased modeling toolset to simulate ductile tearing and thereby improve resid- ual strength values used to train an ANN. Validation results are presented for two ductile-tearing simulations. Chapters 2 through 4 focus on MSFC initiation and propagation in an Al-Mg-Si alloy used to line composite-overwrapped pressure vessels. Chapter 2 describes an experimental study regarding the effect of an alkaline-based chemical milling treatment used to dimensionally reduce the Al-Mg-Si pressure-vessel liners. 3-D scanning electron microscopy is employed to quantify surface pitting caused by the chemical-milling treatment. The 3-D surface characteristics, along with high-magnification fractographs, are used to explain the observed 50% reduction in low-cycle fatigue lives among the chemically-milled specimens compared to a control group. In Chapter 3, an experimental methodology based on post-mortem measurements is developed to quantify 3-D rates of propagation and crack-surface crystallography for a naturally nucleated MSFC in an Al-Mg-Si specimen. The measurements are made possible through recent developments in 3-D characterization methods. Findings from the study demonstrate: 1) the complexity and variability of 3-D MSFC evolution in the Al-Mg-Si alloy and 2) the viability of the post-mortem characterization approach for quantifying 3-D MSFC evolution in polycrystalline alloys. The dissertation culminates with Chapter 4, which, for the first time, demonstrates the 3-D digital reconstruction and numerical simulation of a sequence of directly measured MSFCs, where both MSFC geometry and individual grain morphologies and orientations are explicitly represented at the polycrystalline length scale. The numerical reconstruction is demonstrated using 3-D measurements… Advisors/Committee Members: Ingraffea, Anthony R. (chair), Zehnder, Alan Taylor (committee member), Earls, Christopher J. (committee member), Glaessgen, Edward H (committee member).

Subjects/Keywords: crack propagation; finite element; multiscale

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APA (6^th Edition):

Spear, A. (2014). Numerical And Experimental Studies Of Three-Dimensional Crack Evolution In Aluminum Alloys: Macroscale To Microscale. (Doctoral Dissertation). Cornell University. Retrieved from http://hdl.handle.net/1813/37154

Chicago Manual of Style (16^th Edition):

Spear, Ashley. “Numerical And Experimental Studies Of Three-Dimensional Crack Evolution In Aluminum Alloys: Macroscale To Microscale.” 2014. Doctoral Dissertation, Cornell University. Accessed April 14, 2021. http://hdl.handle.net/1813/37154.

MLA Handbook (7^th Edition):

Spear, Ashley. “Numerical And Experimental Studies Of Three-Dimensional Crack Evolution In Aluminum Alloys: Macroscale To Microscale.” 2014. Web. 14 Apr 2021.

Vancouver:

Spear A. Numerical And Experimental Studies Of Three-Dimensional Crack Evolution In Aluminum Alloys: Macroscale To Microscale. [Internet] [Doctoral dissertation]. Cornell University; 2014. [cited 2021 Apr 14]. Available from: http://hdl.handle.net/1813/37154.

Council of Science Editors:

Spear A. Numerical And Experimental Studies Of Three-Dimensional Crack Evolution In Aluminum Alloys: Macroscale To Microscale. [Doctoral Dissertation]. Cornell University; 2014. Available from: http://hdl.handle.net/1813/37154

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