+publisher:"University of Texas – Austin" +contributor:("Landis, Chad")

University of Texas – Austin

1. -7445-8175. Electromechanical coupling behavior of dielectric elastomer composites.

Degree: MSin Engineering, Engineering Mechanics, 2016, University of Texas – Austin

► Dielectric elastomers have gained substantial interest in the past few decades under research efforts aimed to improve electromechanical transducer technology. This material is often termed… (more)

Subjects/Keywords: Dielectric elastomer composite; Finite element method; Dielectric elastomers; Electromechanical transducers; Transduction efficiency; Transducers

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APA (6^th Edition):

-7445-8175. (2016). Electromechanical coupling behavior of dielectric elastomer composites. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/47086

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Chicago Manual of Style (16^th Edition):

-7445-8175. “Electromechanical coupling behavior of dielectric elastomer composites.” 2016. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/47086.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-7445-8175. “Electromechanical coupling behavior of dielectric elastomer composites.” 2016. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-7445-8175. Electromechanical coupling behavior of dielectric elastomer composites. [Internet] [Masters thesis]. University of Texas – Austin; 2016. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/47086.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-7445-8175. Electromechanical coupling behavior of dielectric elastomer composites. [Masters Thesis]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/47086

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

2. Simpson, Gary Forest Jr. A combined experimental and modeling study of low velocity perforation of thin aluminum plates.

Degree: MSin Engineering, Aerospace engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/34122

► This work conducts a combined experimental and modeling study of low velocity projectile perforation of thin AA5083-H116 aluminum plates. Experiments were performed in order to… (more)

Subjects/Keywords: Ballistic; Perforation; Ductile failure

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APA (6^th Edition):

Simpson, G. F. J. (2015). A combined experimental and modeling study of low velocity perforation of thin aluminum plates. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/34122

Chicago Manual of Style (16^th Edition):

Simpson, Gary Forest Jr. “A combined experimental and modeling study of low velocity perforation of thin aluminum plates.” 2015. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/34122.

MLA Handbook (7^th Edition):

Simpson, Gary Forest Jr. “A combined experimental and modeling study of low velocity perforation of thin aluminum plates.” 2015. Web. 20 Apr 2021.

Vancouver:

Simpson GFJ. A combined experimental and modeling study of low velocity perforation of thin aluminum plates. [Internet] [Masters thesis]. University of Texas – Austin; 2015. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/34122.

Council of Science Editors:

Simpson GFJ. A combined experimental and modeling study of low velocity perforation of thin aluminum plates. [Masters Thesis]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/34122

University of Texas – Austin

3. Yu, Yalin. Measurement of adhesion between soft elastomers with different mixing ratios.

Degree: MSin Engineering, Engineering Mechanics, 2014, University of Texas – Austin

URL: http://hdl.handle.net/2152/32324

► The JKR method is widely used to measure the work of adhesion between soft materials. In this report, the JKR theory is summarized and three… (more)

Subjects/Keywords: Adhesion; Soft elastomers; Mixing ratios

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APA (6^th Edition):

Yu, Y. (2014). Measurement of adhesion between soft elastomers with different mixing ratios. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/32324

Chicago Manual of Style (16^th Edition):

Yu, Yalin. “Measurement of adhesion between soft elastomers with different mixing ratios.” 2014. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/32324.

MLA Handbook (7^th Edition):

Yu, Yalin. “Measurement of adhesion between soft elastomers with different mixing ratios.” 2014. Web. 20 Apr 2021.

Vancouver:

Yu Y. Measurement of adhesion between soft elastomers with different mixing ratios. [Internet] [Masters thesis]. University of Texas – Austin; 2014. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/32324.

Council of Science Editors:

Yu Y. Measurement of adhesion between soft elastomers with different mixing ratios. [Masters Thesis]. University of Texas – Austin; 2014. Available from: http://hdl.handle.net/2152/32324

University of Texas – Austin

4. Hickey, William Fassett. An investigation into the failure of aluminum alloys.

Degree: MSin Engineering, Engineering Mechanics, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-08-4297

► The rate dependence of several aluminum alloys (6061, 7075, 5083) was examined through the means of quasi-static tension tests, dynamic tension tests, and split pressure… (more)

Subjects/Keywords: J-integral; Digitil image correlation; Grain level strain

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APA (6^th Edition):

Hickey, W. F. (2011). An investigation into the failure of aluminum alloys. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-08-4297

Chicago Manual of Style (16^th Edition):

Hickey, William Fassett. “An investigation into the failure of aluminum alloys.” 2011. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/ETD-UT-2011-08-4297.

MLA Handbook (7^th Edition):

Hickey, William Fassett. “An investigation into the failure of aluminum alloys.” 2011. Web. 20 Apr 2021.

Vancouver:

Hickey WF. An investigation into the failure of aluminum alloys. [Internet] [Masters thesis]. University of Texas – Austin; 2011. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-08-4297.

Council of Science Editors:

Hickey WF. An investigation into the failure of aluminum alloys. [Masters Thesis]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-08-4297

University of Texas – Austin

5. He, Jiachuan. Data-driven uncertainty quantification for predictive subsurface flow and transport modeling.

Degree: PhD, Engineering Mechanics, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/1387

► Specification of hydraulic conductivity as a model parameter in groundwater flow and transport equations is an essential step in predictive simulations. It is often infeasible… (more)

▼ Specification of hydraulic conductivity as a model parameter in groundwater flow and transport equations is an essential step in predictive simulations. It is often infeasible in practice to characterize this model parameter at all points in space due to complex hydrogeological environments leading to significant parameter uncertainties. Quantifying these uncertainties requires the formulation and solution of an inverse problem using data corresponding to observable model responses. Several types of inverse problems may be formulated under various physical and statistical assumptions on the model parameters, model response, and the data. Solutions to most types of inverse problems require large numbers of model evaluations. In this study, we incorporate the use of surrogate models based on support vector machines to increase the number of samples used in approximating a solution to an inverse problem at a relatively low computational cost. To test the global capabilities of this type of surrogate model for quantifying uncertainties, we use a framework for constructing pullback and push-forward probability measures to study the data-to-parameter-to-prediction propagation of uncertainties under minimal statistical assumptions. Additionally, we demonstrate that it is possible to build a support vector machine using relatively low-dimensional representations of the hydraulic conductivity to propagate distributions. The numerical examples further demonstrate that we can make reliable probabilistic predictions of contaminant concentration at spatial locations corresponding to data not used in the solution to the inverse problem. This dissertation is based on the article entitled Data-driven uncertainty quantification for predictive flow and transport modeling using support vector machines by Jiachuan He, Steven Mattis, Troy Butler and Clint Dawson [32]. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Advanced Scientific Computing Research, Applied Mathematics program under Award Number DE-SC0009286 as part of the DiaMonD Multifaceted Mathematics Integrated Capability Center. Advisors/Committee Members: Dawson, Clinton N. (advisor), Landis, Chad (committee member), Bui, Tan (committee member), Ghattas, Omar (committee member).

Subjects/Keywords: Stochastic inverse problem; Parameter estimation; Hydraulic conductivity; Measure theory; Support vector regression

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APA (6^th Edition):

He, J. (2019). Data-driven uncertainty quantification for predictive subsurface flow and transport modeling. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/1387

Chicago Manual of Style (16^th Edition):

He, Jiachuan. “Data-driven uncertainty quantification for predictive subsurface flow and transport modeling.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/1387.

MLA Handbook (7^th Edition):

He, Jiachuan. “Data-driven uncertainty quantification for predictive subsurface flow and transport modeling.” 2019. Web. 20 Apr 2021.

Vancouver:

He J. Data-driven uncertainty quantification for predictive subsurface flow and transport modeling. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/1387.

Council of Science Editors:

He J. Data-driven uncertainty quantification for predictive subsurface flow and transport modeling. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/1387

University of Texas – Austin

6. Sermollo, Nebiyu Barsula. A theoretical formulation for flexoelectric membranes.

Degree: MSin Engineering, Engineering Mechanics, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/31902

► Flexoelectricity is electric polarization induced by a strain gradient. This phenomenon has been observed in different types of materials. It has been studied and documented… (more)

Subjects/Keywords: Flexoelectricity; Membranes; Thin-films; Elastomeric membranes

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APA (6^th Edition):

Sermollo, N. B. (2015). A theoretical formulation for flexoelectric membranes. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/31902

Chicago Manual of Style (16^th Edition):

Sermollo, Nebiyu Barsula. “A theoretical formulation for flexoelectric membranes.” 2015. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/31902.

MLA Handbook (7^th Edition):

Sermollo, Nebiyu Barsula. “A theoretical formulation for flexoelectric membranes.” 2015. Web. 20 Apr 2021.

Vancouver:

Sermollo NB. A theoretical formulation for flexoelectric membranes. [Internet] [Masters thesis]. University of Texas – Austin; 2015. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/31902.

Council of Science Editors:

Sermollo NB. A theoretical formulation for flexoelectric membranes. [Masters Thesis]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/31902

University of Texas – Austin

7. Albrecht, Aaron Berkeley. Dynamic response of metal-polymer bilayers subjected to blast loading.

Degree: PhD, Engineering Mechanics, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/19510

► The use of compliant coatings, in particular polyurea, for improved blast protection of structures has been reported recently in the literature. The goal of this… (more)

▼ The use of compliant coatings, in particular polyurea, for improved blast protection of structures has been reported recently in the literature. The goal of this research is to develop a comprehensive understanding of the reasons for improved performance of coated structures through experimentation and correlation with simulation. The different factors influencing the response of an elastomer coated ductile metal subjected to a blast load have been examined and quantified. First, dynamic strain localization in the metal is a precursor to ductile failure; this was characterized for the metal of interest with and without the polymer coating. Experiments with the expanding ring/tube and experiments have demonstrated that for Al 6061-O and Al 3003-H14, the localization strain is unaffected by both deformation rate and the polymer coating; however, two important effects of the coating have been explored. First the additional mass of the coating provides an inertial resistance. Second, the flow resistance of the polymer provides continued dissipation of energy even after the metal has yielded potentially preventing failure in the metal, or at least containing fragments. These effects were examined for two different types of polymers – polyurea, an elastomer and polycarbonate, a thermoplastic shear yielding polymer. It is shown that these two effects can be used to tailor the coating to optimize blast protection of the bilayer system. In order to take advantage of this optimization, the constitutive behavior of the elastomer coating must be determined at strain rates and loading conditions that are experienced in the blast loading; these strain rates are in the range of 1000 to 10,000 per second. This has been accomplished through a hybrid method that combines measurements with numerical simulations to extract the constitutive response of the material. The strain rate dependent behavior of polyurea for rates in the range of 800-8000 per second has been determined by measuring the spatio-temporal evolution of the particle velocity and strain in a thin strip subjected to high speed impact loading that generates uniaxial stress conditions and comparing this with numerical simulations of the one-dimensional problem using the method of characteristics. A similar scheme to track the particle velocity and strain during the axisymmetric deformation of a membrane subjected to high speed loading has also been developed; this requires two projections of the deformation to be obtained in order to facilitate the measurement of axial and kink waves in the membrane. The finite volume method is adapted for simulations of these dynamic uniaxial and axisymmetric problems with a view towards simulating shock waves that are expected to form in some loading conditions. The hybrid method is used once again to characterize the constitutive response. The axisymmetric experiments have demonstrated the inability of the uniaxial models for both polyisoprene rubber and polyurea to completely capture their behavior during a more complex loading, and… Advisors/Committee Members: Ravi-Chandar, K. (advisor), Landis, Chad (committee member), Liechti, Kenneth (committee member), Mear, Mark (committee member), Marder, Michael (committee member).

Subjects/Keywords: Fracture; Fragmentation; Dynamic tension; Polyurea

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APA (6^th Edition):

Albrecht, A. B. (2012). Dynamic response of metal-polymer bilayers subjected to blast loading. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/19510

Chicago Manual of Style (16^th Edition):

Albrecht, Aaron Berkeley. “Dynamic response of metal-polymer bilayers subjected to blast loading.” 2012. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/19510.

MLA Handbook (7^th Edition):

Albrecht, Aaron Berkeley. “Dynamic response of metal-polymer bilayers subjected to blast loading.” 2012. Web. 20 Apr 2021.

Vancouver:

Albrecht AB. Dynamic response of metal-polymer bilayers subjected to blast loading. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2012. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/19510.

Council of Science Editors:

Albrecht AB. Dynamic response of metal-polymer bilayers subjected to blast loading. [Doctoral Dissertation]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/19510

University of Texas – Austin

8. Li, Wenyuan, 1982-. Phase-field modeling of piezoelectrics and instabilities in dielectric elastomer composites.

Degree: PhD, Engineering Mechanics, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-12-4705

► Ferroelectric ceramics are broadly used in applications including actuators, sensors and information storage. An understanding of the microstructual evolution and domain dynamics is vital for… (more)

▼ Ferroelectric ceramics are broadly used in applications including actuators, sensors and information storage. An understanding of the microstructual evolution and domain dynamics is vital for predicting the performance and reliability of such devices. The underlying mechanism responsible for ferroelectric constitutive response is ferroelectric domain wall motion, domain switching and the interactions of domain walls with other material defects. In this work, a combined theoretical and numerical modeling framework is developed to investigate the nucleation and growth of domains in a single crystal of ferroelectric material. The phase-field approach, applying the material electrical polarization as the order parameter, is used as the theoretical modeling framework to allow for a detailed accounting of the electromechanical processes. The finite element method is used for the numerical solution technique. In order to obtain a better understanding of the energetics of fracture within the phase-field setting, the J-integral is modified to include the energies associated with the order parameter. Also, the J- integral is applied to determine the crack-tip energy release rate for common sets of electromechanical crack-face boundary conditions. The calculations confirm that only true equilibrium states exhibit path-independence of J, and that domain structures near crack tips may be responsible for allowing positive energy release rate during purely electrical loading. The small deformation assumption is prevalent in the phase-field modeling approach, and is used in the previously described calculations. The analysis of large deformations will introduce the concept of Maxwell stresses, which are assumed to be higher order effects that can be neglected in the small deformation theory. However, in order to investigate the material response of soft dielectric elastomers undergoing large mechanical deformation and electric field, which are employed in electrically driven actuator devices, manipulators and energy harvesters, a finite deformation theory is incorporated in the phase-field model. To describe the material free energy, compressible Neo-Hookean and Gent models are used. The Jaumann rate of the polarization is used as the objective polarization rate to make the description of the dissipation frame indifferent. To illustrate the theory, electromechanical instabilities in composite materials with different inclusions will be studied using the finite element methods. Advisors/Committee Members: Landis, Chad M. (advisor), Huang, Rui (committee member), Mear, Mark (committee member), Tassoulas, John L. (committee member).

Subjects/Keywords: Phase-field modeling; Piezoelectrics; Instabilities; Dielectric elastomers

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APA (6^th Edition):

Li, Wenyuan, 1. (2011). Phase-field modeling of piezoelectrics and instabilities in dielectric elastomer composites. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-12-4705

Chicago Manual of Style (16^th Edition):

Li, Wenyuan, 1982-. “Phase-field modeling of piezoelectrics and instabilities in dielectric elastomer composites.” 2011. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/ETD-UT-2011-12-4705.

MLA Handbook (7^th Edition):

Li, Wenyuan, 1982-. “Phase-field modeling of piezoelectrics and instabilities in dielectric elastomer composites.” 2011. Web. 20 Apr 2021.

Vancouver:

Li, Wenyuan 1. Phase-field modeling of piezoelectrics and instabilities in dielectric elastomer composites. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2011. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4705.

Council of Science Editors:

Li, Wenyuan 1. Phase-field modeling of piezoelectrics and instabilities in dielectric elastomer composites. [Doctoral Dissertation]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4705

University of Texas – Austin

9. -5718-0493. Evolution of localization in NiTi shape memory alloys and its effect on structures.

Degree: PhD, Engineering mechanics, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/40324

► Nearly equiatomic NiTi can be strained to several percent and fully recover upon unloading (pseudoelastic behavior). This property is derived from solid-state transformations between the… (more)

▼ Nearly equiatomic NiTi can be strained to several percent and fully recover upon unloading (pseudoelastic behavior). This property is derived from solid-state transformations between the austenitic (A) and martensitic (M) phases, which can be induced by either changes in temperature or stress. In concert with prior results in tension, stress-induced phase transformation leads to localized deformation associated with the nucleation and propagation of the M-phase during loading and the A-phase during unloading. By contrast, it is demonstrated that under compression, transformation stresses are higher, strains are smaller, and the deformation is essentially homogeneous. This tension-compression asymmetry and unstable material behavior have an effect on the response and stability of NiTi structures. This is demonstrated with pure bending of tubes, and axial compression of cylindrical shells. Pure bending results in localization that leads to the coexistence of two curvature regimes. In the axial compression of the shell, transformation induces buckling and collapse, both of which are recoverable upon unloading. A requirement for the analysis and design of such structures is constitutive models that capture the material instability and asymmetry. Furthermore, the extensions of these material nonlinearities to the multiaxial setting must be addressed. To this end, results from a series of experiments on pseudoelastic NiTi tubes loaded under combined axial load and internal pressure are presented in which radial stress paths in the axial-hoop stress space were traced. Stereo digital image correlation was used to monitor the evolution of transformation-induced deformation. Results spanning axial-to-hoop stress ratios from -1.0 to uniaxial tension revealed that, but for a narrow region near equibiaxial tension, transformation leads to localized helical deformation bands with helix angles that vary with the stress ratio, while the stresses remain nearly constant. In the vicinity of equibiaxial tension, the material exhibits hardening and homogeneous deformation. Loci of the transformation stresses, while exhibiting minor anisotropy, traced an elongated non-Mises trajectory in the axial-hoop stress space. By contrast, the transformation strains exhibit significant anisotropy between axial and hoop dominant stress paths. Moreover, strains around the equibiaxial stress state, where material hardening and homogeneous deformation was observed, are significantly smaller than in the rest of the stress space. The strain anisotropy has a corresponding reflection on the energy dissipated during transformation with axial dominant stress paths dissipating significantly more energy than hoop dominant ones, with less dissipation observed in the neighborhood of equibiaxial stress. Advisors/Committee Members: Kyriakides, S. (advisor), Landis, Chad M (committee member), Liechti, Kenneth M (committee member), Ravi-Chandar, Krishnaswa (committee member), Kovar, Desiderio (committee member).

Subjects/Keywords: Shape memory alloys; Pseudoelasticity; Biaxial loadings; Localization; Inhomogeneous deformation; NiTi

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APA (6^th Edition):

-5718-0493. (2016). Evolution of localization in NiTi shape memory alloys and its effect on structures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/40324

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-5718-0493. “Evolution of localization in NiTi shape memory alloys and its effect on structures.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/40324.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-5718-0493. “Evolution of localization in NiTi shape memory alloys and its effect on structures.” 2016. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-5718-0493. Evolution of localization in NiTi shape memory alloys and its effect on structures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/40324.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-5718-0493. Evolution of localization in NiTi shape memory alloys and its effect on structures. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/40324

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

10. -7024-1342. Towards the predictive modeling of ductile failure.

Degree: PhD, Aerospace engineering, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/32930

► The ability to predict ductile failure is considered by an experimental examination of the failure process, validation exercises to assess predictive ability, and development of… (more)

▼ The ability to predict ductile failure is considered by an experimental examination of the failure process, validation exercises to assess predictive ability, and development of a coupled experimental-numerical strategy to enhance model development. In situ loading of a polycrystalline metal inside a scanning electron microscope is performed on Al 6061-T6 that reveals matrix-dominated response for both deformation and failure. Highly localized deformation fields are found to exist within each grain as slip accumulates preferentially on a small fraction of crystallographic planes. No evidence of damage or material softening is found, implying that a strain-to-failure model is adequate for modeling fracture in this and similar material. This modeling insight is validated through blind predictive simulations performed in response to the 2012 and 2014 Sandia Fracture Challenges. Constitutive and failure models are calibrated and then embedded in highly refined finite element simulations to perform blind predictions of the failure behavior of the challenge geometries. Comparison of prediction to experiment shows that a well-calibrated model that captures the essential elastic-plastic constitutive behavior is necessary to capture confidently the response for structures with complex stress states, and is a prerequisite for a precise prediction of material failure. The validation exercises exposed the need to calibrate sophisticated plasticity models without a large experimental effort. To answer this need, a coupled experimental and numerical method is developed for characterizing the elastic-plastic constitutive properties of ductile materials using local deformation field information to enrich calibration data. The method is applied to a tensile test specimen and the material’s constitutive model, whose parameters are unknown a priori, is determined through an optimization process that compares these experimental measurements with iterative finite element simulations. The final parameters produce a simulation that tracks the local experimental displacement field to within a couple percent of error. Simultaneously, the percent error in the simulation for the load carried by the specimen throughout the test is less than one percent. The enriched calibration data is found to be sufficient to constrain model parameters describing anisotropy that could not be constrained by the global data alone. Advisors/Committee Members: Ravi-Chandar, K. (advisor), Kovar, Desiderio (committee member), Landis, Chad (committee member), Liechti, Kenneth (committee member), Kyriakides, Stelios (committee member).

Subjects/Keywords: Ductile failure; Plasticity; Inverse problems; Material characterization; FEM; In situ testing; Damage

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APA (6^th Edition):

-7024-1342. (2015). Towards the predictive modeling of ductile failure. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/32930

Note: this citation may be lacking information needed for this citation format:
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Chicago Manual of Style (16^th Edition):

-7024-1342. “Towards the predictive modeling of ductile failure.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/32930.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-7024-1342. “Towards the predictive modeling of ductile failure.” 2015. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-7024-1342. Towards the predictive modeling of ductile failure. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/32930.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-7024-1342. Towards the predictive modeling of ductile failure. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/32930

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

11. -1155-8213. Addressing challenges in modeling of coupled flow and poromechanics in deep subsurface reservoirs.

Degree: PhD, Engineering Mechanics, 2018, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/2120

► In coupled flow and poromechanics phenomena representing hydrocarbon production or CO₂ sequestration in deep subsurface non-fractured reservoirs, the spatial domain in which fluid flow occurs… (more)

▼ In coupled flow and poromechanics phenomena representing hydrocarbon production or CO₂ sequestration in deep subsurface non-fractured reservoirs, the spatial domain in which fluid flow occurs is usually much smaller than the spatial domain over which significant deformation occurs. The vertical extent of the poromechanical domain can be two orders of magnitude more than the characteristic thickness of the flow domain (reservoir). The lateral extent of the poromechanical domain should also be allowed to be substantially larger than that of the flow domain to enable the imposition of far-field boundary conditions on the poromechanical domain. The typical approach is to either impose an overburden pressure directly on the reservoir thus treating it as a coupled problem domain or to model flow on a huge domain with zero permeability cells to mimic the no flow boundary condition on the interface of the reservoir and the surrounding rock. The former approach precludes a study of land subsidence or uplift and further does not mimic the true effect of the overburden on stress sensitive reservoirs whereas the latter approach has huge computational costs. The flow domain requires an areal resolution fine enough to be able to capture the underlying nonlinearities in the multiphase flow equations. If the same grid resolution is employed for the poromechanical domain, the simulator would crash for lack of memory and computing resource. With that in mind, it is imperative to establish a framework in which fluid flow is resolved on a finer grid and poromechanical deformation is resolved on a coarse grid. In addition, the geometry of the flow domain necessitates the use of non-nested grids which allows for freedom of choice of the poromechanical grid resolution. Furthermore, to achieve the goal of rendering realistic simulations of subsurface phenomena, we cannot ignore the heterogeneity in flow and poromechanical properties, as well as the lack in accuracy of the poromechanical calculations if the grid for the poromechanics domain is too coarse. This dissertation is a rendition of how we invoke concepts in computational geometry, parallel computing, applied mathematics and convex optimization in designing and implementing algorithms that tackle all the aforementioned challenges. Advisors/Committee Members: Wheeler, Mary F. (Mary Fanett) (advisor), Landis, Chad (committee member), Huang, Rui (committee member), Balhoff, Matthew (committee member).

Subjects/Keywords: Fixed-stress split iterative scheme; Overlapping nonmatching hexahedral grids; Upscaling and downscaling; Singular value decompositions; Surface intersections; Delaunay triangulations; Mandel’s problem; Biot system; Heterogeneous poroelastic medium; Nested two-grid approach; Contraction mapping; Anisotropic poroelastic medium; Computational homogenization; Hanging nodes; Augmented Lagrangian

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APA (6^th Edition):

-1155-8213. (2018). Addressing challenges in modeling of coupled flow and poromechanics in deep subsurface reservoirs. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/2120

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-1155-8213. “Addressing challenges in modeling of coupled flow and poromechanics in deep subsurface reservoirs.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/2120.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-1155-8213. “Addressing challenges in modeling of coupled flow and poromechanics in deep subsurface reservoirs.” 2018. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-1155-8213. Addressing challenges in modeling of coupled flow and poromechanics in deep subsurface reservoirs. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/2120.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-1155-8213. Addressing challenges in modeling of coupled flow and poromechanics in deep subsurface reservoirs. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://dx.doi.org/10.26153/tsw/2120

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

12. Castonguay, Stephen Thomas. Simulating growth and proppant transport in non-planar hydraulic fractures.

Degree: PhD, Engineering Mechanics, 2017, University of Texas – Austin

URL: http://hdl.handle.net/2152/68191

► A computational model is developed to simulate the growth of non-planar hydraulic fractures. A Symmetric Galerkin Boundary Element Method (SGBEM) is used to simulate the… (more)

▼ A computational model is developed to simulate the growth of non-planar hydraulic fractures. A Symmetric Galerkin Boundary Element Method (SGBEM) is used to simulate the fracture growth process. This involves only weakly singular kernels to be computed, as well as only requiring C [superscript 0,α] (Holder) continuous shape functions. Additionally special crack tip shape functions are utilized to capture the stress intensity factors, which are then used to update the geometry through a mixed mode I/II growth law. Fluid flow equations are derived for the case of flow through a thin channel defined on an arbitrarily curved 2D surface embedded in 3D space. Two separate methods for fluid flow are used to solve these equations. The first adopts the work of Rungamornrat et al. (2005) and utilizes a Galerkin Finite Element Method (GFEM) to calculate the pressure in the fluid. This, coupled with the SGBEM, allows for the investigation into the effects of material properties and wellbore boundary conditions on the simultaneous growth of multiple fractures. Several examples are presented to illustrate that the growth of cracks in three dimensions can exhibit quite complicated behavior, which could not be revealed without having the capability to fully treat the interaction between the non-planar fractures. A particularly interesting phenomenon occurs for initially parallel fractures in the presence of an anisotropic in situ stress, where the cracks petal in order to escape the stress shadows of their neighbors. The second model utilizes the Mixed Hybrid Finite Element Method (MHFEM) for fluid flow. This gives both accurate pressures and velocities by solving the mass and momentum balance equations simultaneously. The velocity fluxes are locally mass conserving over each element and are therefore well suited for use in the advection equation for the proppant. Both Raviart-Thomas and Arnold-Boffi-Falk elements are utilized for the flux degrees of freedom, which do not require the addition of any stabilization terms. The hybrid mixed method avoids the saddle point structure associated with the standard mixed method, and allows for fewer global degrees of freedom as well. A subdivision process of the SGBEM mesh is implemented through a recursive mapping to obtain a finer mesh for the fluid flow. Comparisons are made between solutions from the MHFEM model and the GFEM model, as well as analytical solutions of simplified test problems. The proppant transport process is modeled with an upwind finite volume method which takes into account gravitational settling. The finite volume method is also locally mass conservative, and by using a backwards finite difference for the temporal discretization, the solutions are unconditionally stable for any time step. One set of examples are presented to show how the number of subdivisions affects the ability to accurately track proppant fronts. Another example illustrates the models ability to handle the settling of proppant as well as its build up as the concentration reaches a maximum value. Advisors/Committee Members: Mear, Mark E. (advisor), Rodin, Gregory (committee member), Ravi-Chandar, Krishnaswamy (committee member), Landis, Chad (committee member), Foster, John (committee member).

Subjects/Keywords: Hydraulic fracturing; Symmetric Galerkin Boundary Element Method; Mixed hybrid finite element method

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APA (6^th Edition):

Castonguay, S. T. (2017). Simulating growth and proppant transport in non-planar hydraulic fractures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/68191

Chicago Manual of Style (16^th Edition):

Castonguay, Stephen Thomas. “Simulating growth and proppant transport in non-planar hydraulic fractures.” 2017. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/68191.

MLA Handbook (7^th Edition):

Castonguay, Stephen Thomas. “Simulating growth and proppant transport in non-planar hydraulic fractures.” 2017. Web. 20 Apr 2021.

Vancouver:

Castonguay ST. Simulating growth and proppant transport in non-planar hydraulic fractures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2017. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/68191.

Council of Science Editors:

Castonguay ST. Simulating growth and proppant transport in non-planar hydraulic fractures. [Doctoral Dissertation]. University of Texas – Austin; 2017. Available from: http://hdl.handle.net/2152/68191

University of Texas – Austin

13. Mood, Charles Gordon. Coupled SGBEM-FEM for efficient simulation of height-contained hydraulic fractures.

Degree: PhD, Computational Science, Engineering, and Mathematics, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/5858

► An efficient computational model is developed to simulate the growth of vertically oriented, height-contained hydraulic fractures. A symmetric Galerkin boundary element method, used to model… (more)

▼ An efficient computational model is developed to simulate the growth of vertically oriented, height-contained hydraulic fractures. A symmetric Galerkin boundary element method, used to model the behavior of the fracture, is specialized by exploiting knowledge of the fracture surface geometry and an assumption on the approximately elliptical, vertical cross section of the fracture. This geometric knowledge is used to reduce the governing weakly singular, weak-form traction integral equation from an integral over the fracture surface to an integral along the centerline of the fracture through an analytical integration with respect to the fracture height. The fluid flow within the fracture is treated using a Galerkin finite element method to model one-dimensional flow through an arbitrarily curved channel. Under the assumption that the fluid pressure is uniform over the fracture height (as in the case of a tunnel crack) and using the cross sectional form assumed by the fracture model, a specialized, weak-form, fluid flow equation is developed and integrated analytically with respect to the fracture height. The symmetric Galerkin boundary element method and Galerkin finite element method are coupled and the resulting system is solved using a Newton-Raphson method. The fracture propagation is governed by a mixed mode-I/II growth law based on linear elastic fracture mechanics, with stress intensity factors computed directly from the degrees of freedom associated with special crack tip elements designed to capture the square root behavior near the fracture tip. This new computational model is compared to an existing coupled SGBEM-FEM model designed for general, three-dimensional, non-planar fractures to illustrate the efficiency of the new model and the dramatic speedup it offers for modeling height-contained hydraulic fracturing scenarios. The model is extended to treat various conditions typical of hydraulic fracturing design including fracture growth near completed hydraulic fractures, staged fluid injection scenarios, fracture growth in multiple, vertically stacked pay zones, and the distribution of fluid injection to a set of fractures growing from a shared wellbore. Advisors/Committee Members: Mear, Mark E. (advisor), Demkowicz, Leszek F (committee member), Gonzalez, Oscar (committee member), Landis, Chad M (committee member), Rodin, Gregory J (committee member).

Subjects/Keywords: Hydraulic fracturing; SGBEM; Boundary elements

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APA (6^th Edition):

Mood, C. G. (2019). Coupled SGBEM-FEM for efficient simulation of height-contained hydraulic fractures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/5858

Chicago Manual of Style (16^th Edition):

Mood, Charles Gordon. “Coupled SGBEM-FEM for efficient simulation of height-contained hydraulic fractures.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/5858.

MLA Handbook (7^th Edition):

Mood, Charles Gordon. “Coupled SGBEM-FEM for efficient simulation of height-contained hydraulic fractures.” 2019. Web. 20 Apr 2021.

Vancouver:

Mood CG. Coupled SGBEM-FEM for efficient simulation of height-contained hydraulic fractures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/5858.

Council of Science Editors:

Mood CG. Coupled SGBEM-FEM for efficient simulation of height-contained hydraulic fractures. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/5858

University of Texas – Austin

14. Toshniwal, Deepesh. Isogeometric Analysis : study of non-uniform degree and unstructured splines, and application to phase field modeling of corrosion.

Degree: PhD, Computational Science, Engineering, and Mathematics, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/4799

► Isogeometric Analysis or IGA was introduced by Hughes et al. (2005) to facilitate efficient design-through-analysis cycles for engineered objects. The goal of this technology is… (more)

▼ Isogeometric Analysis or IGA was introduced by Hughes et al. (2005) to facilitate efficient design-through-analysis cycles for engineered objects. The goal of this technology is the unification of geometric modeling and engineering analysis, and this is realized by exploiting smooth spline spaces used for the former as finite element spaces required for the latter. As intended, this allows the use of geometrically exact representations for the purpose of analysis. Several new spline constructions have been devised on grid-like meshes since IGA’s inception. The excellent approximation and robustness offered by them has rejuvenated the study of high order methods, and IGA has been successfully applied to myriad problems. However, an unintended consequence of adopting a splinebased design-through-analysis paradigm has been the inheritance of open problems that lie at the intersection of the fields of modeling and approximation using splines. The first two parts of this dissertation focus on two such problems: splines of non-uniform degree and splines on unstructured meshes. The last part of the dissertation is focused on phase field modeling of corrosion using splines. The development of non-uniform degree splines is driven by the observation that relaxing the requirement for a spline’s polynomial pieces to have the same degree would be very powerful in the context of both geometric modeling and IGA. This dissertation provides a complete solution in the univariate setting. A mathematically sound foundation for an efficient algorithmic evaluation of univariate non-uniform degree splines is derived. It is shown that the algorithm outputs a nonuniform degree B-spline basis and that, furthermore, it can be applied to create C¹ piecewise-NURBS of non-uniform degree with B-spline-like properties. In the bivariate setting, a theoretical study of the dimension of non-uniform degree splines on planar T-meshes and triangulations is carried out. Combinatorial lower and upper bounds on the spline space dimension are presented. For T-meshes, sufficient conditions for the bounds to coincide are provided, while for triangulations it is shown that the spline space dimension is stable in sufficiently high degree. Modeling complex geometries using only quadrilaterals leads, in general, to unstructured meshes. In locally structured regions of the mesh, smooth splines can be built following standard procedures. However, there is no canonical way of constructing smooth splines on an unstructured arrangement of quadrilateral elements. This dissertation proposes new spline constructions for the two types of unstructuredness that can be encountered – polar points (i.e., mesh vertices that are collapsed edges) and extraordinary points (i.e., mesh vertices shared by µ ≠ 4 quadrilaterals). On meshes containing polar points, smooth spline basis functions that form a convex partition of unity are built. Numerical tests presented to benchmark the construction indicate optimal approximation behavior. On meshes containing extraordinary points, two… Advisors/Committee Members: Hughes, Thomas J. R. (advisor), Speleers, Hendrik (committee member), Landis, Chad M. (committee member), Demkowicz, Leszek F. (committee member), Ghattas, Omar (committee member).

Subjects/Keywords: Isogeometric Analysis; Finite elements; Smooth splines; Unstructured meshes; Non-uniform degree splines; Dimension formula; Corrosion modeling

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APA (6^th Edition):

Toshniwal, D. (2019). Isogeometric Analysis : study of non-uniform degree and unstructured splines, and application to phase field modeling of corrosion. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/4799

Chicago Manual of Style (16^th Edition):

Toshniwal, Deepesh. “Isogeometric Analysis : study of non-uniform degree and unstructured splines, and application to phase field modeling of corrosion.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/4799.

MLA Handbook (7^th Edition):

Toshniwal, Deepesh. “Isogeometric Analysis : study of non-uniform degree and unstructured splines, and application to phase field modeling of corrosion.” 2019. Web. 20 Apr 2021.

Vancouver:

Toshniwal D. Isogeometric Analysis : study of non-uniform degree and unstructured splines, and application to phase field modeling of corrosion. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/4799.

Council of Science Editors:

Toshniwal D. Isogeometric Analysis : study of non-uniform degree and unstructured splines, and application to phase field modeling of corrosion. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/4799

University of Texas – Austin

15. Jiao, Rong. Ratcheting, wrinkling and collapse of tubes due to axial cycling.

Degree: PhD, Engineering Mechanics, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-12-4442

► The first instability of circular tubes compressed into the plastic range is axisymmetric wrinkling, which is stable. Compressed further the wrinkle amplitude grows, leading to… (more)

▼ The first instability of circular tubes compressed into the plastic range is axisymmetric wrinkling, which is stable. Compressed further the wrinkle amplitude grows, leading to a limit load instability followed by collapse. The two instabilities can be separated by strain levels of a few percent. This work investigates whether a tube that develops small amplitude wrinkles can be subsequently collapsed by persistent cycling. The problem was first investigated experimentally using SAF 2507 super-duplex steel tubes with D/t of 28.5. The tubes are first compressed to strain levels high enough for mild wrinkles to form and then cycled axially under stress control about a compressive mean stress. This type of cycling usually results in accumulation of compressive strain; here it is accompanied by growth of the amplitude of the initial wrinkles. The tube average strain initially grows nearly linearly with the number of cycles, but as a critical value of wrinkle amplitude is approached, wrinkling localizes, the rate of ratcheting grows exponentially and the tube collapses. Similar experiments were then performed for tubes involving axial cycling under internal pressure and the combined loads cause simultaneous ratcheting in the hoop and axial directions as well as a gradual growth of the wrinkles. The rate of ratcheting and the number of cycles to collapse depend on the initial compressive pre-strain, the internal pressure, and the stress cycle parameters all of which were varied sufficiently to generate vii a sufficient data base. Interestingly, in both the pressurized and unpressurized cases collapse was found to occur when the accumulated average strain reaches the value at which the tube localizes under monotonic compression. A custom shell model of the tube with initial axisymmetric imperfections, coupled to the Dafalias-Popov two-surface nonlinear kinematic hardening model, are presented and used to simulate the experiments performed. It is demonstrated that when suitably calibrated this modeling framework reproduces the prevalent ratcheting deformations and the evolution of wrinkling including the conditions at collapse accurately for all experiments. The calibrated model is then used to evaluate the ratcheting behavior of pipes under thermal-pressure cyclic loading histories experienced by axially restrained pipelines. Advisors/Committee Members: Kyriakides, S. (advisor), Landis, Chad (committee member), Liechti, Kenneth M. (committee member), Ravi-Chandar, K. (committee member), Tassoulas, John (committee member).

Subjects/Keywords: Cyclic loading of tubes; Wrinkling; Ratcheting; Buckling; Collapse

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APA (6^th Edition):

Jiao, R. (2011). Ratcheting, wrinkling and collapse of tubes due to axial cycling. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-12-4442

Chicago Manual of Style (16^th Edition):

Jiao, Rong. “Ratcheting, wrinkling and collapse of tubes due to axial cycling.” 2011. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/ETD-UT-2011-12-4442.

MLA Handbook (7^th Edition):

Jiao, Rong. “Ratcheting, wrinkling and collapse of tubes due to axial cycling.” 2011. Web. 20 Apr 2021.

Vancouver:

Jiao R. Ratcheting, wrinkling and collapse of tubes due to axial cycling. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2011. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4442.

Council of Science Editors:

Jiao R. Ratcheting, wrinkling and collapse of tubes due to axial cycling. [Doctoral Dissertation]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4442

University of Texas – Austin

16. Biju-Duval, Paul, Ph. D. Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction.

Degree: PhD, Civil Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/63687

► Because of its ability to be easily shaped, steel is an attractive material for curved girders. Plate girder and tub girder bridges, for example, are… (more)

▼ Because of its ability to be easily shaped, steel is an attractive material for curved girders. Plate girder and tub girder bridges, for example, are often the preferred solution for direct connectors in highway networks. This flexibility in fabrication, however, presents challenges for structural engineers because of the difficulties associated with accounting for combined bending and torsion with curved geometry. The potential presence of skewed supports is a further source of complexity. In fact, no commercial structural engineering program currently addresses the evaluation of plate girder and tub girder bridges while modeling them to the full extent of their three-dimensional configuration. Most engineers, for example, use a two-dimensional bridge representation, which is often accurate for typical design of a complete bridge but may also be unconservative in many cases. The few programs that allow a full three-dimensional representation require extensive knowledge of finite element theory as well as significant time to model any complex structure. This dissertation presents the assumptions, methodology and calculations involved in the programming of a new structural engineering program designed to assess the behavior and stability or curved plate girder and tub girder bridges during erection or deck placement. It then illustrates the capabilities of the program for various structural systems subjected to a variety of loads, from self-weight to wind and temperature loads. In addition to a linear elastic analysis, multiple types of analysis are offered to the engineer: a geometrically nonlinear analysis provides a more accurate behavior for flexible systems, a linearized buckling analysis yields an upper bound evaluation of the stability of the structure, while a modal dynamic analysis estimates the free vibration modes of that structure. Advisors/Committee Members: Helwig, Todd Aaron, 1965- (advisor), Williamson, Eric B., 1968- (advisor), Bayrak, Oguzhan (committee member), Clayton, Patricia M (committee member), Engelhardt, Michael D (committee member), Landis, Chad M (committee member).

Subjects/Keywords: Steel bridges; Finite element analysis; Structural stability; Curved bridges; Buckling analysis

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APA (6^th Edition):

Biju-Duval, Paul, P. D. (2018). Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/63687

Chicago Manual of Style (16^th Edition):

Biju-Duval, Paul, Ph D. “Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/63687.

MLA Handbook (7^th Edition):

Biju-Duval, Paul, Ph D. “Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction.” 2018. Web. 20 Apr 2021.

Vancouver:

Biju-Duval, Paul PD. Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/63687.

Council of Science Editors:

Biju-Duval, Paul PD. Development of three-dimensional finite element software for curved plate girder and tub girder bridges during construction. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/63687

University of Texas – Austin

17. Ryu, Suk-Kyu. Thermo-mechanical stress analysis and interfacial reliabiity for through-silicon vias in three-dimensional interconnect structures.

Degree: PhD, Aerospace Engineering, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-12-4580

► Continual scaling of devices and on-chip wiring has brought significant challenges for materials and processes beyond the 32-nm technology node in microelectronics. Recently, three-dimensional (3-D)… (more)

▼ Continual scaling of devices and on-chip wiring has brought significant challenges for materials and processes beyond the 32-nm technology node in microelectronics. Recently, three-dimensional (3-D) integration with through-silicon vias (TSVs) has emerged as an effective solution to meet the future interconnect requirements. Among others, thermo-mechanical reliability is a key concern for the development of TSV structures used in die stacking as 3-D interconnects. In this dissertation, thermal stresses and interfacial reliability of TSV structures are analyzed by combining analytical and numerical models with experimental measurements. First, three-dimensional near-surface stress distribution is analyzed for a simplified TSV structure consisting of a single via embedded in a silicon (Si) wafer. A semi-analytic solution is developed and compared with finite element analysis (FEA). For further study, the effects of anisotropic elasticity in Si and metal plasticity in the via on the stress distribution and deformation are investigated. Next, by micro-Raman spectroscopy and bending beam technique, experimental measurements of the thermal stresses in TSV structures are conducted. The micro-Raman measurements characterize the local distribution of the near-surface stresses in Si around TSVs. On the other hand, the bending beam technique measures the average stress and viii deformation in the TSV structures. To understand the elastic and plastic behavior of TSVs, the microstructural evolution of the Cu vias is analyzed using focused ion beam (FIB) and electron backscattering diffraction (EBSD) techniques. To study the impacts of the thermal stresses on interfacial reliability of TSV structures, an analytical solution is developed for the steady-state energy release rate as the upper bound of the driving force for interfacial delamination. The effect of crack length and wafer thickness on the energy release rate is studied by FEA. Furthermore, to model interfacial crack nucleation, an analytical approach is developed by combining a shear lag model with a cohesive interface model. Finally, the effects of structural designs and the variation of the constituent materials on TSV reliability are investigated. The steady state solutions for the energy release rate are developed for various TSV designs and via materials (Al, Cu, Ni, and W) to evaluate the interfacial reliability. The parameters for TSV design optimization are discussed from the perspectives of interfacial reliability. Advisors/Committee Members: Huang, Rui, doctor of civil and environmental engineering (advisor), Liechti, Kenneth (committee member), Landis, Chad (committee member), Ho, Paul S. (committee member), Im, Jang-Hi (committee member).

Subjects/Keywords: 3-D interconnect; Trough-silicon vias; Thermomechanical reliability; Thermal stresses; Bending beam curvature technique; Raman spectroscopy

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APA (6^th Edition):

Ryu, S. (2011). Thermo-mechanical stress analysis and interfacial reliabiity for through-silicon vias in three-dimensional interconnect structures. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-12-4580

Chicago Manual of Style (16^th Edition):

Ryu, Suk-Kyu. “Thermo-mechanical stress analysis and interfacial reliabiity for through-silicon vias in three-dimensional interconnect structures.” 2011. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/ETD-UT-2011-12-4580.

MLA Handbook (7^th Edition):

Ryu, Suk-Kyu. “Thermo-mechanical stress analysis and interfacial reliabiity for through-silicon vias in three-dimensional interconnect structures.” 2011. Web. 20 Apr 2021.

Vancouver:

Ryu S. Thermo-mechanical stress analysis and interfacial reliabiity for through-silicon vias in three-dimensional interconnect structures. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2011. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4580.

Council of Science Editors:

Ryu S. Thermo-mechanical stress analysis and interfacial reliabiity for through-silicon vias in three-dimensional interconnect structures. [Doctoral Dissertation]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-12-4580

University of Texas – Austin

18. Alotaibi, Talal Eid. Applications of phase-field modeling in hydraulic fracture.

Degree: PhD, Engineering Mechanics, 2020, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/8157

► Understanding the mechanisms behind the nucleation and propagation of cracks is of considerable interest in engineering application and design decisions. In many applications in the… (more)

▼ Understanding the mechanisms behind the nucleation and propagation of cracks is of considerable interest in engineering application and design decisions. In many applications in the oil industry, complicated fracture geometries and propagation behaviors are encountered. As a result, the development of modeling approaches that can capture the physics of non-planar crack evolution while being computationally tractable is a critical challenge. The phase-field approach to fracture has been shown to be a powerful tool for simulating very complex fracture topologies, including the turning, splitting, and merging of cracks. In contrast to fracture models that explicitly track the crack surfaces, crack propagation and the evolution thereof arise out of the solution to a partial differential equation governing the evolution of a phase-field damage parameter. As such, the crack growth emerges naturally from solving the set of coupled differential equations linking the phase-field to other field quantities that can drive the fracture process. In the present model, the physics of flow through porous media and cracks is coupled with the mechanics of fracture. Darcy-type flow is modeled in the intact porous medium, which transitions to a Stokes-type flow regime within open cracks. This phase-field model is implemented to gain insights into the propagation behavior of fluid-injected cracks. One outstanding issue with phase-field fracture models is the decomposition of the strain energy required to ensure that compressive stress states do not cause crack propagation and damage evolution. In the present study, the proper representation of the strain energy function to reflect this fracture phenomenon is examined. The strain energy is constructed in terms of principle strains in such a way that it has two parts; the tensile and the compressive. A degradation function only applies to the tensile part enforcing that the crack is driven only by that part of the strain energy. We investigated the split operator proposed by Miehe et al. [1], and then proposed a split approach based on masonry-like material behavior [2, 3]. We have found that when using Miehe’s form for the strain energy function, cracks can propagate under compressive stresses. In contrast, the approach based on a masonry-like materials constitutive model we proposed ensures that cracks do not grow under compressive stresses. To demonstrate the capabilities of phase-field modeling for fluid-driven fractures, four general types of problems are simulated: 1) interactions of fluid-driven, natural, and proppant-filled cracks, 2) crack growth through different material layers, 3) fluid-driven crack growth under the influence of in-situ far-field stresses, and 4) crack interactions with inclusions. The simulations illustrate the capabilities of the phase-field model for capturing interesting and complex crack growth phenomena. To understand how fluid-driven cracks interact with inclusions, AlTammar et al. [4] performed experiments. Three tests with tough inclusions were… Advisors/Committee Members: Landis, Chad M. (advisor), Sharma, Mukul M (committee member), Mear, Mark E (committee member), Ravi-Chandar, Krishnaswa (committee member), Foster, John T (committee member).

Subjects/Keywords: Phase-field modeling; Hydraulic fracture; Fracture mechanics

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APA (6^th Edition):

Alotaibi, T. E. (2020). Applications of phase-field modeling in hydraulic fracture. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/8157

Chicago Manual of Style (16^th Edition):

Alotaibi, Talal Eid. “Applications of phase-field modeling in hydraulic fracture.” 2020. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/8157.

MLA Handbook (7^th Edition):

Alotaibi, Talal Eid. “Applications of phase-field modeling in hydraulic fracture.” 2020. Web. 20 Apr 2021.

Vancouver:

Alotaibi TE. Applications of phase-field modeling in hydraulic fracture. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2020. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/8157.

Council of Science Editors:

Alotaibi TE. Applications of phase-field modeling in hydraulic fracture. [Doctoral Dissertation]. University of Texas – Austin; 2020. Available from: http://dx.doi.org/10.26153/tsw/8157

University of Texas – Austin

19. Pham, Khai Hong. Characterization and modeling of mixed-mode I+III fracture in brittle materials.

Degree: PhD, Engineering mechanics, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/33391

► Mixed-mode I+III fracture in brittle materials presents spectacular, scale-independent pattern formation in nature and engineering applications; and it is one of the last remaining puzzles… (more)

▼ Mixed-mode I+III fracture in brittle materials presents spectacular, scale-independent pattern formation in nature and engineering applications; and it is one of the last remaining puzzles in linear elastic fracture mechanics. This problem has received much attention in the literature over the past few decades both from experiments and analysis, but there are still open challenges that remain. Specifically, the existence of a threshold ratio of mode III to mode I loading below which fragmentation of the crack front (formation of daughter cracks) does not occur and the length scale associated with the spacing of the fragments when they do occur are still under debate. The continued growth of cracks under remote mode I + III loading is also of interest; it is observed that in some cases the fragmented cracks coalesce, while in others they maintain their independent development. We approach this problem through carefully designed experiments to examine the physical aspects of crack initiation and growth. This is then explored further through numerical simulations of the stress state that explore the influence of perturbations on the formation of daughter cracks. We show that a parent crack subjected to combined modes I+III loading exhibits fragmentation of the crack front into daughter cracks without any threshold. The distance between the daughter cracks is dictated by the length scale corresponding to the decay of the elastic field; this decay depends on the characteristic dimension of the parent crack from which the daughter cracks are nucleated. As the daughter cracks continue growing, they coarsen in spacing also through elastic shielding. As the daughter cracks grow farther, the parent crack, pinned at the original position, experiences increased stress intensity factor and the bridging regions begin to crack and the parent crack front advances towards the daughter cracks. This establishes a steady state condition for the system of parent crack with equally spaced daughter cracks to continue growing together. Finally, direct numerical simulation of crack initiation and growth is explored using a phase-field model. The model is first validated for in-plane modes I + II through comparison to experiments, and then used to explore combined modes I + III in order to study the above mechanism of mixed-mode I + III crack growth. Advisors/Committee Members: Ravi-Chandar, K. (advisor), Landis, Chad M (committee member), Liechti, Kenneth M (committee member), Mear, Mark E (committee member), Marder, Michael P (committee member).

Subjects/Keywords: Fracture; Crack front fragmentation; Nucleation of crack fragments; Shielding of crack; Model for mixed-mode I+III crack growth; Phase-field modeling; Glass; Homalite; Hydrogel

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APA (6^th Edition):

Pham, K. H. (2015). Characterization and modeling of mixed-mode I+III fracture in brittle materials. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/33391

Chicago Manual of Style (16^th Edition):

Pham, Khai Hong. “Characterization and modeling of mixed-mode I+III fracture in brittle materials.” 2015. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/33391.

MLA Handbook (7^th Edition):

Pham, Khai Hong. “Characterization and modeling of mixed-mode I+III fracture in brittle materials.” 2015. Web. 20 Apr 2021.

Vancouver:

Pham KH. Characterization and modeling of mixed-mode I+III fracture in brittle materials. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2015. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/33391.

Council of Science Editors:

Pham KH. Characterization and modeling of mixed-mode I+III fracture in brittle materials. [Doctoral Dissertation]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/33391

University of Texas – Austin

20. -6430-5266. A hybridized discontinuous Galerkin method for nonlinear dispersive water waves.

Degree: PhD, Engineering Mechanics, 2017, University of Texas – Austin

URL: http://hdl.handle.net/2152/47354

► Simulation of water waves near the coast is an important problem in different branches of engineering and mathematics. For mathematical models to be valid in… (more)

▼ Simulation of water waves near the coast is an important problem in different branches of engineering and mathematics. For mathematical models to be valid in this region, they should include nonlinear and dispersive properties of the corresponding waves. Here, we study the numerical solution to three equations for modeling coastal water waves using the hybridized discontinuous Galerkin method (HDG). HDG is known to be a more efficient and in certain cases a more accurate alternative to some other discontinuous Galerkin methods, such as local DG. The first equation that we solve here is the Korteweg-de Vries equation. Similar to common HDG implementations, we first express the approximate variables and numerical fluxes in each element in terms of the approximate traces of the scalar variable, and its first derivative. These traces are assumed to be single-valued on each face. We next impose the conservation of the numerical fluxes via two sets of equations on the element boundaries. We solve this equation by Newton-Raphson method. We prove the stability of the proposed method for a proper choice of stabilization parameters. Through numerical examples, we observe that for a mesh with kth order elements, the computed variable and its first and second derivatives show optimal convergence at order k + 1 in both linear and nonlinear cases, which improves upon previously employed techniques. Next, we consider solving the fully nonlinear irrotational Green-Naghdi equation. This equation is often used to simulate water waves close to the shore, where there are significant dispersive and nonlinear effects involved. To solve this equation, we use an operator splitting method to decompose the problem into a dispersive part and a hyperbolic part. The dispersive part involves an implicit step, which has regularizing effects on the solution of the problem. On the other hand, for the hyperbolic sub-problem, we use an explicit hybridized DG method. Unlike the more common implicit version of the HDG, here we start by solving the flux conservation condition for the numerical traces. Afterwards, we use these traces in the original PDEs to obtain the internal unknowns. This process involves Newton iterations at each time step for computing the numerical traces. Next, we couple this solver with the dispersive solver to obtain the solution to the Green-Naghdi equation. We then solve a set of numerical examples to verify and validate the employed technique. In the first example we show the convergence properties of the numerical method. Next, we compare our results with a set of experimental data for nonlinear water waves in different situations. We observe close to optimal convergence rates and a good agreement between our numerical results and the experimental data. Advisors/Committee Members: Dawson, Clinton N. (advisor), Demkowicz, Leszek F (committee member), Gamba, Irene M (committee member), Hodges, Ben R (committee member), Landis, Chad M (committee member), Raja, Laxminarayan L (committee member).

Subjects/Keywords: Discontinuous Galerkin; DG; Hybridized; HDG; Nonlinear shallow water; Green-Naghdi; NSWE; GN; Galerkin method; Water waves; Nonlinear water waves; Dispersive water waves; Water wave simulation; Coastal water waves modeling; Korteweg-de Vries equation

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APA (6^th Edition):

-6430-5266. (2017). A hybridized discontinuous Galerkin method for nonlinear dispersive water waves. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/47354

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Chicago Manual of Style (16^th Edition):

-6430-5266. “A hybridized discontinuous Galerkin method for nonlinear dispersive water waves.” 2017. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/47354.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-6430-5266. “A hybridized discontinuous Galerkin method for nonlinear dispersive water waves.” 2017. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-6430-5266. A hybridized discontinuous Galerkin method for nonlinear dispersive water waves. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2017. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/47354.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6430-5266. A hybridized discontinuous Galerkin method for nonlinear dispersive water waves. [Doctoral Dissertation]. University of Texas – Austin; 2017. Available from: http://hdl.handle.net/2152/47354

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

21. -2943-2689. Peridynamic modeling of large deformation and ductile fracture.

Degree: PhD, Engineering Mechanics, 2020, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/8161

► Prediction of ductile fracture, which is a prevalent failure mode in most engineering structures, is vital to numerous industries. Despite significant advancements in fracture mechanics,… (more)

▼ Prediction of ductile fracture, which is a prevalent failure mode in most engineering structures, is vital to numerous industries. Despite significant advancements in fracture mechanics, ductile fracture modeling has remained a challenging task and a continuing area of research. The peridynamic theory has attracted broad interest in recent years, for its innovative approach for simulating material damage. While peridynamics has been largely utilized to simulate cracking events in brittle materials, its ability in predicting ductile failure remains mostly untested. In this dissertation, a rigorous investigation into the capabilities of peridynamics in simulating ductile fracture in metallic alloys is undertaken. The third Sandia Fracture Challenge, as a true blind prediction challenge, is employed in this examination. In this challenge, the state of the art of the peridynamic modeling of ductile fracture is implemented to predict deformations and failure of an additively manufactured metal, with a complex geometry, under the dynamic tensile experiments performed by Sandia National Laboratories. Following the participation in the challenge, while our modeling approach led to qualitatively good blind predictions and a correctly predicted crack path, it underpredicted the load-carrying capacity of the structure and simulated an early fracture. Our post-experiment analysis identifies the main sources of discrepancy between the blind simulations and experiments to be (1) material instabilities associated with the finite deformation peridynamic model and (2) unreliability of a Lagrangian peridynamic framework in solving problems involving extremely large deformation and extensive damage. To address the aforementioned issues, a novel bond-associated, semi-Lagrangian, constitutive correspondence, peridynamic framework is proposed, in which peridynamic material point interactions depend only on their current properties (e.g. position and stress values) in the deformed configuration, and a rate-based approach is utilized to advance the state of material. A nonlocal version of the velocity gradient is presented to determine the Cauchy stress rate, using local constitutive theories, as an intermediate quantity in computing peridynamic bond forces. A novel bond-associated, correspondence damage modeling is introduced by using the bond-associated internal properties, e.g. stress and strain values, to incorporate classical failure criteria within the peridynamic framework. The new theory is employed to revisit the Sandia Fracture Challenge problem. Our results indicate that the new approach significantly improves the peridynamic predictions of large deformation and ductile fracture Advisors/Committee Members: Foster, John T., Ph. D. (advisor), Landis, Chad M. (committee member), Kyriakides, Stelios (committee member), Ravi-Chandar, Krishnaswa (committee member), Huang, Rui (committee member), Sharma, Mukul M. (committee member).

Subjects/Keywords: Peridynamics; Nonlocal; Modeling; Large deformation; Ductile fracture; Semi-Lagrangian; Sandia Fracture Challenge

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APA (6^th Edition):

-2943-2689. (2020). Peridynamic modeling of large deformation and ductile fracture. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/8161

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-2943-2689. “Peridynamic modeling of large deformation and ductile fracture.” 2020. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/8161.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-2943-2689. “Peridynamic modeling of large deformation and ductile fracture.” 2020. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-2943-2689. Peridynamic modeling of large deformation and ductile fracture. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2020. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/8161.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-2943-2689. Peridynamic modeling of large deformation and ductile fracture. [Doctoral Dissertation]. University of Texas – Austin; 2020. Available from: http://dx.doi.org/10.26153/tsw/8161

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

University of Texas – Austin

22. -0908-0089. Phase-field modeling of fracture for multiphysics problems.

Degree: PhD, Engineering mechanics, 2016, University of Texas – Austin

URL: http://hdl.handle.net/2152/46492

► Several recent works have demonstrated that phase-field methods for modeling fracture are capable of yielding complex crack evolution patterns in materials. This includes the nucleation,… (more)

▼ Several recent works have demonstrated that phase-field methods for modeling fracture are capable of yielding complex crack evolution patterns in materials. This includes the nucleation, turning, branching, and merging of cracks subject to a variety of quasi-static and dynamic loadings. What follows will demonstrate how phase-field methods for fracture can be applied to problems involving materials subject to electromechanical coupling and the problem of hydraulic fracture. Brittle fracture is a major concern in piezoelectric ceramics. Fracture propagation in these materials is heavily influenced by the mechanical and electrical fields within the material as well as the boundary conditions on the crack surfaces. These conditions can lead to complex multi-modal crack growth. We develop a continuum thermodynamics framework for a damaging medium with electromechanical coupling subject to four different crack-face boundary conditions. A theory is presented to reproduce impermeable, permeable, conducting, and energetically consistent crack-face boundary conditions, the latter of which requires a finite deformation formulation. A primary application of hydraulic fracturing involves the injection of fluid into a perforated wellbore with the intention of fracturing the surrounding reservoir and stimulating its overall production. This process involves the coupling of fluid flow with material failure, which must account for the interactions of several cracks, both natural and man-made. Many of the questions on the effects these interactions have on the performance of the frac treatments are unanswered. We develop a continuum thermodynamics framework for fluid flow through a damaging porous medium in order to represent some of the processes and interactions that occur during hydraulic fracturing. The model will be capable of simulating both Stokes flow through cracks and Darcy flow through the porous medium. The flow is coupled to the deformation of the bulk solid medium and the evolution of cracks within the material. We utilize a finite deformation framework in order to capture the opening of the fractures, which can have substantial effects on fluid pressure response. For both models, a fully coupled non-linear finite element formulation is constructed. Several benchmark solutions are investigated to validate the expected behavior and accuracy of the method. In addition, a number of interesting problems are investigated in order to demonstrate the ability of the method to respond to various complexities like material anisotropy and the interaction of multiple cracks. Advisors/Committee Members: Landis, Chad M. (advisor), Hughes, Thomas J.R. (committee member), Mear, Mark E. (committee member), Ravi-Chandar, Krishnaswa (committee member), Foster, John T. (committee member).

Subjects/Keywords: Phase-field; Fracture mechanics; Piezoelectric; Hydraulic fracture

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APA (6^th Edition):

-0908-0089. (2016). Phase-field modeling of fracture for multiphysics problems. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/46492

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-0908-0089. “Phase-field modeling of fracture for multiphysics problems.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/46492.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-0908-0089. “Phase-field modeling of fracture for multiphysics problems.” 2016. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-0908-0089. Phase-field modeling of fracture for multiphysics problems. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/46492.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-0908-0089. Phase-field modeling of fracture for multiphysics problems. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/46492

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

23. -6676-8499. Advanced hydraulic fracture modeling : peridynamics, inelasticity, and coupling to FEM.

Degree: PhD, Petroleum Engineering, 2018, University of Texas – Austin

URL: http://hdl.handle.net/2152/65945

► In the effort to create new technology to enhance our ability to retrieve hydrocarbons, the technique of hydraulic fracturing has shown to be extremely beneficial.… (more)

▼ In the effort to create new technology to enhance our ability to retrieve hydrocarbons, the technique of hydraulic fracturing has shown to be extremely beneficial. This involves pumping fluids at high pressures and high rates to induce and propagate fractures near the wellbore to stimulate production in otherwise low permeability reservoirs. To better understand the physical processes involved, several models have been proposed for numeric simulation. This work expands on an existing hydraulic fracturing model based on the nonlocal theory of peridynamics, detailed in Ouchi et al. [3]. Peridynamics is a relatively new reformulation of continuum mechanics, applicable even when discontinuities such as fractures are introduced. To incorporate the influence of inelasticity in the established model, which may be significant for several geologic materials, a multi-surface yield model is proposed. This yield model builds on a Drucker-Prager related yield model formulated for peridynamics by Lammi et al. [46], adding a tension cut-off surface as well as a cap to include hardening effects associated with inelastic compaction. The formulation of these additional surfaces in the peridynamic framework will be detailed and numerically demonstrated in this dissertation. As the peridynamic based hydraulic fracture model continues to develop complex capabilities, such as inelasticity, computational expense continues to be an ever-growing concern. Although the peridynamic formulation has demonstrated the capability of modeling complex fracture behavior, the computational expense is noted to be quite expensive relative to classic local models. Recently, methods have been introduced for coupling nonlocal bond based peridynamic grids with local finite element meshes, detailed in Galvanetoo et al. [74]. These coupling methods have demonstrated applicability to static equilibrium mechanics problems, while introducing negligible errors. In this work, the coupling method is implemented with the nonlocal hydraulic fracturing model, using peridynamics near existent and propagating fractures, as well as a standard finite element formulation far from the influence of such features. To further increase computational efficiency, a dynamically adaptive mesh coarsened away from the peridynamic region is implemented with the capability of converting finite element nodes to peridynamic nodes. This novel method of coupling peridynamics with a highly efficient mesh in the hydraulic fracture model will be fully detailed in this dissertation. In addition, 2D and 3D results will be provided using this method, demonstrating the capability of the coupled model to simulate complex fracture behavior, as well as discuss its impact on simulation capabilities and performance. Advisors/Committee Members: Foster, John T., Ph. D. (advisor), Sharma, Mukul M. (advisor), Espinoza, David N (committee member), Gray, Kenneth E (committee member), Landis, Chad M (committee member).

Subjects/Keywords: Peridynamic theory; Hydraulic fracturing; Coupling; Inelasticity; Hydraulic fracture modeling; Peridynamics; Peridynamic based hydraulic fracture model; Numeric simulation

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APA (6^th Edition):

-6676-8499. (2018). Advanced hydraulic fracture modeling : peridynamics, inelasticity, and coupling to FEM. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/65945

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-6676-8499. “Advanced hydraulic fracture modeling : peridynamics, inelasticity, and coupling to FEM.” 2018. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/65945.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-6676-8499. “Advanced hydraulic fracture modeling : peridynamics, inelasticity, and coupling to FEM.” 2018. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-6676-8499. Advanced hydraulic fracture modeling : peridynamics, inelasticity, and coupling to FEM. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2018. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/65945.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6676-8499. Advanced hydraulic fracture modeling : peridynamics, inelasticity, and coupling to FEM. [Doctoral Dissertation]. University of Texas – Austin; 2018. Available from: http://hdl.handle.net/2152/65945

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

24. Petrou, Zacharias. Thermo-electro-mechanical behavior of ferroelectric nanodots.

Degree: MSin Engineering, Engineering Mechanics, 2013, University of Texas – Austin

URL: http://hdl.handle.net/2152/21783

► The relatively recent discovery of the giant electrocaloric effect in ferroelectric ceramics may lead to new solid state cooling technologies that are energy efficient, reliable,… (more)

▼ The relatively recent discovery of the giant electrocaloric effect in ferroelectric ceramics may lead to new solid state cooling technologies that are energy efficient, reliable, portable, and environmentally friendly. This phenomenon, along with many other novel field-coupled properties of ferroelectrics, such as piezoelectricity, pyroelectricity, the electro-optic effect, phase changes, and polarization switching, make these materials useful for a wide range of technological applications including sensors, ultrasound, infrared cameras, sonar, diesel engine fuel injectors, ferroelectric random access memory, electro-optic modulators, vibration control, and electrocaloric cooling devices. Most of world’s current cooling and refrigeration technology is based upon the vapor-compression cycle of a refrigerant. Refrigeration systems that are based on this technology are bulky, require moving parts in the compressor and some of them have a less than optimal environmental impact. Thin film devices that utilize the electrocaloric effect could have a significant impact on refrigeration, heat pumps, air conditioning, energy scavenging, and computer cooling systems. Especially for the latter ones, the fan-based solutions are not likely to be able to keep up with the increases in computing power and the resulting current densities in integrated circuits. The ability to make quantitative predictions of the behavior of ferroelectric structures is of significant importance given the experimental efforts on the synthesis of barium titanate nanodots, nanorods, nanowires, and nanotubes, and lead zirconate titanate (PZT) thin films, and nanoparticles, and the potential for technological applications of these structures. The research contained herein implements a full thermo-electro-mechanical continuum framework and numerical methods based on phase-field modeling to study the domain and phase structure evolution associated with the electrocaloric effect in barium titanate ferroelectric nanodots. Advisors/Committee Members: Landis, Chad M. (advisor).

Subjects/Keywords: Nanodots; Ferroelectric materials; Electrocaloric effect; Phase field modelling

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APA (6^th Edition):

Petrou, Z. (2013). Thermo-electro-mechanical behavior of ferroelectric nanodots. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/21783

Chicago Manual of Style (16^th Edition):

Petrou, Zacharias. “Thermo-electro-mechanical behavior of ferroelectric nanodots.” 2013. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/21783.

MLA Handbook (7^th Edition):

Petrou, Zacharias. “Thermo-electro-mechanical behavior of ferroelectric nanodots.” 2013. Web. 20 Apr 2021.

Vancouver:

Petrou Z. Thermo-electro-mechanical behavior of ferroelectric nanodots. [Internet] [Masters thesis]. University of Texas – Austin; 2013. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/21783.

Council of Science Editors:

Petrou Z. Thermo-electro-mechanical behavior of ferroelectric nanodots. [Masters Thesis]. University of Texas – Austin; 2013. Available from: http://hdl.handle.net/2152/21783

25. Erickson, Andrew Jay. Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluid.

Degree: MSin Engineering, Engineering Mechanics, 2012, University of Texas – Austin

URL: http://hdl.handle.net/2152/19986

► In this paper we develop a computational procedure to investigate linear fracture of two-dimensional problems in isotropic linearly elastic media. A symmetric Galerkin boundary element… (more)

Subjects/Keywords: Fracture mechanics; Boundary element method; Weakly singular kernel

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APA (6^th Edition):

Erickson, A. J. (2012). Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluid. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/19986

Chicago Manual of Style (16^th Edition):

Erickson, Andrew Jay. “Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluid.” 2012. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/19986.

MLA Handbook (7^th Edition):

Erickson, Andrew Jay. “Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluid.” 2012. Web. 20 Apr 2021.

Vancouver:

Erickson AJ. Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluid. [Internet] [Masters thesis]. University of Texas – Austin; 2012. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/19986.

Council of Science Editors:

Erickson AJ. Simulation of the growth of multiple interacting 2D hydraulic fractures driven by an inviscid fluid. [Masters Thesis]. University of Texas – Austin; 2012. Available from: http://hdl.handle.net/2152/19986

26. -3712-6304. A continuum modeling approach for the deposition of enamel.

Degree: MSin Engineering, Engineering mechanics, 2015, University of Texas – Austin

URL: http://hdl.handle.net/2152/34129

► In this report continuum methods to analyze organogenesis on curved surfaces is devised. This initial study will investigate a basic system. Dental enamel is the… (more)

▼ In this report continuum methods to analyze organogenesis on curved surfaces is devised. This initial study will investigate a basic system. Dental enamel is the example system used to study the simulation of organogenesis as well as pattern formation. It is observed that dental enamel is created by a number of ameloblast cells migrating generally outward from the dental enamel junction (DEJ). These cells also rearrange locally within the surface that they reside. In this report, the simulations are based on the postulate that the cell motion arises from changes in the local strain environment as the cells migrate. As opposed to a passive movement driven by external driving forces or energy gradients, this theory hypothesizes that motion can arise internally due to the migration of the individual cell influenced by the local cell density and the velocity of the cell relative to its contacting neighbors. To model this kinematically driven approach we first develop a set of continuum equations to describe the velocity of the cells. This consists of two components, one the governs the in-plane rearrangements of the cells based on local strain cues, and a second that governs the velocity of the cells normal to the DEJ, which depends upon if the cells are actively secreting or not. This second feature requires the knowledge of the location of the boundary between secretory and non-secretory cells, which we is called the commencement front. On the secretory side of the commencement front the normal velocity of the cells is a specified quantity, while on the non-secretory side the normal velocity is zero. In order to track the evolution of the commencement front a phase-field description is utilized that treats this boundary as a diffuse instead of a sharp interface. The numerical method that is used to solve the equations is described, and some initial preliminary results for simple surface geometries are presented. Advisors/Committee Members: Landis, Chad M. (advisor), Mear, Mark E (committee member).

Subjects/Keywords: Enamel; Commencement front; Phase-field modeling; Finite element methods

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APA (6^th Edition):

-3712-6304. (2015). A continuum modeling approach for the deposition of enamel. (Masters Thesis). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/34129

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16^th Edition):

-3712-6304. “A continuum modeling approach for the deposition of enamel.” 2015. Masters Thesis, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/34129.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7^th Edition):

-3712-6304. “A continuum modeling approach for the deposition of enamel.” 2015. Web. 20 Apr 2021.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-3712-6304. A continuum modeling approach for the deposition of enamel. [Internet] [Masters thesis]. University of Texas – Austin; 2015. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/34129.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-3712-6304. A continuum modeling approach for the deposition of enamel. [Masters Thesis]. University of Texas – Austin; 2015. Available from: http://hdl.handle.net/2152/34129

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

27. Bouklas, Nikolaos. Modelling and simulations of hydrogels with coupled solvent diffusion and large deformation.

Degree: PhD, Engineering Mechanics, 2014, University of Texas – Austin

URL: http://hdl.handle.net/2152/28394

► Swelling of a polymer gel is a kinetic process coupling mass transport and mechanical deformation. A comparison between a nonlinear theory for polymer gels and… (more)

▼ Swelling of a polymer gel is a kinetic process coupling mass transport and mechanical deformation. A comparison between a nonlinear theory for polymer gels and the classical theory of linear poroelasticity is presented. It is shown that the two theories are consistent within the linear regime under the condition of a small perturbation from an isotropically swollen state of the gel. The relationships between the material properties in the linear theory and those in the nonlinear theory are established by a linearization procedure. Both linear and nonlinear solutions are presented for swelling kinetics of substrate-constrained and freestanding hydrogel layers. A new procedure is suggested to fit the experimental data with the nonlinear theory. A nonlinear, transient finite element formulation is presented for initial boundary value problems associated with swelling and deformation of hydrogels, based on nonlinear continuum theories for hydrogels with compressible and incompressible constituents. The incompressible instantaneous response of the aggregate imposes a constraint to the finite element discretization in order to satisfy the LBB condition for numerical stability of the mixed method. Three problems of practical interests are considered: constrained swelling, flat-punch indentation, and fracture of hydrogels. Constrained swelling may lead to instantaneous surface instability. Indentation relaxation of hydrogels is simulated beyond the linear regime under plane strain conditions, and is compared with two elastic limits for the instantaneous and equilibrium states. The effects of Poisson’s ratio and loading rate are discussed. On the study of hydrogel fracture, a method for calculating the transient energy release rate for crack growth in hydrogels, based on a modified path-independent J-integral, is presented. The transient energy release rate takes into account the energy dissipation due to diffusion. Numerical simulations are performed for a stationary center crack loaded in mode I, with both immersed and non-immersed chemical boundary conditions. Both sharp crack and blunted notch crack models are analyzed over a wide range of applied remote tensile strains. Comparisons to linear elastic fracture mechanics are presented. A critical condition is proposed for crack growth in hydrogels based on the transient energy release rate. The applicability of this growth condition for simulating concomitant crack propagation and solvent diffusion in hydrogels is discussed. Advisors/Committee Members: Huang, Rui, doctor of civil and environmental engineering (advisor), Landis, Chad M. (advisor).

Subjects/Keywords: Hydrogel; Fracture; Swelling; Indentation; Mixed finite element method; Transient response

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APA (6^th Edition):

Bouklas, N. (2014). Modelling and simulations of hydrogels with coupled solvent diffusion and large deformation. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/28394

Chicago Manual of Style (16^th Edition):

Bouklas, Nikolaos. “Modelling and simulations of hydrogels with coupled solvent diffusion and large deformation.” 2014. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/28394.

MLA Handbook (7^th Edition):

Bouklas, Nikolaos. “Modelling and simulations of hydrogels with coupled solvent diffusion and large deformation.” 2014. Web. 20 Apr 2021.

Vancouver:

Bouklas N. Modelling and simulations of hydrogels with coupled solvent diffusion and large deformation. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2014. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/28394.

Council of Science Editors:

Bouklas N. Modelling and simulations of hydrogels with coupled solvent diffusion and large deformation. [Doctoral Dissertation]. University of Texas – Austin; 2014. Available from: http://hdl.handle.net/2152/28394

28. Chen, Kelin. The effect of anisotropy on the localization and failure of aluminum alloys under biaxial loads.

Degree: PhD, Engineering Mechanics, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/5791

► Development of a robust finite element model capable of simulating ductile failure of thin-walled Al-alloy structures under complex loading conditions requires: (a) A suitably calibrated… (more)

▼ Development of a robust finite element model capable of simulating ductile failure of thin-walled Al-alloy structures under complex loading conditions requires: (a) A suitably calibrated constitutive model of the material that includes the prevailing plastic anisotropy, and (b) an appropriately extracted material hardening response to large enough strains. This work addresses these two issues through the analysis of the response up to failure of thin sheets in hydraulic bulge tests, and the large deformation response of tubes under combined shear and tension. Hydraulic bulge tests have been used to extract the material hardening response of sheet metals to large strains. The extraction requires proper knowledge of the plastic anisotropy in the sheets. To this end, the non-quadratic anisotropic yield function of Barlat et al. [2005] was calibrated using a series of uniaxial and biaxial tests and two data from the bulge test. The calibration uses an iterative scheme for evaluating the stress state at the apex. The calibrated yield function is then used to extract the material hardening. The veracity of the scheme is demonstrated by using the calibrated yield function and hardening response in a 3-D finite element model to successfully simulate the bulge test up to failure. The second part of the project simulates the response of Al-alloy tubes under combined tension and torsion. Experiments conducted in parallel with this study have shown that following initial plastic deformation, strain localizes in a narrow zone and grows significantly before rupture. Here, the non-quadratic anisotropy yield function is calibrated using the set of tension-torsion experiments conducted, supplemented by a set of pressure-tension experiments. The constitutive model is then used to extract the material hardening response from a simple shear test accounting for the rotation of the material frame. The two constitutive components are then implemented in a 3-D finite element model to simulate a set of tension-torsion experiments. It is demonstrated that the constitutive model and hardening material response can reproduce the experimental structural responses, the onset of localization and its evolution to strains that correspond to the measured failure strains. This is achieved without the artificial introduction of material softening. Advisors/Committee Members: Kyriakides, S. (advisor), Corona, Edmundo (committee member), Liechti, Kenneth (committee member), Ravi-Chandar, Krishnaswamy (committee member), Landis, Chad (committee member).

Subjects/Keywords: Anisotropy; Material hardening; Hydraulic bulge test; Combined shear and tension; Ductile failure

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APA (6^th Edition):

Chen, K. (2019). The effect of anisotropy on the localization and failure of aluminum alloys under biaxial loads. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/5791

Chicago Manual of Style (16^th Edition):

Chen, Kelin. “The effect of anisotropy on the localization and failure of aluminum alloys under biaxial loads.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/5791.

MLA Handbook (7^th Edition):

Chen, Kelin. “The effect of anisotropy on the localization and failure of aluminum alloys under biaxial loads.” 2019. Web. 20 Apr 2021.

Vancouver:

Chen K. The effect of anisotropy on the localization and failure of aluminum alloys under biaxial loads. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/5791.

Council of Science Editors:

Chen K. The effect of anisotropy on the localization and failure of aluminum alloys under biaxial loads. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/5791

29. Scott, Michael Andrew. T-splines as a design-through-analysis technology.

Degree: PhD, Computational and Applied Mathematics, 2011, University of Texas – Austin

URL: http://hdl.handle.net/2152/ETD-UT-2011-08-3795

► To simulate increasingly complex physical phenomena and systems, tightly integrated design-through-analysis (DTA) tools are essential. In this dissertation, the complementary strengths of isogeometric analysis and… (more)

▼ To simulate increasingly complex physical phenomena and systems, tightly integrated design-through-analysis (DTA) tools are essential. In this dissertation, the complementary strengths of isogeometric analysis and T-splines are coupled and enhanced to create a seamless DTA framework. In all cases, the technology de- veloped meets the demands of both design and analysis. In isogeometric analysis, the smooth geometric basis is used as the basis for analysis. It has been demonstrated that smoothness offers important computational advantages over standard finite elements. T-splines are a superior alternative to NURBS, the current geometry standard in computer-aided design systems. T-splines can be locally refined and can represent complicated designs as a single watertight geometry. These properties make T-splines an ideal discretization technology for isogeometric analysis and, on a higher level, a foundation upon which unified DTA technologies can be built. We characterize analysis-suitable T-splines and develop corresponding finite element technology, including the appropriate treatment of extraordinary points (i.e., unstructured meshing). Analysis-suitable T-splines form a practically useful subset of T-splines. They maintain the design flexibility of T-splines, including an efficient and highly localized refinement capability, while preserving the important analysis-suitable mathematical properties of the NURBS basis. We identify Bézier extraction as a unifying paradigm underlying all isogeometric element technology. Bézier extraction provides a finite element representation of NURBS or T-splines, and facilitates the incorporation of T-splines into existing finite element programs. Only the shape function subroutine needs to be modified. Additionally, Bézier extraction is automatic and can be applied to any T-spline regardless of topological complexity or polynomial degree. In particular, it represents an elegant treatment of T-junctions, referred to as "hanging nodes" in finite element analysis We then detail a highly localized analysis-suitable h-refinement algorithm. This algorithm introduces a minimal number of superfluous control points and preserves the properties of an analysis-suitable space. Importantly, our local refinement algorithm does not introduce a complex hierarchy of meshes. In other words, all local refinement is done on one control mesh on a single hierarchical “level” and all control points have similar influence on the shape of the surface. This feature is critical for its adoption and usefulness as a design tool. Finally, we explore the behavior of T-splines in finite element analysis. It is demonstrated that T-splines possess similar convergence properties to NURBS with far fewer degrees of freedom. We develop an adaptive isogeometric analysis framework which couples analysis-suitable T-splines, local refinement, and Bézier extraction and apply it to the modeling of damage and fracture processes. These examples demonstrate the feasibility of applying T-spline element technology to… Advisors/Committee Members: Hughes, Thomas J. R. (advisor), Sederberg, Thomas W. (advisor), Taylor, Robert L. (committee member), Ghattas, Omar (committee member), Landis, Chad M. (committee member), Ying, Lexing (committee member).

Subjects/Keywords: Isogeometric analysis; T-splines; Design-through-analysis; Local refinement; Fracture; Extraordinary points; Bézier extraction

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APA (6^th Edition):

Scott, M. A. (2011). T-splines as a design-through-analysis technology. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/ETD-UT-2011-08-3795

Chicago Manual of Style (16^th Edition):

Scott, Michael Andrew. “T-splines as a design-through-analysis technology.” 2011. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://hdl.handle.net/2152/ETD-UT-2011-08-3795.

MLA Handbook (7^th Edition):

Scott, Michael Andrew. “T-splines as a design-through-analysis technology.” 2011. Web. 20 Apr 2021.

Vancouver:

Scott MA. T-splines as a design-through-analysis technology. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2011. [cited 2021 Apr 20]. Available from: http://hdl.handle.net/2152/ETD-UT-2011-08-3795.

Council of Science Editors:

Scott MA. T-splines as a design-through-analysis technology. [Doctoral Dissertation]. University of Texas – Austin; 2011. Available from: http://hdl.handle.net/2152/ETD-UT-2011-08-3795

30. Yu, Yalin. Theoretical and numerical study on fracture mechanics of hydrogels.

Degree: PhD, Engineering Mechanics, 2019, University of Texas – Austin

URL: http://dx.doi.org/10.26153/tsw/3013

► Hydrogels consist of cross-linked polymer chains and water molecules. Due to the coupling between deformation of the polymer network and diffusion of the solvent molecules,… (more)

▼ Hydrogels consist of cross-linked polymer chains and water molecules. Due to the coupling between deformation of the polymer network and diffusion of the solvent molecules, the fracture behavior of hydrogels is quite different from that of polymers and rubbers. This dissertation presents theoretical and numerical studies on fracture behavior of hydrogels with linear and nonlinear theories. For the study of stationary cracks, a centered crack model is used for hydrogel specimens under the plane strain condition. Asymptotic analysis of the crack tip fields is presented based on a linear poroelastic formulation for different chemical boundary conditions (immersed and not-immersed). For both cases, a finite element method is developed under different mechanical loading conditions (displacement-control and load-control). The evolution of the crack-tip energy release rate is calculated by a modified path-independent J-integral that takes the effect of energy dissipation due to solvent diffusion into account. Numerical results agree well with the asymptotic solutions of the crack-tip fields. Under load control, the crack-tip energy release rate increases over time, which suggests the onset of crack growth may be delayed until the crack-tip energy release rate reaches a critical value (fracture toughness). For steady-state crack growth of hydrogels, a semi-infinite crack in a long strip specimen subject to plane-strain loading is studied with both asymptotic and numerical analysis. The crack-tip energy release rate is found to be smaller than the applied energy release rate due to poroelastic shielding. The characteristic size of the poroelastic crack-tip field is inversely proportional to the crack speed. For relatively fast crack growth, the crack-tip energy release rate decreases with increasing crack speed. For relatively slow crack growth, the energy release rate increases with increasing crack speed. The present results are found to be qualitatively consistent with previous experiments on the effects of velocity toughening, solvent viscosity and crack-tip soaking. Moreover, the effect of plane stress is examined with a cohesive zone model. Finally, the nonlinear effect due to large deformation is studied numerically based on a nonlinear poroelastic model. Advisors/Committee Members: Huang, Rui, doctor of civil and environmental engineering (advisor), Landis, Chad M. (advisor), Ravi-Chandar , Krishnaswamy (committee member), Mear, Mark E (committee member), Foster, John (committee member).

Subjects/Keywords: Fracture mechanics; Hydrogels

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APA (6^th Edition):

Yu, Y. (2019). Theoretical and numerical study on fracture mechanics of hydrogels. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://dx.doi.org/10.26153/tsw/3013

Chicago Manual of Style (16^th Edition):

Yu, Yalin. “Theoretical and numerical study on fracture mechanics of hydrogels.” 2019. Doctoral Dissertation, University of Texas – Austin. Accessed April 20, 2021. http://dx.doi.org/10.26153/tsw/3013.

MLA Handbook (7^th Edition):

Yu, Yalin. “Theoretical and numerical study on fracture mechanics of hydrogels.” 2019. Web. 20 Apr 2021.

Vancouver:

Yu Y. Theoretical and numerical study on fracture mechanics of hydrogels. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2019. [cited 2021 Apr 20]. Available from: http://dx.doi.org/10.26153/tsw/3013.

Council of Science Editors:

Yu Y. Theoretical and numerical study on fracture mechanics of hydrogels. [Doctoral Dissertation]. University of Texas – Austin; 2019. Available from: http://dx.doi.org/10.26153/tsw/3013

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