+publisher:"University of Illinois – Urbana-Champaign" +contributor:("Masud, Arif")

University of Illinois – Urbana-Champaign

1. Tuttle, Ian Tyler. A framework for damage modeling in multi-constituent laminated materials.

Degree: MS, Civil Engineering, 2018, University of Illinois – Urbana-Champaign

► This work contains analysis of directionally oriented material with heterogeneity across the spacial domain, between materials, and over time. Composite material containing directionally oriented material… (more)

Subjects/Keywords: Composite; Damage; Laminar; Mixture Theory; Thermomechanical; Return Mapping; Discontinuous Galerkin

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APA (6^th Edition):

Tuttle, I. T. (2018). A framework for damage modeling in multi-constituent laminated materials. (Thesis). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/101085

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Tuttle, Ian Tyler. “A framework for damage modeling in multi-constituent laminated materials.” 2018. Thesis, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/101085.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Tuttle, Ian Tyler. “A framework for damage modeling in multi-constituent laminated materials.” 2018. Web. 16 Jan 2021.

Vancouver:

Tuttle IT. A framework for damage modeling in multi-constituent laminated materials. [Internet] [Thesis]. University of Illinois – Urbana-Champaign; 2018. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/101085.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Tuttle IT. A framework for damage modeling in multi-constituent laminated materials. [Thesis]. University of Illinois – Urbana-Champaign; 2018. Available from: http://hdl.handle.net/2142/101085

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

University of Illinois – Urbana-Champaign

2. Gajendran, Harishanker. A unified computational framework for process modeling and performance modeling of multi-constituent materials.

Degree: PhD, Civil Engineering, 2016, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/95274

► This thesis presents new theoretical and computational developments and an integrated approach for interface and interphase mechanics in the process and performance modeling of fibrous… (more)

▼ This thesis presents new theoretical and computational developments and an integrated approach for interface and interphase mechanics in the process and performance modeling of fibrous composite materials. A new class of stabilized finite element methods is developed for the coupled-field problems that arise due to curing and chemical reactions at the bi-material interfaces at the time of the manufacturing of the fiber-matrix systems. An accurate modeling of the degree of curing, because of its effects on the evolving properties of the interphase material, is critical to determining the coupled chemo-mechanical interphase stresses that influence the structural integrity of the composite and its fatigue life. A thermodynamically consistent theory of mixtures for multi-constituent materials is adopted to model curing and interphase evolution during the processing of the composites. The mixture theory model combines the composite constituent behaviors in an effective medium, thereby reducing the computational cost of modeling chemically reacting multi-constituent mixtures, while retaining information involving the kinematic and kinetic responses of the individual constituents. The effective medium and individual constituent behaviors are each constrained to mutually satisfy the balance principles of mechanics. Even though each constituent is governed by its own balance laws and constitutive equations, interactive forces between constituents that emanate from maximization of entropy production inequality provide the coupling between constituent specific balance laws and constitutive models. The mixture model is cast in a finite strain finite element framework that finds roots in the Variational Multiscale (VMS) method. The deformation of multi-constituent mixtures at the Neumann boundaries requires imposing constraint conditions such that the constituents deform in a self-consistent fashion. A set of boundary conditions is presented that accounts for the non-zero applied tractions, and a variationally consistent method is developed to enforce inter constituent constraints at Neumann boundaries in the finite deformation context. The new method finds roots in a local multiscale decomposition of the deformation map at the Neumann boundary. Locally satisfying the Lagrange multiplier field and subsequent modeling of the fine scales via edge bubble functions results in closed-form expressions for a generalized penalty tensor and a weighted numerical flux that are free from tunable parameters. The key novelty is that the consistently derived constituent coupling parameters evolve with material and geometric nonlinearity, thereby resulting in optimal enforcement of inter-constituent constraints. A class of coupled field problems for process modeling and for performance molding of fibrous composites is presented that provides insight into the theoretical models and multiscale stabilized formulations for computational modeling of multi-constituent materials. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (advisor), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20Armando%22%29&pagesize-30">Duarte, Armando (committee member), Champaign%22%20%2Bcontributor%3A%28%22Elbanna%2C%20Ahmed%22%29&pagesize-30">Elbanna, Ahmed (committee member), Champaign%22%20%2Bcontributor%3A%28%22Uddin%2C%20Rizwan%22%29&pagesize-30">Uddin, Rizwan (committee member).

Subjects/Keywords: Variational multiscale method; Mixture theory; Process modeling; Performance modeling; Composites

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

APA (6^th Edition):

Gajendran, H. (2016). A unified computational framework for process modeling and performance modeling of multi-constituent materials. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/95274

Chicago Manual of Style (16^th Edition):

Gajendran, Harishanker. “A unified computational framework for process modeling and performance modeling of multi-constituent materials.” 2016. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/95274.

MLA Handbook (7^th Edition):

Gajendran, Harishanker. “A unified computational framework for process modeling and performance modeling of multi-constituent materials.” 2016. Web. 16 Jan 2021.

Vancouver:

Gajendran H. A unified computational framework for process modeling and performance modeling of multi-constituent materials. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2016. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/95274.

Council of Science Editors:

Gajendran H. A unified computational framework for process modeling and performance modeling of multi-constituent materials. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2016. Available from: http://hdl.handle.net/2142/95274

University of Illinois – Urbana-Champaign

3. Plews, Julia A. Multiscale analysis of localized, nonlinear, three-dimensional thermo-structural effects.

Degree: PhD, Civil Engineering, 2015, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/88953

► There are a wide range of computational modeling challenges associated with structures subjected to sharp, local heating effects. Problems of this nature are prevalent in… (more)

▼ There are a wide range of computational modeling challenges associated with structures subjected to sharp, local heating effects. Problems of this nature are prevalent in diverse engineering applications such as structural analysis of hypersonic flight vehicles in extreme environments, computational modeling of weld processes, and development of semiconductor processing technology. Complex temperature gradients in the materials cause three-dimensional, localized, intense thermomechanical stress/strain variation and residual deformations, making multiphysics analysis necessary to accurately predict structural response. Localized damage or deformation may impact global structural behavior, yet bridging spatial scales between local- and structural-scale response is a nontrivial task. Because of these issues, standard finite element analysis techniques lead to cumbersome and prohibitively expensive numerical simulations for this class of problems. This study proposes a Generalized or eXtended Finite Element Method (G/XFEM) for analyzing three-dimensional solid, coupled physics problems exhibiting localized heating and thermomechanical effects. The method is based on the GFEM with global–local enrichment functions (GFEMgl), which involves the solution of interdependent coarse- (global) and fine-scale (local) problems. The global problem captures coarse-scale behavior, while local problems resolve sharp solution features in regions where fine-scale phenomena may govern the overall structural response. To address the intrinsic coupling of scales, local solution information is embedded in the global solution space via a partition of unity approach. This method extends the capabilities of traditional hp-adaptive FEM or GFEM—consisting of heavy mesh refinement (h) and local high-order polynomial approximations (p)—to one-way coupled thermo-structural problems, providing meshing flexibility while remaining accurate and efficient. Linear thermoelasticity and nonlinear thermoplasticity problems are considered, involving both steady-state and transient heating effects. The GFEMgl is further extended to capture multiscale thermal and thermomechanical effects induced by material-scale heterogeneity, which may also impact structural behavior at the coarse scale. Due to the extraordinary level of fidelity required to resolve fine-scale effects at the global scale, strategies for distributing large workloads on a parallel computer and improving the computational efficiency of the proposed method are needed. Studies have shown that the GFEMgl benefits from straightforward parallelism. However, inexact, coarse-scale boundary conditions on fine-scale may lead to large errors in global solutions. Traditional strategies aimed at improving or otherwise lessening the effect of poor local boundary conditions in the GFEMgl may be impractically expensive in the problems of interest, such as transient or nonlinear simulations involving many time or load steps. Thus, inexpensive and optimized approaches for improving boundary conditions on… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (advisor), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Olson%2C%20Luke%22%29&pagesize-30">Olson, Luke (committee member), Champaign%22%20%2Bcontributor%3A%28%22Eason%2C%20Thomas%20G.%2C%20III%22%29&pagesize-30">Eason, Thomas G., III (committee member).

Subjects/Keywords: Generalized Finite Element Method (GFEM); extended finite element method; multiphysics; multiscale; parallel; thermomechanical; thermoelasticity; thermoplasticity; plasticity; heterogeneous materials

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

APA (6^th Edition):

Plews, J. A. (2015). Multiscale analysis of localized, nonlinear, three-dimensional thermo-structural effects. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/88953

Chicago Manual of Style (16^th Edition):

Plews, Julia A. “Multiscale analysis of localized, nonlinear, three-dimensional thermo-structural effects.” 2015. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/88953.

MLA Handbook (7^th Edition):

Plews, Julia A. “Multiscale analysis of localized, nonlinear, three-dimensional thermo-structural effects.” 2015. Web. 16 Jan 2021.

Vancouver:

Plews JA. Multiscale analysis of localized, nonlinear, three-dimensional thermo-structural effects. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2015. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/88953.

Council of Science Editors:

Plews JA. Multiscale analysis of localized, nonlinear, three-dimensional thermo-structural effects. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2015. Available from: http://hdl.handle.net/2142/88953

University of Illinois – Urbana-Champaign

4. Chowdhury, Piyas Bal. Modeling mechanical properties – linking atomistics to continuum.

Degree: PhD, Mechanical Engineering, 2016, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/90474

► A combination of atomistic simulations and experiments is used to study the microscopic deformation mechanisms of materials. Atomic scale simulation tools include molecular dynamics and… (more)

▼ A combination of atomistic simulations and experiments is used to study the microscopic deformation mechanisms of materials. Atomic scale simulation tools include molecular dynamics and density functional theory. The experiments involve uniaxial tension and compression tests on: (a) single crystals of low stacking fault energy Co-33%Ni alloys, (b) polycrystalline nano-twinned Ni-x%Co alloys (x = 1, 1.62, 2.9 and 5.6), and (c) equiatomic NiTi shape memory alloys. The reason these materials are chosen as candidates for study is that these materials have very distinct microstructure and mechanical properties. The single crystals of Co-33%Ni alloys demonstrated a competition between slip and twinning based deformations. Depending on the single crystal orientation and loading direction (tension/compression), either mode is activated. A Schmid factor analysis demonstrated that slip or twinning is triggered when the resolved shear stress on the respective systems is the maximum. In other words, the critical resolved shear stress (CRSS) for slip and twinning are found to be around 15 MPa and 38 MPa respectively. To rationalize the experimental observations, the fault energy surfaces (generalized stacking/planar fault energies) are computed. Using a Peierls-Nabarro based modeling framework, the CRSS levels for slip and twinning are predicted on a physical ground. On the whole, the results indicate the inherent material propensity to select either mode of plasticity originates from the underlying fault energetics. Using the fault energy considerations, the anomalous composition dependence of Ni-x%Co alloys (x = 1, 1.62, 2.9 and 5.6) is clarified. The experimental stress-strain curves demonstrated a non-uniform strengthening attributes with respect to the composition. This effect is traced back to the atomic level fault energy surface as a direct consequence of alloying. The existence of competing mechanisms (solid solution hardening versus Suzuki segregation) was discovered. The presence of nano-sized twins in the microstructure (as unveiled by electron backscatter diffraction and transmission electron microcopy) serve to enhance the atomic scale energetics in the form of slip characteristics. Using molecular dynamics simulations, various slip transfer mechanisms at the coherent twin boundary is categorized. The extrinsic levels of the energy barriers to the dislocation slip for individual mechanisms are computed. The corresponding frictional stresses are extracted to eventually arrive at CRSS values. These CRSS values for each alloys represents those for the nano-twinned microstructure. A reasonably good agreement between the experiments and theory lends credence to the modeling approach. Using similar atomistic simulations, we resolve the mechanistic origin of the NiTi superelasticity. Using a newly developed pair potential, the compressive load/unload behavior of austenitic NiTi (consisting of B2 lattice) is examined. The material is demonstrated to undergo full strain recover upon 5% of straining. The origin of such… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Sehitoglu%2C%20Huseyin%22%29&pagesize-30">Sehitoglu, Huseyin (advisor), Champaign%22%20%2Bcontributor%3A%28%22Sehitoglu%2C%20Huseyin%22%29&pagesize-30">Sehitoglu, Huseyin (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Saif%2C%20Taher%22%29&pagesize-30">Saif, Taher (committee member), Champaign%22%20%2Bcontributor%3A%28%22Ertekin%2C%20Elif%22%29&pagesize-30">Ertekin, Elif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member).

Subjects/Keywords: Atomistic modeling; mechanical properties

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

APA (6^th Edition):

Chowdhury, P. B. (2016). Modeling mechanical properties – linking atomistics to continuum. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/90474

Chicago Manual of Style (16^th Edition):

Chowdhury, Piyas Bal. “Modeling mechanical properties – linking atomistics to continuum.” 2016. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/90474.

MLA Handbook (7^th Edition):

Chowdhury, Piyas Bal. “Modeling mechanical properties – linking atomistics to continuum.” 2016. Web. 16 Jan 2021.

Vancouver:

Chowdhury PB. Modeling mechanical properties – linking atomistics to continuum. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2016. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/90474.

Council of Science Editors:

Chowdhury PB. Modeling mechanical properties – linking atomistics to continuum. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2016. Available from: http://hdl.handle.net/2142/90474

University of Illinois – Urbana-Champaign

5. Salazar De Troya, Miguel Angel A. Adaptive mesh refinement in topology optimization.

Degree: PhD, Mechanical Engineering, 2019, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/104776

► This dissertation presents developments in stress constrained topology optimization with Adaptive Mesh Refinement (AMR). Regions with stress concentrations dominate the optimized design. As such, we… (more)

▼ This dissertation presents developments in stress constrained topology optimization with Adaptive Mesh Refinement (AMR). Regions with stress concentrations dominate the optimized design. As such, we first present an approach to obtain designs with accurately computed stress fields within the context of topology optimization. To achieve this goal, we invoke threshold and AMR operations during the optimization. We do so in an optimal fashion, by applying AMR techniques that use error indicators to refine and coarsen the mesh as needed. In this way, we obtain accurate simulations and greater resolution of the design domain in a computationally efficient manner. We present results in two dimensions to demonstrate the efficacy of our method. The topology optimization community has regularly employed optimization algorithms from the operations research community. However, these algorithms are implemented in the Euclidean space instead of the proper function space where the design, i.e. volume fraction, field resides. In this thesis, we show that, when discretizing the volume fraction field over a non-uniform mesh, algorithms in Euclidean space are mesh dependent. We do so by first explaining the functional analysis tools necessary to understand why convergence is affected by the mesh. Namely, the distinction between derivative and gradient definitions and the role of the mesh dependent inner product. These tools are subsequently used to make the Globally Convergent Method of Moving Asymptotes (GCMMA), a popular optimization algorithm in the topology optimization community, mesh independent. We then benchmark our algorithm with three common problems in topology optimization. High resolution three-dimensional design models optimized for arbitrary cost and constraint functions are absolutely necessary ingredients for the solution of real{world engineering design problems. However, such requirements are non trivial to implement. In this thesis, we address this dilemma by developing a large scale topology optimization framework with AMR. We discuss the need for efficient parallelizable regularization methods that work across different mesh resolutions, iterative solvers and data structures. Furthermore, the optimization algorithm needs to be implemented with the same data structure that is used for the design field. To demonstrate the versatility of our framework, we optimize the designs of a three dimensional stress constrained benchmark L-bracket and a stress-constrained compliant mechanism. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Tortorelli%2C%20Daniel%20A.%22%29&pagesize-30">Tortorelli, Daniel A. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Tortorelli%2C%20Daniel%20A.%22%29&pagesize-30">Tortorelli, Daniel A. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Phillipe%22%29&pagesize-30">Geubelle, Phillipe (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22James%2C%20Kai%22%29&pagesize-30">James, Kai (committee member).

Subjects/Keywords: topology; optimization; adaptive; mesh; refinement; stress; constrained

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

APA (6^th Edition):

Salazar De Troya, M. A. A. (2019). Adaptive mesh refinement in topology optimization. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/104776

Chicago Manual of Style (16^th Edition):

Salazar De Troya, Miguel Angel A. “Adaptive mesh refinement in topology optimization.” 2019. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/104776.

MLA Handbook (7^th Edition):

Salazar De Troya, Miguel Angel A. “Adaptive mesh refinement in topology optimization.” 2019. Web. 16 Jan 2021.

Vancouver:

Salazar De Troya MAA. Adaptive mesh refinement in topology optimization. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2019. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/104776.

Council of Science Editors:

Salazar De Troya MAA. Adaptive mesh refinement in topology optimization. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2019. Available from: http://hdl.handle.net/2142/104776

University of Illinois – Urbana-Champaign

6. Tumkur Revannasiddaiah, Ravi Kumar. Modal interactions and targeted energy transfers in laminar vortex-induced vibrations of a rigid cylinder with strongly nonlinear internal attachments.

Degree: PhD, 4048, 2014, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/46870

► We study the effect of coupling an essentially nonlinear element to a sprung rigid circular cylinder undergoing ``vortex-induced vibration'' (VIV) in an incompressible flow. The… (more)

▼ We study the effect of coupling an essentially nonlinear element to a sprung rigid circular cylinder undergoing ``vortex-induced vibration'' (VIV) in an incompressible flow. The essentially nonlinear device is termed a ``nonlinear energy sink'' (NES); in this work we use two configurations of NES: translational NES and rotational NES. For the translational NES, consisting of a mass, a linear damper, and an essentially nonlinear spring, the NES mass is constrained to move perpendicular to the mean flow. For the rotational case, the NES mass is constrained to rotate at a fixed radius about the oscillating center of the cylinder. Using a variational multiscale residual-based stabilized finite-element method, we consider the intermediate Reynolds number (Re) regime 20 ≤ Re≤ 120, with the cylinder motion constrained to be perpendicular to the mean flow. The nonlinear interaction of the NES and flow via the rigid body motion of the cylinder leads to several new response regimes of the coupled system of flow-cylinder-NES. The translational NES promotes nearly one-way transfer of energy to itself from the primary structure (the cylinder) and the flow, resulting in reduction of the amplitude of the limit-cycle oscillation (LCO) by as much as 75%, depending on the parameters characterizing the NES. Various mechanisms of VIV suppression by the NES are discussed. A reduced-order model (ROM) based on a single-degree-of-freedom (DOF) self-excited oscillator is developed to approximate the limit-cycle oscillation of the cylinder undergoing VIV. This self-excited oscillator models the interaction of the flow and the cylinder and, in principle, is similar to other phenomenological ROMs considered in the literature. Then, a coupled two-DOF reduced-order model for the system with the internal NES is constructed by coupling the single-DOF NES to the single-DOF self-excited oscillator. Hence, the infinite-dimensional system of flow-cylinder-NES is reduced to a two-DOF model. We examine carefully the range of system parameters where the coupled ROM is valid. The two targeted energy transfer mechanisms responsible for passive VIV suppression that are observed in the finite-element computations are fully reproduced using the two-DOF reduced-order model within the range of validity of the ROM. This reduction of the dynamics to a tractable low-dimensional reduced-order model facilitates the approximate analysis of the underlying dynamics and provides the basis for predictive design of the NES for VIV suppression. Two other approaches of model reduction to obtain a more advanced ROM that can be predictive were also considered, the first based on ``proper orthogonal decomposition'' (POD), and the second based on dynamics of the pressure around the cylinder. We show that, besides passive VIV suppression, the rotational NES can also lead to a flow state that is qualitatively different from the usual K´arm´an vortex street, with the length and width of the attached vortices significantly altered, and the amplitude and frequency of the… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Bergman%2C%20Lawrence%20A.%22%29&pagesize-30">Bergman, Lawrence A. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Vakakis%2C%20Alexander%20F.%22%29&pagesize-30">Vakakis, Alexander F. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Bergman%2C%20Lawrence%20A.%22%29&pagesize-30">Bergman, Lawrence A. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Vakakis%2C%20Alexander%20F.%22%29&pagesize-30">Vakakis, Alexander F. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Pearlstein%2C%20Arne%20J.%22%29&pagesize-30">Pearlstein, Arne J. (committee member).

Subjects/Keywords: vortex-induced vibration (VIV); nonlinear energy sink; targeted energy transfer; passive VIV suppression; passive wake modification; bifurcations in laminar VIV; sub-critical Re VIV

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

APA (6^th Edition):

Tumkur Revannasiddaiah, R. K. (2014). Modal interactions and targeted energy transfers in laminar vortex-induced vibrations of a rigid cylinder with strongly nonlinear internal attachments. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/46870

Chicago Manual of Style (16^th Edition):

Tumkur Revannasiddaiah, Ravi Kumar. “Modal interactions and targeted energy transfers in laminar vortex-induced vibrations of a rigid cylinder with strongly nonlinear internal attachments.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/46870.

MLA Handbook (7^th Edition):

Tumkur Revannasiddaiah, Ravi Kumar. “Modal interactions and targeted energy transfers in laminar vortex-induced vibrations of a rigid cylinder with strongly nonlinear internal attachments.” 2014. Web. 16 Jan 2021.

Vancouver:

Tumkur Revannasiddaiah RK. Modal interactions and targeted energy transfers in laminar vortex-induced vibrations of a rigid cylinder with strongly nonlinear internal attachments. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/46870.

Council of Science Editors:

Tumkur Revannasiddaiah RK. Modal interactions and targeted energy transfers in laminar vortex-induced vibrations of a rigid cylinder with strongly nonlinear internal attachments. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/46870

University of Illinois – Urbana-Champaign

7. Goudarzi, Taha. Iterative and variational homogenization methods for filled elastomers.

Degree: PhD, 0106, 2014, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/50629

► Elastomeric composites have increasingly proved invaluable in commercial technological applications due to their unique mechanical properties, especially their ability to undergo large reversible deformation in… (more)

▼ Elastomeric composites have increasingly proved invaluable in commercial technological applications due to their unique mechanical properties, especially their ability to undergo large reversible deformation in response to a variety of stimuli (e.g., mechanical forces, electric and magnetic fields, changes in temperature). Modern advances in organic materials science have revealed that elastomeric composites hold also tremendous potential to enable new high-end technologies, especially as the next generation of sensors and actuators featured by their low cost together with their biocompatibility, and processability into arbitrary shapes. This potential calls for an in-depth investigation of the macroscopic mechanical/physical behavior of elastomeric composites directly in terms of their microscopic behavior with the objective of creating the knowledge base needed to guide their bottom-up design. The purpose of this thesis is to generate a mathematical framework to describe, explain, and predict the macroscopic nonlinear elastic behavior of filled elastomers, arguably the most prominent class of elastomeric composites, directly in terms of the behavior of their constituents — i.e., the elastomeric matrix and the filler particles — and their microstructure — i.e., the content, size, shape, and spatial distribution of the filler particles. This will be accomplished via a combination of novel iterative and variational homogenization techniques capable of accounting for interphasial phenomena and finite deformations. Exact and approximate analytical solutions for the fundamental nonlinear elastic response of dilute suspensions of rigid spherical particles (either firmly bonded or bonded through finite size interphases) in Gaussian rubber are first generated. These results are in turn utilized to construct approximate solutions for the nonlinear elastic response of non-Gaussian elastomers filled with a random distribution of rigid particles (again, either firmly bonded or bonded through finite size interphases) at finite concentrations. Three-dimensional finite element simulations are also carried out to gain further insight into the proposed theoretical solutions. Inter alia, we make use of these solutions to examine the effects of particle concentration, mono- and poly-dispersity of the filler particle size, and the presence of finite size interphases on the macroscopic response of filled elastomers. The solutions are found able to explain and describe experimental results that to date have been understood only in part. More generally, the solutions provide a robust tool to efficiently guide the design of filled elastomers with desired macroscopic properties. The homogenization techniques developed in this work are not limited to nonlinear elasticity, but can be readily utilized to study multi-functional properties as well. For demonstration purposes, we work out a novel exact solution for the macroscopic dielectric response of filled elastomers with interphasial space charges. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Lopez-Pamies%2C%20Oscar%22%29&pagesize-30">Lopez-Pamies, Oscar (advisor), Champaign%22%20%2Bcontributor%3A%28%22Lopez-Pamies%2C%20Oscar%22%29&pagesize-30">Lopez-Pamies, Oscar (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Paulino%2C%20Glaucio%20H.%22%29&pagesize-30">Paulino, Glaucio H. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Chasiotis%2C%20Ioannis%22%29&pagesize-30">Chasiotis, Ioannis (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Johnson%2C%20Harley%20T.%22%29&pagesize-30">Johnson, Harley T. (committee member).

Subjects/Keywords: Iterative Homogenization methods; comparison medium methods; finite deformation; filled elastomers; hydrodynamic effect; interphasial effects; homogenization with body charges

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

APA (6^th Edition):

Goudarzi, T. (2014). Iterative and variational homogenization methods for filled elastomers. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/50629

Chicago Manual of Style (16^th Edition):

Goudarzi, Taha. “Iterative and variational homogenization methods for filled elastomers.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/50629.

MLA Handbook (7^th Edition):

Goudarzi, Taha. “Iterative and variational homogenization methods for filled elastomers.” 2014. Web. 16 Jan 2021.

Vancouver:

Goudarzi T. Iterative and variational homogenization methods for filled elastomers. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/50629.

Council of Science Editors:

Goudarzi T. Iterative and variational homogenization methods for filled elastomers. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/50629

University of Illinois – Urbana-Champaign

8. Gupta, Varun. Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics.

Degree: PhD, 0106, 2014, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/49724

► Many problems of engineering relevance in computational mechanics involve analysis of structural behavior spanning different spatial scales. Examples of such industrial problems include fracture in… (more)

▼ Many problems of engineering relevance in computational mechanics involve analysis of structural behavior spanning different spatial scales. Examples of such industrial problems include fracture in engine components, structural members of aircrafts, and pipeline joints. The presence of small cracks can lead to failure of these structures, due to intense thermal and mechanical loadings. Therefore, engineering decisions regarding such structures require accurate response prediction methodologies. The efficacy of the Generalized/eXtended Finite Element Method (GFEM or XFEM) in solving problems involving cracks, material interfaces or localized stress concentrations in large, complex, three-dimensional domains has been well established in the recent past. The superior properties of the GFEM/XFEM rely on the use of preselected enrichment functions that are known to ap- proximate the solution of a problem well. However, closed-form analytical enrichment functions are not always available. This research work focuses on advances of a two-scale GFEM for the accurate and efficient computation of the numerical solution for problems where only limited a priori knowledge about the solution is available. This method, termed as the Generalized FEM with global-local enrichments (GFEM gl ) is based on the solution of interdependent global and local scale problems, and can be applied to a broad class of multiscale problems of relevance to the industry. In this approach, the enrichment functions are obtained from the numerical solution of a fine-scale boundary value problem defined around a localized region of interest. The local problems focus on the resolution of fine-scale features of the solution, while the global problem addresses the macro-scale structural behavior. The local solutions are embedded into the global solution space using the Partition of Unity Method. A rigorous a priori error estimate for the method is presented along with numerical verification of convergence properties predicted by the estimate. The analysis shows optimal convergence of the method on problems with strong singularities and the method can deliver the same accuracy as direct numerical simulations (DNS) while using much fewer degrees of freedom as compared to the DNS. This document further reports on extensions of the method to two-scale fracture problems exhibiting nonlinear material behavior. The nonlinear model problem focuses on structures with plastic deformations at regions that are orders of magnitude smaller than the dimensions of the structural component. It is shown that the GFEMgl can produce accurate nonlinear solutions at a computational cost much lower than available FEMs. The issue of ill-conditioning of the system of equations obtained with the GFEM/XFEM has been well known since the inception of these methods more than a decade ago. The Stable GFEM (SGFEM) provides a robust, yet simple solution to this ill-conditioning. The SGFEM involves a simple local modification of the enrichments employed in… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (advisor), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Eason%2C%20Thomas%20G.%2C%20III%22%29&pagesize-30">Eason, Thomas G., III (committee member), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member).

Subjects/Keywords: Generalized Finite Element Method (GFEM); Extended finite element method (XFEM); Buffer Zone; Global-Local Analysis; Fracture Mechanics; Cracks; Singularity; Nonlinear Fracture; Plasticity; Blending elements; Condition number; Optimal convergence; Enrichment; Stress Intensity factors; Extraction domain

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

APA (6^th Edition):

Gupta, V. (2014). Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/49724

Chicago Manual of Style (16^th Edition):

Gupta, Varun. “Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/49724.

MLA Handbook (7^th Edition):

Gupta, Varun. “Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics.” 2014. Web. 16 Jan 2021.

Vancouver:

Gupta V. Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/49724.

Council of Science Editors:

Gupta V. Improved conditioning and accuracy of a two-scale generalized finite element method for fracture mechanics. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/49724

University of Illinois – Urbana-Champaign

9. Hernandez, Jaime Alberto. Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions.

Degree: PhD, Civil Engineering, 2015, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/89127

► Even though continuous improvements have been seen in the analysis of flexible pavements, one of the most important factors is still oversimplified: the tire. This… (more)

▼ Even though continuous improvements have been seen in the analysis of flexible pavements, one of the most important factors is still oversimplified: the tire. This can result in costly decisions, such as poor structural road design, incorrect damage prediction, and inappropriate adoption of maintenance/rehabilitation techniques. Moreover, accurate analysis of the tire-pavement system improves predictions of rolling resistance, fuel consumption, and greenhouse gas emissions. The main contribution of this research lies in the evaluation of tire and pavement as a semi-coupled system, assuming both are deformable bodies, while focusing on contact stresses, rolling resistance, and pavement responses. In addition to load and tire inflation pressure, temperature, speed, and rolling conditions were considered. A series of necessary advancements in the tire model, such as appropriate material characterization (hyperelastic and visco-hyperelastic), accurate geometry, and model validation using experimental measurements, were implemented. The experimental program provided information for validation (contact area, tire deflection, and contact stresses/loads). In addition, based on the experimental measurements, a procedure including analytical expression was proposed to predict the variation of the vertical and transverse contact loads along the contact length. Four tire finite element (FE) models having accurate geometry and material characterization were developed to predict contact stresses and rolling resistance force. First, a hyperelastic tire was used on a rigid surface to predict contact stresses under various rolling and loading conditions. Second, the influence of tire speed and temperature was investigated using a visco-hyperelastic tire rolling on rigid surface. Third, hyperelastic tire on deformable elastic body was used to assess the sensitivity of the contact stresses to the body's stiffness. Fourth, the relevance of surface temperature and tire speed was determined using a hyperelastic tire on a deformable viscoelastic body. Finally, the deformable tire and pavement model were integrated to evaluate critical pavement responses, rolling resistance force, and structure-induced rolling resistance. Vertical and transverse contact loads for all conditions and longitudinal contact stresses at full braking were successfully fitted to analytical expressions, thus easing their potential application in pavement analysis. Based on the hyperelastic tire FE results, the vertical contact stresses were unaffected by traveling speed and rolling condition, and the rolling condition mainly modified the longitudinal contact stresses. After altering the rubber component’s material model to visco-hyperelastic, the contact area increased 6.8% due to temperature and decreased 3.8% due to speed. In addition, longitudinal contact stresses were the most affected by temperature and speed: increments in peak value caused by speed were as high as 17%, and the reduction caused by temperature reached 33.1%. On the other hand,… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Al-Qadi%2C%20Imad%20L%22%29&pagesize-30">Al-Qadi, Imad L (advisor), Champaign%22%20%2Bcontributor%3A%28%22Al-Qadi%2C%20Imad%20L%22%29&pagesize-30">Al-Qadi, Imad L (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Little%2C%20Dallas%22%29&pagesize-30">Little, Dallas (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Ozer%2C%20Hasan%22%29&pagesize-30">Ozer, Hasan (committee member), Champaign%22%20%2Bcontributor%3A%28%22Radulescu%2C%20Robert%22%29&pagesize-30">Radulescu, Robert (committee member), Champaign%22%20%2Bcontributor%3A%28%22Thompson%2C%20Marshall%22%29&pagesize-30">Thompson, Marshall (committee member).

Subjects/Keywords: Tire-pavement interaction; pavement responses; rolling resistance; contact stresses; finite element modeling

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

APA (6^th Edition):

Hernandez, J. A. (2015). Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/89127

Chicago Manual of Style (16^th Edition):

Hernandez, Jaime Alberto. “Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions.” 2015. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/89127.

MLA Handbook (7^th Edition):

Hernandez, Jaime Alberto. “Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions.” 2015. Web. 16 Jan 2021.

Vancouver:

Hernandez JA. Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2015. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/89127.

Council of Science Editors:

Hernandez JA. Development of deformable tire-pavement interaction: contact stresses and rolling resistance prediction under various driving conditions. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2015. Available from: http://hdl.handle.net/2142/89127

University of Illinois – Urbana-Champaign

10. Gupta, Piyush. A generalized finite element method for the simulation of non-planar three-dimensional hydraulic fracture propagation.

Degree: PhD, Civil Engineering, 2016, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/90534

► Hydraulic fractures are a class of tensile fractures that occur in brittle and quasi-brittle materials due to the injection of a viscous fluid. Hydraulic fractures… (more)

▼ Hydraulic fractures are a class of tensile fractures that occur in brittle and quasi-brittle materials due to the injection of a viscous fluid. Hydraulic fractures occur both naturally and created deliberately for engineering applications. In the oil and gas industry, it is a preferred method to enhance the recovery of hydrocarbons by creation of permeable pathways. A successful hydraulic fracturing treatment may increase the production tens of times, making the technique economically attractive. Yet, there are concerns about the environmental impact of the toxic fluids used in reservoir treatment. The potential of groundwater contamination from the hydraulic fracturing treatments has been one of the major roadblocks for its rapid development. One of the main reasons for this concern is the lack of a thorough understanding of induced hydraulic fracture propagation. With the advent of real-time monitoring techniques fully three-dimensional models that can be used to update treatment designs in real time as information is fed back into the models. Typically, hydraulic fracturing of low-permeability shale reservoirs involves modeling of three coupled processes: (i) the mechanical deformation of the rock induced by the applied fluid pressure on fracture faces; (ii) the flow of viscous fracturing fluid in the fracture; and (iii) the fracture propagation in the rock from the induced hydraulic loading. Additional difficulties in modeling of this already challenging problem are, for example, change in magnitude and/or orientation of the in-situ confining stresses, presence of a nearby natural fracture/fault, transport of suspended proppant particles within the fracture etc. In this work, we develop a fully-coupled system of equations for modeling non-planar three-dimensional hydraulic fracture propagation with a Generalized/Extended Finite Element Method (G/XFEM). This method greatly facilitates the discretization of complex 3-D fractures since the finite element mesh is not required to fit the crack surface(s). Adaptive surface triangulations are used to represent complex 3-D fracture surfaces. Such explicit surface representation retains the finer and complex details of the fracture, thus providing a high fidelity numerical simulation. The proposed coupled formulation does not make any assumptions about the geometry of the solid domain or the fracture surface except that the fracture geometry is such that the fluid flow in the fracture can be modeled using the Reynolds lubrication equation. A modified Newton – Raphson algorithm to solve the nonlinear system of coupled equations is also developed. The stress and pressure singularities of the solution of hydraulic fracturing problems require adaptive mesh refinement for efficient discretization error control. Dealing with adaptive mesh refinement in time-dependent problems is challenging for any method. This is typically handled through mappings of solutions at every time step. In this work, we avoid volume mappings by taking advantage of the explicit… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20Carlos%20Armando%22%29&pagesize-30">Duarte, Carlos Armando (advisor), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20Carlos%20Armando%22%29&pagesize-30">Duarte, Carlos Armando (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Valocchi%2C%20Albert%20J%22%29&pagesize-30">Valocchi, Albert J (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Elbanna%2C%20Ahmed%20E%22%29&pagesize-30">Elbanna, Ahmed E (committee member), Champaign%22%20%2Bcontributor%3A%28%22Gordon%2C%20Peter%22%29&pagesize-30">Gordon, Peter (committee member).

Subjects/Keywords: Hydraulic fracturing; Generalized Finite Element Method (GFEM); Extended Finite Element Method (XFEM); Multi-physics; Coupled formulation; Hydro-mechanical coupling; Non-planar fracture propagation; Injection fracturing; Reynold’s lubrication theory; Fluid flow; Fluid-Driven fracturing; Geomechanics

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

APA (6^th Edition):

Gupta, P. (2016). A generalized finite element method for the simulation of non-planar three-dimensional hydraulic fracture propagation. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/90534

Chicago Manual of Style (16^th Edition):

Gupta, Piyush. “A generalized finite element method for the simulation of non-planar three-dimensional hydraulic fracture propagation.” 2016. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/90534.

MLA Handbook (7^th Edition):

Gupta, Piyush. “A generalized finite element method for the simulation of non-planar three-dimensional hydraulic fracture propagation.” 2016. Web. 16 Jan 2021.

Vancouver:

Gupta P. A generalized finite element method for the simulation of non-planar three-dimensional hydraulic fracture propagation. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2016. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/90534.

Council of Science Editors:

Gupta P. A generalized finite element method for the simulation of non-planar three-dimensional hydraulic fracture propagation. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2016. Available from: http://hdl.handle.net/2142/90534

University of Illinois – Urbana-Champaign

11. Filipov, Evgueni T. Tailoring stiffness of deployable origami structures.

Degree: PhD, Civil Engineering, 2016, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/95597

► Origami has gained popularity in science and engineering because a compactly stowed system can be folded into a transformable 3D structure with increased functionality. Origami… (more)

▼ Origami has gained popularity in science and engineering because a compactly stowed system can be folded into a transformable 3D structure with increased functionality. Origami can also be reconfigured and programmed to change shape, function, and mechanical properties. In this thesis, we explore origami from structural and stiffness perspectives, and in particular we study how geometry affects origami behavior and characteristics. Understanding origami from a structural standpoint can allow for conceptualizing and designing feasible applications in all scales and disciplines of engineering. We improve, verify, and test a bar and hinge model that can analyze the elastic stiffness, and estimate deformed shapes of origami. The model simulates three distinct behaviors: stretching and shearing of thin sheet panels; bending of the flat panels; and bending along prescribed fold lines. We explore the influence of panel geometry on origami stiffness, and provide a study on fold line stiffness characteristics. The model formulation incorporates material characteristics and provides scalable, and isotopic behavior. It is useful for practical problems such as optimization and parametrization of geometric origami variations. We explore the stiffness of tubular origami structures based on the Miura-ori folding pattern. A unique orientation for zipper coupling of rigidly foldable origami tubes substantially increases stiffness in higher order modes and permits only one flexible motion through which the structure can deploy. Deployment is permitted by localized bending along folds lines, however other deformations are over-constrained and engage the origami sheets in tension and compression. Furthermore, we couple compatible origami tubes into a variety of cellular assemblages that can enhance mechanical characteristics and geometric versatility. Practical applications such as deployable slabs, roofs, and arches are also explored. Finally, we introduce origami tubes with polygonal cross-sections that can reconfigure into numerous geometries. The tubular structures satisfy the mathematical definitions for flat and rigid foldability, meaning that they can fully unfold from a flattened state with deformations occurring only at the fold lines. From a global viewpoint, the tubes do not need to be straight, and can be constructed to follow a non-linear curved line when deployed. From a local viewpoint, their cross-sections and kinematics can be reprogrammed by changing the direction of folding at some folds. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Paulino%2C%20Glaucio%20H%22%29&pagesize-30">Paulino, Glaucio H (advisor), Champaign%22%20%2Bcontributor%3A%28%22Paulino%2C%20Glaucio%20H%22%29&pagesize-30">Paulino, Glaucio H (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Schenk%2C%20Mark%22%29&pagesize-30">Schenk, Mark (committee member), Champaign%22%20%2Bcontributor%3A%28%22Tachi%2C%20Tomohiro%22%29&pagesize-30">Tachi, Tomohiro (committee member), Champaign%22%20%2Bcontributor%3A%28%22Gardoni%2C%20Paolo%22%29&pagesize-30">Gardoni, Paolo (committee member).

Subjects/Keywords: deployable structures; mechanics of origami; scalable properties of origami; structural analysis of origami; bar and hinge model; origami tubes; zipper coupled tubes; thin sheet assemblages; cellular assemblages; reconfigurable systems; deployable arches and roofs; tunable metamaterials; polygonal tubes; curved origami tubes; variable cross-section tubes; programmable structures and materials

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

APA (6^th Edition):

Filipov, E. T. (2016). Tailoring stiffness of deployable origami structures. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/95597

Chicago Manual of Style (16^th Edition):

Filipov, Evgueni T. “Tailoring stiffness of deployable origami structures.” 2016. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/95597.

MLA Handbook (7^th Edition):

Filipov, Evgueni T. “Tailoring stiffness of deployable origami structures.” 2016. Web. 16 Jan 2021.

Vancouver:

Filipov ET. Tailoring stiffness of deployable origami structures. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2016. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/95597.

Council of Science Editors:

Filipov ET. Tailoring stiffness of deployable origami structures. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2016. Available from: http://hdl.handle.net/2142/95597

12. Chen, Pinlei. A variational framework for mathematically nonsmooth problems in solid and structure mechanics.

Degree: PhD, Civil Engineering, 2018, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/101813

► This dissertation presents a new paradigm for addressing multi-physics problems with interfaces in the field of Additive Manufacturing and the modeling of fibrous composite materials.… (more)

▼ This dissertation presents a new paradigm for addressing multi-physics problems with interfaces in the field of Additive Manufacturing and the modeling of fibrous composite materials. The unique process of adding the material layer by layer in the AM techniques raises the issue about the stability of the interfaces between the layers and along the boundaries of multi-constituent materials. A stabilized interface formulation is developed to model debonding in monotonic loading, fatigue effects in cyclic loading, and thermal effects at interfaces which severely impact the functional life of those materials and structures. The formulation is based on embedding Discontinuous Galkerin (DG) ideas in a Continuous Galerkin (CG) framework. Starting from a mixed method incorporating the Lagrange multiplier along the interface, a pure displacement formulation is derived using the Variational Multiscale Method (VMS). From a mathematical and computational perspective, the key factor influencing the accuracy and robustness of the interface formulation is the design of the numerical flux and the penalty or stability terms. Analytical expressions that are free from user-defined parameters are naturally derived for the numerical flux and stability tensor which are functions of the evolving geometric and material nonlinearity. The proposed framework is extended for debonding at finite strains across general bimaterial interfaces. An interfacial gap function is introduced that evolves subject to constraints imposed by opening and/or sliding interfaces. An internal variable formalism is derived together with the notion of irreversibility of damage results in a set of evolution equations for the gap function that seamlessly tracks interface debonding by treating damage and friction in a unified way. Tension debonding, compression damage, and frictional sliding are accommodated, and return mapping algorithms in the presence of evolving strong discontinuities are developed. This derivation variationally embeds the interfacial kinematic models that are crucial to capturing the physical and mathematical properties involving large strains and damage. The framework is extended for monolithic coupling of thermomechanical fields in the class of problems that have embedded weak and strong discontinuities in the mechanical and thermal fields. Since the derived expressions are a function of the mechanical and thermal fields, the resulting stabilized formulation contains numerical flux and stability tensors that provide an avenue to variationally embed interfacial kinetic and kinematic models for more robust representation of interfacial physics. Representative numerical tests involving large strains and rotations, damage phenomena, and thermal effects are performed to confirm the robustness and accuracy of the method. Comparison of the results with both experimental and numerical results from literature are presented. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (advisor), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (committee member), Champaign%22%20%2Bcontributor%3A%28%22Lopez-Pamies%2C%20Oscar%22%29&pagesize-30">Lopez-Pamies, Oscar (committee member), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (committee member).

Subjects/Keywords: Variational Multiscale framework; Interfaces; Damage; Thermomechanical coupled framework; Stabilized methods; Finite strains; Discontinuous Galerkin method; Multi-constituents; Debonding; Fatigue

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Record Details Similar Records Cite « Share

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

APA (6^th Edition):

Chen, P. (2018). A variational framework for mathematically nonsmooth problems in solid and structure mechanics. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/101813

Chicago Manual of Style (16^th Edition):

Chen, Pinlei. “A variational framework for mathematically nonsmooth problems in solid and structure mechanics.” 2018. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/101813.

MLA Handbook (7^th Edition):

Chen, Pinlei. “A variational framework for mathematically nonsmooth problems in solid and structure mechanics.” 2018. Web. 16 Jan 2021.

Vancouver:

Chen P. A variational framework for mathematically nonsmooth problems in solid and structure mechanics. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2018. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/101813.

Council of Science Editors:

Chen P. A variational framework for mathematically nonsmooth problems in solid and structure mechanics. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2018. Available from: http://hdl.handle.net/2142/101813

13. Kwack, Jaehyuk. A variational multiscale framework for non-Newtonian fluid models.

Degree: PhD, 0106, 2013, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/45311

► This dissertation presents stabilized mixed finite element formulations for non-Newtonian models for complex fluids. One class of non-Newtonian fluids is shear-rate dependent fluids that include… (more)

▼ This dissertation presents stabilized mixed finite element formulations for non-Newtonian models for complex fluids. One class of non-Newtonian fluids is shear-rate dependent fluids that include nonlinear viscosity functions of the second invariant of the rate-of-deformation tensor, thereby resulting in shear-thinning or shear-thickening effects. Another is viscoelastic fluid models that embody elastic stress term as well as viscous stress term, and therefore reveal memory effects via elasticity in the fluid motion. These two model classes can be combined into shear-rate dependent viscoelastic fluid models that are mathematically sophisticated and reflect complicated fluid motions. Since the complexity of the mathematical constructs in non-Newtonian fluid models deteriorates numerical stability of discretized formulations, advanced numerical methods with enhanced stability properties are required for efficient numerical implementations. In this dissertation, the Variational Multiscale (VMS) framework is employed to derive stabilized mixed formulations for advection-diffusion, shear-rate dependent, viscoelastic, and shear-rate dependent viscoelastic fluid models. The VMS framework leads to a two-level description of the primary variables, leading to coarse-scale and fine-scale problems. Consistent linearization of the fine-scale problem with respect to the fine-scale fields and the use of bubble functions to expand the fine-scale trial and test functions lead to analytical models for the fine-scale. These nonlinear fine-scale models are variationally embedded in the nonlinear coarse-scale stabilized formulations for the various non-Newtonian fluid models. Advanced computational algorithms that are based on quadratic convergence properties of consistent tangent tensors are derived for efficient nonlinear solution of the system of equations. The new methods are implemented for equal-order linear and quadratic finite elements in two and three-dimensional space (triangular, quadrilateral, tetrahedral and hexahedral elements). The methods are verified via benchmark problems and then extended to human artery models to highlight the significantly distinctive non-Newtonian fluid response in human blood-flow simulations. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (advisor), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Heath%2C%20Michael%20T.%22%29&pagesize-30">Heath, Michael T. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (committee member), Champaign%22%20%2Bcontributor%3A%28%22Hilgenfeldt%2C%20Sascha%22%29&pagesize-30">Hilgenfeldt, Sascha (committee member).

Subjects/Keywords: Variational Multiscale framework; non-Newtonian fluids; stabilized finite element method; blood flow simulations; large-scale computing; viscoelastic fluids

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APA (6^th Edition):

Kwack, J. (2013). A variational multiscale framework for non-Newtonian fluid models. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/45311

Chicago Manual of Style (16^th Edition):

Kwack, Jaehyuk. “A variational multiscale framework for non-Newtonian fluid models.” 2013. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/45311.

MLA Handbook (7^th Edition):

Kwack, Jaehyuk. “A variational multiscale framework for non-Newtonian fluid models.” 2013. Web. 16 Jan 2021.

Vancouver:

Kwack J. A variational multiscale framework for non-Newtonian fluid models. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2013. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/45311.

Council of Science Editors:

Kwack J. A variational multiscale framework for non-Newtonian fluid models. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2013. Available from: http://hdl.handle.net/2142/45311

14. Truster, Timothy. A variational multiscale computational framework for nonlinear interfacial solid mechanics.

Degree: PhD, 0106, 2013, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/44348

► This dissertation develops a robust computational framework for solving solid mechanics problems containing strong or weak discontinuities arising from interfaces. The framework consists of a… (more)

▼ This dissertation develops a robust computational framework for solving solid mechanics problems containing strong or weak discontinuities arising from interfaces. The framework consists of a stabilized version of the Discontinuous Galerkin method to handle interfaces combined with a stabilized mixed method for elasticity with a built-in error estimation module. The unifying approach for deriving these components is the Variational Multiscale (VMS) method, a guiding philosophy for recovering stability through the modeling of features that are filtered out by discretization. The enhanced stability of the framework enables the treatment of various interface kinematics, such as nonmatching meshes in domain decomposition or substructure modeling, contact and friction in mechanical systems, and delamination at bi-material interfaces in composites. The common launching point for developing the components of this framework according to the VMS approach is an additive decomposition of the solution field into coarse scales and fine scales. This separation into numerical scales is an artifact of the discretization process whereby the coarse scales represented on the finite element mesh are unable to resolve the fine-scale features of the solution, and failure to account for the fine scales manifests instabilities in the computed results. In the case of interfaces, the source of instability is the discontinuity and/or nonconformity of the primary field along with the inf-sup condition governing the nontrivial selection of Lagrange multiplier interpolations. Likewise, the choice of displacement-pressure interpolations for mixed elasticity leads to instability in the discrete setting. In this work, models for these fine scales in the interior and along the interface are constructed using simple polynomial bubble functions. The variational embedding of these models serves as a vehicle for systematically deriving a robust interface framework that is mathematically consistent, admits common element types, and is free from user-defined tuning parameters. Additionally, the fine-scale models serve as a natural mechanism for estimating the numerical error, thereby providing built-in feedback on assessing confidence in the computed results. The underlying mathematical structure of the framework enables ready extension of the stabilization and error estimation methods to problems involving nonlinearity in the material and interface responses. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (advisor), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Bergman%2C%20Lawrence%20A.%22%29&pagesize-30">Bergman, Lawrence A. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (committee member), Champaign%22%20%2Bcontributor%3A%28%22Heath%2C%20Michael%20T.%22%29&pagesize-30">Heath, Michael T. (committee member).

Subjects/Keywords: Variational Multiscale framework; Interfaces; Discontinuous Galerkin method; Nitsche method; Stabilized methods; Mixed methods; Bubble functions; A posteriori error estimation; Residual-based estimators; Finite strains; Incompressible elasticity; Composites; Debonding; Contact mechanics; Friction

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

APA (6^th Edition):

Truster, T. (2013). A variational multiscale computational framework for nonlinear interfacial solid mechanics. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/44348

Chicago Manual of Style (16^th Edition):

Truster, Timothy. “A variational multiscale computational framework for nonlinear interfacial solid mechanics.” 2013. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/44348.

MLA Handbook (7^th Edition):

Truster, Timothy. “A variational multiscale computational framework for nonlinear interfacial solid mechanics.” 2013. Web. 16 Jan 2021.

Vancouver:

Truster T. A variational multiscale computational framework for nonlinear interfacial solid mechanics. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2013. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/44348.

Council of Science Editors:

Truster T. A variational multiscale computational framework for nonlinear interfacial solid mechanics. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2013. Available from: http://hdl.handle.net/2142/44348

15. Calderer Elias, Ramon. Residual-based turbulence models for incompressible flows in domains with moving boundaries.

Degree: PhD, 0106, 2012, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/31130

► This dissertation presents residual-based turbulence models for problems with moving boundaries and interfaces. The method is derived employing the Variational Multiscale (VMS) framework, which gives… (more)

▼ This dissertation presents residual-based turbulence models for problems with moving boundaries and interfaces. The method is derived employing the Variational Multiscale (VMS) framework, which gives rise to several modeling options that are exploited to obtain accurate turbulence models. To accommodate problems with moving boundaries such as fluid-structure interaction and free-surface problems, the formulation is cast in an Arbitrary Lagrangian-Eulerian (ALE) frame of reference. Multiple models of increasing degree of mathematical and algorithmic sophistication are presented. In all the cases, we assume a multiscale decomposition of the solution fields into overlapping components of different scale. The scales that can be accurately captured by the finite element discretization are numerically resolved, and are termed as the coarse scales, while the sub-grid scales, which may not be accurately represented by the finite element discretization, are termed as the fine-scales. The key idea of the VMS framework is to derive models for the fine scales in terms of the coarse scales, and then variationally project the fine-scale models onto coarse-scale space. This approach results in formulations that only depend on the coarse scales, while the effects of the fine scales on the coarse-scale fields are fully accounted for via the additional terms that arise due to the multiscale decomposition of the solution fields. In this dissertation, the fine scales are modeled using a bubble functions approach. This enables the fine-scale problem to be solved on elements or patches of elements. As a consequence, the presented algorithms are amenable for parallel implementation. The simplest fine-scale model presented here is derived introducing up-winding ideas to the discrete problem that governs the fine scales. To derive expressions for more sophisticated fine-scale models, VMS ideas are also applied to the fine-scale sub-problem. A significant feature of the bubble functions approach adopted here is that the derived turbulence models are free of any embedded or tunable parameters. Another significant feature of the method is that it is mathematically consistent because the fine-scale models are driven by the residual of the Euler-Lagrange equations for the coarse scales. Consequently, when the coarse scales are able to represent the exact solution of the problem, the fine-scale models vanish. Numerical attributes of the developed models are investigated via an exhaustive set of numerical tests. One of the classes of problems investigated has fix boundaries while the other has moving boundaries. The results are compared to reference experimental and numerical results, and excellent agreements are observed. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (advisor), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Freund%2C%20Jonathan%20B.%22%29&pagesize-30">Freund, Jonathan B. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Heath%2C%20Michael%20T.%22%29&pagesize-30">Heath, Michael T. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Garcia%2C%20Marcelo%20H.%22%29&pagesize-30">Garcia, Marcelo H. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Gropp%2C%20William%20D.%22%29&pagesize-30">Gropp, William D. (committee member).

Subjects/Keywords: Turbulence modeling; Moving boundaries; Tetrahedral meshes; Variational Multiscale method

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

APA (6^th Edition):

Calderer Elias, R. (2012). Residual-based turbulence models for incompressible flows in domains with moving boundaries. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/31130

Chicago Manual of Style (16^th Edition):

Calderer Elias, Ramon. “Residual-based turbulence models for incompressible flows in domains with moving boundaries.” 2012. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/31130.

MLA Handbook (7^th Edition):

Calderer Elias, Ramon. “Residual-based turbulence models for incompressible flows in domains with moving boundaries.” 2012. Web. 16 Jan 2021.

Vancouver:

Calderer Elias R. Residual-based turbulence models for incompressible flows in domains with moving boundaries. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2012. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/31130.

Council of Science Editors:

Calderer Elias R. Residual-based turbulence models for incompressible flows in domains with moving boundaries. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2012. Available from: http://hdl.handle.net/2142/31130

University of Illinois – Urbana-Champaign

16. Truster, Timothy J. A variational multiscale a-posteriori error estimation method for nearly incompressible elasticity.

Degree: MS, 0106, 2010, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/15985

► This work presents an error estimation framework for a mixed displacement-pressure finite element method for nearly incompressible elasticity that is based on variational multiscale concepts.… (more)

Subjects/Keywords: Mixed methods; Multiscale formulation; Stabilized finite elements; A posteriori error estimation; Residual-based estimators

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

APA (6^th Edition):

Truster, T. J. (2010). A variational multiscale a-posteriori error estimation method for nearly incompressible elasticity. (Thesis). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/15985

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Truster, Timothy J. “A variational multiscale a-posteriori error estimation method for nearly incompressible elasticity.” 2010. Thesis, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/15985.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Truster, Timothy J. “A variational multiscale a-posteriori error estimation method for nearly incompressible elasticity.” 2010. Web. 16 Jan 2021.

Vancouver:

Truster TJ. A variational multiscale a-posteriori error estimation method for nearly incompressible elasticity. [Internet] [Thesis]. University of Illinois – Urbana-Champaign; 2010. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/15985.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Truster TJ. A variational multiscale a-posteriori error estimation method for nearly incompressible elasticity. [Thesis]. University of Illinois – Urbana-Champaign; 2010. Available from: http://hdl.handle.net/2142/15985

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

17. Shahane, Shantanu Shashank. Numerical simulations of die casting with uncertainty quantification and optimization using neural networks.

Degree: PhD, Mechanical Engineering, 2019, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/105582

► Die casting is one type of metal casting in which liquid metal is solidified in a reusable die. In such a complex process, measuring and… (more)

▼ Die casting is one type of metal casting in which liquid metal is solidified in a reusable die. In such a complex process, measuring and controlling the process parameters is difficult. Conventional deterministic simulations are insufficient to completely estimate the effect of stochastic variation in the process parameters on product quality. In this research, a framework to simulate the effect of stochastic variation together with verification, validation, uncertainty quantification and design optimization is proposed. This framework includes high-speed numerical simulations of solidification, micro-structure and mechanical properties prediction models along with experimental inputs for calibration and validation. In order to have a better prediction of product quality, both experimental data and stochastic variations in process parameters with numerical modeling are employed. This enhances the utility of traditional numerical simulations used in die casting. OpenCast, a novel and comprehensive computational framework to simulate solidification problems in materials processing is developed. Heat transfer, solidification and fluid flow due to natural convection are modeled. Empirical relations are used to estimate the microstructure parameters and mechanical properties. The fractional step algorithm is modified to deal with the numerical aspects of solidification by suitably altering the coefficients in the discretized equation to simulate selectively only in the liquid and mushy zones. This brings significant computational speed up as the simulation proceeds. Complex domains are represented by unstructured hexahedral elements. The algebraic multigrid method, blended with a Krylov subspace solver is used to accelerate convergence. Multiple case studies are presented by coupling surrogate models such as polynomial chaos expansion (PCE) and neural network with OpenCast for uncertainty quantification and optimization. The effects of stochasticity in the alloy composition, boundary and initial conditions on the product quality of die casting are analyzed using PCE. Further, a high dimensional stochastic analysis of the natural convection problem is presented to model uncertainty in the material properties and boundary conditions using neural networks. In die casting, heat extraction from molten metal is achieved by cooling lines in the die which impose nonuniform boundary temperatures on the mold wall. This boundary condition along with the initial molten metal temperature affect the product quality quantified in terms of micro-structure parameters and yield strength. Thus, a multi-objective optimization problem is solved to demonstrate a procedure for improvement of product quality and process efficiency. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Vanka%2C%20Surya%20Pratap%22%29&pagesize-30">Vanka, Surya Pratap (advisor), Champaign%22%20%2Bcontributor%3A%28%22Kapoor%2C%20Shiv%20G%22%29&pagesize-30">Kapoor, Shiv G (advisor), Champaign%22%20%2Bcontributor%3A%28%22Aluru%2C%20Narayana%20R%22%29&pagesize-30">Aluru, Narayana R (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Ferreira%2C%20Placid%22%29&pagesize-30">Ferreira, Placid (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Tawfick%2C%20Sameh%22%29&pagesize-30">Tawfick, Sameh (committee member).

Subjects/Keywords: Computational Fluid Dynamics and Heat Transfer; Solidification; Neural Network; Uncertainty Quantification; Sensitivity Analysis; Optimization; Genetic Algorithm

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

APA (6^th Edition):

Shahane, S. S. (2019). Numerical simulations of die casting with uncertainty quantification and optimization using neural networks. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/105582

Chicago Manual of Style (16^th Edition):

Shahane, Shantanu Shashank. “Numerical simulations of die casting with uncertainty quantification and optimization using neural networks.” 2019. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/105582.

MLA Handbook (7^th Edition):

Shahane, Shantanu Shashank. “Numerical simulations of die casting with uncertainty quantification and optimization using neural networks.” 2019. Web. 16 Jan 2021.

Vancouver:

Shahane SS. Numerical simulations of die casting with uncertainty quantification and optimization using neural networks. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2019. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/105582.

Council of Science Editors:

Shahane SS. Numerical simulations of die casting with uncertainty quantification and optimization using neural networks. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2019. Available from: http://hdl.handle.net/2142/105582

18. Wilcox, Bryan R. On the use of impact-induced nonlinearities in limit switch design.

Degree: PhD, 0133, 2011, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/24228

► This dissertation explores the use of grazing bifurcations in impacting mechanical systems as a useful means of creating fast-acting limit switches. Using analytical, numerical, and… (more)

Subjects/Keywords: limit switch; dynamical systems; bifurcation; electromechanical coupling; microelectromechanical systems (MEMS)

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APA (6^th Edition):

Wilcox, B. R. (2011). On the use of impact-induced nonlinearities in limit switch design. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/24228

Chicago Manual of Style (16^th Edition):

Wilcox, Bryan R. “On the use of impact-induced nonlinearities in limit switch design.” 2011. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/24228.

MLA Handbook (7^th Edition):

Wilcox, Bryan R. “On the use of impact-induced nonlinearities in limit switch design.” 2011. Web. 16 Jan 2021.

Vancouver:

Wilcox BR. On the use of impact-induced nonlinearities in limit switch design. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2011. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/24228.

Council of Science Editors:

Wilcox BR. On the use of impact-induced nonlinearities in limit switch design. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2011. Available from: http://hdl.handle.net/2142/24228

19. Denavit, Mark D. Characterization of behavior of steel-concrete composite members and frames with applications for design.

Degree: PhD, 0106, 2013, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/42420

► Steel-concrete composite frames are seeing increased use in practice. Their excellent structural characteristics, including high strength, stiffness, and ductility, make them an appealing option for… (more)

▼ Steel-concrete composite frames are seeing increased use in practice. Their excellent structural characteristics, including high strength, stiffness, and ductility, make them an appealing option for many building configurations. However, there exist gaps in the knowledge of behavior and the design provisions for these structures. This work seeks to document composite member and frame behavior and address key design issues through targeted studies utilizing advanced computational formulations and detailed examination of experimental results. A three-dimensional distributed plasticity beam finite element formulation suitable for nonlinear static and dynamic analyses of steel-concrete composite frames has been developed. The formulation is suitable for both concrete-filled steel tubes (CFT) and steel reinforced concrete (SRC) members, as well as steel wide-flange and hollow structural steel sections that are part of composite frames. A mixed basis for the formulation was chosen to allow for accurate modeling of both material and geometric nonlinearities. The formulation utilizes uniaxial cyclic constitutive relations for the concrete and steel that account for the salient features of each material, as well as the interaction between the two, including concrete confinement and local buckling. The accuracy of the formulation was verified against a wide variety of monotonic and cyclic experimental results of composite members, demonstrating the capability of the formulation to accurately produce realistic simulations of element and frame behavior. Aspects of the behavior of composite columns were assessed through an examination of results from a series of experiments on full-scale slender CFT beam-columns conducted by project collaborators. Additionally, comparative computational analyses were performed using the mixed beam formulation and detailed data interpretation focusing on the beam-column interaction strength was conducted. Several aspects of the design of steel-concrete composite structures were examined. The natural bond behavior of CFT columns was investigated through an examination of prior experimental work and new provisions were developed for the assessment of natural bond strength of CFT connections. The in-plane stability behavior of steel-concrete composite members and frames was assessed through a parametric study on small non-redundant benchmark frames, leading to the development of new elastic flexural rigidities for elastic analysis of composite members; new effective flexural rigidities for calculating the axial compressive strength of SRC members; new Direct Analysis stiffness reductions for composite members; and new recommendations for the construction of the interaction diagram for composite members. The seismic behavior of composite moment and braced frames was assessed through static pushover and incremental dynamic analyses. The analyses were performed on a suite of 60 archetype frames that were designed according to current design provisions. Connections were assumed to be strong;… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Hajjar%2C%20Jerome%20F.%22%29&pagesize-30">Hajjar, Jerome F. (advisor), Champaign%22%20%2Bcontributor%3A%28%22LaFave%2C%20James%20M.%22%29&pagesize-30">LaFave, James M. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Hajjar%2C%20Jerome%20F.%22%29&pagesize-30">Hajjar, Jerome F. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Leon%2C%20Roberto%20T.%22%29&pagesize-30">Leon, Roberto T. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Fahnestock%2C%20Larry%20A.%22%29&pagesize-30">Fahnestock, Larry A. (committee member).

Subjects/Keywords: Composite Construction; Steel; Concrete; Nonlinear Analysis; Load Transfer; Stability; Seismic

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

APA (6^th Edition):

Denavit, M. D. (2013). Characterization of behavior of steel-concrete composite members and frames with applications for design. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/42420

Chicago Manual of Style (16^th Edition):

Denavit, Mark D. “Characterization of behavior of steel-concrete composite members and frames with applications for design.” 2013. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/42420.

MLA Handbook (7^th Edition):

Denavit, Mark D. “Characterization of behavior of steel-concrete composite members and frames with applications for design.” 2013. Web. 16 Jan 2021.

Vancouver:

Denavit MD. Characterization of behavior of steel-concrete composite members and frames with applications for design. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2013. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/42420.

Council of Science Editors:

Denavit MD. Characterization of behavior of steel-concrete composite members and frames with applications for design. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2013. Available from: http://hdl.handle.net/2142/42420

20. Joumaa, Hady. Elastodynamics and wave propagation in fractal media.

Degree: PhD, 0133, 2013, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/42478

► The elastodynamics and wave propagation in three-dimensional fractal media is explored through the application of analytic and computational methods. In particular, two different mechanical models… (more)

▼ The elastodynamics and wave propagation in three-dimensional fractal media is explored through the application of analytic and computational methods. In particular, two different mechanical models are introduced; with each one applied to characterize an elastodynamic problem pertaining to some fractal media of distinctive properties. The first model considers media whose fractality is uniform in all the directions, thus denoted ``isotropic''. The formulation which governs the propagation of waves in this model is first developed from fractional hydrodynamic laws, and then, boundary value problems are solved analytically and numerically on spherical domains. In the second model, the fractality is direction dependent, thus the designation ``anisotropic''. This model, which implements the concept of product measures to regularize fractional integrals in deriving the balance laws, is assigned to treat the elastodynamics of fractal solid materials. Here, the application of Hooke’s relation (classical elasticity) in the constitutive law is limited to dilatational wave motion. In order to treat general problems, a non-classical (Cosserat-type) constitutive model is incorporated, featuring the introduction of microrotation and couple-stress variables into the micropolar element and, subsequently, the balance laws. Various eigenvalue-type problems of different kinematic configurations are solved analytically, while a transient analysis based on modal excitation is simulated numerically, resulting in validated computational tools capable of solving complex elastodynamic problems of arbitrary settings. The development and verification of these two fractal models promotes the consideration of the more challenging acoustic-solid interaction problems in the fractal paradigm. Indeed an idealized problem is first handled in the continuum framework, where the mathematical steps of the solution are analysed, and then, its demonstration in the fractal domain is performed, illustrating the effectiveness of the fractal models discussed before. In conclusion, our analytical and computational investigation advances the mechanics of fractal media for applications which cannot be studied with classical continuum mechanics. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Ostoja-Starzewski%2C%20Martin%22%29&pagesize-30">Ostoja-Starzewski, Martin (advisor), Champaign%22%20%2Bcontributor%3A%28%22Ostoja-Starzewski%2C%20Martin%22%29&pagesize-30">Ostoja-Starzewski, Martin (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Vakakis%2C%20Alexander%20F.%22%29&pagesize-30">Vakakis, Alexander F. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22DeVille%2C%20Robert%20E.%22%29&pagesize-30">DeVille, Robert E. (committee member).

Subjects/Keywords: Elastodynamics; Fractal Media; Wave Propagation; Micropolar Elasticity; Acoustic-Solid Interaction

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APA (6^th Edition):

Joumaa, H. (2013). Elastodynamics and wave propagation in fractal media. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/42478

Chicago Manual of Style (16^th Edition):

Joumaa, Hady. “Elastodynamics and wave propagation in fractal media.” 2013. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/42478.

MLA Handbook (7^th Edition):

Joumaa, Hady. “Elastodynamics and wave propagation in fractal media.” 2013. Web. 16 Jan 2021.

Vancouver:

Joumaa H. Elastodynamics and wave propagation in fractal media. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2013. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/42478.

Council of Science Editors:

Joumaa H. Elastodynamics and wave propagation in fractal media. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2013. Available from: http://hdl.handle.net/2142/42478

21. Manchakattil Sucheendran, Mahesh. Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct.

Degree: PhD, 4048, 2013, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/44263

► The design of supersonic and hypersonic vehicles involves the challenging task of designing thin panels that can withstand severe unsteady pressure and thermal loads. A… (more)

▼ The design of supersonic and hypersonic vehicles involves the challenging task of designing thin panels that can withstand severe unsteady pressure and thermal loads. A good understanding and accurate prediction of the coupled structural-acoustic response of thin panels subjected to sound waves are key elements of this design process. Due to the cost of in-flight testing, the experimental assessment of the structural-acoustic response of skin panels is usually conducted in ground-based facilities consisting of a duct in which acoustic waves propagate at grazing incidence with skin panels mounted along the duct walls. A key limitation of such facility is the absence of flow, the impact of which on the structural-acoustic response of the skin panel is still poorly understood. To shed some insight on this key contribution, this analytical and numerical study focuses on the structural-acoustic interaction of sound with a thin elastic plate mounted flush on a wall in a rectangular duct in the presence of a uniform mean subsonic and supersonic flow. A linear, time-harmonic theory based on modal descriptions of the plate velocity and duct acoustic fields is first developed. The theory includes the effect of uniform mean flow in the duct and clamped and simply-supported boundary conditions for the plate. The sound radiated by the plate is calculated using Doak’s theory, extended in this work to account for subsonic and supersonic uniform mean flow in the duct, and verified using the numerical solver. The theoretical model provides important insight on the effect of flow in the duct on the coupled response of the plate. Four metrics characterizing the coupled response are considered: the deviation of the peak response frequency from the in vacuo natural frequency of plate, the amplitude of the peak response, the effective acoustic damping of the plate, and the plate modal coupling through the duct acoustic field. The theory is extended to estimate the onset of instability in the structural response of a duct-mounted clamped-plate with grazing flow for estimating its range of applicability. Numerical simulations of the coupled response of a duct-mounted clamped plate are performed using a 3D coupled numerical solver, which includes a high-fidelity finite difference fluid solver and an implicit finite element structural solver in a fully coupled framework. The 3D solver is used to predict the response of duct-mounted thin plates to plane waves with a broadband frequency content and in the presence of a uniform mean flow. The spectral response of the integral average of the rms plate velocity is computed for two plate thicknesses at various Mach numbers, and is compared with that computed using linear theory. The predictions provided by the theoretical model compare well with the numerical models except in the presence of an instability. For a typical aerospace structure, the plate-fluid coupling does little to change the fundamental vibration frequencies from their in vacuo values but… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Bodony%2C%20Daniel%20J.%22%29&pagesize-30">Bodony, Daniel J. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Bodony%2C%20Daniel%20J.%22%29&pagesize-30">Bodony, Daniel J. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Freund%2C%20Jonathan%20B.%22%29&pagesize-30">Freund, Jonathan B. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member).

Subjects/Keywords: structural-acoustic interaction; duct acoustics; modal solution

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APA (6^th Edition):

Manchakattil Sucheendran, M. (2013). Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/44263

Chicago Manual of Style (16^th Edition):

Manchakattil Sucheendran, Mahesh. “Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct.” 2013. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/44263.

MLA Handbook (7^th Edition):

Manchakattil Sucheendran, Mahesh. “Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct.” 2013. Web. 16 Jan 2021.

Vancouver:

Manchakattil Sucheendran M. Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2013. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/44263.

Council of Science Editors:

Manchakattil Sucheendran M. Effect of grazing flow on structural-acoustic response of an elastic plate with sound in a duct. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2013. Available from: http://hdl.handle.net/2142/44263

22. Breitenfeld, Michael. Quasi-static non-ordinary state-based peridynamics for the modeling of 3D fracture.

Degree: PhD, 4048, 2014, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/49545

► A majority of the efforts in modeling crack propagation have used continuum models built upon partial derivatives with respect to the spatial coordinates in the… (more)

▼ A majority of the efforts in modeling crack propagation have used continuum models built upon partial derivatives with respect to the spatial coordinates in the force and displacement relationship. These methods are inherently incompatible for modeling cracks because the partial derivatives are undefined at crack faces due to the discontinous displacement field. Furthermore, these methods fall short on robustness and computational complexity when involving heterogeneous materials, crack initiation and crack branching, especially in a 3D setting. A recent addition to the list of numerical methods used in fracture mechanics, peridynamics is a particle-based continuum model that addresses some shortcomings of other methods. In this work, a quasi-static linearly elastic implicit parallel implementation of the non-ordinary state-based peridynamics formulation is presented for both stationary and propagating cracks. Emphasis is placed on assessing the accuracy of the numerical scheme in the vicinity of the crack front and other sources of stress concentration. The near-tip solution is affected by the presence of zero-energy modes, particularly in regions of high strain gradients, caused by the nonlocal definition of the strains. A systematic comparative study is presented between the various methods introduced to address this numerical instability. The accuracy of the peridynamics scheme, including the impact of the grid spacing and configuration, is assessed through a detailed analysis of the near-tip stress and displacement fields and the extraction of key fracture parameters such as stress intensity factors and conservation integrals. This assessment includes a verification study based on the classical 3D penny-shaped crack problem and a validation study of a 3D notched fracture specimen. For the modeling of propagating cracks, the emphasis of the assessment study is placed on the ability of the method to predict crack path. To that effect, a variety of verification and validation problems corresponding to classical test geometries (double cantilever beam, four-point bend specimen and V-notched Brazilian disc) are simulated. Lastly, an analytical and numerical study linking peridynamics and cohesive zone modeling under Mode I, Mode II and mixed-mode loading is developed. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Lambros%2C%20John%22%29&pagesize-30">Lambros, John (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Aluru%2C%20Narayana%20R.%22%29&pagesize-30">Aluru, Narayana R. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Weckner%2C%20Olaf%22%29&pagesize-30">Weckner, Olaf (committee member).

Subjects/Keywords: peridynamics; nonlocal; meshless; fracture; 3D; non-ordinary; state-based

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APA (6^th Edition):

Breitenfeld, M. (2014). Quasi-static non-ordinary state-based peridynamics for the modeling of 3D fracture. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/49545

Chicago Manual of Style (16^th Edition):

Breitenfeld, Michael. “Quasi-static non-ordinary state-based peridynamics for the modeling of 3D fracture.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/49545.

MLA Handbook (7^th Edition):

Breitenfeld, Michael. “Quasi-static non-ordinary state-based peridynamics for the modeling of 3D fracture.” 2014. Web. 16 Jan 2021.

Vancouver:

Breitenfeld M. Quasi-static non-ordinary state-based peridynamics for the modeling of 3D fracture. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/49545.

Council of Science Editors:

Breitenfeld M. Quasi-static non-ordinary state-based peridynamics for the modeling of 3D fracture. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/49545

23. Eriten, Melih. Multiscale physics-based modeling of friction.

Degree: PhD, 0133, 2012, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/31078

► Frictional contacts between solids exist in nature and in a wide range of engineering applications. Friction causes energy loss, and it is the main source… (more)

▼ Frictional contacts between solids exist in nature and in a wide range of engineering applications. Friction causes energy loss, and it is the main source of wear and surface degradation which limits the lifetime of mechanical systems. Yet, friction is needed to walk, run, accelerate, slow down or stop moving systems. Whether desirable or not, friction is a very complex physical phenomenon. The behavior of systems with friction is nonlinear, and the physical mechanisms governing friction behavior span a wide range of spatial and temporal scales. A thorough study of friction should employ experimentalists and theoreticians in chemistry, materials science, tribology, mechanics, dynamics, and structural engineering. High spatial and temporal resolutions are required to capture and model essential physics of a frictional contact. However, such a detailed model is impractical in large-scale structural dynamics simulations; especially since frictional contacts can be numerous in a given application. Reduced-order models (ROMs) achieve broader applicability by compromising several aspects and accounting for the important physics. Hence, rather simple Coulomb friction is still the most ubiquitous model in the modeling and simulation literature. As an alternative, a reduced-order friction model built-up from micromechanics of surfaces is proposed in this work. Continuum-scale formulation of pre-sliding friction behavior is combined with material-strength-based friction coefficients to develop a physics-based friction model at asperity-scale. Then, the statistical summation technique is utilized to build a multiscale modeling framework. A novel joint fretting setup is designed for friction experiments in a practical setting, and the developed models are tested. Both asperity and rough surface friction models show good agreement with experimental data. The influences of materials, surface roughness and contact contamination on the friction are also studied. Finally, the developed models are incorporated in to a simple dynamical system to illustrate broader applicability. The models proposed in this work account for loading-history dependence, partial slip, gross slip, nonlinear stiffness and energy dissipation characteristics of frictional contacts. In doing so, the models require no curve-fit or look-up parameters. Instead, the formulations are developed from continuum mechanics, and the required parameters can be determined from simple tension/compression and surface roughness tests. In this sense, the developed models are physics-based and predictive. The parameters employed in the models depend on the contact conditions, surface roughness and material properties. For instance, the developed models use a dry-contact formulation at asperity-scale, and the macroscale friction predictions are tested only for dry contacts. However, the multiscale modeling approach can be applied to model the effect of lubrication provided that asperity-scale contact accounts for it. Besides, frictional contacts of certain materials exhibit… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Polycarpou%2C%20Andreas%20A.%22%29&pagesize-30">Polycarpou, Andreas A. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Polycarpou%2C%20Andreas%20A.%22%29&pagesize-30">Polycarpou, Andreas A. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Bergman%2C%20Lawrence%20A.%22%29&pagesize-30">Bergman, Lawrence A. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Johnson%2C%20Harley%20T.%22%29&pagesize-30">Johnson, Harley T. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Vakakis%2C%20Alexander%20F.%22%29&pagesize-30">Vakakis, Alexander F. (committee member).

Subjects/Keywords: Friction; partial slip; multiscale modeling; roughness; fretting; bolted joints

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

APA (6^th Edition):

Eriten, M. (2012). Multiscale physics-based modeling of friction. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/31078

Chicago Manual of Style (16^th Edition):

Eriten, Melih. “Multiscale physics-based modeling of friction.” 2012. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/31078.

MLA Handbook (7^th Edition):

Eriten, Melih. “Multiscale physics-based modeling of friction.” 2012. Web. 16 Jan 2021.

Vancouver:

Eriten M. Multiscale physics-based modeling of friction. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2012. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/31078.

Council of Science Editors:

Eriten M. Multiscale physics-based modeling of friction. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2012. Available from: http://hdl.handle.net/2142/31078

24. Lee, Young Joo. Finite-element-based system reliability analysis and updating of fatigue-induced sequential failures.

Degree: PhD, 0106, 2012, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/30920

► Fatigue is one of the main causes of structural failure. In fact, many structural systems such as bridges, offshore platforms, and aircraft are subjected to… (more)

▼ Fatigue is one of the main causes of structural failure. In fact, many structural systems such as bridges, offshore platforms, and aircraft are subjected to the risk of fatigue-induced failure caused by repeated loading over their life cycle. Therefore, structural systems should be designed and maintained such that they have an adequate level of structural redundancy to prevent local fatigue-induced failures from progressing toward system-level failure such as collapse, which may result in complete loss of the structural system and catastrophic consequences. For decision-making with respect to the design, maintenance and retrofit of robust structural systems, it is thus essential to estimate their reliability and identify critical sequences of local failures leading to system failures. In addition, it is desirable to update the original reliability based on inspection results, which will facilitate reliability-based structural maintenance based on the actual conditions of structures. Performing reliability analysis and updating of fatigue-induced sequential failure of a structural system is a challenging task. First, the reliability analysis should be performed at the system level in conjunction with sophisticated finite element analysis to account for the complex behavior of the structure during fatigue-induced sequential failures including the impact of load re-distribution caused by failures at other locations. Second, one might need to explore a huge number of failure sequences to estimate the failure risk accurately, especially for complex structural systems with high level of redundancy. Third, for accurate system reliability updating, precise system reliability estimation should be performed first and then the results should be incorporated into a method that can update the original reliability based on inspection results. This thesis proposes novel finite-element-based methods for system reliability analysis and updating for structures that are subject to the risk of fatigue-induced sequential failures. First of all, a new computational framework is developed which performs finite element reliability analysis (FE-RA) at the system level. While many of the existing FE-RA software packages aim at reliability analysis at the component level or have the limited capability of their FE modules, the new framework enables us to perform system reliability analysis in conjunction with sophisticated finite element analysis. Secondly, a new Branch-and Bound method employing system reliability Bounds (termed the B3 method) is developed to perform system reliability analysis for the fatigue-induced sequential failures of structures. Describing sequential failures as disjoint events, the B3 method enables us to estimate the system-level failure probability and identify critical failure sequences, more accurately and efficiently than other existing methods. The B3 method was originally developed for reliability analysis of discrete structures such as a truss, but the method is further developed for its applications to… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Song%2C%20Junho%22%29&pagesize-30">Song, Junho (advisor), Champaign%22%20%2Bcontributor%3A%28%22Song%2C%20Junho%22%29&pagesize-30">Song, Junho (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Spencer%2C%20Billie%20F.%2C%20Jr.%22%29&pagesize-30">Spencer, Billie F., Jr. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Millwater%2C%20Harry%20R.%22%29&pagesize-30">Millwater, Harry R. (committee member).

Subjects/Keywords: Finite element; System reliability; Reliability updating; Fatigue; Sequential Failure; Branch-and-bound; B3 method; Structural inspection

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APA (6^th Edition):

Lee, Y. J. (2012). Finite-element-based system reliability analysis and updating of fatigue-induced sequential failures. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/30920

Chicago Manual of Style (16^th Edition):

Lee, Young Joo. “Finite-element-based system reliability analysis and updating of fatigue-induced sequential failures.” 2012. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/30920.

MLA Handbook (7^th Edition):

Lee, Young Joo. “Finite-element-based system reliability analysis and updating of fatigue-induced sequential failures.” 2012. Web. 16 Jan 2021.

Vancouver:

Lee YJ. Finite-element-based system reliability analysis and updating of fatigue-induced sequential failures. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2012. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/30920.

Council of Science Editors:

Lee YJ. Finite-element-based system reliability analysis and updating of fatigue-induced sequential failures. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2012. Available from: http://hdl.handle.net/2142/30920

25. Hubbard, Sean. Stability enhancement of a transonic wing using a passive nonlinear energy sink.

Degree: PhD, 4048, 2014, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/50731

► This study examined the use of targeted energy transfer (TET) as a mechanism for passive mitigation of transonic aeroelastic instabilities of a wind-tunnel model wing.… (more)

▼ This study examined the use of targeted energy transfer (TET) as a mechanism for passive mitigation of transonic aeroelastic instabilities of a wind-tunnel model wing. Medium- and high-fidelity computational aeroelastic models were used to study the transonic aeroelastic instabilities of the wing and to design a nonlinear energy sink (NES) to enhance stability. Several flutter-suppression mechanisms were identified and it was demonstrated that a properly designed NES can increase the dynamic pressure at flutter by 15% in the transonic dip. Furthermore, it was shown that only one of the suppression mechanisms is robust enough to survive for a wide variety of initial conditions. Based on an effective NES design identified in the computational aeroelastic study, a prototype winglet-mounted NES was designed and built. Computational aeroelastic analysis of the wing, modeled with the winglet and NES using experimentally identified parameters, showed that the prototype improves aeroelastic stability, but external housings for the NES – like the winglet – must be carefully designed to avoid destabilizing effects. To study how the NES affects the dynamics of the wing, a series of experimental and computational ground vibration tests of the wing were performed. They showed that the NES has a profound effect on the second bending mode of the wing, even for small wingtip oscillations. This is a strong indication that the prototype NES will be effective in wind-tunnel tests, because the frequency of the second bending mode is within the range of experimental and computational flutter frequencies of the wing. The final part of this work examined some of the challenges associated with algorithm-based design and optimization of an NES for aeroelastic stabilization. Performance metrics were proposed and robust methods by which to evaluate them were developed. The performance metrics and methods were tested by using a multi-objective genetic algorithm to seek effective NES designs. Analysis of the resulting designs and their performance showed that it is possible to identify the nature of aeroelastic responses and quantify the performance of an NES using simple metrics, but more than one is required to do this effectively. Furthermore, the demonstration showed that optimization algorithms can be used with the proposed performance metrics to design effective NESs. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Bergman%2C%20Lawrence%20A.%22%29&pagesize-30">Bergman, Lawrence A. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Vakakis%2C%20Alexander%20F.%22%29&pagesize-30">Vakakis, Alexander F. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Bergman%2C%20Lawrence%20A.%22%29&pagesize-30">Bergman, Lawrence A. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Vakakis%2C%20Alexander%20F.%22%29&pagesize-30">Vakakis, Alexander F. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22McFarland%2C%20Donald%20M.%22%29&pagesize-30">McFarland, Donald M. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member).

Subjects/Keywords: Targeted Energy Transfer; Nonlinear Energy Sink; Computational Transonic Aeroelasticity

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APA (6^th Edition):

Hubbard, S. (2014). Stability enhancement of a transonic wing using a passive nonlinear energy sink. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/50731

Chicago Manual of Style (16^th Edition):

Hubbard, Sean. “Stability enhancement of a transonic wing using a passive nonlinear energy sink.” 2014. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/50731.

MLA Handbook (7^th Edition):

Hubbard, Sean. “Stability enhancement of a transonic wing using a passive nonlinear energy sink.” 2014. Web. 16 Jan 2021.

Vancouver:

Hubbard S. Stability enhancement of a transonic wing using a passive nonlinear energy sink. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2014. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/50731.

Council of Science Editors:

Hubbard S. Stability enhancement of a transonic wing using a passive nonlinear energy sink. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2014. Available from: http://hdl.handle.net/2142/50731

University of Illinois – Urbana-Champaign

26. Le, Chau H. Developments in topology and shape optimization.

Degree: PhD, 0106, 2010, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/16064

► Our contribution consists of three parts: a gradient-based parameter-free shape optimization method; a stress-constrained topology optimization; and a wave tailoring topology optimization. In shape optimization,… (more)

▼ Our contribution consists of three parts: a gradient-based parameter-free shape optimization method; a stress-constrained topology optimization; and a wave tailoring topology optimization. In shape optimization, the independent node movement approach, wherein finite element node coordinates are used directly as design variables, allows the most freedom for shape change and avoids the time-consuming parameterization process. However, this approach lacks length scale control that is necessary to ensure a well-posed shape optimization problem and avoid numerical instability. Motivated by the success of filtering techniques that impose minimum length scales in topology optimization, we introduce a consistent filtering scheme to provide length scale control and thereby ensure smoothness in shape optimization while preserving the advantages of the independent node movement approach. In topology optimization we propose an effective algorithm to incorporate local stress constraints. To generate a well-posed problem we use the restriction method whereby we utilize a density filter for length scale control. The solid isotropic material with penalization (SIMP) is incorporated to generate black-and-white designs. To resolve the stress singularity phenomenon, we introduce a SIMP-motivated stress definition and a global/regional stress measure combined with an adaptive normalization scheme to control the local stress level. Lastly, we apply topology optimization to tailor the stress wave propagation in a two-phase composite plate. To generate a well-posed topology optimization problem we use the relaxation approach which requires homogenization theory to relate the macroscopic material properties to the microstructure, here a sequentially ranked laminate. We introduce an algorithm whereby the laminate volume fractions and orientations are optimized at each material point. To resolve numerical instabilities associated with the dynamic simulation and constrained optimization problem, we filter the laminate parameters. This also has the effect of generating smoothly varying microstructures. Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Tortorelli%2C%20Daniel%20A.%22%29&pagesize-30">Tortorelli, Daniel A. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Duarte%2C%20C.%20Armando%22%29&pagesize-30">Duarte, C. Armando (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Tortorelli%2C%20Daniel%20A.%22%29&pagesize-30">Tortorelli, Daniel A. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Ha%2C%20Christopher%22%29&pagesize-30">Ha, Christopher (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Geubelle%2C%20Philippe%20H.%22%29&pagesize-30">Geubelle, Philippe H. (committee member).

Subjects/Keywords: topology optimization; shape optimization; material design; homogenization; transient optimization

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

APA (6^th Edition):

Le, C. H. (2010). Developments in topology and shape optimization. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/16064

Chicago Manual of Style (16^th Edition):

Le, Chau H. “Developments in topology and shape optimization.” 2010. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/16064.

MLA Handbook (7^th Edition):

Le, Chau H. “Developments in topology and shape optimization.” 2010. Web. 16 Jan 2021.

Vancouver:

Le CH. Developments in topology and shape optimization. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2010. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/16064.

Council of Science Editors:

Le CH. Developments in topology and shape optimization. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2010. Available from: http://hdl.handle.net/2142/16064

University of Illinois – Urbana-Champaign

27. Kim, Jun Hee. Hybrid mathematical and informational modeling of beam-to-column connections.

Degree: PhD, 0106, 2010, University of Illinois – Urbana-Champaign

URL: http://hdl.handle.net/2142/16075

► The analysis of steel and composite frames has traditionally been carried out by idealizing beam-to-column connections as either rigid or pinned. Although some advanced analysis… (more)

▼ The analysis of steel and composite frames has traditionally been carried out by idealizing beam-to-column connections as either rigid or pinned. Although some advanced analysis methods have been proposed to account for semi-rigid connections, the performance of these methods strongly depends on the proper modeling of connection behavior. The primary challenge of modeling beam-to-column connections is their inelastic response and continuously varying stiffness, strength, and ductility. In this dissertation, two distinct approaches—mathematical models and informational models—are proposed to account for the complex hysteretic behavior of beam-to-column connections. The performance of the two approaches is examined and is then followed by a discussion of their merits and deficiencies. To capitalize on the merits of both mathematical and informational representations, a new approach, a hybrid modeling framework, is developed and demonstrated through modeling beam-to-column connections. Component-based modeling is a compromise spanning two extremes in the field of mathematical modeling: simplified global models and finite element models. In the component-based modeling of angle connections, the five critical components of excessive deformation are identified. Constitutive relationships of angles, column panel zones, and contact between angles and column flanges, are derived by using only material and geometric properties and theoretical mechanics considerations. Those of slip and bolt hole ovalization are simplified by empirically-suggested mathematical representation and expert opinions. A mathematical model is then assembled as a macro-element by combining rigid bars and springs that represent the constitutive relationship of components. Lastly, the moment-rotation curves of the mathematical models are compared with those of experimental tests. In the case of a top-and-seat angle connection with double web angles, a pinched hysteretic response is predicted quite well by complete mechanical models, which take advantage of only material and geometric properties. On the other hand, to exhibit the highly pinched behavior of a top-and-seat angle connection without web angles, a mathematical model requires components of slip and bolt hole ovalization, which are more amenable to informational modeling. An alternative method is informational modeling, which constitutes a fundamental shift from mathematical equations to data that contain the required information about underlying mechanics. The information is extracted from observed data and stored in neural networks. Two different training data sets, analytically-generated and experimental data, are tested to examine the performance of informational models. Both informational models show acceptable agreement with the moment-rotation curves of the experiments. Adding a degradation parameter improves the informational models when modeling highly pinched hysteretic behavior. However, informational models cannot represent the contribution of individual components and therefore… Advisors/Committee Members: Champaign%22%20%2Bcontributor%3A%28%22Elnashai%2C%20Amr%20S.%22%29&pagesize-30">Elnashai, Amr S. (advisor), Champaign%22%20%2Bcontributor%3A%28%22Ghaboussi%2C%20Jamshid%22%29&pagesize-30">Ghaboussi, Jamshid (advisor), Champaign%22%20%2Bcontributor%3A%28%22Elnashai%2C%20Amr%20S.%22%29&pagesize-30">Elnashai, Amr S. (Committee Chair), Champaign%22%20%2Bcontributor%3A%28%22Ghaboussi%2C%20Jamshid%22%29&pagesize-30">Ghaboussi, Jamshid (committee member), Champaign%22%20%2Bcontributor%3A%28%22Hashash%2C%20Youssef%20M.%22%29&pagesize-30">Hashash, Youssef M. (committee member), Champaign%22%20%2Bcontributor%3A%28%22Masud%2C%20Arif%22%29&pagesize-30">Masud, Arif (committee member), Champaign%22%20%2Bcontributor%3A%28%22Song%2C%20Junho%22%29&pagesize-30">Song, Junho (committee member).

Subjects/Keywords: Hybrid modeling; mathematical modeling; informational modeling; neural-network; hysteretic behavior; beam-to-column connection

Record Details Similar Records Cite « Share

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

APA (6^th Edition):

Kim, J. H. (2010). Hybrid mathematical and informational modeling of beam-to-column connections. (Doctoral Dissertation). University of Illinois – Urbana-Champaign. Retrieved from http://hdl.handle.net/2142/16075

Chicago Manual of Style (16^th Edition):

Kim, Jun Hee. “Hybrid mathematical and informational modeling of beam-to-column connections.” 2010. Doctoral Dissertation, University of Illinois – Urbana-Champaign. Accessed January 16, 2021. http://hdl.handle.net/2142/16075.

MLA Handbook (7^th Edition):

Kim, Jun Hee. “Hybrid mathematical and informational modeling of beam-to-column connections.” 2010. Web. 16 Jan 2021.

Vancouver:

Kim JH. Hybrid mathematical and informational modeling of beam-to-column connections. [Internet] [Doctoral dissertation]. University of Illinois – Urbana-Champaign; 2010. [cited 2021 Jan 16]. Available from: http://hdl.handle.net/2142/16075.

Council of Science Editors:

Kim JH. Hybrid mathematical and informational modeling of beam-to-column connections. [Doctoral Dissertation]. University of Illinois – Urbana-Champaign; 2010. Available from: http://hdl.handle.net/2142/16075

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