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Friction And Heat Transfer Modeling Of The Tool And Workpiece Interface In Friction Stir Welding Of Aa 6061-T6 For Improved Simulation Accuracy, Ryan Melander
Theses and Dissertations
Friction stir welding (FSW) is a solid-state joining process that offers advantages over traditional fusion welding. The amount of heat generated during a FSW process greatly influences the final properties of the weld. The heat is generated through two main mechanisms: friction and plastic deformation, with friction being the larger contributor in a FSW process. There is a need to develop better predictive models of the heat generation and heat transfer in FSW. Almost all models seen in the literature validate temperature predictions on only one side of the tool/workpiece interface, thus ignoring possible inaccuracy that comes from incorrect partitioning …
U-Splines: Splines Over Unstructured Meshes, Steven K. Schmidt
U-Splines: Splines Over Unstructured Meshes, Steven K. Schmidt
Theses and Dissertations
U-splines are a novel approach to the construction of a spline basis for representing smooth objects in Computer-Aided Design (CAD) and Computer-Aided Engineering (CAE). A spline is a piecewise-defined function that satisfies continuity constraints between adjacent cells in a mesh. U-splines differ from existing spline constructions, such as Non-Uniform Rational B-splines (NURBS), subdivision surfaces, T-splines, and hierarchical B-splines, in that they can accommodate local variation in cell size, polynomial degree, and smoothness simultaneously over more varied mesh configurations. Mixed cell types (e.g., triangle and tetrahedron and quadrilateral and hexahedral cells in the same mesh) and T-junctions are also supported. The …
Spline-Based Contact: Algorithms And Applications, Pulama Bhattacharya
Spline-Based Contact: Algorithms And Applications, Pulama Bhattacharya
Theses and Dissertations
Contact is one of the most challenging nonlinearities to solve in solid mechanics. In traditional linear finite element analysis, the contact surface is only C^0 continuous, as a result, the normal to the contact surface is not continuous. The normal contact force is directed along the normal in the direction of the contact surface, and therefore, the contact force is discontinuous. This issue is tackled in linear finite element analysis using various surface smoothing techniques, however, a better solution is to use isogeometric analysis where the solution space is spanned by smooth spline basis functions. Unfortunately, spline-based isogeometric contact analysis …
Linear And Nonlinear Dimensionality-Reduction-Based Surrogate Models For Real-Time Design Space Exploration Of Structural Responses, Gregory David Bird
Linear And Nonlinear Dimensionality-Reduction-Based Surrogate Models For Real-Time Design Space Exploration Of Structural Responses, Gregory David Bird
Theses and Dissertations
Design space exploration (DSE) is a tool used to evaluate and compare designs as part of the design selection process. While evaluating every possible design in a design space is infeasible, understanding design behavior and response throughout the design space may be accomplished by evaluating a subset of designs and interpolating between them using surrogate models. Surrogate modeling is a technique that uses low-cost calculations to approximate the outcome of more computationally expensive calculations or analyses, such as finite element analysis (FEA). While surrogates make quick predictions, accuracy is not guaranteed and must be considered. This research addressed the need …
Characterization And Modeling Of The Martensite Transformation In Advanced High-Strength Steels, Stephen Roy Cluff
Characterization And Modeling Of The Martensite Transformation In Advanced High-Strength Steels, Stephen Roy Cluff
Theses and Dissertations
Multiple studies on the microstructures of advanced high-strength steels are presented here that seek to add to the already substantial body of knowledge on martensite in steel. These studies seek to gain additional insight into the role that the martensite transformation has on the observed mechanical properties of modern steels. Crystallographic Reconstruction of Parent Austenite Twin Boundaries in a Lath Martensitic Steel The study of post-transformation microstructures and their properties can be greatly enhanced by studying their dependence on the grain boundary content of parent microstructures. Recent work has extended the crystallographic reconstruction of parent austenite in steels to include …
Predicting Hardness Of Friction Stir Processed 304l Stainless Steel Using A Finite Element Model And A Random Forest Algorithm, Tyler Alan Mathis
Predicting Hardness Of Friction Stir Processed 304l Stainless Steel Using A Finite Element Model And A Random Forest Algorithm, Tyler Alan Mathis
Theses and Dissertations
Friction stir welding is an advanced welding process that is being investigated for use in many different industries. One area that has been investigated for its application is in healing critical nuclear reactor components that are developing cracks. However, friction stir welding is a complicated process and it is difficult to predict what the final properties of a set of welding parameters will be. This thesis sets forth a method using finite element analysis and a random forest model to accurately predict hardness in the welding nugget after processing. The finite element analysis code used and ALE formulation that enabled …
Application And Evaluation Of Full-Field Surrogate Models In Engineering Design Space Exploration, Christopher Murray Thelin
Application And Evaluation Of Full-Field Surrogate Models In Engineering Design Space Exploration, Christopher Murray Thelin
Theses and Dissertations
When designing an engineering part, better decisions are made by exploring the entire space of design variations. This design space exploration (DSE) may be accomplished manually or via optimization. In engineering, evaluating a design during DSE often consists of running expensive simulations, such as finite element analysis (FEA) in order to understand the structural response to design changes. The computational cost of these simulations can make thorough DSE infeasible, and only a relatively small subset of the designs are explored. Surrogate models have been used to make cheap predictions of certain simulation results. Commonly, these models only predict single values …
Parametric Study On Multi-Story, Partially Grouted, Perforated, Masonry Shear Walls By Finite Element Analysis, Kyle Henry Chavez
Parametric Study On Multi-Story, Partially Grouted, Perforated, Masonry Shear Walls By Finite Element Analysis, Kyle Henry Chavez
Theses and Dissertations
In this study, parameters related to material properties, geometry, and external stimuli were examined individually to determine their influence on multi-story, partially grouted, perforated (openings), masonry shear walls using a finite element software FormWorks. The parameters studied were: the strength of grouted masonry prisms f'm,grouted; the strength of un-grouted (hollow) masonry prisms f'm,ungrouted; the ratio of mortar shear strength to masonry compressive strength; vertical and horizontal reinforcement ratios in terms of size and spacing of reinforcement; axial load; aspect ratio; and openings that were vertically and horizontally altered. To perform this study, finite element models were …
Parametric Study On Multi-Story, Partially Grouted, Perforated, Masonry Shear Walls By Finite Element Analysis, Kyle Henry Chavez
Parametric Study On Multi-Story, Partially Grouted, Perforated, Masonry Shear Walls By Finite Element Analysis, Kyle Henry Chavez
Theses and Dissertations
In this study, parameters related to material properties, geometry, and external stimuli were examined individually to determine their influence on multi-story, partially grouted, perforated (openings), masonry shear walls using a finite element software FormWorks. The parameters studied were: the strength of grouted masonry prisms f<&trade>m,grouted; the strength of un-grouted (hollow) masonry prisms f<&trade>m,ungrouted; the ratio of mortar shear strength to masonry compressive strength; vertical and horizontal reinforcement ratios in terms of size and spacing of reinforcement; axial load; aspect ratio; and openings that were vertically and horizontally altered. To perform this study, finite element models were validated against …
Finite Element Modeling Of Shallowly Embedded Connections To Characterize Rotational Stiffness, Trevor Alexander Jones
Finite Element Modeling Of Shallowly Embedded Connections To Characterize Rotational Stiffness, Trevor Alexander Jones
Theses and Dissertations
Finite element models were created in Abaqus 6.14 to characterize the rotational stiffness of shallowly embedded column-foundation connections. Scripts were programmed to automate the model generation process and allow study of multiple independent variables, including embedment length, column size, baseplate geometry, concrete modulus, column orientation, cantilever height, and applied axial load. Three different connection types were investigated: a tied or one part model; a contact-based model; and a cohesive-zone based model. Cohesive-zone modeling was found to give the most accurate results. Agreement with previous experimental data was obtained to within 27%. Baseplate geometry was found to affect connection stiffness significantly, …
Numerical Analysis Of Passive Force On Skewed Bridge Abutments, Zifan Guo
Numerical Analysis Of Passive Force On Skewed Bridge Abutments, Zifan Guo
Theses and Dissertations
Accounting for seismic forces and thermal expansion in bridge design requires an accurate passive force-deflection relationship for the abutment wall. Current design codes make no allowance for skew effects on passive force; however, large scale field tests indicate that there is a substantial reduction in peak passive force as skew angle increases. A reduction in passive force also reduces the transverse shear resistance on the abutment. The purpose of this study is to validate three-dimensional model using PLAXIS 3D, against large scale test results performed at Brigham Young University and to develop a set of calibrated finite element models. The …
Ligament Model Fidelity In Finite Element Analysis Of The Human Lumbar Spine, Mitchell Scott Hortin
Ligament Model Fidelity In Finite Element Analysis Of The Human Lumbar Spine, Mitchell Scott Hortin
Theses and Dissertations
The purpose of this project is to quantify the effects of increasing spinal ligament fidelity on the mechanics of the human lumbar spine using finite element analysis (FEA). In support of this goal, a material characterization study was completed to provide anisotropic, nonlinear material parameters for the human anterior longitudinal ligament. (ALL). Cadaveric samples of the human ALL were tested using a punch test technique. Multi- axial force-deformation data were gathered and fit to a commonly used transversely isotropic material model using an FEA system identification routine. The resulting material parameters produced a curve that correlated well with the experimental …
Modeling Stokes Flow Using Hierarchical Structure-Preserving B-Splines, Kendrick Monroe Shepherd
Modeling Stokes Flow Using Hierarchical Structure-Preserving B-Splines, Kendrick Monroe Shepherd
Theses and Dissertations
A new spline space, the hierarchical structure-preserving B-spline space, is introduced and implemented in the analysis of Stokes flow. The space, when properly constrained, is shown to be stable and to have at least optimal convergence rates in the velocity field and suboptimal convergence rates in the pressure field. However, results show that superoptimal convergence can often be expected in the pressure field, likely due to error reduction in the velocity field. Like other hierarchical spline spaces, these splines are shown to greatly increase accuracy and to drastically lower computation times for analyses on domains whose solution fields have singularities …
Shear-Dominated Bending Behavior Of Carbon/Epoxy Composite Lattice Isobeam Structures, Kirsten Bramall Hinds
Shear-Dominated Bending Behavior Of Carbon/Epoxy Composite Lattice Isobeam Structures, Kirsten Bramall Hinds
Theses and Dissertations
Composite lattice structures known as the IsoBeam™ made with unidirectional carbon/epoxy were manufactured and tested in shear-dominated bending. The manufacturing process consisted of placing tows of carbon fiber pre-impregnated with epoxy resin onto a pin-type mandrel to create members with interwoven joints. The members were consolidated with a half spiral aramid sleeve. The IsoBeam structure consists of two main types of members: longitudinal and diagonal members measuring nominally 0.4 in. (10.2 mm) and 0.2 in. (5.1 mm) in diameter, respectively. The hand-manufactured specimens measured nominally 6 in. (152.4 mm) high by 3 in. (76.2 mm) wide by 2 ft (0.61 …
Developing An Architecture Framework For Cloud-Based, Multi-User, Finite Element Pre-Processing, Jared Calvin Briggs
Developing An Architecture Framework For Cloud-Based, Multi-User, Finite Element Pre-Processing, Jared Calvin Briggs
Theses and Dissertations
This research proposes an architecture for a cloud-based, multi-user FEA pre-processing system, where multiple engineers can access and operate on the same model in a parallel environment. A prototype is discussed and tested, the results of which show that a multi-user preprocessor, where all computing is done on a central server that is hosted on a high performance system, provides significant benefits to the analysis team. These benefits include a shortened preprocessing time, and potentially higher-quality models.
Design Exploration And Analysis Of Carbon-Infiltrated Carbon Nanotube Vascular Stents, Darrell John Skousen
Design Exploration And Analysis Of Carbon-Infiltrated Carbon Nanotube Vascular Stents, Darrell John Skousen
Theses and Dissertations
The purpose of this research was to design, develop, and test coronary stent designs composed of carbon-infiltrated carbon nanotubes (CI-CNTs). Coronary stents currently have two major complications: restenosis and thrombosis. CI-CNT stents have potential to address both of these issues, and therefore may provide improved clinical outcomes. CI-CNT stent geometry is patterned using high-resolution photolithography that provide advantages in design possibilities.To develop a coronary stent, a standard design process was followed including: background, design specifications, concept generation, development, analysis, and testing. Background research was first completed and general design specifications for coronary stent performance were compiled. Multiple design concepts were …
Real-Time Visualization Of Finite Element Models Using Surrogate Modeling Methods, Ryan C. Heap
Real-Time Visualization Of Finite Element Models Using Surrogate Modeling Methods, Ryan C. Heap
Theses and Dissertations
Finite element analysis (FEA) software is used to obtain linear and non-linear solutions to one, two, and three-dimensional (3-D) geometric problems that will see a particular load and constraint case when put into service. Parametric FEA models are commonly used in iterative design processes in order to obtain an optimum model given a set of loads, constraints, objectives, and design parameters to vary. In some instances it is desirable for a designer to obtain some intuition about how changes in design parameters can affect the FEA solution of interest, before simply sending the model through the optimization loop. This could …
The Biomechanical Implications Of An Intrinsic Decompressive Pre-Load On A Posterior Dynamic Stabilization System, Jeffrey Ellis Harris
The Biomechanical Implications Of An Intrinsic Decompressive Pre-Load On A Posterior Dynamic Stabilization System, Jeffrey Ellis Harris
Theses and Dissertations
The purpose of this research was to investigate the influence of applying an intrinsic decompressive pre-load to a particular dynamic stabilization device on the biomechanical response of the lumbar spine. The FlexSPAR, which supports this ability, was used as a test case. A finite element model of a full lumbar spine was developed and validated against experimental data, and tested in the primary modes of spinal motion. The model was used to compare five lumbar spine test cases: healthy, degenerate, implanted with a pre-loaded device, implanted with a device without a pre-load, and implanted with rigid fixators. Results indicated that …
Biomechanical Implications Of Lumbar Spinal Ligament Transectiona Finite Element Study, Gregory Allen Von Forell
Biomechanical Implications Of Lumbar Spinal Ligament Transectiona Finite Element Study, Gregory Allen Von Forell
Theses and Dissertations
The purpose of this work was to determine the possible effects of isolated spinal ligament transection on the biomechanics of the lumbar spine. A finite element model of a lumbar spine was developed and validated against experimental data. The model was tested in the primary modes of spinal motion in the intact condition, followed by comparative analysis of isolated removal of each spinal ligament. Results showed that stress increased in the remaining ligaments once a ligament was removed, potentially leading to ligament damage. Results also showed changes in bone remodeling "stimulus" which could lead to changes in bone density. Isolated …
Using Buckling-Restrained Braces In Eccentric Configurations, Gary S. Prinz
Using Buckling-Restrained Braces In Eccentric Configurations, Gary S. Prinz
Theses and Dissertations
Ductile braced frames are often used to resist lateral earthquake loads in steel buildings; however the presence of a brace element can sometimes interfere with architectural features. One common type of ductile braced frame system sometimes used to accommodate architectural features is the eccentrically braced frame (EBF). In order to dissipate seismic forces, EBF beam regions (called links) must sustain large inelastic deformations. EBF links with column connections must transmit large moments and shear forces to facilitate link rotation. Experiments have shown that welded link-to-column connections tend to fracture in the link flange prior to large link rotations. This study …
Isogeometric Finite Element Analysis Using T-Splines, Jingang Li
Isogeometric Finite Element Analysis Using T-Splines, Jingang Li
Theses and Dissertations
Non-uniform rational B-splines (NURBS) methodology is presented, on which the isogeometric analysis is based. T-splines are also introduced as a surface design methodology, which are a generalization of NURBS and permit local refinement. Isogeometric analysis using NURBS and T-splines are applied separately to a structural mechanics problem. The results are compared with the closed-form solution. The desirable performance of isogeometric analysis using T-splines on engineering analysis is demonstrated.
Parametric Optimization Design System For A Fluid Domain Assembly, Matthew Jackson Fisher
Parametric Optimization Design System For A Fluid Domain Assembly, Matthew Jackson Fisher
Theses and Dissertations
Automated solid modeling, integrated with computational fluid dynamics (CFD) and optimization of a 3D jet turbine engine has never been accomplished. This is due mainly to the computational power required, and the lack of associative parametric modeling tools and techniques necessary to adjust and optimize the design. As an example, the fluid domain of a simple household fan with three blades may contain 500,000 elements per blade passage. Therefore, a complete turbine engine that includes many stages, with sets of thirty or more blades each, will have hundreds of millions of elements. The fluid domains associated with each blade creates …
Rectification Of 2-D To 3-D Finite Element Analysis In Buried Concrete Arches Under Discrete Loading, Adam D. Aagard
Rectification Of 2-D To 3-D Finite Element Analysis In Buried Concrete Arches Under Discrete Loading, Adam D. Aagard
Theses and Dissertations
Construction of tunnels and small- to medium-span bridges is a $12 billion per year industry in the United States, with a significant portion going into buried arch structures. Notwithstanding such expenditure, modern arch design and construction, in many cases, is highly conservative. This is because the closed-form solutions used by most designers today do not correctly account for soil-structure interaction. In fact, soil-structure interaction makes a closed form solution impossible. With the advent of high power computers in recent years, some designers have turned to finite element (FE)modeling as the main vehicle of analysis. Such numerical procedures provide an accurate …
Interior Node Projection Techniques In Sweeping Algorithms, Michael Andrew Scott
Interior Node Projection Techniques In Sweeping Algorithms, Michael Andrew Scott
Theses and Dissertations
The enhancement of node projection techniques in sweeping is the subject of this thesis. Sweeping is a method used to produce all-hexahedral finite element meshes on certain classes of geometry. The placement of nodes in the interior of the geometry during the sweeping process remains a difficult problem. This thesis presents advancements in this area which improve the speed of the algorithm and the resulting element quality. A comparison of existing projection methods was performed. The existing Faceted projection sweeping method was extended to be applicable to more general classes of sweepable geometry. This comparison and extension of node projection …
Development Of Commercial Applications For Recycled Plastics Using Finite Element Analysis, Nanjunda Narasimhamurthy
Development Of Commercial Applications For Recycled Plastics Using Finite Element Analysis, Nanjunda Narasimhamurthy
Theses and Dissertations
This thesis investigates the suitability of thermo-kinetically recycled plastics for use in commercial product applications using finite element analysis and statistics. Different recycled material blends were tested and evaluated for their use in commercial product applications. There are six different blends of thermo-kinetically recycled plastics used for testing and CATIA is used for finite element analysis. The different types of thermo-kinetically recycled plastics blends are: pop bottles made of PolyethyleneTeraphthalate (PET), milk jugs made of High-Density Polyethylene (HDPE), Vinyl seats made of Poly Vinyl Chloride (PVC) and small amount of Polypropylene (PP) and Urethane, electronic scrap made of engineering resins …
Analytical Modeling Of Wood-Frame Shear Walls And Diaphragms, Johnn Paul Judd
Analytical Modeling Of Wood-Frame Shear Walls And Diaphragms, Johnn Paul Judd
Theses and Dissertations
Analytical models of wood-frame shear walls and diaphragms for use in monotonic, quasi-static (cyclic), and dynamic analyses are developed in this thesis. A new analytical model is developed to accurately represent connections between sheathing panels and wood framing members (sheathing-to-framing connections) in structural analysis computer programs. This new model represents sheathing–to–framing connections using an oriented pair of nonlinear springs. Unlike previous models, the new analytical model for sheathing-to-framing connections is suitable for both monotonic, cyclic, or dynamic analyses. Moreover, the new model does not need to be scaled or adjusted. The new analytical model may be implemented in a general …