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Title: ANALYSIS OF DAMPING LAYER TREATMENTS FOR PLATES USING EXPERIMENTALLY DETERMINED MODE SHAPES.
Creator: JAISING, VINOD R., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: A method of analysis is presented to determine the natural frequencies and loss factors of a plate covered with viscoelastic coating, using experimentally obtained mode shapes. The mode shapes for a square plate clamped on all edges are determined using an HP 5423 A Structural Dynamics Analyzer. A computer program, based on the method of analysis, is developed to determine the natural frequencies and loss factors of a rectangular plate covered with viscoelastic material, and clamped on all...
Show moreA method of analysis is presented to determine the natural frequencies and loss factors of a plate covered with viscoelastic coating, using experimentally obtained mode shapes. The mode shapes for a square plate clamped on all edges are determined using an HP 5423 A Structural Dynamics Analyzer. A computer program, based on the method of analysis, is developed to determine the natural frequencies and loss factors of a rectangular plate covered with viscoelastic material, and clamped on all edges. It was found that, for a fully coated plate, and for a mesh with twenty-five mesh points, the error in the fundamental frequency was approximately 5 percent. A comparison between the mode shapes for the bare plate and for the fully coated plate revealed no significant difference. It was also found that increasing the number of measurement points would not significantly improve the results.
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Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14050
Subject Headings: Plates (Engineering)--Vibration, Damping (Mechanics)
Format: Document (PDF)

Title: EXPERIMENTAL DETERMINATION OF NATURAL FREQUENCIES AND LOSS FACTORS OF A CLAMPED RECTANGULAR PLATE WITH PARTIAL CONSTRAINED LAYER DAMPING TREATMENTS.
Creator: BHAT, RAJENDRA AGHUT., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: An experimental investigation to determine the effectiveness of partial constrained layer damping treatments for a clamped rectangular plate is described. The impulse testing technique was used with a Hewlett Packard '5423A structural Dynamics Analyzer' to determine modal parameters of the first five flexural modes. The results obtained are compared with theoretical results and they are in agreement. The results indicate that partial constrained layer damping treatments, if properly used, can...
Show moreAn experimental investigation to determine the effectiveness of partial constrained layer damping treatments for a clamped rectangular plate is described. The impulse testing technique was used with a Hewlett Packard '5423A structural Dynamics Analyzer' to determine modal parameters of the first five flexural modes. The results obtained are compared with theoretical results and they are in agreement. The results indicate that partial constrained layer damping treatments, if properly used, can be more effective than complete treatments.
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Date Issued: 1983
PURL: http://purl.flvc.org/fcla/dt/14188
Subject Headings: Plates (Engineering)--Vibration, Damping (Mechanics)
Format: Document (PDF)

Title: Weight function approach for stress analysis of the surface crack in a finite plate subjected to nonuniform stress fields.
Creator: Jani, Jayant Shivkumar., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The effects of various nonuniform stress fields on the stress intensity factors for the semi-elliptic surface crack (three-dimensional problem) in a finite plate are determined using the weight function approach. The formulation satisfies the linear elastic fracture mechanics criteria and the principle of conservation of energy. Based on the knowledge of stress intensity solutions for the reference load/stress system, the expression for the crack opening displacement function for the surface...
Show moreThe effects of various nonuniform stress fields on the stress intensity factors for the semi-elliptic surface crack (three-dimensional problem) in a finite plate are determined using the weight function approach. The formulation satisfies the linear elastic fracture mechanics criteria and the principle of conservation of energy. Based on the knowledge of stress intensity solutions for the reference load/stress system, the expression for the crack opening displacement function for the surface crack is derived. Using the crack opening displacement function and the reference stress intensity factor, the three-dimensional weight functions and subsequently the stress intensity solutions for the surface crack subjected to nonuniform stress fields are derived. The formulation is then applied to determine the effects of linear, quadratic, cubic, and pure bending stress fields on the stress intensity factor for the surface crack in a finite plate. In the initial stage of the study a two-dimensional problem of an edge-crack emanating from the weld-toe in a T-joint is considered. The effect of parameters such as plate thickness, weld-toe radius, and weld-flank angle on the stress intensity factor for an edge-crack is studied. Finite element analyses of the welded T-joints are performed to study the effects of plate thickness, weld-toe radius and the weld-flank angle on the local stress distribution. The ratio of plate thickness to weld-toe radius ranging from 13.09 to 153.93, and the weld-flank angles of 30, 45, and 60 degrees are considered in the analyses. Based on the results from FEM analyses, a parametric equation for the local stress concentration factor and a polynomial expression for the local stress distribution across the plate thickness are derived using the method of least squares and the polynomial curve-fitting technique.
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Date Issued: 1990
PURL: http://purl.flvc.org/fcla/dt/12254
Subject Headings: Strains and stresses, Plates (Engineering), Fracture mechanics
Format: Document (PDF)

Title: VIBRATION ANALYSIS OF RECTANGULAR PLATES WITH COMPLETE AND PARTIAL CONSTRAINED-LAYER DAMPING TREATMENTS.
Creator: HSU, HONG-YUAN., Florida Atlantic University, Stevens, Karl K.
Abstract/Description: A theoretical analysis for predicting the system loss factors and natural frequencies of rectangular plates with complete and partial constrained-layer damping treatments has been presented. This analysis is based upon an energy approach to the free vibration of plates. Results predicted were compared with those from experiments. Satisfactory agreement has been reached. Both the theoretical and the experimental results presented in this thesis indicate clearly that partial constrained-layer...
Show moreA theoretical analysis for predicting the system loss factors and natural frequencies of rectangular plates with complete and partial constrained-layer damping treatments has been presented. This analysis is based upon an energy approach to the free vibration of plates. Results predicted were compared with those from experiments. Satisfactory agreement has been reached. Both the theoretical and the experimental results presented in this thesis indicate clearly that partial constrained-layer damping treatments can provide effective, or even superior, amounts of damping, and that their use can lead to significant savings in material costs and weight.
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Date Issued: 1983
PURL: http://purl.flvc.org/fcla/dt/14160
Subject Headings: Damping (Mechanics), Vibration, Plates (Engineering)--Vibration
Format: Document (PDF)

Title: A METHOD OF ANALYSIS FOR EVALUATING THE EFFECTIVENESS OF PARTIAL DAMPING LAYER TREATMENTS FOR SQUARE PLATES.
Creator: KUNG, CHUN-HUA., Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: An energy method for predicting the natural frequency and loss factor for square plates with partial and complete coatings is developed. Both simply-supported and edge-fixed bonndary conditions are considered. An impulse testing technique is used to provide an experimental verification of the analysis for the case of an edge-fixed square plate. The analytical and experimental results are in close agreement, and indicate that partial coatings can provide effective damping treatments.
Date Issued: 1981
PURL: http://purl.flvc.org/fcla/dt/14045
Subject Headings: Plates (Engineering)--Vibration, Damping (Mechanics)
Format: Document (PDF)

Title: Influence of Median Grain Size Ratio on the Strength and Liquefaction Potential of Loose Granular Fills.
Creator: Waganaar, Spencer, Sobhan, Khaled, Florida Atlantic University, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: The characterization of silty soils is usually designated by the percentage of silt contained within the soil matrix, along with the soil’s void ratio, which is used to describe the soil’s current state. The use of these parameters to assess a soil’s strength and undrained behavior is limited when finer material is contained within the soil. Therefore, additional parameters must be considered in order to correctly assess the strength and liquefaction potential of silty soils. These additional...
Show moreThe characterization of silty soils is usually designated by the percentage of silt contained within the soil matrix, along with the soil’s void ratio, which is used to describe the soil’s current state. The use of these parameters to assess a soil’s strength and undrained behavior is limited when finer material is contained within the soil. Therefore, additional parameters must be considered in order to correctly assess the strength and liquefaction potential of silty soils. These additional parameters include the skeleton void ratio, equivalent void ratio and granulometric factors. The current research investigates the influence of granulometric parameters, specifically the Median Grain Size Ratio (D50/d50), denoted as μDR (or MDR within graphs and charts), on the strength and liquefaction potential of loose silty sands. A series of undrained monotonic triaxial compression tests (σ3’= 69, 83, and 103 kPa) are performed on reconstituted soil samples, using three different base sand samples and a constant silt material. As a result, three distinct median grain size ratios (μDR = 4.2, 6.75, and 9) were tested with fines content ranging from 0-30% for each μDR. The undrained shear strength at all confining pressures tends to increase with in μDR; beyond 10% fines content there was no noticeable influence of μDR. At any μDR the excess PWP is higher than that of clean sand, when fines content is larger than 5% fines content. The slope of the instability line and phase transformation line are directly affected by the μDR and fines content, with an increase in the instability line and decrease in the phase transformation line with a growing μDR. The results indicate loose granular fills can be designed to be stronger and more resilient under extreme conditions by careful choice of materials in which the μDR>6.75 and the fines content does not exceed 10%.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004639, http://purl.flvc.org/fau/fd/FA00004639
Subject Headings: Slopes (Soil mechanics), Soils., Soil liquefaction., Geotechnical engineering.
Format: Document (PDF)

Title: Buckling of composite cylindrical shells with geometric, thickness and material imperfections.
Creator: Li, Yiwei., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: This dissertation deals with the determination of buckling loads of composite cylindrical shell structures which involve uncertainty either in geometry, namely thickness variation, or in material properties. Systematic research has been carried out, which evolves from the simple isotropic cases to anisotropic cases. Since the initial geometric imperfection has a dominant role in the reduction of those imperfection-sensitive structures such as cylindrical shells, the combined effect of...
Show moreThis dissertation deals with the determination of buckling loads of composite cylindrical shell structures which involve uncertainty either in geometry, namely thickness variation, or in material properties. Systematic research has been carried out, which evolves from the simple isotropic cases to anisotropic cases. Since the initial geometric imperfection has a dominant role in the reduction of those imperfection-sensitive structures such as cylindrical shells, the combined effect of thickness variation and initial imperfection is also investigated in depth. Both analytic and numerical methods are used to derive the solutions to the problems and asymptotic formulas relating the buckling load to the geometric (thickness variation and/or initial imperfection) parameter are established. It is shown that the axisymmetric thickness variation has the most detrimental effect on the buckling load when the modal number of thickness variation is twice as much as that of the classical buckling mode. For the composite shells with uncertainty in material properties, the convex modelling is employed to evaluate the variability of buckling load. Based on the experimental data for the elastic moduli of the composite laminates, the upper and lower bounds of the buckling load are derived, which are numerically substantiated by the results from nonlinear programming. These bounds will be useful in practice and can provide engineers with a better view of the real load-carrying capacity of the composite structure. Finally, the elastic modulus is modeled as a function of coordinates to complete the study on variability of material property so that the result can be obtained to account for the situation where the elastic modulus is different from one place to another in the structure.
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Date Issued: 1996
PURL: http://purl.flvc.org/fcla/dt/12444
Subject Headings: Composite materials, Buckling (Mechanics), Shells (Engineering), Structural dynamics
Format: Document (PDF)

Title: Applications of evolutionary algorithms in mechanical engineering.
Creator: Nelson, Kevin M., Florida Atlantic University, Huang, Ming Z., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Many complex engineering designs have conflicting requirements that must be compromised to effect a successful product. Traditionally, the engineering approach breaks up the complex problem into smaller sub-components in known areas of study. Tradeoffs occur between the conflicting requirements and a sub-optimal design results. A new computational approach based on the evolutionary processes observed in nature is explored in this dissertation. Evolutionary algorithms provide methods to solve...
Show moreMany complex engineering designs have conflicting requirements that must be compromised to effect a successful product. Traditionally, the engineering approach breaks up the complex problem into smaller sub-components in known areas of study. Tradeoffs occur between the conflicting requirements and a sub-optimal design results. A new computational approach based on the evolutionary processes observed in nature is explored in this dissertation. Evolutionary algorithms provide methods to solve complex engineering problems by optimizing the entire system, rather than sub-components of the system. Three standard forms of evolutionary algorithms have been developed: evolutionary programming, genetic algorithms and evolution strategies. Mathematical and algorithmic details are described for each of these methods. In this dissertation, four engineering problems are explored using evolutionary programming and genetic algorithms. Exploiting the inherently parallel nature of evolution, a parallel version of evolutionary programming is developed and implemented on the MasPar MP-1. This parallel version is compared to a serial version of the same algorithm in the solution of a trial set of unimodal and multi-modal functions. The parallel version had significantly improved performance over the serial version of evolutionary programming. An evolutionary programming algorithm is developed for the solution of electronic part placement problems with different assembly devices. The results are compared with previously published results for genetic algorithms and show that evolutionary programming can successfully solve this class of problem using fewer genetic operators. The finite element problem is cast into an optimization problem and an evolutionary programming algorithm is developed to solve 2-D truss problems. A comparison to LU-decomposition showed that evolutionary programming can solve these problems and that it has the capability to solve the more complex nonlinear problems. Finally, ordinary differential equations are discretized using finite difference representation and an objective function is formulated for the application of evolutionary programming and genetic algorithms. Evolutionary programming and genetic algorithms have the benefit of permitting over-constraining a problem to obtain a successful solution. In all of these engineering problems, evolutionary algorithms have been shown to offer a new solution method.
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Date Issued: 1997
PURL: http://purl.flvc.org/fcla/dt/12514
Subject Headings: Mechanical engineering, Genetic algorithms, Evolutionary programming (Computer science)
Format: Document (PDF)

Title: Vibration tailoring of inhomogeneous beams and circular plates.
Creator: Pentaras, Demetris., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The vibrational behavior of inhomogeneous beams and circular plates is studied, utilizing the semi-inverse method developed by I. Elishakoff and extensively discussed in his recent monograph (2005). The main thread of his methodology is that the knowledge of the mode shape is postulated. The candidate mode shapes can be adopted from relevant static, dynamic or buckling problems. In this study, the exact mode shapes are sought as polynomial functions, in the context of vibration tailoring, i.e...
Show moreThe vibrational behavior of inhomogeneous beams and circular plates is studied, utilizing the semi-inverse method developed by I. Elishakoff and extensively discussed in his recent monograph (2005). The main thread of his methodology is that the knowledge of the mode shape is postulated. The candidate mode shapes can be adopted from relevant static, dynamic or buckling problems. In this study, the exact mode shapes are sought as polynomial functions, in the context of vibration tailoring, i.e. designing the structure that possesses the pre-specified value. Apparently for the first time in the literature, several closed-form solutions for vibration tailoring have been derived for vibrating inhomogeneous beams and circular plates. Twelve new closed-form solutions for vibration tailoring have been derived for an inhomogeneous polar orthotropic plate that is either clamped or simply supported around its circumference. Also, the vibration tailoring of a polar orthotropic circular plate with translational spring is analyzed. There is considerable potential of utilizing the developed method for design of functionally graded materials.
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Date Issued: 2006
PURL: http://purl.flvc.org/fcla/dt/13344
Subject Headings: Acoustical engineering, Plates (Engineering)--Vibration--Mathematical models, Buckling (Mechanics), Structural analysis
Format: Document (PDF)

Title: Improving the Mechanical Properties of Nano-Hydroxyapatite.
Creator: Khanal, Suraj P., Leventouri, Theodora, Florida Atlantic University, Charles E. Schmidt College of Science, Department of Physics
Abstract/Description: Hydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and...
Show moreHydroxyapatite (HAp) is an ideal bioactive material that is used in orthopedics. Chemical composition and crystal structure properties of HAp are similar to the natural bone hence it promotes bone growth. However, its mechanical properties of synthetic HAp are not sufficient for major load-bearing bone replacement. The potential of improving the mechanical properties of synthetic hydroxyapatite (HAp) by incorporating carboxyl functionalized single walled carbon nanotubes (CfSWCNT) and polymerized ɛ-caprolactam (nylon) is studied. The fracture toughness, tensile strength, Young’s modulus, stiffness and fracture energy were studied for a series of HAp samples with CfSWCNT concentrations varying from 0 to 1.5 wt. % without, and with nylon addition. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Differential Scanning Calorimetry (DSC) were used to characterize the samples. The fracture toughness and tensile test was performed under the standard protocol of ASTM D5045 and ASTM D638-02a respectively. Reproducible maximum values of (3.60 ± 0.3) MPa.m1/2 for fracture toughness and 65.38 MPa for tensile strength were measured for samples containing 1 wt. % CfSWCNT and nylon. The Young’s modulus, stiffness and fracture energy of the samples are 10.65 GPa, 1482.12 N/mm, and 644 J/m2 respectively. These values are comparable to those of the cortical bone. Further increase of the CfSWCNT content results to a decreased fracture toughness and tensile strength and formation of a secondary phase.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004675, http://purl.flvc.org/fau/fd/FA00004675
Subject Headings: Biomedical engineering -- Materials, Biomedical materials -- Mechanical properties, Nanostructured materials -- Mechanical properties
Format: Document (PDF)

Title: Effects of Granulometric Parameters and Mix Proportions on the Shear Strength of Binary Granular Mixtures.
Creator: Gonzalez Moya, Daniel E., Sobhan, Khaled, Florida Atlantic University, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: Geotechnical engineers are commonly faced with the need to perform ground improvement techniques to achieve the necessary bearing capacity for a project. Some of the most common techniques involve the excavation and replenishment of problematic geomaterial with one of better quality. Common projects, such as road embankments and retaining walls, also require the selection of backfill material. The guidelines for selecting backfill material are typically limited to complying with certain...
Show moreGeotechnical engineers are commonly faced with the need to perform ground improvement techniques to achieve the necessary bearing capacity for a project. Some of the most common techniques involve the excavation and replenishment of problematic geomaterial with one of better quality. Common projects, such as road embankments and retaining walls, also require the selection of backfill material. The guidelines for selecting backfill material are typically limited to complying with certain gradation bands, relative densities and allowable fines content. Round-grained silica sand, and beach sand from Boca Raton, FL, were used to generate a total of 16 binary granular mixtures containing different amounts of finer material, for which a series of direct shear tests were conducted. Based on the experimental results, it may be possible to provide an alternative criteria for selecting backfill material based on granulometric parameters and the amount of finer material.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004714, http://purl.flvc.org/fau/fd/FA00004714
Subject Headings: Continuum mechanics, Geotechnical engineering, Granular materials -- Dynamic testing, Micromechanics -- Mathematical models, Soil liquefaction
Format: Document (PDF)

Title: The acoustic far field of a turbulent boundary layer flow calculated from RANS simulations of the flow.
Creator: Blanc, Jean-Baptiste., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Boundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average Navier-Stokes (RANS) equations. A frequency spectrum is reconstructed using a representation of...
Show moreBoundary layers are regions where turbulence develops easily. In the case where the flow occurs on a surface showing a certain degree of roughness, turbulence eddies will interact with the roughness elements and will produce an acoustic field. This thesis aims at predicting this type of noise with the help of the Computational Fluid Dynamics (CFD) simulation of a wall jet using the Reynolds Average Navier-Stokes (RANS) equations. A frequency spectrum is reconstructed using a representation of the turbulence with uncorrelated sheets of vorticity. Both aerodynamic and acoustic results are compared to experimental measurements of the flow. The CFD simulation of the flow returns consistent results but would benefit from a refinement of the grid. The surface pressure spectrum presents a slope in the high frequencies close to the experimental spectrum. The far field noise spectrum has a 5dB difference to the experiments.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/368611
Subject Headings: Computational fluid dynamics, Turbulence, Mathematical models, Fluid mechanics, Mathematical models, Acoustical engineering
Format: Document (PDF)

Title: Vibration, buckling and impact of carbon nanotubes.
Creator: Pentaras, Demetris., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Natural frequencies of the double and triple-walled carbon nanotubes are determined exactly and approximately for both types. Approximate solutions are found by using Bubnov-Galerkin and Petrov-Galerkin methods. For the first time explicit expressions are obtained for the natural frequencies of double and triple-walled carbon nanotubes for different combinations of boundary conditions. Comparison of the results with recent studies shows that the above methods constitute quick and effective...
Show moreNatural frequencies of the double and triple-walled carbon nanotubes are determined exactly and approximately for both types. Approximate solutions are found by using Bubnov-Galerkin and Petrov-Galerkin methods. For the first time explicit expressions are obtained for the natural frequencies of double and triple-walled carbon nanotubes for different combinations of boundary conditions. Comparison of the results with recent studies shows that the above methods constitute quick and effective alternative techniques to exact solution for studying the vibration properties of carbon nanotubes. The natural frequencies of the clamped-clamped double-walled carbon nanotubes are obtained; exact solution is provided and compared with the solution reported in the literature. In contrast to earlier investigation, an analytical criterion is derived to establish the behavior of the roots of the characteristic equation. Approximate Bubnov-Galerkin solution is also obtained to compare natural frequencies at the lower end of the spectrum. Simplified version of the Bresse-Timoshenko theory that incorporates the shear deformation and the rotary inertia is proposed for free vibration study of double-walled carbon nanotubes. It is demonstrated that the suggested set yields extremely accurate results for the lower spectrum of double-walled carbon nanotube. The natural frequencies of double-walled carbon nanotubes based on simplified versions of Donnell shell theory are also obtained. The buckling behavior of the double-walled carbon nanotubes under various boundary conditions is studied. First, the case of the simply supported double-walled carbon nanotubes at both ends is considered which is amenable to exact solution., Then, approximate methods of Bubnov-Galerkin and Petrov-Galerkin are utilized to check the efficacy of these approximations for the simply supported double-walled carbon nanotubes. Once the extreme accuracy is demonstrated for simply supported conditions, the approximate techniques are applied to two other cases of the boundary conditions, namely to clamped-clamped and simply supported-clamped double-walled carbon nanotubes. For the first time in the literature approximate expression for the buckling loads are reported for these boundary conditions. The dynamic deflection of a single-walled carbon nanotube under impact loading is analyzed by following a recently study reported on the energy absorption capacity of carbon nanotubes under ballistic impact.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/186764
Subject Headings: Nanostructured materials, Buckling (Mechanics), Plates (Engineering), Vibration, Mathematical models, Structural analysis
Format: Document (PDF)

Title: Internal waves on a continental shelf.
Creator: Jagannathan, Arjun., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In this thesis, a 2D CHebyshev spectral domain decomposition method is developed for simulating the generation and propagation of internal waves over a topography. While the problem of stratified flow over topography is by no means a new one, many aspects of internal wave generation and breaking are still poorly understood. This thesis aims to reproduce certain observed features of internal waves by using a Chebyshev collation method in both spatial directions. The numerical model solves the...
Show moreIn this thesis, a 2D CHebyshev spectral domain decomposition method is developed for simulating the generation and propagation of internal waves over a topography. While the problem of stratified flow over topography is by no means a new one, many aspects of internal wave generation and breaking are still poorly understood. This thesis aims to reproduce certain observed features of internal waves by using a Chebyshev collation method in both spatial directions. The numerical model solves the inviscid, incomprehensible, fully non-linear, non-hydrostatic Boussinesq equations in the vorticity-streamfunction formulation. A number of important features of internal waves over topography are captured with the present model, including the onset of wave-breaking at sub-critical Froude numbers, up to the point of overturning of the pycnoclines. Density contours and wave spectra are presented for different combinations of Froude numbers, stratifications and topographic slope.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3358549
Subject Headings: Engineering geology, Mathematical models, Chebyshev polynomials, Fluid dynamics, Continuum mechanics, Spectral theory (Mathematics)
Format: Document (PDF)

Title: A perturbation method for the vibration analysis of beams and plates with free-layer damping treatments.
Creator: Shen, Sueming, Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: The feasibility of using structural modification techniques to determine the effect of added viscoelastic damping treatments on the modal properties of a distinct eigenvalue system and a degenerate system is investigated. Linear perturbation equations for the changes introduced into the system eigenproperties are derived and applied to several examples involving the flexural vibration of beams and square plates with varying degrees of damping treatment. Both large and small perturbations are...
Show moreThe feasibility of using structural modification techniques to determine the effect of added viscoelastic damping treatments on the modal properties of a distinct eigenvalue system and a degenerate system is investigated. Linear perturbation equations for the changes introduced into the system eigenproperties are derived and applied to several examples involving the flexural vibration of beams and square plates with varying degrees of damping treatment. Both large and small perturbations are considered. An FEM code has been developed to compute the dynamic system parameters which are subsequently used in an iterative method to determine the modal properties. The perturbation approach described can accommodate temperature and frequency-dependent material properties, and the procedures involved are illustrated in the examples considered. Results obtained for these examples are compared with those available from closed form or finite element solutions, or from experiments. Excellent agreement of the results of the present method with those of other contemporary methods demonstrates the validity, overall accuracy, efficiency and convergence rate of this technique. The perturbation approach appears to be particularly well suited for systems with temperature and frequency dependent material properties, and for design situations where a number of damping configurations must be investigated.
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Date Issued: 1989
PURL: http://purl.flvc.org/fcla/dt/12239
Subject Headings: Girders--Vibration, Plates (Engineering)--Vibration, Perturbation (Mathematics), Damping (Mechanics)
Format: Document (PDF)

Title: Stability Analysis of Geosynthetic Reinforced MSW Landfill Slopes Considering Effects of Biodegradation and Extreme Wind Loading.
Creator: Pant, Sharmila, Sobhan, Khaled, Florida Atlantic University, College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: A numerical investigation was conducted to evaluate the geotechnical safety and slope stability of Municipal Solid Waste (MSW) landfills, considering the effects of geosynthetic reinforcements, biodegradation of the waste, and associated changes in material properties, and extreme wind force simulating hurricane conditions. Three different landfill slopes, 1:1, 1:2, and 1:3 having the height of 122m and width of 2134m, were analyzed using Limit Equilibrium Method (SLOPE/W) and Finite Element...
Show moreA numerical investigation was conducted to evaluate the geotechnical safety and slope stability of Municipal Solid Waste (MSW) landfills, considering the effects of geosynthetic reinforcements, biodegradation of the waste, and associated changes in material properties, and extreme wind force simulating hurricane conditions. Three different landfill slopes, 1:1, 1:2, and 1:3 having the height of 122m and width of 2134m, were analyzed using Limit Equilibrium Method (SLOPE/W) and Finite Element Modeling (ANSYS). Techniques developed in this study were used to analyze a case history involving a geogrid reinforced mixed landfill expansion located in Austria. It was found that few years after construction of the landfill, there is a significant decrease in the FS due to biodegradation. Extreme wind loading was also found to cause a substantial loss in the FS. The geosynthetic reinforcement increased the slope stability and approximately compensated for the damaging effects of biodegradation and wind loading.
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Date Issued: 2016
PURL: http://purl.flvc.org/fau/fd/FA00004707, http://purl.flvc.org/fau/fd/FA00004707
Subject Headings: Engineering geology -- Mathematical models, Fills (Earthwork), Geogrids -- Performance, Geosynthetics, Reinforced soils, Retaining walls -- Performance, Sanitary landfills, Slopes (Soil mechanics) -- Stability, Soil stabilization, Structural analysis (Engineering)
Format: Document (PDF)

Title: Fire performance of high strength concrete materials and structural concrete.
Creator: Liu, Lixian., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: In recent years, high strength concrete (HSC) is becoming an attractive alternative to traditional normal strength concrete (NSC), and is used in a wide range of applications. With the increased use of HSC, concern has developed regarding the behavior of such concrete in fire. Until now, the fire performance of HSC is not fully understood and more research is needed. Full-scale fire testing is time consuming and expensive, and the real fire scenario is different from the standard fire....
Show moreIn recent years, high strength concrete (HSC) is becoming an attractive alternative to traditional normal strength concrete (NSC), and is used in a wide range of applications. With the increased use of HSC, concern has developed regarding the behavior of such concrete in fire. Until now, the fire performance of HSC is not fully understood and more research is needed. Full-scale fire testing is time consuming and expensive, and the real fire scenario is different from the standard fire. Performance-based assessment methods, including numerical analysis and simplified method, are being accepted in an increasing number of countries. In this dissertation, the fire testing results both of HSC and NSC are presented, performance-based numerical models are developed to study the fire performance of reinforced concrete (RC) members, and simplified calculation methods are proposed to estimate the load capacity of fire-damaged RC columns/beams. A detailed and comprehensive literature review is presented that provides background information on the high temperature behavior of concrete materials and RC members, as well as information on fire performance assessment procedures and objectives. The fire testing results of seven batches of HSC and NSC are presented and discussed. The test results indicated that the post-fire re-curing results in substantial strength and durability recovery, and its extent depends upon the types of concrete, temperature level, and re-curing age. The fire tests also showed that violent explosive reduced the risk of HSC explosive spalling. The surface crack widths were also reduced during the re-curing process, and in most cases, they were found within the maximum limits specified by the American Concrete Institute (ACI) building code., Numerical models are developed herein to investigate the behavior in fire of RC columns and beams. The models have been validated against fire test data available in literature, and used to conduct parametric studies, which focused on the size effect on fire resistance of RC columns, and the effect of concrete cover thickness on fire endurance of RC beams. Simplified calculation methods have been developed to predict the load capacity of fire damaged RC columns/beams. This method is validated by five case studies, including thirty-five RC columns tested by other investigators. The predicted results are compared with the experimental results, and the good agreement indicates the adequacy of the simplified method for practical engineering applications.
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Date Issued: 2009
PURL: http://purl.flvc.org/FAU/369189
Subject Headings: Reinforced concrete, Thermodynamics, Concrete, Effect of temperature on, Heat engineering, High strength concrete, Mechanical properties, Concrete, Permeability, Testing
Format: Document (PDF)

Title: Effect of median grain size ratio on the compaction behavior of binary granular mixes.
Creator: Brenner, Tara Devine., College of Engineering and Computer Science, Department of Civil, Environmental and Geomatics Engineering
Abstract/Description: Optimization of compaction in granular material without the use of traditional ground improvement methods may be possible by optimizing the percentage of finer material and the median grain size ratio in binary soil mixtures. In this study, the median grain size ratio D50/d50 was explored as a fundamental parpmeter affecting the compaction characteristics of binary mixes made from natural sands as opposed to singular measurements such as fines content and mean grain size traditionally used to...
Show moreOptimization of compaction in granular material without the use of traditional ground improvement methods may be possible by optimizing the percentage of finer material and the median grain size ratio in binary soil mixtures. In this study, the median grain size ratio D50/d50 was explored as a fundamental parpmeter affecting the compaction characteristics of binary mixes made from natural sands as opposed to singular measurements such as fines content and mean grain size traditionally used to represent granular soils. A total of 18 binary granular mixes were synthetically generated from natural sands obtained from Longboat Key, Florida and evaluated through grain size analysis, laboratory compaction and determination of relative density. Results indicate that the D50/d50 ratio shows promise as a fundamental parameter for compaction optimization in binary mixes with values exceeding six approaching the densest packing configuations.
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Date Issued: 2012
PURL: http://purl.flvc.org/FAU/3358329
Subject Headings: Granular materials, Dynamic testing, Engineering geology, Soil mechanics, Testing, Micromechanics, Mathematical models
Format: Document (PDF)

Title: Aerodynamic analysis of a propeller in a turbulent boundary layer flow.
Creator: Lachowski, Felipe Ferreira., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description: Simulating the exact chaotic turbulent flow field about any geometry is a dilemma between accuracy and computational resources, which has been continuously studied for just over a hundred years. This thesis is a complete walk-through of the entire process utilized to approximate the flow ingested by a Sevik-type rotor based on solutions to the Reynolds Averaged Navier-Stokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYS-FLUENT and results are...
Show moreSimulating the exact chaotic turbulent flow field about any geometry is a dilemma between accuracy and computational resources, which has been continuously studied for just over a hundred years. This thesis is a complete walk-through of the entire process utilized to approximate the flow ingested by a Sevik-type rotor based on solutions to the Reynolds Averaged Navier-Stokes equations (RANS). The Multiple Reference Frame fluid model is utilized by the code of ANSYS-FLUENT and results are validated by experimental wake data. Three open rotor configurations are studied including a uniform inflow and the rotor near a plate with and without a thick boundary layer. Furthermore, observations are made to determine the variation in velocity profiles of the ingested turbulent flow due to varying flow conditions.
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Date Issued: 2013
PURL: http://purl.flvc.org/fcla/dt/3360798
Subject Headings: Acoustical engineering, Boundary layer control, Multiphase flow, Mathematical models, Fluid mechanics, Mathematical models, Turbulence, Mathematical models, Computatioinal fluid dynamics
Format: Document (PDF)

Title: Permanent strain accumulation in a granular material due to cyclic loading.
Creator: Genduso, Michael J., Florida Atlantic University, Sobhan, Khaled Dr.
Abstract/Description: To better characterize the accumulation of permanent deformation in a granular material, 40 Consolidated Drained (CD) triaxial tests (14 static and 26 cyclic) were performed under various stress conditions. A Digital Image Correlation (DIC) technique was utilized in some Repeated Load Triaxial (RLT) tests to measure global and localized strains visually in a non-contact manner. Additionally, the experimentally determined resilient material properties were used in a finite element based...
Show moreTo better characterize the accumulation of permanent deformation in a granular material, 40 Consolidated Drained (CD) triaxial tests (14 static and 26 cyclic) were performed under various stress conditions. A Digital Image Correlation (DIC) technique was utilized in some Repeated Load Triaxial (RLT) tests to measure global and localized strains visually in a non-contact manner. Additionally, the experimentally determined resilient material properties were used in a finite element based pavement modeling software called MICH-PAVE. Under cyclic loading, the permanent strain accumulation was found to obey the relationship of the form epsilonp =aNb, and the Resilient Modulus was used to develop the nonlinear K-theta model for granular materials. The observed/measured permanent strains using DIC/LVDT techniques compared favorably with the values obtained by the finite element simulation, and the evaluation of granular material by multiple methods seems promising for improved pavement design.
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Date Issued: 2005
PURL: http://purl.flvc.org/fcla/dt/13264
Subject Headings: Soils--Testing, Soil mechanics, Soil-structure interaction, Engineering geology, Rocks--Testing, Materials--Dynamic testing
Format: Document (PDF)

Damping (Mechanics) (5)	+ -
Mathematical models (5)	+ -
Plates (Engineering)--Vibration (5)	+ -
Acoustical engineering (3)	+ -
Buckling (Mechanics) (3)	+ -

Engineering geology (3)	+ -
Continuum mechanics (2)	+ -
Fluid mechanics (2)	+ -
Plates (Engineering) (2)	+ -
Soil mechanics (2)	+ -
Structural analysis (2)	+ -
Testing (2)	+ -
Turbulence (2)	+ -
Vibration (2)	+ -
Adaptive control systems. (1)	+ -
Aggregates (Building materials ) -- Recycling (1)	+ -
Air-supported structures--Design and construction. (1)	+ -
Biomedical engineering -- Materials (1)	+ -
Biomedical materials -- Mechanical properties (1)	+ -
Boundary layer control (1)	+ -
Cement composites--Testing (1)	+ -
Chebyshev polynomials (1)	+ -
Composite materials (1)	+ -
Computatioinal fluid dynamics (1)	+ -
Computational fluid dynamics (1)	+ -
Concrete (1)	+ -
Concrete -- Mechanical properties (1)	+ -
Concrete construction (1)	+ -
Concrete, Effect of temperature on (1)	+ -
Concrete--Mechanical properties--Testing (1)	+ -

Florida (1)	+ -
Longboat Key (1)	+ -

College of Engineering and Computer Science (17)	+ -
Florida Atlantic University (17)	+ -
Department of Ocean and Mechanical Engineering (12)	+ -
Department of Civil, Environmental and Geomatics Engineering (5)	+ -
Stevens, Karl K. (5)	+ -

Sobhan, Khaled (4)	+ -
Elishakoff, Isaac (2)	+ -
Pentaras, Demetris. (2)	+ -
Sobhan, Khaled Dr. (2)	+ -
Arockiasamy, Madasamy (1)	+ -
BHAT, RAJENDRA AGHUT. (1)	+ -
Blanc, Jean-Baptiste. (1)	+ -
Brenner, Tara Devine. (1)	+ -
Charles E. Schmidt College of Science (1)	+ -
Department of Physics (1)	+ -
Fraser, Jamie Barbara (1)	+ -
Genduso, Michael J. (1)	+ -
Gonzalez Moya, Daniel E. (1)	+ -
Gonzalez, Lillian (1)	+ -
HSU, HONG-YUAN. (1)	+ -
Huang, Ming Z. (1)	+ -
JAISING, VINOD R. (1)	+ -
Jagannathan, Arjun. (1)	+ -
Jani, Jayant Shivkumar. (1)	+ -
KUNG, CHUN-HUA. (1)	+ -
Khanal, Suraj P. (1)	+ -
Lachowski, Felipe Ferreira. (1)	+ -
Leventouri, Theodora (1)	+ -
Li, Yanjun (1)	+ -
Li, Yiwei. (1)	+ -

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