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- Title
- Compression failure of sandwich specimens with and without face/core debonds.
- Creator
- Vadakkeveedu, Vinod P., Florida Atlantic University, Carlsson, Leif A., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The objective of this thesis is to report on an experimental study on the compressive behavior of foam cored sandwich composite specimens with and without face/core debond. A test fixture was designed which enables a precisely machined sandwich specimen instrumented with back-to-back strain gages to be loaded in edgewise compression. Tests were conducted on specimens without implanted face/core interface debonds over a range of core densities and gage lengths. The experimentally determined...
Show moreThe objective of this thesis is to report on an experimental study on the compressive behavior of foam cored sandwich composite specimens with and without face/core debond. A test fixture was designed which enables a precisely machined sandwich specimen instrumented with back-to-back strain gages to be loaded in edgewise compression. Tests were conducted on specimens without implanted face/core interface debonds over a range of core densities and gage lengths. The experimentally determined compression strengths and failure modes were compared to closed-form predictions and finite element analysis. Specimens with an implanted through-the-width face/core debond were also tested and mechanism of failure was analyzed using finite element analysis. Good agreement between collapse loads predicted using geometrically nonlinear analysis and experimentally measured strengths was observed.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/13047
- Subject Headings
- Sandwich construction, Strains and stresses, Structural analysis (Engineering)
- Format
- Document (PDF)
- Title
- Computations of normal vortex interaction with blades and circular cylinders.
- Creator
- Yalamanchili, Ramakrishna., Florida Atlantic University, Marshall, Jeffrey S., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A numerical model for the simulation of three-dimensional normal blade-vortex interaction has been developed to study the bending and variation of core radius of the vortex due to the influence of the blade and the subsequent unsteady force on the blade. For thin blades, a procedure to enable instantaneous cutting of the vortex has been employed to study the vortex response to cutting. The vortex is represented by a filament model which includes axial flow within the core and non-uniform core...
Show moreA numerical model for the simulation of three-dimensional normal blade-vortex interaction has been developed to study the bending and variation of core radius of the vortex due to the influence of the blade and the subsequent unsteady force on the blade. For thin blades, a procedure to enable instantaneous cutting of the vortex has been employed to study the vortex response to cutting. The vortex is represented by a filament model which includes axial flow within the core and non-uniform core area. The vortex is convected with self-induced velocities given by the Biot-Savart line integral, and the effect of the cylinder is obtained using a vortex sheet panel method. The governing equations for the vortex axial velocity have a form similar to that of the one-dimensional gas dynamics equations and admit "shock-like" discontinuities. The results indicate that the amount of vortex bending due to interaction with the blade is primarily dependent on the ratio of blade thickness T to ambient vortex core radius sigma o, although for a given amount of bending of the vortex axis, increase in cylinder forward speed results in a decrease in vortex core radius. For blades with T/sigma o < 0(1), very little bending is observed for attack angles under the stall limit. In the case of vortex cutting by a blade, vortex shocks and expansion waves are observed to propagate on the vortex axis away from the blade.
Show less - Date Issued
- 1993
- PURL
- http://purl.flvc.org/fcla/dt/14985
- Subject Headings
- Helicopters, Blades--Noise, Rotors (Helicopters), Vortex-motion
- Format
- Document (PDF)
- Title
- Computed tomographic measurements of void fraction and modeling of the flow in bubble columns.
- Creator
- Kumar, Sailesh B., Florida Atlantic University, Moslemian, Davood, Dudukovic, M. P., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A complete understanding of the gas-liquid two phase flow in bubble columns is required for the development of reliable models for scale-up of these multiphase reactors. Although several models have been proposed to describe the hydrodynamics. lack of adequate experimental data has hindered meaningful evaluation of model parameters and model predictions. The Computer Automated Radioactive Particle Tracking ( CARPT) facility that was implemented earlier has provided interesting results on the...
Show moreA complete understanding of the gas-liquid two phase flow in bubble columns is required for the development of reliable models for scale-up of these multiphase reactors. Although several models have been proposed to describe the hydrodynamics. lack of adequate experimental data has hindered meaningful evaluation of model parameters and model predictions. The Computer Automated Radioactive Particle Tracking ( CARPT) facility that was implemented earlier has provided interesting results on the recirculation patterns of the liquid phase. The technique has provided quantitative information on liquid velocities and turbulence parameters as well. In addition to these hydrodynamic parameters the measurement of void fraction is also important. To complement the capabilities of CARPT a scanner for ;-ray Computed Tomography (CT) was implemented to quantify the local void fraction and its distribution in two phase flow systems. The automated scanner is capable of imaging flows in test sections between 0.02.5 m and 0..15 m in diameter at different elevations above the distributor. The scanner makes use of the same detectors used in the CARPT facility and with the use of a specially designed moving collimator provides a spatial resolution of about 5 mm. A non-conventional algorithm based on maximum likelihood principles called the E-M algorithm was used for imagw reconstruction. Long scanning times are required leading to time averaged density profiles. Although the system is only capable of providing time averaged void fraction distributions. it can provide unique information concerning the structure of two phase flow. The system performance was evaluated by identifying the sources of errors in measurement and their bounds. The capabilities of the scanner for imaging void fraction distribution was demonstrated both qualitatively and quantitatively. Fse of existing radiation detectors and the associated signal processing and data acquisition system helped in reducing the cost of the system. The scanner was utilized to quantify the local void fraction and its distribution in bubble columns of five diameters (0.10. 0.14, 0.19, 0.26. 0.30 m internal diameter) and at four superficial gas velocities. The effect of various operating parameters such as column diameter, superficial gas velocity. the type of distributor. the static liquid height and some changes in the physical properties of the liquid phase were studied. For the first time a comprehensive characterization of the void fraction in an air water bubble column using a non-invasive technique was achieved. The experimental data obtained using CARPT and CT under identical operating conditions was used for developing a methodology for scale-up of bubble columns using a one dimensional model for liquid recirculation. Successful scale-up of liquid hydrodynamics using a one dimensional model requires an adequate closure scheme for the Reynolds shear stress. The existing correlations for the prescription of the eddy viscosity or the mixing length scale are demonstrated to be applicable only for a limited range of conditions. and consequently cannot be used for scale-up predictions. A method for estimating the mixing length scale has been explored and an attempt at unifying a wide range of data available in the literature within the pun·iew of the method has been made. The futility of such an attempt is attributed to the non-reproducibility of the flow in different laboratories and the conasequent lack of data obtained under identical conditions. It is demonstrated, however, that scale-up based on the mixing length distribution is possible when it is obtained from a consistent set of data for liquid velocity and gas void fraction profiles. Using the present method for prescribing the mixing length scale. model predictions for scale-up compare satisfactorily for the data that was obtained as part of this research. The achievement was that the turbulence length scale estimated in one column diameter was successfully used in predicting the liquid velocities in larger diameter columns.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/12384
- Subject Headings
- Two-phase flow, Hydrodynamics, Bubble chambers, Tomography, Emission
- Format
- Document (PDF)
- Title
- Control of response of tall multi-story buildings under wind excitation.
- Creator
- Qiu, Xin., Florida Atlantic University, Lin, Y. K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Theoretical investigation is carried out into the extent to which floor accelerations of a wind-excited tall building can be reduced by increasing damping in those components in a building which are generally regarded to be non-structural elements, and by using active control. The wind loads are modeled as stochastic processes, which are correlation-stationary in time. Only the drag wind forces are considered in the analyses. The spectral densities and cross-spectral densities of two commonly...
Show moreTheoretical investigation is carried out into the extent to which floor accelerations of a wind-excited tall building can be reduced by increasing damping in those components in a building which are generally regarded to be non-structural elements, and by using active control. The wind loads are modeled as stochastic processes, which are correlation-stationary in time. Only the drag wind forces are considered in the analyses. The spectral densities and cross-spectral densities of two commonly used models, proposed by Davenport and by Simiu, are compared. The Davenport spectrum is used in the numerical calculation for illustration purposes. Several structural models are discussed: an ideal spatially periodic model, an ideal piece-wise spatially periodic model, a nominal spatially periodic model with random disorder in periodicity, and an ideal spatially periodic model equipped with an active mass damper control system. The problems are formulated using the transfer matrix approach in the frequency domain. Analytical solutions are obtained for the spectral densities and the mean-square values of the floor accelerations and those of the active control force. Numerical examples are given for illustration.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/12495
- Subject Headings
- Tall buildings--Aerodynamics, Wind-pressure, Damping (Mechanics)
- Format
- Document (PDF)
- Title
- Control design for highly maneuverable autonomous underwater vehicles.
- Creator
- Poirrier, Ronald., Florida Atlantic University, Leonessa, Alexander, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Accurate Autonomous Underwater Vehicles positioning requires an appropriate control design which takes into account the nonlinear coupling between the different degrees of freedom. Assuming a vehicle equipped with two side-thruster modules including two tunnel thrusters each, the control problem will be split into an outer control loop handling the motion of the vehicle, and an inner control loop designed to track the thrust commanded to each thruster. A multivariable Lyapunov function based...
Show moreAccurate Autonomous Underwater Vehicles positioning requires an appropriate control design which takes into account the nonlinear coupling between the different degrees of freedom. Assuming a vehicle equipped with two side-thruster modules including two tunnel thrusters each, the control problem will be split into an outer control loop handling the motion of the vehicle, and an inner control loop designed to track the thrust commanded to each thruster. A multivariable Lyapunov function based approach, characterized by robustness properties with respect to parametric uncertainties and linearly bounded control output, will be proposed for the outer-loop and simulation results will be discussed. Regarding the low-level control framework, the performance of nine different controllers including conventional PI, sliding mode fuzzy controllers, and adaptive schemes such as model reference and sliding mode adaptive controllers, will be compared through theoretical derivations and experimental results. Such a comparison will show the advantages of the adaptive schemes in terms of tuning, robustness, and tracking performances.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fau/fd/FADT12777
- Subject Headings
- Submersibles--Automatic control, Oceanographic submersibles
- Format
- Document (PDF)
- Title
- Creep and shrinkage effects on integral abutment bridges.
- Creator
- Munuswamy, Sivakumar., Florida Atlantic University, Arockiasamy, Madasamy, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Integral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and...
Show moreIntegral abutment bridges provide bridge engineers an economical design alternative to traditional bridges with expansion joints owing to the benefits, arising from elimination of expensive joints installation and reduced maintenance cost. The superstructure for integral abutment bridges is cast integrally with abutments. Time-dependent effects of creep, shrinkage of concrete, relaxation of prestressing steel, temperature gradient, restraints provided by abutment foundation and backfill and statical indeterminacy of the structure introduce time-dependent variations in the redundant forces. An analytical model and numerical procedure to predict instantaneous linear behavior and non-linear time dependent long-term behavior of continuous composite superstructure are developed in which the redundant forces in the integral abutment bridges are derived considering the time-dependent effects. The redistributions of moments due to time-dependent effects have been considered in the analysis. The analysis includes nonlinearity due to cracking of the concrete, as well as the time-dependent deformations. American Concrete Institute (ACI) and American Association of State Highway and Transportation Officials (AASHTO) models for creep and shrinkage are considered in modeling the time dependent material behavior. The variations in the material property of the cross-section corresponding to the constituent materials are incorporated and age-adjusted effective modulus method with relaxation procedure is followed to include the creep behavior of concrete. The partial restraint provided by the abutment-pile-soil system is modeled using discrete spring stiffness as translational and rotational degrees of freedom. Numerical simulation of the behavior is carried out on continuous composite integral abutment bridges and the deformations and stresses due to time-dependent effects due to typical sustained loads are computed. The results from the analytical model are compared with the published laboratory experimental and field data. The behavior of the laterally loaded piles supporting the integral abutments is evaluated and presented in terms of the lateral deflection, bending moment, shear force and stress along the pile depth.
Show less - Date Issued
- 2004
- PURL
- http://purl.flvc.org/fau/fd/FADT12067
- Subject Headings
- Bridges--Abutments, Concrete--Creep, Concrete--Expansion and contraction
- Format
- Document (PDF)
- Title
- DEVELOPMENT OF A TWO-DIMENSIONAL LINEAR STATIC FINITE ELEMENT PROGRAM FOR A DESKTOP MICROCOMPUTER.
- Creator
- SCHWEET, RICHARD RAYMOND., Florida Atlantic University, Stevens, Karl K., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The finite element method is widely used in many areas of engineering and applied science, including structures, fluids, heat transfer, and electromagnetism. Several commercial programs exist which have extensive capabilites in these areas, but they usually require special training and mainframe computers to use. This creates a series of problems in an engineering organization because of the inefficiencies of timeshared computer systems and remote processing. These problems result in poor...
Show moreThe finite element method is widely used in many areas of engineering and applied science, including structures, fluids, heat transfer, and electromagnetism. Several commercial programs exist which have extensive capabilites in these areas, but they usually require special training and mainframe computers to use. This creates a series of problems in an engineering organization because of the inefficiencies of timeshared computer systems and remote processing. These problems result in poor productivity of the analyst. This work demonstrates the feasibility of using a desktop microcomputer to perform finite element structural analysis. A program is developed which is capable of solving two-dimensional linear static problems using truss, beam and plane stress elements. The program includes extensive pre- and post-processing capabilities and graphic displays. It allows problems with up to 500 degrees-of-freedom to be solved within a few hours and requires only about one-half hour of instruction to use. The program theory, a user's manual, and verification problems are presented.
Show less - Date Issued
- 1984
- PURL
- http://purl.flvc.org/fcla/dt/14225
- Subject Headings
- Microcomputers--Programming, Electronic data processing--Engineering
- Format
- Document (PDF)
- Title
- DESIGN OF A ROBUST MULTIVARIABLE JET ENGINE CONTROL SYSTEM.
- Creator
- LARKIN, LOUIS JOSEPH., Florida Atlantic University, Duyar, Ahmet, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Until recently, control design techniques for multivariable systems, such as pole placement or optimal control design, have been either too complex to be usable, or yielded designs which were liable to instability if the parameters of the plant varied from those used in the design. A technique which uses the singular values of the system transfer function matrix is now available. This technique yields control designs which are guaranteed to be robust with respect to plant parameter variations...
Show moreUntil recently, control design techniques for multivariable systems, such as pole placement or optimal control design, have been either too complex to be usable, or yielded designs which were liable to instability if the parameters of the plant varied from those used in the design. A technique which uses the singular values of the system transfer function matrix is now available. This technique yields control designs which are guaranteed to be robust with respect to plant parameter variations. This technique, combined with a novel technique for shaping the frequency responses of the singular values is used to design a control system for a gas turbine jet engine. It is shown that adjusting the crossover frequency of the open loop singular values affects the closed loop time and frequency response in the same manner that adjusting the open loop gain affects the response of a single-input/single-output control system.
Show less - Date Issued
- 1985
- PURL
- http://purl.flvc.org/fcla/dt/14235
- Subject Headings
- Flight control, Jet propulsion--Research
- Format
- Document (PDF)
- Title
- The role of calcium-hydroxide in the maintenance of passivity of steel.
- Creator
- Sohanghpurwala, Ali Akbar S., Florida Atlantic University, Hartt, William H., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The objective of this study was to determine whether the presence of undissolved calcium hydroxide at the steel interface helped maintain or delay the breakdown of passivity under adverse conditions, such as the presence of chlorides and carbonation. Saturated calcium hydroxide solution was used as an electrolyte in the test cell, and steel specimens were exposed to a range of chloride ion concentration and carbonation. The results indicate that undissolved calcium hydroxide has an important...
Show moreThe objective of this study was to determine whether the presence of undissolved calcium hydroxide at the steel interface helped maintain or delay the breakdown of passivity under adverse conditions, such as the presence of chlorides and carbonation. Saturated calcium hydroxide solution was used as an electrolyte in the test cell, and steel specimens were exposed to a range of chloride ion concentration and carbonation. The results indicate that undissolved calcium hydroxide has an important role in the passivation of reinforcing steel. Also, the critical chloride to hydroxide ratio may be more relevant in characterizing the breakdown of passivity than the threshold value of total or soluble chloride present in the electrolyte. It was noted that in the presence of undissolved calcium hydroxide, steel remained passive for as high a chloride ion concentration as 0.54% (by weight of electrolyte).
Show less - Date Issued
- 1988
- PURL
- http://purl.flvc.org/fcla/dt/14429
- Subject Headings
- Chlorides, Steel--Corrosion
- Format
- Document (PDF)
- Title
- The microprocessor design team assignment problem with a new multistage stochastic/Brownian motion model.
- Creator
- O'Grady, Thomas James., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
The Microprocessor Design Team Assignment Problem models the microprocessor design efforts of Intel Corporation over a 29-year period from 1972 until 2001. The basic model is a Erlang queuing system based probability model of the individual programming-design team daily operations. After extensive research the Erlang Loss/Delay Blocked Multiserver Model is utilized throughout the dissertation The Erlang loss-delay model takes into account the Key Man Constraint for team leaders and...
Show moreThe Microprocessor Design Team Assignment Problem models the microprocessor design efforts of Intel Corporation over a 29-year period from 1972 until 2001. The basic model is a Erlang queuing system based probability model of the individual programming-design team daily operations. After extensive research the Erlang Loss/Delay Blocked Multiserver Model is utilized throughout the dissertation The Erlang loss-delay model takes into account the Key Man Constraint for team leaders and programming team personnel. The Microprocessor Design Team Assignment Problem Case Study and massive research effort, into Intel Corporations design efforts, is complicated by modeling a major programming-design team operation without any current data or assistance from Intel Corporation. However much of the lack of assistance and data was obtained by utilizing a critical managerial design team decomposition which answered most major questions about Intels lack of adequate personnel and overutilization of team leaders and asst. team leaders throughout the 48 months of most major design projects. The study-dissertation concludes that Intels and Hewlett Packards current positions in the computer industry are relatively secure because of extremely high entry level costs exceeding $850,000,000.00 million dollars. Many individual issues about programming-design team operations are analyzed in a great amount of detail. This is the first time that much of this design-programming team material and information is being made public for future research and continuing improvement upon large scale project managerial methods and techniques. The basic design-programming team effort is also modeled with Erlang probability models and stochastic Riccati differential equations. This modeling effort is discussed in great detail in chapter 5 and Appendix Alpha. It is believed that this fundamental research leads the way for more advanced efforts in manufacturing systems and possibly mechatronics for further models utilizing strong Markov properties. This research effort substantially advances the basic research and knowledge of Partially Observable Markov Decision Processes and Strong Brownian Motion with the basic unit being strong Markov properties.
Show less - Date Issued
- 2001
- PURL
- http://purl.flvc.org/fcla/dt/11962
- Subject Headings
- Brownian motion processes, Stochastic analysis, Microprocessors
- Format
- Document (PDF)
- Title
- The measurement of structural power flow in thin plate structures.
- Creator
- Padiyar, Satish., Florida Atlantic University, Cuschieri, Joseph M., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
An analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case...
Show moreAn analytical and experimental investigation of the flow of vibrational power in a thin, L-shaped, finite plate structure subjected to mechanical and acoustic excitation is presented. In the analytical approach, mobility functions are used to determine the structural intensity vectors at various locations on the plate structure. Simulation results of intensity vectors estimated using three different measurement schemes are compared. The experimentally measured intensity vectors, for the case of mechanical excitation, using a four accelerometer array, are presented. They are found to match well with the results from the corresponding simulation. Similar results are obtained for the case of acoustic excitation of the L-shaped plate. The general pattern of the structural intensity vectors is found to be in agreement with the expected results.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14678
- Subject Headings
- Plates (Engineering)--Vibration
- Format
- Document (PDF)
- Title
- A method for the optimization of product development resource allocation.
- Creator
- Worp, Nicholas Jacob., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This thesis presents a model designed to optimize the allocation of corporate resources required for the success of a product in the marketplace. The product development resources used in the model are: market research, applied research, product design, cost reduction and advertising. The key goals of this thesis are to provide industry with a usable tool: (1) Implement strategic plans through effective budgeting; (2) Optimize both short and long term profits; (3) Evaluate the impact of...
Show moreThis thesis presents a model designed to optimize the allocation of corporate resources required for the success of a product in the marketplace. The product development resources used in the model are: market research, applied research, product design, cost reduction and advertising. The key goals of this thesis are to provide industry with a usable tool: (1) Implement strategic plans through effective budgeting; (2) Optimize both short and long term profits; (3) Evaluate the impact of resource inter-dependencies; (4) Enable accountability that leads to goal achievement and checks unnecessary growth; (5) Remove much of the negative political and emotional variability; (6) Easily adapt to internal and external changes; (7) Output a specific allocation for each resource as a percentage of sales; (8) Output an estimate of future profitability. Genetic Algorithms are particularly well suited for this application because an exact optima is not required and the search space can be extremely large, complex, and non-linear.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/15519
- Subject Headings
- Genetic algorithms, Resource allocation, Strategic planning, Business planning
- Format
- Document (PDF)
- Title
- A model of the horseshoe vortex in juncture flows.
- Creator
- Monnier, Elie Bertrand., Florida Atlantic University, Dhanak, Manhar R., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
When a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well...
Show moreWhen a boundary-layer flow, either laminar or turbulent, encounters a hemispherical body extending from a surface, a horseshoe-shaped vortex forms at the juncture. In this thesis, we study the evolution of this vortex using a numerical inviscid model and laboratory experiments. The numerical model is based on determining the evolution of the filament using the cut-off method. The assumption is that although the generation of the vortex depends on viscous effects, the dynamic evolution is well described by inviscid equations of motion. It is found that the vortex filament is fairly steady on the upstream side but on the downstream side, travelling waves appear on it which cannot be suppressed through evolution. For a range of Reynolds number, steady horseshoe-shaped vortex was obtained in the experiments, revealing the shape past the hemisphere. This is compared with the numerical results.
Show less - Date Issued
- 1996
- PURL
- http://purl.flvc.org/fcla/dt/15326
- Subject Headings
- Boundary layer, Cascades (Fluid dynamics), Flow visualization, Vortex generators
- Format
- Document (PDF)
- Title
- A new methodology in accelerated testing of mechanical heart valve prostheses.
- Creator
- Wu, Changfu., Florida Atlantic University, Lin, Y. K., Cai, Guo-Qiang, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
Mechanical heart valve (MHV) prosthesis is used commonly for clinical replacement of a diseased or dysfunctional natural valve. It is expected to operate uninterruptedly in the human chest for at least 10 years. Classified as Class III medical devices, MHVs of a new design are required by the Food and Drug Administration (FDA) to undergo accelerated durability test for up to 600 million cycles, before a pre-market approval (PMA) can be considered. Knowledge of potential damage/failure...
Show moreMechanical heart valve (MHV) prosthesis is used commonly for clinical replacement of a diseased or dysfunctional natural valve. It is expected to operate uninterruptedly in the human chest for at least 10 years. Classified as Class III medical devices, MHVs of a new design are required by the Food and Drug Administration (FDA) to undergo accelerated durability test for up to 600 million cycles, before a pre-market approval (PMA) can be considered. Knowledge of potential damage/failure mechanisms is of practical interest in assessing the results obtained from accelerated testing. During such tests, an MHV is subjected to higher stresses at higher cycling frequency, and to more severe hydrodynamic environment than those under normal physiological conditions. Three primary factors contributable to damage/failure of an MHV are investigated, namely, contact stresses, water hammer effect, and cavitation. Parametric study is conducted on the contact-induced damage, using the model of a ball-indentation test. Four possible modes of contact damage are identified. Schemes for the selection of appropriate coating parameters to minimize contact stresses in a valve component are discussed. Experimental results of dynamic stresses on a leaflet are presented. The water hammer effect at the instant of valve closure is studied. The destructive force of cavitation is investigated, by incorporating bubble dynamics in a damage tolerance analysis. Cavitation is found to have a greater effect on potential valve damage/failure during accelerated testing. A new measure, cavitation impulse (CI), is introduced to quantify the intensity of MHV cavitation. It is defined as the area under the trace of the high-frequency pressure bursts generated by collapses of cavitation bubbles. CI is modeled as a stationary stochastic process with a discrete parameter (beats), the probability structure of which is estimated from the experimental data. Each CI accounts for both the magnitude and the time-duration of the impinging high pressure of cavitation; therefore, it correlates more closely with cavitation damage on MHV components, thus the time-to-failure (life) of an MHV undergoing testing.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fau/fd/FADT12077
- Subject Headings
- Heart valve prosthesis, Cavitation, Accelerated life testing
- Format
- Document (PDF)
- Title
- A structural analysis of the rigging system for an ocean racing yacht.
- Creator
- Troy, R. Talbot., Florida Atlantic University, Yong, Yan, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
A static analysis of the rigging structure for Matador, an 80-ton ocean racing yacht, is performed, and the results are compared to load cell data taken during close haul sailing. The purpose of the analysis is to examine the nature of the loading of the shrouds when heeling, backstay cylinder adjustment and runner tensions are considered. Also, the relative rotation between the shrouds and their joints and possibilities of bending stresses developed by friction are discussed. The sail forces...
Show moreA static analysis of the rigging structure for Matador, an 80-ton ocean racing yacht, is performed, and the results are compared to load cell data taken during close haul sailing. The purpose of the analysis is to examine the nature of the loading of the shrouds when heeling, backstay cylinder adjustment and runner tensions are considered. Also, the relative rotation between the shrouds and their joints and possibilities of bending stresses developed by friction are discussed. The sail forces acting on the mast are calculated with simple foil theory to estimate sail lift coefficients and drag angles. The heeling angle is considered so that weight of mast and rigging is accounted for. The adjustment of the backstay cylinder is simulated by displacement of the lower end of the backstay, and the runner tensions are modeled as point loads on the mast.
Show less - Date Issued
- 1990
- PURL
- http://purl.flvc.org/fcla/dt/14624
- Subject Headings
- Masts and rigging, Yachts and yachting--Models
- Format
- Document (PDF)
- Title
- A study of ambient noise in shallow water.
- Creator
- Pirie, Rachel Louise., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
-
This thesis describes a series of measurements that took place over the duration of one year on the South Florida Testing Facility (SFTF) range, Dania, in order to survey the shallow water ambient acoustic environment. Three groups of data sets were taken in December 1998, May 1999 and July 1999. The data was collected using the Ambient Noise Sonar (ANS) that was developed in the Ocean Engineering department at Florida Atlantic University. The ambient acoustic environment was found to be...
Show moreThis thesis describes a series of measurements that took place over the duration of one year on the South Florida Testing Facility (SFTF) range, Dania, in order to survey the shallow water ambient acoustic environment. Three groups of data sets were taken in December 1998, May 1999 and July 1999. The data was collected using the Ambient Noise Sonar (ANS) that was developed in the Ocean Engineering department at Florida Atlantic University. The ambient acoustic environment was found to be highly variable with two main components. Boat noise was found to primarily be associated with the inlet and a source of snapping shrimp situated on the shallow water 30ft reef became apparent through 24hr observation. The effects of adverse weather were not studied due to the absence of this source during the measurement periods.
Show less - Date Issued
- 1999
- PURL
- http://purl.flvc.org/fcla/dt/15738
- Subject Headings
- Underwater acoustics, Noise--Measurement, Acoustic surface waves
- Format
- Document (PDF)
- Title
- A sparse volume array for imaging ocean ambient noise in the near-shore region.
- Creator
- Olivieri, Marc P., Florida Atlantic University, Glegg, Stewart A. L., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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Ocean ambient noise has been studied extensively in the past, and several models have been developed to predict its level and to characterize it in different ocean environments. However, most of these studies have been motivated by the need to reduce the negative effect of the ambient noise on measurements. Recently, several studies have used the ambient noise to obtain information about the ocean floor and to achieve passive target detection. This dissertation describes the development of an...
Show moreOcean ambient noise has been studied extensively in the past, and several models have been developed to predict its level and to characterize it in different ocean environments. However, most of these studies have been motivated by the need to reduce the negative effect of the ambient noise on measurements. Recently, several studies have used the ambient noise to obtain information about the ocean floor and to achieve passive target detection. This dissertation describes the development of an Ambient Noise Sonar (ANS) which can be used to measure ambient noise directivity to obtain information about the environment. The system was designed for use on an Autonomous Underwater Vehicle (AUV) and has been used to study the ambient noise in the near shore region by investigating different types of noise in shallow water, such as boat traffic, biological noise and naturally occurring noise up to 20 kHz. There are two advantages to the ANS. First, when mounted on an AUV its mobility will allow the ambient noise to be mapped over an extended area. Second, the very small number of transducers (6 total) used in the array, makes this system suitable for AUV operations because it uses a limited amount of space and power. This dissertation presents the theory of the array processing and preliminary results including examples of boat noise, and biological noise. It was found that the noise from biological sources such as snapping shrimp contributed to the anisotropic component of the acoustic field. These biological sources were found to be concentrated around artificial structures such as piers and groins, and also around natural reefs. Finally noise maps of coastal areas are presented to illustrate the potential of this system to measure the noise field in the coastal region and to evaluate acoustic propagation using passive sources such as the biological noise clusters found along the coast. In the future the ANS will be integrated onto the AUV 'Ocean Explorer II'.
Show less - Date Issued
- 1997
- PURL
- http://purl.flvc.org/fcla/dt/12534
- Subject Headings
- Underwater acoustics, Acoustic imaging
- Format
- Document (PDF)
- Title
- A unified theory of coordination for robotic mechanisms with general parallel or hybrid structures.
- Creator
- Ling, Shou-Hung., Florida Atlantic University, Huang, Ming Z., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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A well designed robot manipulator should have adequate workspace and good static-dynamic performance. It is well known that serial manipulators, while compared to similar size parallel ones, have larger workspace. However, due to their cantilever-like structure, the serial manipulators suffer from the disadvantage of having relatively poor static-dynamic performance. Contrarily, for fully parallel manipulators the good static-dynamic performance comes from the sacrifice of the workspace....
Show moreA well designed robot manipulator should have adequate workspace and good static-dynamic performance. It is well known that serial manipulators, while compared to similar size parallel ones, have larger workspace. However, due to their cantilever-like structure, the serial manipulators suffer from the disadvantage of having relatively poor static-dynamic performance. Contrarily, for fully parallel manipulators the good static-dynamic performance comes from the sacrifice of the workspace. Therefore, manipulators with more general geometries, in particular those with both the serial and the parallel modules, namely the hybrid manipulators, have attracted much of the research attention in robotics recently. While it can be asserted that kinematic theories and techniques are well established for fully serial-chain manipulators, the same assertion cannot be made when they are considered in the above general context. The research described in this dissertation is an undertaking toward the establishment of a general theory of coordination for robotic mechanisms with general parallel or hybrid structures. The scope of this research is concentrated in the kinematics aspect of the aforementioned class of robot manipulators with the main emphasis on the velocity (instantaneous) kinematics. A kinestatic approach, which is based on screw system theory, is adopted in this dissertation. This kinestatic approach leads to the establishment of a fundamental theorem, dubbed as the Parallel Manipulator Coordination Theorem, which integrates the idea of parallel and serial manipulators. Furthermore, the theorem enables us to develop an analysis strategy for systematic formulation and characterization of robotic mechanisms with general parallel (non-redundant) and hybrid geometries. The analysis strategy entails constraints, statics, velocity, and singularity considerations. One distinct advantage of using the screw system theory as the analysis tool is that it facilitates the analysis in a fashion that physical meanings are preserved through out the derivation. The very aspect of preserving the physical meaning distinguishes this method from other algebraically-based and numerically-based methods. An intelligent fault-tolerant system has been studied at the end. The technique and conclusions from the study of parallel manipulator modules have been used to analyze the proposed design.
Show less - Date Issued
- 1994
- PURL
- http://purl.flvc.org/fcla/dt/12385
- Subject Headings
- Manipulators (Mechanism), Robotics, Kinematics, Screws, Theory of
- Format
- Document (PDF)
- Title
- A three-dimensional finite element model for the biomechanical analysis of total ankle replacement.
- Creator
- Vo, Ha Van., Florida Atlantic University, Han, Chingping (Jim), College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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The artificial ankle joint implant has been developed since 1970 after the relatively successful total hip and knee arthroplasty. The main goal of ankle replacement is to eliminate pain and preserve joint motion. Unfortunately, total ankle replacement (TAR) has not been effective as implant of other joints. Recently, published studies of early series showed that the newer second-generation ankle prosthesis have been improved with time. However, only one of the three current ankle designs is...
Show moreThe artificial ankle joint implant has been developed since 1970 after the relatively successful total hip and knee arthroplasty. The main goal of ankle replacement is to eliminate pain and preserve joint motion. Unfortunately, total ankle replacement (TAR) has not been effective as implant of other joints. Recently, published studies of early series showed that the newer second-generation ankle prosthesis have been improved with time. However, only one of the three current ankle designs is allowed by FDA to be used widely in the U.S. This study provides a new ankle design with an advanced approach in designs, biomechanical rationale, and implantation using finite element method (FEM). The new ankle prosthesis in designed to be optimal in terms of ultimate stress, implant parameter that correlating with minimal bone removal using finite element model created from CT scan. In addition, its implantation is less invasive and traumatic compared to the current TAR with longer expecting service life time. Case study showed that the thickness meniscus of the new ankle design obtained from FEM is well within the recommendation ranges by the expert in the ankle joint implantation field.
Show less - Date Issued
- 2003
- PURL
- http://purl.flvc.org/fcla/dt/12052
- Subject Headings
- Ankle--Effect of implants on, Artificial joints, Ankle--Mechanical properties, Finite element method
- Format
- Document (PDF)
- Title
- A petri net framework for the simulation and control of automated systems.
- Creator
- Murgatroy, Richard John, Jr., Florida Atlantic University, Masory, Oren, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
- Abstract/Description
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This thesis presents a programming framework in the C language to execute a petri net simulation and real-time control for an automated system. This framework allows for the simulation of a proposed flexible automated system, and also the simultaneous development of the real-time control. The system is based on petri nets, which are used to model the system. Basic petri net theory and the construction of models using petri nets are discussed. The program is designed to allow a hierarchical...
Show moreThis thesis presents a programming framework in the C language to execute a petri net simulation and real-time control for an automated system. This framework allows for the simulation of a proposed flexible automated system, and also the simultaneous development of the real-time control. The system is based on petri nets, which are used to model the system. Basic petri net theory and the construction of models using petri nets are discussed. The program is designed to allow a hierarchical structure to the petri net model, and a modular approach to the program design is taken using some concepts from object oriented programming. The program provides a time-based diagnostic system incorporated into the framework to detect problems during the execution of the actual system. An example application is provided to demonstrate the implementation of the framework to both simulate and control an actual system.
Show less - Date Issued
- 1995
- PURL
- http://purl.flvc.org/fcla/dt/15226
- Subject Headings
- Petri nets, Computer integrated manufacturing systems--Computer simulation, Flexible manufacturing systems--Computer simulation
- Format
- Document (PDF)
