Current Search: Case, Robert O. (x)
View All Items
 Title
 Hybrid method of finite element and photoelasticity to analyze stress concentrations on threaded cylinders.
 Creator
 Gonella, Julio Cesar., Florida Atlantic University, Case, Robert O.
 Abstract/Description

This paper studies the stress concentrations at the root of the threads of a cylinder. A photoelastic analysis using the stress freezing procedure is used to calculate the stress along the cylinder and the stress concentrations at the root of the threads. These values are compared to that of similar cylinders with different threaded configurations. A finite element model is built by using the photoelastic data to find a suitable load distribution along the threaded region. The finite element...
Show moreThis paper studies the stress concentrations at the root of the threads of a cylinder. A photoelastic analysis using the stress freezing procedure is used to calculate the stress along the cylinder and the stress concentrations at the root of the threads. These values are compared to that of similar cylinders with different threaded configurations. A finite element model is built by using the photoelastic data to find a suitable load distribution along the threaded region. The finite element model predicted results similar to the photoelastic analysis and showed a method of reducing the stress concentrations on the threads by redesigning a pressure ring on the cylinder.
Show less  Date Issued
 1990
 PURL
 http://purl.flvc.org/fcla/dt/14581
 Subject Headings
 Stress concentration, Cylinders
 Format
 Document (PDF)
 Title
 Hybrid stress analysis using digitized photoelastic data and numerical methods.
 Creator
 Mahfuz, Hassan, Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Equations of stressdifference elasticity, derived from the equations of equilibrium and compatibility for a twodimensional stress field, are solved for arbitrarily digitized, singly and multiply connected domains. Photoelastic data determined experimentally along the boundary provide the boundary values for the solution of the three elliptic partial differential equations by the finite difference method. A computerized method is developed to generate grid mesh, weighting functions and nodal...
Show moreEquations of stressdifference elasticity, derived from the equations of equilibrium and compatibility for a twodimensional stress field, are solved for arbitrarily digitized, singly and multiply connected domains. Photoelastic data determined experimentally along the boundary provide the boundary values for the solution of the three elliptic partial differential equations by the finite difference method. A computerized method is developed to generate grid mesh, weighting functions and nodal connectivity within the digitized boundary for the solution of these partial differential equations. A method is introduced to digitize the photoelastic fringes, namely isochromatics and isoclinics, and to estimate the values of sigma1  sigma2, sigma x  sigma y and tau xy at each nodal point by an interpolation technique. Interpolated values of the stress parameters are used to improve the initial estimate and hence the convergence of the iterative solution of the system of equations. Superfluous boundary conditions are added from the digitized photoelastic data for further speeding up the rate of convergence. The boundary of the domain and the photoelastic fringes are digitized by physically traversing the cursor along the boundary, and the digitized information is scanned horizontally and vertically to generate internal and boundary nodal points. A linear search determines the nodal connectivity and isolates the boundary points for the input of the boundary values. A similar scanning method estimates the photoelastic parameters at each nodal point and also finds the points closest to the tint of passage of each photoelastic fringe. Stress values at these close points are determined without interpolation and are subsequently used as superfluous boundary conditions in the iteration scheme. Successive overrelaxation is applied to the classical GaussSeidel method for final enhancement of the convergence of the iteration process. The iteration scheme starts with an accelerating factor other than unity and estimates the spectral radius of the iteration matrix from the two vector norms. This information is used to estimate a temporary value of the optimum relaxation parameter, omega[opt], which is used for a fixed number of iterations to approximate a better value of the accelerating factor. The process is continued until two successive estimates differ by a given tolerance or the stopping criteria are reached. Detailed techniques of developing the code for mesh generation, photoelastic data collection and boundary value interpolation to solve the elliptic boundary value problems are presented. Three separate examples with varying stress gradients and fringe patterns are presented to test the validity of the code and the overall method. Results are compared with the analytical and experimental solutions, and the significant improvement in the rate of convergence is demonstrated.
Show less  Date Issued
 1989
 PURL
 http://purl.flvc.org/fcla/dt/11934
 Subject Headings
 Strains and stresses, Photoelasticity, Numerical analysisData processing
 Format
 Document (PDF)
 Title
 Nine multiply separated precision point synthesis of coplanar four bar linkages.
 Creator
 Smith, Donn Alan., Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This study presents the equations of motion for nine multiply separated precision point synthesis of coplanar four bar linkages. A computer program called NINEPT is introduced which employs the equations of motion to solve the problem of nine finitely separated precision point synthesis. The algorithms of NINEPT are described in detail and a program listing is provided.
 Date Issued
 1990
 PURL
 http://purl.flvc.org/fcla/dt/14601
 Subject Headings
 Links and linkmotion
 Format
 Document (PDF)
 Title
 Finite element analysis to study the structural behavior of an underwater acoustic tower.
 Creator
 Sambandam, Sundaresakumar., Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

This thesis deals with the static analysis of a three dimensional underwater acoustic tower exclusively designed and fabricated by Harbor Branch Oceanographic Institution, Ft. Pierce, Florida. A commercial finite element package COSMOS/M was used for the finite element analysis. The structural modeling as well as processing of the results was performed using GEOSTAR Ver. 1.65 interactive graphics package. The analysis was concentrated on the main instrument pipe carrying the required...
Show moreThis thesis deals with the static analysis of a three dimensional underwater acoustic tower exclusively designed and fabricated by Harbor Branch Oceanographic Institution, Ft. Pierce, Florida. A commercial finite element package COSMOS/M was used for the finite element analysis. The structural modeling as well as processing of the results was performed using GEOSTAR Ver. 1.65 interactive graphics package. The analysis was concentrated on the main instrument pipe carrying the required instruments for data acquisition. Various environmental loading induced by ocean currents, hydrostatic pressure, buoyancy and self weight of the tower have been considered in the analysis. The construction aspects of the tower as well as the finite element analysis of tower substructures are also discussed. The deflection of the tower due to the imposed loading is studied and deflection profiles are drawn.
Show less  Date Issued
 1992
 PURL
 http://purl.flvc.org/fcla/dt/14846
 Subject Headings
 Finite element method, Offshore structures, underwater acousticsData processing
 Format
 Document (PDF)
 Title
 THREEDIMENSIONAL PHOTOELASTIC STRESS ANALYSIS OF A METALTOMETAL CONTACT BOLTED FLANGE.
 Creator
 Mahfuz, Hassan, Florida Atlantic University, Case, Robert O., College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

Threedimensional photoelastic stress analysis techniques are used to determine the stress distribution in a metaltometal contact bolted flange. The flange belongs to a thinwalled stage support casing of a jet aircraft engine. Of special interest is the state of stress experienced at flange separation due to axial and bending loads during severe inflight maneuvering. Details of model development, data collection and discussion of results for the stresses in the bolts and in the vicinity...
Show moreThreedimensional photoelastic stress analysis techniques are used to determine the stress distribution in a metaltometal contact bolted flange. The flange belongs to a thinwalled stage support casing of a jet aircraft engine. Of special interest is the state of stress experienced at flange separation due to axial and bending loads during severe inflight maneuvering. Details of model development, data collection and discussion of results for the stresses in the bolts and in the vicinity of the flange are presented.
Show less  Date Issued
 1986
 PURL
 http://purl.flvc.org/fcla/dt/14319
 Subject Headings
 Strains and stresses, Photoelasticity, MaterialsTesting
 Format
 Document (PDF)
 Title
 Evolution and application of a parallel algorithm for explicit transient finite element analysis on SIMD/MIMD computers.
 Creator
 Das, Partha S., Florida Atlantic University, Case, Robert O., Tsai, ChiTay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The development of a parallel data structure and an associated elemental decomposition algorithm for explicit finite element analysis for massively parallel SIMD computer, the DECmpp 12000 (MasPar MP1) machine, is presented, and then extended to implementation on the MIMD computer, CrayT3D. The new parallel data structure and elemental decomposition algorithm are discussed in detail and is used to parallelize a sequential Fortran code that deals with the application of isoparametric...
Show moreThe development of a parallel data structure and an associated elemental decomposition algorithm for explicit finite element analysis for massively parallel SIMD computer, the DECmpp 12000 (MasPar MP1) machine, is presented, and then extended to implementation on the MIMD computer, CrayT3D. The new parallel data structure and elemental decomposition algorithm are discussed in detail and is used to parallelize a sequential Fortran code that deals with the application of isoparametric elements for the nonlinear dynamic analysis of shells of revolution. The parallel algorithm required the development of a new procedure, called an 'exchange', which consists of an exchange of nodal forces at each time step to replace the standard gatherassembly operations in sequential code. In addition, the data was reconfigured so that all nodal variables associated with an element are stored in a processor along with other element data. The architectural and Fortran programming language features of the MasPar MP1 and CrayT3D computers which are pertinent to finite element computations are also summarized, and sample code segments are provided to illustrate programming in a data parallel environment. The governing equations, the finite element discretization and a comparison between their implementation on Von Neumann and SIMDMIMD parallel computers are discussed to demonstrate their applicability and the important differences in the new algorithm. Various large scale transient problems are solved using the parallel data structure and elemental decomposition algorithm and measured performances are presented and analyzed in detail. Results show that CrayT3D is a very promising parallel computer for finite element computation. The 32 processors of this machine shows an overall speedup of 2728, i.e. an efficiency of 85% or more and 128 processors shows a speedup of 7077, i.e. an efficiency of 55% or more. The CrayT3D results demonstrated that this machine is capable of outperforming the CrayYMP by a factor of about 10 for finite element problems with 4K elements, therefore, the method of developing the parallel data structure and its associated elemental decomposition algorithm is recommended for implementation on other finite element code in this machine. However, the results from MasPar MP1 show that this new algorithm for explicit finite element computations do not produce very efficient parallel code on this computer and therefore, the new data structure is not recommended for further use on this MasPar machine.
Show less  Date Issued
 1997
 PURL
 http://purl.flvc.org/fcla/dt/12500
 Subject Headings
 Finite element method, Algorithms, Parallel computers
 Format
 Document (PDF)
 Title
 The finite element method as a parametric tool in the design and analysis of a pressure vessel having a threaded closure.
 Creator
 Merkl, Garrett Andrew., Florida Atlantic University, Case, Robert O., Tsai, ChiTay, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
 Abstract/Description

The finite element method is a very powerful tool used to analyze a variety of problems in engineering. This thesis looks at the finite element method as a tool and several important modeling features of concern. A well known finite element software package, ANSYS, will be used to demonstrate a diverse number of its capabilities, and several procedures followed in solving a specific engineering problem. The subject matter involves a nonlinear contact analysis of a pressure vessel having a...
Show moreThe finite element method is a very powerful tool used to analyze a variety of problems in engineering. This thesis looks at the finite element method as a tool and several important modeling features of concern. A well known finite element software package, ANSYS, will be used to demonstrate a diverse number of its capabilities, and several procedures followed in solving a specific engineering problem. The subject matter involves a nonlinear contact analysis of a pressure vessel having a threaded closure. The choice of this application is prompted by an interest in better understanding how the finite element method is implemented in the design and analysis of different pressure vessel parameters. A parametric finite element analysis was performed. Load and stress distributions along the threaded region of the vessel were examined for parameters including number of threads, thread pitch, diameter ratio, closure plug length, and thread profile.
Show less  Date Issued
 1996
 PURL
 http://purl.flvc.org/fcla/dt/15243
 Subject Headings
 Finite element method, Pressure vesselsDesign and construction, Strains and stressesMathematical models
 Format
 Document (PDF)