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Buckling of composite cylindrical shells with geometric, thickness and material imperfections
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)
Dynamic stability of fluid-conveying pipes on uniform or non-uniform elastic foundations
Title
Dynamic stability of fluid-conveying pipes on uniform or non-uniform elastic foundations.
Creator
Vittori, Pablo J., Florida Atlantic University, Elishakoff, Isaac, College of Engineering and Computer Science, Department of Ocean and Mechanical Engineering
Abstract/Description
The dynamic behavior of straight cantilever pipes conveying fluid is studied, establishing the conditions of stability for systems, which are only limited to move in a 2D-plane. Internal friction of pipe and the effect of the surrounding fluid are neglected. A universal stability curve showing boundary between the stable and unstable behaviors is constructed by finding solution to equation of motion by exact and high-dimensional approximate methods. Based on the Boobnov-Galerkin method, the...
Show moreThe dynamic behavior of straight cantilever pipes conveying fluid is studied, establishing the conditions of stability for systems, which are only limited to move in a 2D-plane. Internal friction of pipe and the effect of the surrounding fluid are neglected. A universal stability curve showing boundary between the stable and unstable behaviors is constructed by finding solution to equation of motion by exact and high-dimensional approximate methods. Based on the Boobnov-Galerkin method, the critical velocities for the fluid are obtained by using both the eigenfunctions of a cantilever beam (beam functions), as well as the utilization of Duncan's functions. Stability of cantilever pipes with uniform and non-uniform elastic foundations of two types are considered and discussed. Special emphasis is placed on the investigation of the paradoxical behavior previously reported in the literature.
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Date Issued
2004
PURL
http://purl.flvc.org/fcla/dt/13167
Subject Headings
Strains and stresses, Structural dynamics, Structural stability, Fluid dynamics, Vibration
Format
Document (PDF)