Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"Geometric Imperfections"”.
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Fabrication and buckling of thin spherical shells containing precise geometric imperfections
… uniform pressure and explore the effect that geometric imperfections can have on their buckling behavior. Since the 1960s, numerous theoretical and computational studies have addressed the imperfection sensitivity of buckling of thin elastic shells. However, there is a lack of precise …
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A new scheme for the optimum design of stiffened composite panels with geometric imperfections
… property of being highly sensitive to geometrical imperfections. Existing analysis codes are able to predict the nonlinear postbuckling behavior of a structure with specified imperfections. However, it is impossible to determine the geometric imperfection profile of a nonexistent …
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Effect of Geometric Imperfections (Wrinkles) on the Circumferential Strength of a Composite Polymer Liner for Pressure Pipes
… iron water pipes can result in the formation of geometric imperfections (wrinkles) as the external diameter of the liner often exceeds the internal diameter of the host pipe. Previous studies have suggested that the wrinkles have a detrimental effect on the structural performance of the liner. In …
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Nonlinear Stability Analysis of Frame-Type Structures with Random Geometric Imperfections Using a Total-Lagrangian Finite Element Formulation
… that a structure having random initial geometric imperfections will become unstable at a load less than a specified fraction of the perfect critical load. The overall objective of this dissertation is to present such a method for frame-type structures that become unstable at limit …
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Thermal Bending, Buckling and Post-Buckling Analysis of Unsymmetrically Laminated Composite Beams with the Effects of Moisture and Geometric Imperfections
… derived by taking into account the von-Karman geometrical nonlinearity for an imperfect unsymmetrical laminated composite beam. Classical beam theory (CBT) as well as first order shear deformation theory (FSDT) will be used. The effects of temperature, angle of orientation, moisture variations, …
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Reliability analyses of the collapse and burst of elastic/plastic tubes
… of burst and collapse of tubes with random geometric imperfections under internal or external pressure. Steel tubes have broad applications in petroleum offshore engineering and must be designed to a safe but yet economical standard. The variation of imperfections from tube to tube …
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Numerical and experimental investigation of the bending response of thin-walled composite cylinders
… [±45/02]S and [±45/902]s, are studied. A geometrically nonlinear special-purpose analysis, based on Donnell's nonlinear shell equations, is developed to study the prebuckling responses and gain insight into the effects of non-ideal boundary conditions and initial geometric imperfections. A …
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Active control of passive safety in passenger motor vehicles : a feasibility study investigating dynamic denting of members using pyrotechnic devices
… to determine the limitations imposed on the geometric imperfections that could be achieved by the use of explosive. It was found that all the explosively induced deformations were rounded, i.e. the dents were hemi-spherical in shape. It was also found that a smooth edged round hole could be …
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Análise modal assintótica da estabilidade de estruturas reticuladas espaciais
… also permits the study of the influence of small geometric imperfections.
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Estabilidade local de painéis cilíndricos enrijecidos
… as well as modal interaction and inicial geometric imperfections are investigated. It is shown that the use of slender stiffeners as suggested by the orthotropic theory, can lead to interaction between local and overall modes resulting in primary bifurcation loads lower than the classical …
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Influência da interação entre modos e imperfeições na flambagem de cascas cilíndricas axialmente comprimidas
… are the effects that mode coupling and initial geometric imperfections have on the non-linear buckling behaviour. It is shown, through the inspection of energy distributions, that the stabilizing membrane energy contributions are eroded substantialy during the imperfection-sensitive non-linear …
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Collapse behaviour of double layer grid structures in steel
… behaviour and sensitivity of such structures to geometric imperfections for selected cases but have not developed the full spectrum of DLG behaviour. A parameter study was therefore undertaken to identify desirable DLG pre-critical yielding behaviour and post-critical increases in grid structural …
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Large deformation behavior of long shallow cylindrical composite panels
… influence the nonlinear static response. Initial geometric imperfections, observed during testing, were found to influence the response of the panels. However, the overall correlation of analytic and experimental results were good.
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Free vibration and nonlinear transient analysis of imperfect laminated structures
… structures is studied in the presence of geometric and stress imperfections. The stress imperfections are the initial stresses as caused by preloads. Using a 48 degrees of freedom thin shell element, the effect of complex, arbitrary in-plane and out-of-plane loads on the transverse …
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Impact response of composite structures to rigid and flexible projectiles
… plate theory, which is capable of modeling geometric imperfections is used to model the shell. Linear and geometrically nonlinear transient responses are obtained using reduction methods based on the use of (i) natural modes and (ii) the Ritz vectors (also called Lanczos’ vectors) as the …
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Effects of residual stresses and initial imperfections on earthquake response of steel moment frames
… seismic loading, includes the effects of initial geometric imperfections and inelastic behavior compounded by residual stresses, it is critical to explore the impact of these parameters on the seismic behavior of typical steel buildings before the DM is required for seismic design. To examine …
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Nonlinear Finite Element Analyses of the End Web Crippling Strength of W-Shape Steel Beams
… large deformation effects and initial geometric imperfections were taken into account in the finite element models. The validation results shown that the finite element models closely predicted the ultimate load and web crippling failure mode shape of the tested beams. Conclusions based …
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Buckling and postbuckling of flat and curved laminated composite panels under thermomechanical loadings incorporating non-classical effects
… of shallow shells that include the effects of geometric nonlinearities and initial geometric imperfections. Within the first model (Model I), the kinematic continuity at the contact surfaces between the contiguous layers and the free shear traction condition on the outer bounding surfaces are …
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Evaluation of moment redistribution for hybrid HPS 70W bridge girders
… are capable of addressing the influences of both geometric and material non-linearity. Specific ABAQUS subroutines were developed for this effort that are used to introduce specified geometric imperfections and residual stresses in the FEA models.;Results from the parametric studies are used to …
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