Nonlinear stability of elastic elliptical cylindrical shells under uniform bending

Xu, Zixiang; Gardner, Leroy; Sadowski, Adam J.

doi:10.1016/j.ijmecsci.2017.05.022

Cited by 23 publications

(22 citation statements)

References 25 publications

(58 reference statements)

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“…For every combination of length, boundary condition and imperfection form, eight normalised equivalent geometric deviations d e /t of 0.1, 0.25, 0.35, 0.5, 0.75, 1.0, 1.5 and 2.0 were investigated with GNIAs, although LBAs and GNAs were also performed on the perfect shell at each combination of length and boundary condition. The study purposefully omits d e /t amplitudes deeper than 2.0 for the imposed ovalisation imperfection form as such geometries are closer to elliptical cylinders than circular ones and were the focus of a recent dedicated study by Xu et al (2017). A summary of the individual computational analyses is presented in Table 1. In the second part, the extent to which the findings of the first part may considered to be independent of the r/t ratio are explored through an additional set of GNIAs performed at varying O (i.e.…”

Section: Summary Of Parameter Studies and Automation Of Computationalmentioning

confidence: 99%

Imperfection sensitivity in cylindrical shells under uniform bending

Fajuyitan

Sadowski

2018

Advances in Structural Engineering

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Efforts are ongoing to characterise a comprehensive resistance function for cylindrical shells under uniform bending, a ubiquitous structural system that finds application in load-bearing circular hollow sections, tubes, piles, pipelines, wind turbine support towers, chimneys and silos. A recent computational study by Rotter et al. (2014) demonstrated that nonlinear buckling of perfect elastic cylinders under bending is governed by four length-dependent domains-'short', 'medium', 'transitional' and 'long'-depending on the relative influence of end boundary conditions and cross-section ovalisation. The study additionally transformed its resistance predictions into compact algebraic relationships for use as design equations within the recently-developed framework of Reference Resistance Design (RRD). This paper extends on the above to present a detailed computational investigation into the imperfection sensitivity of thin elastic cylindrical shells across the most important length domains, using automation to carry out the vast number of necessary finite element analyses. Geometric imperfections in three forms-the classical linear buckling eigenmode, an imposed cross-section ovalisation, and a realistic manufacturing 'weld depression' defectare applied to demonstrate that imperfection sensitivity is strongly length-dependent but significantly less severe than for the closely-related load case of cylinders under uniform axial compression. The axisymmetric weld depression almost always controls as the most deleterious imperfection. The data is processed computationally to offer an accurate yet conservative lower-bound algebraic design characterisation of imperfection sensitivity for use within the RRD framework. The outcomes are relevant to researchers and designers of large metal shells under bending and will appeal to computational enthusiasts who are encouraged to adopt the automation methodology described herein to explore other structural systems.

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Section: Summary Of Parameter Studies and Automation Of Computationalmentioning

confidence: 99%

Imperfection sensitivity in cylindrical shells under uniform bending

Fajuyitan

Sadowski

2018

Advances in Structural Engineering

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“…7. Such curves were previously constructed for cylinders under uniform bending and global transverse shear (Xu et al, 2017;Liu et al, 2018), and Xu et al (2017) had also used the original algebraic relationship of Brazier (1927) to show that 'infinitely long' cylinders under uniform bending attain an upper bound of Umax ≈ 0.34 at fully-developed ovalisation. These distributions confirm that cylinders with low load eccentricities (dominated by uniform compression) exhibit very little pre-buckling ovalisation, but those with higher eccentricities undergo increasingly higher levels of ovalisation approaching the Umax upper bound as ξ → π/2…”

Section: Geometric Nonlinearities In Cylindrical Shells Under Combinementioning

confidence: 99%

“…A cylindrical shell under the combined actions of uniform axial compression and uniform bending constitutes a common generic system that finds widespread practical application, for example as wind turbine support towers, chimneys, tubular piles and circular hollow section (CHS) beam-column members. The ultimate resistance of these 33 is known to be controlled by many phenomena, including material plasticity (Rotter and Sadowski, 2017), nonlinearity of the stress-strain relationship in metals other than mild steel (Zhao et al, 2016a;2016b), elastic and elastic-plastic instability (Yamaki, 1984;36 Chen et al, 2008;Rotter et al, 2014), geometric imperfections (Rotter and Teng, 1989; 37 Rotter and Al-Lawati, 2016; and, where long members are subject to bending, cross-sectional ovalisation (Brazier, 1927;Rotter et al, 2014;Xu et al, 2017;. The ovalisation phenomenon may be especially pronounced in long thin-walled cylinders if the pre-buckling behaviour is dominated by the elastic fundamental response.…”

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confidence: 99%

Elastic Imperfect Cylindrical Shells of Varying Length under Combined Axial Compression and Bending

Wang

Sadowski

2020

J. Struct. Eng.

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This paper presents a comprehensive computational investigation into the elastic nonlinear buckling response of near-perfect and highly imperfect uniform thickness thin cylindrical shells of varying length under combined uniform compression and bending. In particular, the elastic ovalisation phenomenon in cylindrical shell of sufficient length under combined compression and bending was systematically investigated with finite elements for the first time. The study considered a representative range of practical lengths up to very long cylinders where ovalisation is fully developed under uniform bending and Euler column buckling controls under uniform axial compression. The imperfection sensitivity of the system was also studied by introducing a single idealised axisymmetric weld depression imperfection at the midspan of the cylinder. The predictions permit an exploration of the nonlinear mechanics of the generally unfavourable interaction between bending and axial compression at the elastic nonlinear buckling limit state in thin long cylinders. The interaction is at its most unfavourable in cylinders where Euler column buckling is about to become critical, and is qualitatively very different from the favourable moment-force interaction at the reference plastic limit state of circular tubes. A simple closed-form algebraic characterisation of the interaction is proposed considering both imperfections and ovalisation.

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“…Figure 22c also depicts a similar structure, although the ellipses present a bigger eccentricity compared to the ellipses in Figure 22b, due to the new distribution of the filaments in the thread. The phenomenon which studies the deformation of these ellipses is known as buckling [46].…”

Section: Deformation Of Woven Structuresmentioning

confidence: 99%

From Threads to Smart Textile: Parametric Characterization and Electromagnetic Analysis of Woven Structures

et al. 2019

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This paper presents a complete and enhanced description of a parametric characterization and an electromagnetic analysis technique in order to simulate complex woven structures for the design of wearable microwave circuits and antennas based on smart textile. On the one hand, the parametric characterization consists of achieving the mathematical models which describe the different patterns conformed by the threads of the woven structures. This characterization takes into account the possible deformations of the materials inside the woven structure. On the other hand, the electromagnetic analysis technique consists of studying the conductive or dielectric parameters which describe the materials from which the threads have been extruded, and predicting the electromagnetic behavior of whole woven structures using the already explained parametric characterization. For this purpose, three different, although electromagnetically equivalent, models of the involved materials are needed, which subsequently reduce the computational resources required in the simulations. As a result, the woven structures can be characterized from the involved threads and the electromagnetic behavior can be analyzed in order to design wearable antennas or circuits.

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Nonlinear stability of elastic elliptical cylindrical shells under uniform bending

Cited by 23 publications

References 25 publications

Imperfection sensitivity in cylindrical shells under uniform bending

Imperfection sensitivity in cylindrical shells under uniform bending

Elastic Imperfect Cylindrical Shells of Varying Length under Combined Axial Compression and Bending

From Threads to Smart Textile: Parametric Characterization and Electromagnetic Analysis of Woven Structures

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