1,721,050 research outputs found
Geometrically nonlinear refined shell theories by Carrera Unified Formulation
Full text linkIn this work, a unified formulation of full geometrically nonlinear refined shell theory is developed
for the accurate analysis of highly flexible shell structures. The tensor calculus is utilized to explicitly derive the linear and nonlinear differential operator matrices of the geometrical relation in
the orthogonal parallel curvilinear coordinate system. By employing the Carrera Unified
Formulation (CUF), various kinematics of two-dimensional shell structures are consistently formulated via an appropriate index notation and a generalized expansion of the primary variables by
arbitrary functions in the thickness direction, leading to lower- to higher-order shell models with
only pure displacement variables. Furthermore, the principle of virtual work and a finite element
approximation are exploited to straightforwardly formulate the nonlinear governing equations in a
total Lagrangian approach. Particularly, the path-following Newton–Raphson linearization method
based on the arc-length constraint is used to deal with the full geometrically nonlinear problem.
Independent of the theory approximation order, the forms of the fundamental nuclei of the secant
and tangent stiffness matrices of the unified shell element are formulated via the CUF and the
three-dimensional Green-Lagrange strain components. Numerical assessments and comparisons of
the present results with those provided in the literature for popular benchmark problems involving different metallic shell structures are found to be excellent and demonstrate the capabilities of
the developed CUF shell model to predict the post-buckling, large-deflection, snap-through and
snap-back nonlinear responses with high accurac
Tuning the pull-in instability of soft dielectric elastomers through loading protocols
No full textPull-in (or electro-mechanical) instability occurs when a drastic decrease in the thickness of a dielectric elastomer results in electrical breakdown, which limits the applications of dielectric devices. Here we derive the criterions for determining the pull-in instability of dielectrics actuated by different loading methods: voltage-control, charge-control, fixed pre-stress and fixed pre-stretch, by analyzing the free energy of the actuated systems. The Hessian criterion identifies a maximum in the loading curve beyond which the elastomer will stretch rapidly and lose stability, and can be seen as a path to failure. We present numerical calculations for neo-Hookean ideal dielectrics, and obtain the maximum allowable actuation stretch of a dielectric before failure by electrical breakdown. We find that applying a fixed pre-stress or a fixed pre-stretch to a charge-driven dielectric may decrease the stretchability of the elastomer, a scenario which is the opposite of what happens in the case of a voltage-driven dielectric. Results show that a reversible large actuation of a dielectric elastomer, free of the pull-in instability, can be achieved by tuning the actuation method
Sustainable cycles and management of plastics: A brief review of RCR publications in 2019 and early 2020
Full text linkPlastics have been playing a vital role in the industrialized economy, resulting in the growing amount of plastic waste and the surging attentions to plastics sustainability challenge. This is well reflected in the growing amount of submissions to and publications in Resources, Conservation, and Recycling on plastics, which made the editorial board decide to edit a Virtual Special Issue (VSI) on the “sustainable cycles and management of plastics” in 2018. The call for the VSI has attracted many submissions and twelve were accepted for publication. Together with several other relevant studies, we collected and summarized a total of 26 papers published in RCR mainly during 2019–2020 in this editorial. These papers mostly apply system approach and cover very wide topics such as material flows analysis and circular economy, life cycle assessment and eco-design, regional and global plastic emissions, and human consumption behavior. The whole collection of them offer a comprehensive view of the plastic waste challenges, as well as insights into achieving sustainability in plastic cycles and management. We believe these papers are helpful for government, industries, and individuals in exploring policy implications for building a more sustainable plastics system
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Propagation of non-axisymmetric waves in an infinite soft electroactive hollow cylinder under uniform biasing fields
No full textBased on Dorfmann and Ogden's nonlinear theory of electroelasticity and the associated linear incremental theory, the non-axisymmetric wave propagation in an infinite incompressible soft electroactive hollow cylinder under biasing fields is investigated. The biasing fields are uniform, including an axial pre-stretch and a radial stretch in the plane perpendicular to the axis of the cylinder as well as an axial electric displacement. Such biasing fields make the originally isotropic electroactive material behave during its incremental motion like a conventional transversely isotropic piezoelectric material, hence greatly facilitating the following analysis. The three-dimensional equations of wave motion in cylindrical coordinates are derived and exactly solved by introducing three displacement functions. The exact solution is expressed in terms of Bessel functions, and explicit frequency equations are presented in different cases. For a prototype nonlinear model of electroactive material, numerical results are given and discussed. It is found that the initial biasing fields as well as the geometrical parameters of the hollow cylinder have significant influences on the wave propagation characteristics
Large-deflection and post-buckling analyses of isotropic rectangular plates by Carrera Unified Formulation
No full textVariations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Nonlinear static analysis of metamaterial structures based on the Kagome lattice using beam finite elements and component-wise approach
No full textThis work numerically investigates the mechanical behavior of metamaterial structures inspired by the Kagome lattice mechanism using the Carrera Unified Formulation (CUF). The proposed numerical model employs enhanced one-dimensional finite elements with three-dimensional capabilities, enabling precise predictions of deformation patterns and stress–strain responses under various loading conditions. With CUF, any three-dimensional effects can be captured, allowing for the analysis of the width direction of these metamaterial structures, potentially accounting for varying geometric properties. The model's robustness is demonstrated through its ability to capture critical phenomena such as buckling, post-buckling behavior, and rigid-body rotations of lattice triangles, which are hallmarks of the Kagome lattice's unique mechanical properties. The introduction of stiffer hinges highlights the potential for tailoring mechanical responses to meet specific design requirements, such as enhanced load-carrying capacity and optimized energy absorption. This study demonstrates the versatility of Kagome lattice-based metamaterials and lays the groundwork for future research, including the analysis of 3D Kagome-lattice metamaterials facilitated to the proposed numerical model
Accurate stress fields of post-buckled laminated composite beams accounting for various kinematics
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