1,720,965 research outputs found
Modeling and Design of Multi-Stable Composite Structures
Full text linkL'abstract è presente nell'allegato / the abstract is in the attachmen
Dynamic response analysis of structures through component-wise models
No full textThis paper investigates the enhanced capabilities of the Component-Wise approach (CW) in the case of dynamic loadings. 1D (beam) advanced finite element models and the Newmark time integration scheme are employed as in [1]. The structural models are obtained by means of the Carrera Unified Formulation (CUF)[2, 3]. By means of the CUF, arbitrarily refined 2D and 1D structural models can be implemented in a unified and hierarchical manner. CUF models provide extremely accurate results with very low computational costs, e.g. 10 to 100 times less degrees of freedom than shell and solid models. The use of Lagrange polynomials to model the cross-sectional displacement field leads to the CW modeling. The CW provides a detailed physical description of the real structure since each component can be modelled with its material characteristics, that is, no homogenization techniques are required. Furthermore, although 1D models are exploited, the problem unknown variables can be placed on the physical surfaces of the real 3D model. No artificial surfaces or lines have to be defined to build the structural model. In this paper, a number of numerical assessments are carried out. Closed form solutions and shell/solid models are employed for comparison purposes. Compact and thin-walled structures are considered. Isotropic and composite materials are used. The results prove that the present 1D CW approach offers shell- and solid-like accuracy with lower computational cost
A static analysis of three-dimensional sandwich beam structures by hierarchical finite elements modelling
Full text linkA static analysis of three-dimensional sandwich beam structures using one-dimensional modelling approach is presented within this paper. A family of several one-dimensional beam elements is obtained by hierarchically expanding the displacements over the cross-section and letting the expansion order a free parameter. The finite element approximation order over the beam axis is also a formulation free parameter (linear, quadratic and cubic elements are considered). The principle of virtual displacements is used to obtain the problem weak form and derive the beam stiffness matrix and equivalent load vectors in a nuclear, generic form. Displacements and stresses are presented for different load and constraint configurations. Results are validated towards three-dimensional finite element solutions and experimental results. Sandwich beams present a three-dimensional stress state and higher-order models are necessary for an accurate description. Numerical investigations show that fairly good results with reduced computational costs can be obtained by the proposed finite element formulation
Evaluation of Damage Effects on Metallic and Composite Aerospace Structures via Refined Models
No full textThis paper presents the structural dynamics analysis of damaged structures by means of 1D (beam) advanced finite element models. Metallic and composite structures for aerospace applications are considered and the Component-Wise (CW) modelling approach is adopted. The structural models are obtained by means of the Carrera Unified Formulation (CUF)[1, 2]. By means of the CUF, arbitrarily refined 2D and 1D structural models can be implemented in a unified and hierarchical manner. CUF models provide extremely accurate results with very low computational costs. In particular, 1D CUF models require 10 to 100 times less degrees of freedom than shell and solid models, respectively. The use of Lagrange polynomials to model the cross-sectional displacement field leads to the CW modeling. The CW provides a detailed physical description of the real structure since each component can be modelled with its material characteristics, that is, no homogenization techniques are required. Furthermore, although 1D models are exploited, the problem unknown variables can be placed on the physical surfaces of the real 3D model. No artificial surfaces or lines have to be defined to build the structural model. Global and local damages are introduced by decreasing the stiffness properties of the material in the damaged regions as in [3]. In this paper, free vibration and dynamic response analyses are carried out to provide guidelines on the mechanical behavior of damaged structure
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
A thermal stress analysis of functionally graded beam structures by hierarchical finite elements
No full textIn this study, the thermoelastic behaviour of three-dimensional functionally graded beams is investigated. The temperature field is treated as an external load within the mechanical analysis and it is obtained by exactly solving Fourier's heat conduction equation. The three-dimensional beam is modelled through advanced one-dimensional finite elements derived via hierarchical expansion of the displacements over the cross-section. The approximation order of the displacement field is a free parameter that leads to the formulation of a family of several beam elements. The number of nodes per elements is also a free parameter. Linear, quadratic and cubic variations over the beam axis are considered. The governing algebraic equations are obtained via the Principle of Virtual Displacements. Displacements and stresses are evaluated and results are validated towards three-dimensional FEM results as well as analytical solutions. The temperature load results in a three-dimensional stress state that calls for accurate models. Numerical investigations show that the proposed finite elements yield accurate yet computationally efficient solutions
A thermal stress finite element analysis of isotropic and laminated beams via unified formulation
No full textIn this work the mechanical and thermal behaviour of three-dimensional isotropic and laminated beams is investigated. The beam-like three dimensional structure is modelled through refined 1D finite elements obtained via hierarchical expansion of the displacement field over the cross-section coordinates. The approximation order of the displacements is a free parameter that leads to the formulation of a family of several beam elements. Linear, quadratic and cubic one-dimensional finite elements are considered. The governing algebraic equations are obtained via the Principle of Virtual Displacements.The temperature field is obtained by exactly solving Fourier's heat conduction equation and it is treated as an external load within the mechanical analysis. Results in terms of displacements and stresses are validated towards three-dimensional FEM results as well as analytical solutions. Numerical investigations show that the proposed finite elements yield accurate yet computationally efficient solutions for the three-dimensional stress state generated by the thermal load
Variations 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
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
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