1,721,074 research outputs found
Free vibrations analysis of cracked variable stiffness composite plates by the eXtended Ritz method
Full text linkVariable stiffness composite laminates show advantageous structural features related to their enlarged design space. They are attractive candidates for advanced engineering applications where the assessment of static and dynamic behavior and strength in the presence of cracks is often required. In the present work, a single-domain extended Ritz formulation is proposed to study the free vibrations of cracked variable stiffness composite plates. The plate model is based on the first-order shear deformation theory whose primary variable, i.e. displacements and rotations, are approximated via a set of orthogonal polynomial trial functions enriched with a set of special crack functions. These functions are able to inherently account for crack opening and crack tip singular fields. The plate governing equations are deduced by the stationarity of the energy functional and the formulation has been implemented in a computer code. The method has been validated by comparing the present results with literature solutions for cracked isotropic plates and uncracked variable stiffness plates as, to the best of author's knowledge, no data on cracked variable stiffness plates free vibrations are available. An explicative and representative study on the free vibrations of variable angle tow composite laminates is finally presented with the aim of illustrating the approach capabilities, providing benchmarck results and identifying distinctive features and opportunities of the variable stiffness concept for the design of advanced damage tolerant structures
IMPLICIT MESH DISCONTINUOUS GALERKIN FOR VARIABLE ANGLE TOW MULTILAYERED PLATES
No full textThis works presents a novel computational scheme for variable angle tow (VAT) multilayered
plates [1]. The characteristic features of the proposed scheme are the combined
use of a discontinuous Galerkin (dG) formulation and an implicitly defined mesh. The
formulation is based on the principle of virtual displacements (PVD) and the Equivalent
Single Layer (ESL) assumption for the mechanical behavior of the VAT plates [2].
The problem is first placed within the dG framework by suitably introducing an auxiliary
variable and by rewriting the set of equations governing ESL VAT plates as a firstorder
system of differential equations. Following Arnold et al.[3] and by introducing
suitably defined average and jump operators, the primal formulation for ESL theories of
VAT multilayered plates is obtained. Two dG formulations are considered, namely the
Internal Penalty and the Compact Discontinuous Galerkin methods, which are obtained
by suitably specifying the corresponding numerical fluxes.
Subsequently the numerical implementation is discussed. First, the mesh elements are
defined using a reference background quad-tree grid and the implicit representation of the
considered domain’s boundaries. Then, the elemental matrices are computed using the
algorithm proposed by Saye [4] for the integration over implicitly defined domains and
boundaries. To show the potential of the scheme, numerical tests are performed on VAT
plates with simple and more complex geometries such as curved edges and cutouts
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
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
NONLOCAL LAYER-WISE ADVANCED THEORIES FOR LAMINATED PLATES
No full textEringen nonlocal layer-wise models for the analysis of multilayered plates are formulated in the framework of the Carrera Unified Formulation and the Reissner Mixed Variational Theorem (RMVT). The use of the layer-wise approach and RMVT ensures the fulfilment of the transverse stress equilibrium at the layers’ interfaces and allows the analysis of plates with layers exhibiting different characteristic lengths in their nonlocal behaviour. A Navier solution has been implemented and tested for the static bending of rectangular simply-supported plates. The obtained results favourably compare against available three-dimensional analytic results and demonstrate the features of the proposed theories
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
VIRTUAL ELEMENT METHOD FOR COMPUTATIONAL HOMOGENIZATIONS OF UNIDIRECTIONAL FIBER-REINFORCED COMPOSITE MATERIALS
No full textThe Virtual Element Method (VEM) is a generalization of the Finite Element Method (FEM) for the treatment of general polygonal/polyhedral mesh elements. Despite its recent introduction, VEM has been applied to several problems in structural mechanics. Due to such capability of dealing with mesh elements of general shape and of naturally addressing the presence of hanging nodes, the VEM ensures a noticeable simplification in the data preparation stage of the analysis, allowing implementing a mesh generation process over complex multi-domain geometries in a fully automated way. Moreover, for the lowest order VEM used in this contribution,no numerical integration is required to compute the system stiffness matrix, thus considerably reducing the computational cost of the analysis with respect to standard FEM. In this contribution, we present an application of the lowest order VEM to the material homogenisation of unidirectional (UD) fibre-reinforced materials. The representation of a material microstructure generally constitutes a remarkable effort in terms of input preparation, especially when there is not evident microstructural symmetry. For such a reason, computational icromechanics may represent a challenging benchmark for showing the potential of VEM, which forms the aim of the present work
A BOUNDARY ELEMENT FORMULATION FOR MICROMECHANICAL HOMOGENIZATION OF POLYCRYSTALLINE MATERIALS WITH PIEZOELECTRIC COUPLING
No full textA novel boundary element formulation for the evaluation of the effective properties of threedimensional polycrystalline aggregates with piezoelectric coupling is presented. The aggregates are modelled at the scale of their constituent crystals and are artificially generated through Voronoi-Laguerre tessellations. The electro-mechanical behaviour of each crystal is represented upon introducing an ad-hoc mesh of its boundary and a generalised integral representation of the governing equations of the piezoelectric problem. The behaviour of the whole aggregate is then retrieved upon introducing a suitable set of electro-mechanical interface conditions at the grain boundaries. With respect to classic FE formulations, the present approach has the advantages of: i) expressing the problems in term of boundary values only, thus allowing a natural expression of the interface conditions; ii) requiring the grain boundary mesh only, thus reducing the meshing effort; iii) reducing the number of degrees of freedom of the problem, which is highly desirable in three-dimensional problems. Numerical analyses are performed to study the effect of the statistical distribution of the grains’ orientation on the effective properties of BaTiO3 aggregates. The obtained results are consistent with theoretical estimates and the results available in the literature, showing the potential and accuracy of the proposed formulation
SHM of Vibrating Stay-Cables by Microwave Remote Sensing
Full text linkA radar equipment was used to measure the deflection response of bridge stay-cables induced by ambient and traffic excitation. After a concise description of the radar equipment and a summary of advantages and potential issues of the microwave technology, the paper focuses on the experimental tests performed on all stay-cables of the curved cable-stayed bridge erected in the commercial harbor of Porto Marghera, Venice, Italy. The bridge consists of an inclined concrete tower, single-plane cables and a composite deck; the curved deck has a centerline length of 231 m, with two different side spans and 9 cables supporting each side span. Three series of ambient vibration tests were performed (on July 2010, April 2011 and October 2019) on the two arrays of cables of the bridge by using conventional accelerometers and microwave interferometer. The availability of simultaneously collected radar and accelerometer data (which are usually regarded as reference data in dynamic tests) allowed to investigate the accuracy of the radar technique (in terms of natural frequencies and tensile force estimated from natural frequencies) and the errors/uncertainties in radar results. Furthermore, the tests allowed to verify the repeatability of radar survey, with SHM purposes.Accepted author manuscriptMechanics and Physics of Structure
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