1,720,981 research outputs found
Advanced Variable Kinematics Ritz and Galerkin Formulations for Accurate Buckling andVibration analysis of Anisotropic Laminated Composite Plates
No full textSome results on thermal stress of layered plates and shells by using unified formulation
No full textThis work presents some results on two-dimensional modelling of thermal stress problems in multilayered structures. The governing equations are written by referring to the Unified Formulation (UF) introduced by the first author. These equations are obtained in a compact form, that doesn't depend on the order of expansion of variables in the thickness direction or the variable description (layer-wise models and equivalent single layers models). Classical and refined theories based on the Principle of Virtual Displacements (PVD) and advanced mixed theories based on the Reissner Mixed Variational Theorem (RMVT) are both considered. As a result, a large variety of theories are derived and compared. The temperature profile along the thickness of the plate/shell is calculated by solving the Fourier's heat conduction equation. Alternatively, thermo-mechanical coupling problems can be considered, in which the thermal variation is influenced by mechanical loading. Exact closed-form solutions are provided for plates and shells, but also the applications of the Ritz method and the Finite Element Method (FEM) are presented. Copyright © Taylor & Francis Group, LLC
A novel instrumentation for contact force measurement in cam-follower pairs
No full textA new test rig has been designed and built to study cam-follower pairs. The apparatus is able to measure all components of the contact force by a novel six axes dynamometer, and the lubricant film thickness by optical interferometry. The aim of this work is to describe the equipment and the procedure used for characterization of the six axes dynamometer. The system contains three groups of annular quartz load cells, whose calibration is not an easy task. A specific equipment based on a particular pulleys system has been designed and realized, that allows the application of known dead weights along known directions to the dynamometer. In this way a calibration matrix, that relates the generalized contact force vector and the load cells output voltage, is evaluated
Thermal stress analysis of composite beams, plates and shells: Computational modelling and applications
No full textThermal Stress Analysis of Composite Beams, Plates and Shells: Computational Modelling and Applications presents classic and advanced thermal stress topics in a cutting-edge review of this critical area, tackling subjects that have little coverage in existing resources. It includes discussions of complex problems, such as multi-layered cases using modern advanced computational and vibrational methods. Authors Carrera and Fazzolari begin with a review of the fundamentals of thermoelasticity and thermal stress analysis relating to advanced structures and the basic mechanics of beams, plates, and shells, making the book a self-contained reference. More challenging topics are then addressed, including anisotropic thermal stress structures, static and dynamic responses of coupled and uncoupled thermoelastic problems, thermal buckling, and post-buckling behavior of thermally loaded structures, and thermal effects on panel flutter phenomena, amongst others
A 1D Ritz–Jacobi formulation for the modal analysis of 3D anisotropic laminated composite and soft-core sandwich beam structures through 2D polynomials
No full textThe present article deals with the computation of natural frequencies of 3D fibre-reinforced anisotropic laminated composite and soft-core sandwich beams by using a 1D Ritz–Jacobi formulation. Generalised higher-order beam models, based on both 2D Taylor and 2D Chebyshev polynomials, are employed in the investigation. The weak-form of the governing equations (GEs) is derived via the classical Hamilton’s principle. Jacobi polynomials are selected to be the admissible functions used to solve the GEs. Various subsets of these polynomials are considered: Legendre polynomials, Lobatto polynomials, Gegenbauer polynomials (or Ultraspherical polynomials) and Chebyshev polynomials of 1st, 2nd, 3rd and 4th kind. Convergence and stability of both cross sectional functions and admissible functions are thoroughly analysed. Several parametric analyses are performed and the effect of some relevant parameters, e.g. lamination angle, boundary condition, stacking sequence, slenderness ratio and composite type, is studied
Experimental aspects of a cam-follower contact
No full textAn experimental apparatus for investigations on cam-follower contacts is briefly described and some results related to a tested cam are presented. The apparatus is able to measure the film thickness and shape using optical interferometry and all components of the contact force through a system of nine annular load cells. The equations for the evaluation of the fundamental kinematic quantities of cam-follower pairs are reported. They are applied to the tested cam for detecting the angular positions of the most interesting conditions, as the points of maximum lift, velocity and acceleration, and the trend of the entraining velocity. The methodologies used for recording by a high speed camera connected to a microscope the interference images for the analysis of the lubricated contact are described. Some sample interference images recorded both at low and high magnification are presented showing the different conditions of the contact during a complete rotation of the cam and the capabilities of the experimental apparatus
1D-Hierarchical Ritz and 2D-GDQ Formulations for the free vibration analysis of circular/elliptical cylindrical shells and beam structures
No full textThe present paper proposes a comparison between two different computational techniques to evaluate the natural frequencies of some selected structural components. More specifically, three case studies are investigated: i) Isotropic circular and elliptical cylindrical shells; ii) Non-homogeneous circular cylindrical shell sectors; iii) Homogeneous and non-homogeneous rectangular beams. The 1D-Hierarchical Ritz Formulation (HRF) with 3D capabilities and the 2D-Generalized Differential Quadrature (GDQ) formulation (both in a weak- and a strong-form) are assessed by using a Finite Element Method (FEM) software. For both computational methodologies the Method of Power Series Expansion of the Displacement Components (MPSEDCs) has been employed. A parametric investigation is performed to study the sensitivity of the natural frequencies to some significant parameters, namely, the boundary conditions, the length-to-thickness ratio, as well as some material and geometrical properties. The main advantages of the proposed solution techniques are discussed in terms of convergence and accuracy, for each selected case study
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
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