1,721,167 research outputs found
Contact with friction between beams in 3-D Space
No full textIn this paper a formulation to deal with friction between straight beams undergoing large displacements in 3-D space is proposed. The detection of the contact point and the computation of the amount of sliding are carried out using a completely symmetric treatment between the two contacting beams. Starting from the virtual work equation the consistent linearization of the frictional contact contribution is computed and the complete equation set is arranged in matrix form suitable for FE implementation. Some numerical examples are added to show the eectiveness of the method
A formulation for frictionless contact problems using a weak form introduced by Nitsche
No full textIn this paper a finite element formulation for frictionless contact problems with non-matching meshes in the contact interface is presented. It is based on a non-standard variational formulation due to Nitsche and leads to a matrix formulation in the primary variables. The method modifies the unconstrained functional by adding extra terms and a stabilization which is related to the classical penalty method. These new terms are characterized by the presence of con- tact forces that are computed from the stresses in the contin- uum elements. They can be seen as a sort of Lagrangian-type contributions. Due to the computation of the contact forces from the continuum elements, some additional degrees-of- freedom are involved in the stiffness matrix parts related to contact. These degrees-of-freedom are associated with nodes not belonging to the contact surfaces
Interaction between different internal length scales for strain localisation analysis of single phase materials
No full textIt is well known that both rate dependent and
gradient-dependent constitutive models introduce internal
length scales in dynamic initial value problems. As a result,
numerical solutions of such initial value problems involving
strain-softening no longer exhibit excessive mesh
dependence. In this paper, the length scales included in a
solid model which exhibits both above mentioned constitutive
behaviours are discussed. The internal length
scales derived from damping effects, which are typical for
the viscoplastic models, and the wave length, obtained
from the critical wave number for which the wave speed is
not imaginary, are used together to give a prediction of the
internal length scale of the combined model. The approach
proposed here for prediction of the internal length scale is
more general than commonly used procedures and permits
to explain phenomena observed in viscoplastic and
gradient dependent models. A one dimensional example is
given to illustrate the theoretical findings
Electric-Mechanical Beam-to-beam Contact
No full textIn this paper the formulation of an electric-mechanical beam-to-beam contact element is presented. Beams with circular cross-sections are assumed to get in contact in a point-wise manner and with clean metallic surfaces. The voltage distribution is influenced by the contact mechanics, since the current flow is constricted through small contacting spots. Therefore the solution is governed by the contacting areas and hence by the contact forces. As a consequence the problem is semi-coupled with the mechanical field influencing the electric one. The electric-mechanical contact constraints are enforced with the penalty method within the Finite Element technique. The virtual work equations for the mechanical and electric fields are written and consistently linearized to achieve a good level of computational efficiency with the FE method. The equations set is solved with a monolithic approach
Electro-Mechanical Coupling in Beam-To-Beam Contact
No full textThis paper is a further step towards the full analysis of the complex behaviour of contacting beams in the coupled thermo-electro-mechanical field. Now we add to our previous work the coupling with the thermal field. The coupling between electric, mechanical and thermal fields is manifested in: dependence of material parameters on the temperature, frictional heating, heat generation by the electric current flow, dependence of the contact area on the temperature, dependence of thermal and electric fields on the change of the contact area and the contact point position. In the present preliminary analysis we take into account only the last aspect. We also consider the indirect influence of thermal contact on the mechanical field using the thermo-mechanical beam element. The contact constraints are enforced with the penalty method within the finite element technique. It is assumed that the heat flow in the contact area is unlimited which leads to the equalling of temperatures between two contacting bodies. This constraint is also introduced by the penalty method. The set of governing equations including the coupling is solved by the monolithic scheme. The problem is non-linear, hence the linearized version of equations is derived. The consistent linearization leading to the consistent tangent stiffness matrix and the corresponding residual vector is performed to apply efficiently the Newton-Raphson method and to ensure the quadratic convergence. Some numerical examples are presented to show the efficiency of the suggested approach
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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