1,721,026 research outputs found
A review on 2D models for the description of pantographic fabrics
No full textA review on models for pantographic fabrics, a new promising kind of metamaterials, is presented. We treat those models that are able to capture the peculiar effects conferred by their specific microstructure and that can be generalized for the description of more complex metamaterials. For each approach, model formulation and modeling assumptions are discussed along with the presentation of numerical solutions in exemplary cases and no attempt is made to model damage and failure phenomena
Fluid diffusion related aging effect in a concrete dam modeled as a Timoshenko beam
No full textAging related damage within a concrete dam is often associated with the diffusion of certain particles which then activate internal chemical action. In this paper, a hemivariational method for a nonhomogeneous and damaged Timoshenko beam model is proposed in order to describe damage and deformation in a dam caused by the diffusion of an aging fluid. The proposed model is used to perform a suite of parametric studies. In these studies, the dam is subjected not only to the concentrated and distributed external forces and couples (dual of displacement and rotation of the section, respectively) but also to the dual of the concentration of the aging fluid, called external distributed aging fluid influx pressure, that drives the incoming flow of the aging fluid which is, for this purpose, coupled with the damage evolution. The results are utilized to predict the life time of the dam. The life of big structures is a crucial point in civil engineering because it is linked with the safeguarding of human life
A novel structural resilience index: definition and applications to frame structures
No full textResilience is the ability to undergo disruptive events without suffering complete failure and minimizing undesirable consequences thereof. Many attempts have been done in the recent literature in order to define quantitatively synthetic resilience measures of mechanical structures. They have been conceived as to be useful in comparing and classifying the resilience of different structures. In this paper we propose a novel rational and deterministic structural resilience index, based on a worst-case disruptive event, and making use of a minimalistic kinematics-based mechanical description. Particular emphasis is given to the computation of such a new structural resilience index for a generic frame structure, it being possible without the use of automated algorithms and an analytic expression of it has been achieved in terms of the numbers of ports (modules) and floors. First of all, keeping fixed the number of modules, the resilience index decreases as the number of floors increases. Secondly, keeping fixed the number of floors, the resilience index increases as the number modules increases. Finally, we notice that the case with infinite floors has a lower resilience index with respect to case of infinite modules, which is, as expectable, more resilient
Hemivariational continuum approach for granular solids with damage-induced anisotropy evolution
No full textMechanical behavior of materials with granular microstructures is confounded by unique features of their grain-scale mechano-morphology, such as the tension–compression asymmetry of grain interactions and irregular grain structure. Continuum models, necessary for the macro-scale description of these materials, must link to the grain-scale behavior to describe the consequences of this mechano-morphology. Here, we consider the damage behavior of these materials based upon purely mechanical concepts utilizing energy and variational approach. Granular micromechanics is accounted for through Piola’s ansatz and objective kinematic descriptors obtained for grain-pair relative displacement in granular materials undergoing finite deformations. Karush–Kuhn–Tucker (KKT)-type conditions that provide the evolution equations for grain-pair damage and Euler–Lagrange equations for evolution of grain-pair relative displacement are derived based upon a non-standard (hemivariational) variational approach. The model applicability is illustrated for particular form of grain-pair elastic energy and dissipation functionals through numerical examples. Results show interesting damage-induced anisotropy evolution including the emergence of a type of chiral behavior and formation of finite localization zones
Identification of two-dimensional pantographic structures with a linear d4 orthotropic second gradient elastic model accounting for external bulk double forces
No full textInverse analysis of metamaterials and parameter determination by means of an automatized optimization problem
Full text linkIn this paper, a novel parameter determination technique is developed for material models in continuum mechanics aimed at describing metamaterials. Owing to their peculiar mechanical properties and behaviors, such as extreme elasticity or high strength‐to‐weight ratio, metamaterials are of interest to be simulated by reduced‐order modeling by means of the generalized mechanics. Such models incorporate constitutive parameters to be determined; we develop an automatized optimization process specifically for obtaining metamaterials parameters. The process aims at minimizing a mechanically meaningful error function measuring the deviation of the continuum from a detailed description by using the Trust Region Reflective optimization method. The parameter identification procedure is tested for an exemplary extension experiment of a metamaterial, proving to be robust and reliable.TU Berlin, Open-Access-Mittel - 202
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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