1,721,204 research outputs found
Le leghe a memoria di forma nell’analisi numerica: implementazione e confronto di modelli
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A 3D coupled model for SMA composites
No full textIn the wide and always expanding world of composite materials, the shape-memory-alloy (SMA) composites are having a more and more relevant role. Incorporating SMA with other structural or functional materials, it is possible to produce "smart materials", able to tune their behavior according with some external stimuli, to exploit the peculiar characteristics of the individual elements to achieve multiple responses and optimal properties.
The most common composites are realized introducing SMA wires in a metallic or polymeric matrix. These materials are able to increase the dissipation and resistance capability of the structure as well as to control structure shape changes; hence they are mainly used for displacement, vibration and cracking control.
This work studies numerically the mechanical response of a composite in which SMA wires, previously deformed, are embedded in a matrix and are able to recover the original (undeformed) shape through heating (shape memory effect). The thermal increment is obtained imposing a potential difference at the edges of the structure: the electric conduction produces heat through joule effect. The composite 3D model is developed in the frame of the finite element code FEAP by the definition of a user element where the electrical, thermal and mechanical problem are coupled. In particular for the mechanical constitutive law of SMA it has been used the discrete model previously proposed by the authors. Various tests are performed to verify the correctness and the efficiency of the model
A three-dimensional model describing stress-temperature induced solid phase transformations: thermomechanical coupling and hybrid composite application
No full textBetween composite materials, shape memory alloy (SMA) composites are having a more and more
relevant role. Typically, SMA wires are embedded in a metallic or a polymeric matrix to obtain materials
with native multi-functionality and adaptive properties. This work approaches the computational
study of the mechanical response of a composite in which SMA wires, previously deformed, are
activated by electrical current heating, and accordingly try to recover the original shape inducing a
shape change or a prestress in the structure.
In particular, since the SMA behaviour is strongly affected by the thermo-mechanical coupling,
in the first part of this work we present a 3D phenomenological model able to take into account
this aspect. The model time-discrete counterpart is used to develop a 3D solid finite element able to
describe the thermo-electro-mechanical coupled problem due to shape memory alloy response and to
Joule effect. Finally, in the second part of the paper, we employ the developed computational tool to
simulate different feasible SMA composite applications
Polyproline peptides and TAT transduction peptides in the study of rapid actions mediated by steroid receptors
No full textA mixed FSDT finite element for monoclinic laminated plates
No full textA 4-node finite element for the analysis of laminated composite plates with monoclinic layers, as it occurs for example in piezoelectric applications, is developed. The element is built through the linked interpolation scheme proposed by Taylor and Auricchio [Int J Numer Meth Eng 1993;36:3057-66] and is a generalization of the element presented in [Auricchio F, Sacco E. A mixed-enhanced finite-element for the analysis of laminated composite plates. Int J Numer Meth Eng 1999;44:1481-1504]. Starting from a first-order shear deformation theory (FSDT), a mixed-enhanced variational formulation is considered. It includes as primary variables the resultant shear stresses as well as enhanced incompatible modes, which are introduced to improve in-plane deformations. Bubble functions for rotation degrees of freedom and functions linking transversal displacement to rotations are employed. The solvability of the variational formulation is proved whereas effectiveness and convergence of the proposed finite element are confirmed through several numerical applications. Finally, numerical results are compared with the corresponding analytical solutions as well as to other finite-element solutions
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
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