323,342 research outputs found
Correction to: Validity of the Italian multiple sclerosis neuropsychological screening questionnaire (Neurological Sciences, (2021), 42, 11, (4583-4589), 10.1007/s10072-021-05141-1)
No full textThe original article contains an error in author name. In the published article, author name Girolama Alessandra Marfia was incorrectly captured as GirolamaAlessandraAlessandra Alessandra Marfia. Author name is corrected above. The original article has been corrected
A thermodynamical formulation for the constitutive modeling of a shape memory alloy with two martensite phases
No full textThis paper presents a thermodynamical
formulation for the one-dimensional constitutive
model for shape memory alloys (SMAs) proposed by
the authors in Marfia and Rizzoni (Eur J Mech A
Solids 40:166–185, 2013) and able to describe the
pseudo-elastic and shape memory effects and the
martensite detwinning. The model takes into account
the asymmetric behavior in tension and compression
and the different elastic properties of the three phases
considered for the SMA material: austenite, tensile
and compressive martensite. A new formulation based
on two specific energy potentials, the Helmholtz and
the Gibbs free energies, is proposed. For the two
potentials an expression is given, depending on the
martensite volume fractions taken as internal variables,
and incorporating a mixing energy of the three
phases as proposed in Fre ́mond (C R Acad Sci Paris
304:239–244, 1987). An original analysis of the non
dissipative and dissipative processes is carried out in
the general framework of tension-compression asymmetry
and different elastic properties of the three
phases; in particular, in the dissipative case the nonnegativity
of the dissipation is used to restrict evolutive
processes. The numerical procedure developed
in Marfia and Rizzoni (Eur J Mech A Solids
40:166–185, 2013) is applied to time integrate the
evolutive equations of the internal variables. Applications
are carried out in order to verify the effectiveness
of the proposed model and to compare the
numerical results of the model with the experimental
results, available in the literature
Micro-macro analysis of shape memory alloy composites
No full textThe aim of the paper is to develop a micro–macro approach for the analysis of the mechanical behavior of composites obtained embedding long fibers of Shape Memory Alloys (SMA) into an elastic matrix. In order to determine the overall constitutive response of the SMA composites, two homogenization techniques are proposed: one is based on the self-consistent method while the other on the analysis of a periodic composite. The overall response of the SMA composites
is strongly influenced by the pseudo-elastic and shape memory effects occurring in the SMA material. In particular, it is assumed that the phase transformations in the SMA are governed by the wire temperature and by the average stress tensor acting in the fiber. A possible prestrain of the fibers is taken into account in the model.
Numerical applications are developed in order to analyze the thermo-mechanical behavior of the SMA composite. The results obtained by the proposed procedures are compared with the ones determined through a micromechanical analysis of a periodic composite performed using suitable finite elements.
Then, in order to study the macromechanical response of structural elements made of SMA composites, a threedimensional finite element is developed implementing at each Gauss point the overall constitutive laws of the SMA composite obtained by the proposed homogenization procedures. Some numerical applications are developed in order to assess the efficiency of the proposed micro–macro model
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