Browsing by Author "Trovalusci, Patrizia"

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Citation - WoS: 23
Citation - Scopus: 21
Bending characteristics of carbon nanotubes: Micropolar elasticity models and molecular dynamics simulations
(TAYLOR & FRANCIS INC, 2021) Razie Izadi; Meral Tuna; Patrizia Trovalusci; Nicholas Fantuzzi; Fantuzzi, Nicholas; Trovalusci, Patrizia; Izadi, Razie; Tuna, Meral
The present paper aims at evaluating non-classical continuum parameters for each class of armchair and zigzag single-walled CNTs focusing on the scale effect in their flexural behavior observed in molecular dynamics (MD) simulations. Through a non-linear optimization approach the bending rigidities obtained from atomistic simulations are compared to those derived from non-classical continua. For MD simulations a novel method ensuring pure bending is introduced and for continuum modeling micropolar constrained micropolar and modified couple stress theories are employed. The results reveal that adopted non-classical theories notably micropolar theory provide reasonable outcomes with an obvious failure of classical Cauchy theory.
Citation - WoS: 1
Erratum to “Stress distribution around an elliptic hole in a plate with ‘implicit’ and ‘explicit’ non-local models” (Composite Structures (2021) 256 (S0263822320329299) (10.1016/j.compstruct.2020.113003))
(Elsevier Ltd, 2021) Meral Tuna; Patrizia Trovalusci; Tuna, Meral; Trovalusci, Patrizia
The publisher regrets that the Fig. 1 is missing in the printed version. The publisher would like to apologise for any inconvenience caused. [Figure presented] Fig. 1. Illustration of geodetic and Euclidean paths for points M and N. © 2023 Elsevier B.V. All rights reserved.
Citation - Scopus: 5
‘Explicit’ and ‘Implicit’ Non-local Continuum Descriptions: Plate with Circular Hole
(Springer Science and Business Media Deutschland GmbH, 2021) Meral Tuna; Lorenzo Leonetti; Patrizia Trovalusci; Mesut Kirca; Trovalusci, Patrizia; Tuna, Meral; Leonetti, Lorenzo; Kirca, Mesut
Classical theory of elasticity fails to reflect the true behaviour of solids with internal material organization when internal and external length scales are of comparable orders. This drawback leads to emergence of non-classical continuum theories which are offered to be distinguished as ‘implicit’/‘weak’ and ‘explicit’/‘strong’ non-local models according to different interpretations of the incorporation of characteristic length scales. As an extension of recent works of authors the presented chapter is focused on the correspondence between ‘implicit’ type Cosserat (micropolar) and ‘explicit’ type Eringen’s two-phase local/non-local models in terms of characteristic quantities. To this end an example problem of practical importance, a plate with a circular hole is studied by employing standard displacement based finite element method. The non-locality of Eringen’s model is optimized regarding stress concentration factors reported for infinite Cosserat plates. The analysis of Eringen’s model is repeated by adopting both Euclidean and geodetical distance during incorporation of long range interactions. According to the results stress fields of explicitly and implicitly non-local models seem to be in a very good agreement considering plates with large scale ratios as the missing neighbour relations appeared at domain boundaries of Eringen’s model are not effective at the vicinity of the hole. Yet obtaining different ‘explicit’ material parameters for each sample problem reveals that it is unlikely to have a unified relationship between characteristic quantities of Cosserat’s and Eringen’s models. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 24
Citation - Scopus: 24
Stress distribution around an elliptic hole in a plate with ‘implicit’ and ‘explicit’ non-local models
(Elsevier Ltd, 2021) Meral Tuna; Patrizia Trovalusci; Tuna, Meral; Trovalusci, Patrizia
Understanding the effects of defects is crucial due to their deliberate or unintentional presence in many materials. Classical theory of elasticity may not be the best candidate to describe behaviour of structures with defects of comparable size of its underlying material organization as it lacks in internal scale parameters. In this respect present study focused on comparison of two well-established non-local theories, ‘implicit/weak’ as micropolar (Cosserat) and ‘explicit/strong’ as Eringen's model with that of classical model to highlight their differences in a common case study: infinite plates weakened with an elliptic hole of different aspect ratios under remote uniaxial tension. Fraction coefficient providing identical stress concentration factor with micropolar plates is searched for two-phase local/nonlocal Eringen's model. Results are obtained by adopting finite element method with quadrilateral elements. To account for the discontinuities within domain Eringen's model is modified by using geodetical distance instead of Euclidean one and a computationally very efficient procedure is developed to exploit the symmetric character of the problem without losing long-range interactions. The results suggest that non-local effects reducing the maximum stress become more pronounced with increasing geometric discontinuity quantified by the aspect ratio of ellipse which also influences equivalency between characteristic lengths of non-local models. © 2021 Elsevier B.V. All rights reserved.
Citation - WoS: 35
Citation - Scopus: 34
Torsional Characteristics of Carbon Nanotubes: Micropolar Elasticity Models and Molecular Dynamics Simulation
(MDPI, 2021) Razie Izadi; Meral Tuna; Patrizia Trovalusci; Esmaeal Ghavanloo; Ghavanloo, Esmaeal; Trovalusci, Patrizia; Izadi, Razie; Tuna, Meral
Efficient application of carbon nanotubes (CNTs) in nano-devices and nano-materials requires comprehensive understanding of their mechanical properties. As observations suggest size dependent behaviour non-classical theories preserving the memory of body's internal structure via additional material parameters offer great potential when a continuum modelling is to be preferred. In the present study micropolar theory of elasticity is adopted due to its peculiar character allowing for incorporation of scale effects through additional kinematic descriptors and work-conjugated stress measures. An optimisation approach is presented to provide unified material parameters for two specific class of single-walled carbon nanotubes (e.g. armchair and zigzag) by minimizing the difference between the apparent shear modulus obtained from molecular dynamics (MD) simulation and micropolar beam model considering both solid and tubular cross-sections. The results clearly reveal that micropolar theory is more suitable compared to internally constraint couple stress theory due to the essentiality of having skew-symmetric stress and strain measures as well as to the classical local theory (Cauchy of Grade 1) which cannot accounts for scale effects. To the best of authors' knowledge this is the first time that unified material parameters of CNTs are derived through a combined MD-micropolar continuum theory.