ORCID Profile
0000-0002-8191-0000
Current Organisation
University of Adelaide
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Publisher: Springer Science and Business Media LLC
Date: 06-12-2018
Publisher: Informa UK Limited
Date: 12-04-2022
Publisher: Elsevier BV
Date: 06-2022
Publisher: MDPI AG
Date: 28-07-2022
DOI: 10.3390/NANO12152598
Abstract: The impetus of writing this paper is to propose an efficient detection mechanism to scan the surface profile of a micro-s le using cantilever-based atomic force microscopy (AFM), operating in non-contact mode. In order to implement this scheme, the principal parametric resonance characteristics of the resonator are employed, benefiting from the bifurcation-based sensing mechanism. It is assumed that the microcantilever is made from a hyperelastic material, providing large deformation under small excitation litude. A nonlinear strain energy function is proposed to capture the elastic energy stored in the flexible component of the device. The tip–s le interaction is modeled based on the van der Waals non-contact force. The nonlinear equation governing the AFM’s dynamics is established using the extended Hamilton’s principle, obeying the Euler–Bernoulli beam theory. As a result, the vibration behavior of the system is introduced by a nonlinear equation having a time-dependent boundary condition. To capture the steady-state numerical response of the system, a developed Galerkin method is utilized to discretize the partial differential equation to a set of nonlinear ordinary differential equations (ODE) that are solved by the combination of shooting and arc-length continuation method. The output reveals that while the resonator is set to be operating near twice the fundamental natural frequency, the response litude undergoes a significant drop to the trivial stable branch as the s le’s profile experiences depression in the order of the picometer. According to the performed sensitivity analysis, the proposed working principle based on principal parametric resonance is recommended to design AFMs with ultra-high detection resolution for surface profile scanning.
Publisher: Elsevier BV
Date: 2018
Publisher: Bentham Science Publishers Ltd.
Date: 03-2021
DOI: 10.2174/2666184501999201005211608
Abstract: Carbon nanotubes (CNTs) reinforced structures are the main elements of structural equipment. Hence a wide range of investigations has been performed on the response of these structures. A lot of studies covered the static and dynamic phenomenon of CNTs reinforced beams, plates and shells. However, there is no study on the free vibration analysis of a doubly-curved nano-size shell made of CNTs reinforced composite materials. This work utilized a general third-order shear deformation theory to model the nanoshell where the general strain gradient theory is used in order to capture both nonlocality and strain gradient size-dependency. The Navier solution solving procedure is adopted to solve the partial differential equations (PDEs) and get the natural frequency of the system which is obtained through the Hamilton principle. The current study shows the importance of small-scale coefficients. The natural frequency increases with rising the strain gradient-size dependency which is because of stiffness enhancement, while the natural frequency decreases by increasing the nonlocality. In addition, the numerical ex les covered the CNTs distribution patterns. This work also studied the importance of shell panel’s shape. It has been observed that spherical shell panel has a higher frequency compared to the hyperbolic one. Furthermore, the frequency of the system increases with growing length-to-thickness ration.
Publisher: Elsevier BV
Date: 07-2021
Publisher: Elsevier BV
Date: 09-2020
Publisher: IOP Publishing
Date: 25-09-2019
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 2018
Publisher: Informa UK Limited
Date: 12-07-2017
Publisher: Elsevier BV
Date: 11-2019
Publisher: IOP Publishing
Date: 03-08-2017
Publisher: Elsevier BV
Date: 02-2019
Publisher: Elsevier BV
Date: 07-2019
Publisher: Elsevier BV
Date: 12-2018
Publisher: Informa UK Limited
Date: 09-01-2023
Publisher: Informa UK Limited
Date: 17-11-2017
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 02-2018
Publisher: MDPI AG
Date: 24-12-2018
DOI: 10.3390/NANO9010022
Abstract: This study aims at investigating the wave propagation of porous nanoshells. The Bi-Helmholtz non-local strain gradient theory is employed in conjunction with a higher-order shear deformation shell theory, in order to include the size-dependent effects. The nanoshells are made of a porous functionally graded material (P-FGM), whose properties vary continuously along the thickness direction. A variational approach is here applied to handle the governing equations of the problem, which are solved analytically to compute the wave frequencies and phase velocities as function of the wave numbers. The sensitivity of the wave response is analyzed for a varying porosity volume fraction, material properties, non-local parameters, strain gradient length scales, temperature, humidity, and wave numbers. Based on the results, it is verified that the size-dependence of the response is almost the same to the one of plates, beams and tubes.
Publisher: Elsevier BV
Date: 09-2022
Publisher: Elsevier BV
Date: 10-2019
Publisher: Elsevier BV
Date: 2018
Publisher: Elsevier BV
Date: 05-2019
Publisher: Elsevier BV
Date: 03-2021
Publisher: Elsevier BV
Date: 03-2019
Publisher: Elsevier BV
Date: 03-2022
Publisher: SAGE Publications
Date: 06-02-2018
Abstract: The effective elastic-piezoelectric properties of nanostructures have been shown to be strongly size-dependent. In this paper, a nonlocal second-order shear deformation formulation is presented to study the size-dependent thermal buckling of embedded sandwich piezoelectric nanoplates with functionally graded core. Temperature is considered as uniform and nonlinear distributions across plate’s thickness direction. Based on the developed nonlocal second-order shear deformation theory, the size-dependent equations of motion are derived. The nonlocal thermal buckling responses of simply supported nanoplates are solved via Navier method. The reliability of present approach is verified by comparing the existing results provided in the open literature. The influences of nonlocal parameter, gradient index, electric voltage, and Winkler–Pasternak parameters on the thermal buckling characteristics of functionally graded nanoplates are examined.
Publisher: Elsevier BV
Date: 08-2020
Publisher: Computers, Materials and Continua (Tech Science Press)
Date: 2020
Publisher: IOP Publishing
Date: 31-07-2019
Publisher: Elsevier BV
Date: 06-2022
Publisher: Springer Science and Business Media LLC
Date: 22-10-2019
Publisher: Elsevier BV
Date: 10-2019
Publisher: Elsevier BV
Date: 11-2019
Publisher: Elsevier BV
Date: 08-2023
Publisher: Springer Science and Business Media LLC
Date: 2020
Publisher: World Scientific Pub Co Pte Lt
Date: 30-12-2016
DOI: 10.1142/S0217984916504212
Abstract: In this paper, the effect of magnetic field on the wave propagation in rectangular nanoplates based on two-variable refined plate theory is studied. In order to capture the size effects, the strain gradient theory with one length scale parameter is used. From our knowledge, it is the first time that two-variable refined plate theory is adopted for studying bulk waves in nanoplates. This type of refined plate theory has only two unknowns which reduces the complexity of the governing equations. To show the accuracy of this work, several comparisons are made with available results in open literature.
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 04-2022
Publisher: Informa UK Limited
Date: 22-04-2019
Publisher: Elsevier BV
Date: 12-2020
Publisher: Elsevier BV
Date: 02-2020
Publisher: MDPI AG
Date: 05-04-2021
DOI: 10.3390/APP11073250
Abstract: This paper presents a mathematical continuum model to investigate the static stability buckling of cross-ply single-walled (SW) carbon nanotube reinforced composite (CNTRC) curved sandwich nanobeams in thermal environment, based on a novel quasi-3D higher-order shear deformation theory. The study considers possible nano-scale size effects in agreement with a nonlocal strain gradient theory, including a higher-order nonlocal parameter (material scale) and gradient length scale (size scale), to account for size-dependent properties. Several types of reinforcement material distributions are assumed, namely a uniform distribution (UD) as well as X- and O- functionally graded (FG) distributions. The material properties are also assumed to be temperature-dependent in agreement with the Touloukian principle. The problem is solved in closed form by applying the Galerkin method, where a numerical study is performed systematically to validate the proposed model, and check for the effects of several factors on the buckling response of CNTRC curved sandwich nanobeams, including the reinforcement material distributions, boundary conditions, length scale and nonlocal parameters, together with some geometry properties, such as the opening angle and slenderness ratio. The proposed model is verified to be an effective theoretical tool to treat the thermal buckling response of curved CNTRC sandwich nanobeams, ranging from macroscale to nanoscale, whose ex les could be of great interest for the design of many nanostructural components in different engineering applications.
Publisher: Elsevier BV
Date: 02-2020
Publisher: Elsevier BV
Date: 08-2018
Publisher: Elsevier BV
Date: 11-2019
Publisher: Elsevier BV
Date: 03-2018
Publisher: Elsevier BV
Date: 06-2019
Publisher: Springer Science and Business Media LLC
Date: 19-03-2022
Publisher: MDPI AG
Date: 27-08-2019
DOI: 10.3390/APP9173517
Abstract: In this work, the nonlocal strain gradient theory is applied to study the free vibration response of a Timoshenko beam made of triclinic material. The governing equations of the problem and the associated boundary conditions are obtained by means of the Hamiltonian principle, whereby the generalized differential quadrature (GDQ) method is implemented as numerical tool to solve the eigenvalue problem in a discrete form. Different combinations of boundary conditions are also considered, which include simply-supports, cl ed supports and free edges. Starting with some pioneering works from the literature about isotropic nanobeams, a convergence analysis is first performed, and the accuracy of the proposed size-dependent anisotropic beam model is checked. A large parametric investigation studies the effect of the nonlocal, geometry, and strain gradient parameters, together with the boundary conditions, on the vibration response of the anisotropic nanobeams, as useful for practical engineering applications.
Publisher: Elsevier BV
Date: 08-2022
Publisher: Springer Science and Business Media LLC
Date: 08-09-2018
Publisher: SAGE Publications
Date: 17-06-2018
Abstract: Flexural and longitudinal wave behaviors of nanobeams made of nanoporous-graded materials while surrounded by Winkler-Pasternak foundation, subjected to the longitudinal magnetic field and exposed to the hygrothermal environment are studied analytically. To this end, the governing equation derived by Euler–Bernoulli beam theory in conjunction with the nonlocal strain gradient theory is defined by employing Hamilton’s principle. By adopting an analytic model, the flexural and longitudinal dispersion relations between phase velocity and wave number are derived. The reliability of the present method is confirmed by comparing the obtained results with those stored in the literature. Finally, the effects of the power-law index, porosity volume fraction, nonlocal and material characteristic parameters, uniform temperature and moisture rise, elastic foundation parameters, magnetic field intensity, and wave number are also investigated in detail. It is found that the small-scale parameters are more influential in higher wave numbers where the wavelength is close to the length scale of nanostructures. However, foundation parameters, porosity volume fraction, and longitudinal magnetic field are more influential in lower wave numbers.
Publisher: MDPI AG
Date: 29-07-2019
DOI: 10.3390/MOLECULES24152750
Abstract: This work deals with the size-dependent buckling response of functionally graded carbon nanotube-reinforced composite (FG-CNTRC) (FG-CNTRC) curved beams based on a higher-order shear deformation beam theory in conjunction with the Eringen Nonlocal Differential Model (ENDM). The material properties were estimated using the rule of mixtures. The Hamiltonian principle was employed to derive the governing equations of the problem which were, in turn, solved via the Galerkin method to obtain the critical buckling load of FG-CNTRC curved beams with different boundary conditions. A detailed parametric study was carried out to investigate the influence of the nonlocal parameter, CNTs volume fraction, opening angle, slenderness ratio, and boundary conditions on the mechanical buckling characteristics of FG-CNTRC curved beams. A large parametric investigation was performed on the mechanical buckling behavior of FG-CNTRC curved beams, which included different CNT distribution schemes, as useful for design purposes in many practical engineering applications.
Publisher: Elsevier BV
Date: 12-2021
Publisher: Elsevier BV
Date: 11-2018
Publisher: Springer Science and Business Media LLC
Date: 26-08-2023
Publisher: Springer Science and Business Media LLC
Date: 25-08-2021
No related grants have been discovered for Behrouz Karami.