• Structural Engineering and Mechanics
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• 제69권2호
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• pp.131-143
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• 2019

In this study, the nonlinear vibration analysis of the composite nanoplate is studied. The composite nanoplate is fabricated by the functional graded (FG) core and lipid face sheets. The material properties in the FG core vary in three directions. The Kelvin-Voigt model is used to study the viscoelastic effect of the lipid layers. By using the Von-Karman assumptions, the nonlinear differential equation of the vibration analysis of the composite nanoplate is obtained. The foundation of the system is modeled by the nonlinear Pasternak foundation. The Bubnov-Galerkin method and the multiple scale method are used to solve the nonlinear differential equation of the composite nanoplate. The free and force vibration analysis of the composite nanoplate are studied. A comparison between the presented results and the reported results is done and good achievement is obtained. The reported results are verified by the results which are obtained by the Runge-Kutta method. The effects of different parameters on the nonlinear vibration frequencies, the primary, the super harmonic and subharmonic resonance cases are investigated. This work will be useful to design the nanosensors with high biocompatibility.

• Structural Engineering and Mechanics
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• 제80권5호
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• pp.523-538
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• 2021

The mechanical behaviour and stability of coal mining engineering underground is significantly affected by ground water. In this study, nuclear magnetic resonance imaging (NMRI) technique was employed to determine the water distribution characteristics in coal specimens during saturation process, based on which the functional rule for water distribution was proposed. Then, using discrete element method (DEM), an innovative numerical modelling method was developed to simulate water-weakening effect on coal behaviour considering moisture content and water distribution. Three water distribution numerical models, namely surface-wetting model, core-wetting model and uniform-wetting model, were established to explore the water distribution influences. The feasibility and validity of the surface-wetting model were further demonstrated by comparing the simulation results with laboratory results. The investigation reveals that coal mechanical properties are affected by both water saturation coefficient and water distribution condition. For all water distribution models, micro-cracks always initiate and nucleate in the water-rich area and thus lead to distinct macro fracture characteristics. With the increase of water saturation coefficient, the failure of coal tends to be less violent with less cracks and ejected fragments. In addition, the core-wetting specimen is more sensitive to water than specimens with other water distribution models.

• Membrane and Water Treatment
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• 제13권6호
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• pp.321-335
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• 2022

Copper-based Metal-organic framework (MOF) namely ([Cu (INA)₂]-MOF) is synthesized by ball milling and characterized using scanning electron microscopy (SEM) for the topography, microstructure, and elemental evidence determination, powdered X-ray diffraction (XRD) for the crystallinity measurement, thermogravimetric (TG) analysis was performed to determine the thermal stability of the material, and Fourier transformed infrared (FTIR) spectroscopy for functional groups identification. The use of [Cu (INA)₂]-MOF as hazardous removal material of β-agonists as persistent hazardous micro-pollutants in our environmental water is first reported in this study. The removal efficiency of the Cu-MOF is successfully determined to be 97.7% within 40 minutes, and the MOF has established an exceptional removal capacity of 835 mg L^-1 with 95 % percent removal on Clenbuterol (CLB) even after the 5th consecutive cycle. The Langmuir model of the adsorption isotherms was shown to be more favourable, while the pseudo-second-order model was found to be favoured in the kinetics. The reaction was exothermic and spontaneous from a thermodynamic standpoint, and the higher temperatures were unfavourable for the adsorption study of the CLB. As a result, the studied MOF have shown promising properties as possible adsorbents for the removal of CLB in wastewater.

• Membrane and Water Treatment
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• 제13권3호
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• pp.129-137
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• 2022

In this study, the removal of Ciprofloxacin (CPX) from aqueous solutions was investigated by a new activated carbon adsorbent prepared from orange peel (ACOP) with chemical activation using ZnCl₂. The physicochemical properties of orange peel activated carbon were characterized by proximate and ultimate analysis, scanning electron microscopy, BET surface area determination and Fourier transformation infrared spectroscopic studies. According to Brunauer-Emmett-Teller isotherm and non-local-density functional theory, the cumulative surface area, pore volume and pore size of ACOP were determined as 1193 m² g^-1, 0.83 cc g^-1 and 12.7 Å, respectively. The effects of contact time, pH, temperature and ACOP dose on the batch adsorption of CPX were studied. Adsorption equilibrium data of CPX with ACOP were found to be compatible with both the Langmuir and Freundlich isotherms. CPX adsorption capacity of ACOP was calculated as 181.8 mg g^-1 using Langmuir isotherm. The CPX adsorption kinetics were found to be harmonious with the pseudo-second-order kinetic model. Conclusively, ACOP can be assessable as an effective adsorbent for the removal of ciprofloxacin (CPX) from aqueous solutions.

• Structural Engineering and Mechanics
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• 제85권5호
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• pp.621-633
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• 2023

The major objective of this paper is to study the receding contact problem between two functional graded layers under a flat indenter. The gravity is assumed negligible, and the shear moduli of both layers are assumed to vary exponentially along the thickness direction. In the absence of body forces, the problem is reduced to a system of Fredholm singular integral equations with the contact pressure and contact size as unknowns via Fourier integral transform, which is transformed into an algebraic one by the Gauss-Chebyshev quadratures and polynomials of both the first and second kinds. Then, an iterative speediest descending algorithm is proposed to numerically solve the system of algebraic equations. Both semi-analytical and finite element method, FEM solutions for the presented problem validate each other. To improve the accuracy of the numerical result of FEM, a graded FEM solution is performed to simulate the FGM mechanical characteristics. The results reveal the potential links between the contact stress/size and the indenter size, the thickness, as well as some other material properties of FGM.

• Coupled systems mechanics
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• 제12권4호
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• pp.391-407
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• 2023

This paper presents a static study of a rectangular functional graded material (FGM) plate, simply supported on its four edges, adopting a refined higher order theory that looks for, only,four unknowns,without taking into account any corrective factor of the deformation energy with the satisfaction of the zero shear stress conditions on the upper and lower faces of the plate. We will have determined the contribution of these stresses in the transverse deflection of the plate, as well as their effects on the axial stress within the interfaces between the layers(to avoid any problem of imperfections such as delamination) and on the top and bottom edges of the plate in order to take into account the fatigue phenomenon when choosing the distribution law of the properties used during the design of the plate. A numerical statement, in percentage, of the contribution of the shear effect is made in order to show the reliability of the adopted theory. We will also have demonstrated the need to add the shear effect when the aspect ratio is small or large. Code routines are programmed to obtain numerical results illustrating the validity of the model proposed in the theory compared to those available in the literature.

• Steel and Composite Structures
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• 제45권3호
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• pp.305-330
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• 2022

This article aims to investigate the static deflection and stress analysis of bi-directional functionally graded porous plate (BDFGPP) modeled by unified higher order kinematic theories to include the shear stress effects, which not be considered before. Different shear functions are described according to higher order models that satisfy the zero-shear influence at the top and bottom surfaces, and hence refrain from the need of shear correction factor. The material properties are graded through two spatial directions (i.e., thickness and length directions) according to the power law distribution. The porosities and voids inside the material constituent are described by different cosine functions. Hamilton's principle is implemented to derive the governing equilibrium equation of bi-directional FG porous plate structures. An efficient numerical differential integral quadrature method (DIQM) is exploited to solve the coupled variable coefficients partial differential equations of equilibrium. Problem validation and verification have been proven with previous prestigious work. Numerical results are illustrated to present the significant impacts of kinematic shear relations, gradation indices through thickness and length, porosity type, and boundary conditions on the static deflection and stress distribution of BDFGP plate. The proposed model is efficient in design and analysis of many applications used in nuclear, mechanical, aerospace, naval, dental, and medical fields.

• Steel and Composite Structures
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• 제51권5호
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• pp.499-507
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• 2024

The paper delves into an emerging paradigm shift in architectural design, focusing on the development of a cutting-edge methodological framework for the artistic enhancement of nanocomposite brick facades in building construction. This innovative approach represents a fusion of art and science, harnessing the potential of advanced nanotechnology to redefine the aesthetic and functional properties of building exteriors. Central to this new methodology is the integration of state-of-the-art materials and fabrication techniques, aimed at not only elevating the visual appeal of architectural structures but also enhancing their structural robustness and environmental sustainability. By leveraging the unique characteristics of nanocomposite materials, the proposed method opens up new possibilities for pushing the boundaries of traditional brick facade design. Through a meticulous exploration of the intricacies involved in implementing this novel approach, the paper elucidates the transformative impact it can have on the architectural landscape. By marrying creativity with technical precision, the method environment for art design of nanocomposite brick facades promises to usher in a new era of sustainable, visually captivating, and structurally resilient building facades that are poised to redefine the very essence of architectural aesthetics.

• Structural Engineering and Mechanics
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• 제48권4호
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• pp.547-567
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• 2013

Nonlinear behavior of functionally graded material (FGM) plates under thermal loads is investigated here using an efficient sinusoidal shear deformation theory. The displacement field is chosen based on assumptions that the in-plane and transverse displacements consist of bending and shear components, and the shear components of in-plane displacements give rise to the sinusoidal distribution of transverse shear stress through the thickness in such a way that shear stresses vanish on the plate surfaces. Therefore, there is no need to use shear correction factor. Unlike the conventional sinusoidal shear deformation theory, the proposed efficient sinusoidal shear deformation theory contains only four unknowns. The material is graded in the thickness direction and a simple power law based on the rule of mixture is used to estimate the effective material properties. The neutral surface position for such FGM plates is determined and the sinusoidal shear deformation theory based on exact neutral surface position is employed here. There is no stretching-bending coupling effect in the neutral surface-based formulation, and consequently, the governing equations and boundary conditions of functionally graded plates based on neutral surface have the simple forms as those of isotropic plates. The non-linear strain-displacement relations are also taken into consideration. The thermal loads are assumed as uniform, linear and non-linear temperature rises across the thickness direction. Closed-form solutions are presented to calculate the critical buckling temperature, which are useful for engineers in design. Numerical results are presented for the present efficient sinusoidal shear deformation theory, demonstrating its importance and accuracy in comparison to other theories.

• Smart Structures and Systems
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• 제3권2호
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• pp.189-200
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• 2007

As a functional material, shape memory alloy (SMA) has attracted much attention and research effort to explore its unique properties and its applications in the past few decades. Some of its properties, in particular the electrical resistance (ER) based self-sensing property of SMA, have not been fully studied. Electrical resistance of an SMA wire varies during its phase transformation. This variation is an inherent property of the SMA wire, although it is highly nonlinear with hysteresis. The relationship between the displacement and the electrical resistance of an SMA wire is deterministic and repeatable to some degree, therefore enabling the self-sensing ability of the SMA. The potential of this self-sensing ability has not received sufficient exploration so far, and even the previous studies in literature lack generality. This paper concerns the utilization of the self-sensing property of a spring-biased Nickel-Titanium (Nitinol) SMA actuator for two applications: ER feedback position control of an SMA actuator without a position sensor, and estimation of the opening of a SMA actuated valve. The use of the self-sensing property eliminates the need for a position sensor, therefore reducing the cost and size of an SMA actuator assembly. Two experimental apparatuses are fabricated to facilitate the two proposed applications, respectively. Based on open-loop testing results, the curve fitting technique is used to represent the nonlinear relationships between the displacement and the electrical resistance of the two SMA wire actuators. Using the mathematical models of the two SMA actuators, respectively, a proportional plus derivative controller is designed for control of the SMA wire actuator using only electrical resistance feedback. Consequently, the opening of the SMA actuated valve can be estimated without using an extra sensor.