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Vibration analysis of FG annular sector in moderately thick plates with two piezoelectric layers

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Applied mathematics and mechanics(English Edition) 2019年第6期40卷 783-804页

作者： S.AZARIPOUR m.baghani School of mechanical Engineering College of Engineering University of Tehran

Free vibration of functionally graded (FG) annular sector plates embedded with two piezoelectric layers is studied with a generalized differential quadrature (GDQ) method. Based on the first-order shear deformation (FSD) plate theory and Hamilton’s principle with parameters satisfying maxwell’s electrostatics equation in the piezoelectric layers, governing equations of motion are developed. Both open and closed circuit (shortly connected) boundary conditions on the piezoelectric surfaces, which are respective conditions for sensors and actuators, are accounted for. It is observed that the open circuit condition gives higher natural frequencies than a shortly connected condition. For the simulation of the potential electric function in piezoelectric layers, a sinusoidal function in the transverse direction is considered. It is assumed that properties of the FG material (FGm) change continuously through the thickness according to a power distribution law. The fast rate convergence and accuracy of the GDQ method with a small number of grid points are demonstrated through some numerical examples. With various combinations of free, clamped, and simply supported boundary conditions, the effects of the thicknesses of piezoelectric layers and host plate, power law index of FGms, and plate geometrical parameters (e.g., angle and radii of annular sector) on the in-plane and out-of-plane nat-ural frequencies for different FG and piezoelectric materials are also studied. Results can be used to predict the behaviors of FG and piezoelectric materials in mechanical systems.

关键词： free vibration annular sector piezoelectric functionally graded material (FGm) first-order shear deformation (FSD)

Transient swelling-induced finite bending of hydrogel-based bilayers:analytical and FEm approaches

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Applied mathematics and mechanics(English Edition) 2023年第2期44卷 273-288页

作者： A.AmIRI m.BANIASSADI m.baghani School of mechanical Engineering College of EngineeringUniversity of TehranTehran ***Iran

Hydrogels with their time-dependent intrinsic behaviors have recently been used widely in soft structures as sensors/*** of the most interesting structures is the bilayer made up of hydrogels which may undergo swelling-induced *** this work,by proposing a semi-analytical method,the transient bending of hydrogel-based bilayers is *** nonlinear solid mechanics,a robust semi-analytical solution is developed which captures the transient finite bending of hydrogel-based ***,the multiphysics model of the hydrogels is implemented in the finite element method(FEm) framework to verify the developed semi-analytical procedure *** effects of different material properties are investigated to illustrate the nonlinear behavior of these *** von-mises stress contour extracted from FEm shows that the critical area of these soft structures is at the interface of the layers which experiences the maximum stress,and this area is most likely to rupture in large deformations.

关键词： hydrogel transient swelling bilayer multiphysics finite bending

An investigation on multilayer shape memory polymers under finite bending through nonlinear thermo-visco-hyperelasticity

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Applied mathematics and mechanics(English Edition) 2023年第1期44卷 73-88页

作者： A.BAKHTIYARI m.baghani S.SOHRABPOUR School of mechanical Engineering College of EngineeringUniversity of TehranTehran ***Iran Department of mechanical Engineering Sharif University of TechnologyTehran ***Iran

This study presents a semi-analytical solution to describe the behavior of shape memory polymers(SmPs) based on the nonlinear thermo-visco-hyperelasticity which originates from the concepts of internal state variables and rational *** method is developed for the finite bending of multilayers in a dual-shape memory effect(SmE) *** layer number and layering order are investigated for two different SmPs and a hyperelastic *** addition to the semi-analytical solution,the finite element simulation is performed to verify the predicted results,where the outcomes demonstrate the excellent accuracy of the proposed solution for predicting the behavior of the multilayer *** this method has a much lower computational cost than the finite element method(FEm),it can be used as an effective tool to analyze the SmP behavior under different conditions,including different materials,different geometries,different layer numbers,and different layer arrangements.

关键词： smart material shape memory polymer(SmP) semi-analytical solution thermo-visco-hyperelasticity finite strain bending

Swelling-induced finite bending of functionally graded pH-responsive hydrogels:a semi-analytical method

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Applied mathematics and mechanics(English Edition) 2019年第5期40卷 679-694页

作者： m.SHOJAEIFARD m.R.BAYAT m.baghani School of mechanical Engineering College of Engineering University of Tehran

Recently, pH-sensitive hydrogels have been utilized in the diverse applications including sensors, switches, and actuators. In order to have continuous stress and deformation ?elds, a new semi-analytical approach is developed to predict the swelling induced?nite bending for a functionally graded(FG) layer composed of a pH-sensitive hydrogel,in which the cross-link density is continuously distributed along the thickness direction under the plane strain condition. Without considering the intermediary virtual reference,the initial state is mapped into the deformed con?guration in a circular shape by utilizing a total deformation gradient tensor stemming from the inhomogeneous swelling of an FG layer in response to the variation of the pH value of the solvent. To enlighten the capability of the presented analytical method, the ?nite element method(FEm) is used to verify the accuracy of the analytical results in some case studies. The perfect agreement con-?rms the accuracy of the presented method. Due to the applicability of FG pH-sensitive hydrogels, some design factors such as the semi-angle, the bending curvature, the aspect ratio, and the distributions of deformation and stress ?elds are studied. Furthermore, the tangential free-stress axes are illustrated in deformed con?guration.

关键词： pH-sensitive hydrogel functionally graded(FG)layer finite bending semianalytical solution finite element method(FEm)

Design and fluid-structure interaction analysis for a microfluidic T-junction with chemo-responsive hydrogel valves

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Applied mathematics and mechanics(English Edition) 2020年第6期41卷 939-952页

作者： E.KHANJANI A.HAJARIAN A.KARGAR-ESTAHBANATY N.ARBABI A.TAHERI m.baghani School of mechanical Engineering College of EngineeringUniversity of TehranTehran ***Iran Bourns College of Engineering University of CaliforniaRiversideCalifornia 92521U.S.A. Department of mechanical Engineering University of British ColumbiaOntario V6T 1Z2Canada Department of mechanical Engineering University of LarestanLar ***Iran

Due to the deformation ability even under small loads, hydrogels have been widely used as a type of soft materials in various applications such as actuating and sensing, and have attracted many researchers to study their behaviors. In this paper, the behavior of hydrogel micro-valves with reverse sensitivity to the p H inside a T-junction flow sorter is investigated. With the fluid-structure interaction(FSI) approach, the effects of various parameters such as the inlet pressure and the p H value on the stress and deformation of the micro-valves are examined, and the results with and without FSI,including the flow rate and the closure p H, are compared. In order to reduce the response time of hydrogels, the effects of three different patterns on the performance of the microvalves are explored. Eventually, it is concluded that FSI is a key influential factor in designing and analyzing the behaviors of hydrogels.

关键词： hydrogel pH-sensitive T-junction flow sorter fluid-structure interaction(FSI) micro-valve