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Thermoelastic Analysis of Non-uniform Pressurized Functionally graded Cylinder with Variable Thickness Using First Order Shear Deformation Theory(FSDT) and Perturbation Method

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Chinese Journal of Mechanical Engineering 2015年第6期28卷 1149-1156页

作者： KhOShgOFTAR M J MIRZAALI M J rahimi g h Faculty of Mechanical Engineering Tarbiat Modares University Department of Mechanical Engineering Faculty of Engineering Arak University Department of Mechanical Engineering Politecnico di Milano

Recently application of functionally graded materials（FgMs） have attracted a great deal of interest. These materials are composed of various materials with different micro-structures which can vary spatially in FgMs. Such composites with varying thickness and non-uniform pressure can be used in the aerospace engineering. Therefore, analysis of such composite is of high importance in engineering problems. Thermoelastic analysis of functionally graded cylinder with variable thickness under non-uniform pressure is considered. First order shear deformation theory and total potential energy approach is applied to obtain the governing equations of non-homogeneous cylinder. Considering the inner and outer solutions, perturbation series are applied to solve the governing equations. Outer solution for out of boundaries and more sensitive variable in inner solution at the boundaries are considered. Combining of inner and outer solution for near and far points from boundaries leads to high accurate displacement field distribution. The main aim of this paper is to show the capability of matched asymptotic solution for different non-homogeneous cylinders with different shapes and different non-uniform pressures. The results can be used to design the optimum thickness of the cylinder and also some properties such as high temperature residence by applying non-homogeneous material.

关键词： non-homogenous cylinder First order Shear Deformation Theory matched asymptotic method perturbation method functionally graded material

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Large deflection of flexible tapered functionally graded beam

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Acta Mechanica Sinica 2011年第5期27卷 767-777页

作者： A.R.Davoodinik g.h.rahimi Department of Mechanical Engineering Tarbiat Modares UniversityTehranIran

In this paper the semi-analytical analyses of the flexible cantilever tapered functionally graded beam under combined inclined end loading and intermediate loading are *** order to derive the fully non-linear equations governing the non-linear deformation,a curvilinear coordinate system is introduced.A general non-linear second order differential equation that governs the shape of a deflected beam is derived based on the geometric nonlinearities,infinitesimal local displacements and local rotation concepts with remarkable physical properties of functionally graded *** solutions obtained from semi-analytical methods are numerically compared with the existing elliptic integral solution for the case of a flexible uniform cantilever functionally graded *** effects of taper ratio,inclined end load angle and material property gradient on large deflection of the beam are *** Adomian decomposition method will be useful toward the design of tapered functionally graded compliant mechanisms driven by smart actuators.

关键词： Large deflection · Flexible tapered functionally graded beam · Analytical solution · Experimental results · Adomian-polynomials

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Three-dimensional magneto-thermo-elastic analysis of functionally graded cylindrical shell

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 479-494页

作者： A. MEhDITABAR g.h. rahimi S. ANSARI SADRABADI Department of Mechanical Engineering School of Mechanical EngineeringTarbiat Modares UniversityTehran 14115-111Iran

The present paper presents the three-dimensional magneto-thermo-elastic analysis of the functionally graded cylindrical shell immersed in applied thermal and magnetic fields under non-uniform internal pressure. The inhomogeneity of the shell is assumed to vary along the radial direction according to a power law function, whereas Poisson＇s ratio is supposed to be constant through the thickness. The existing equations in terms of the displacement components, temperature, and magnetic parameters are derived, and then the effective differential quadrature method （DQM） is used to acquire the analytical solution. Based on the DQM, the governing heat differential equations and edge boundary conditions are transformed into algebraic equations, and discretized in the series form. The effects of the gradient index and rapid temperature on the displacement, stress components, temperature, and induced magnetic field are graphically illustrated. The fast convergence of the method is demonstrated and compared with the results obtained by the finite element method （FEM）.

关键词： magneto-thermo-elastic functionally graded material (FgM) cylindrical shell differential quadrature method (DQM)

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Thermal vibration of functionally graded porous nanocomposite beams reinforced by graphene platelets

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Applied Mathematics and Mechanics(English Edition) 2020年第8期41卷 1209-1226页

作者： M.h.YAS S.rahimi Department of Mechanical Engineering Razi UniversityKermanshah 67346-67149Iran

The thermal vibration of functionally graded(Fg)porous nanocomposite beams reinforced by graphene platelets(gPLs)is *** beams are exposed to the thermal gradient with a multilayer *** temperature varies linearly across the thickness *** different types of dispersion patterns of gPLs as well as porosity distributions are *** material properties vary along the thickness *** using the mechanical parameters of closed-cell cellular solid,the variation of Poisson’s ratio and the relation between the porosity coefficient and the mass density under the gaussian random field(gRF)model are *** using the halpin-Tsai micromechanics model,the elastic modulus of the nanocomposite is *** equations of motion based on the Timoshenko beam theory are obtained by using hamilton’s *** equations are discretized and solved by using the generalized differential quadrature method(gDQM)to obtain the fundamental *** effects of the weight fraction,the dispersion model,the geometry,and the size of gPLs,as well as the porosity distribution,the porosity coefficient,the boundary condition,the metal matrix,the slenderness ratio,and the thermal gradient are presented.

关键词： thermal vibration functionally graded(Fg) porous material graphene platelet(gPL) Timoshenko beam

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Application and analysis of functionally graded piezoelectrical rotating cylinder as mechanical sensor subjected to pressure and thermal loads

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Applied Mathematics and Mechanics(English Edition) 2011年第8期32卷 997-1008页

作者： g.h.rahimi M.AREFI M.J.KhOShgOFTAR Department of Mechanical Engineering Tarbiat Modares University

The exact thermoelastic analysis of a functionally graded piezoelectrical （FgP） rotating cylinder is investigated analytically. The cylinder is subjected to a com- bination of electrical, thermal, and mechanical loads simultaneously. The structure is a simplified model of a rotational sensor or actuator. The basic governing differential equation of the system is obtained by using the energy method. A novel term, named as the additional energy, is introduced to exact the evaluation of the energy functional. The solution to the governing differential equation is presented for two types of boundary conditions including free rotating and rotating cylinders exposed to the inner pressure. The effect of the angular velocity is investigated on the radial distribution of various components. The mentioned structure can be considered as a sensor for measuring the angular velocity of the cylinder subjected to the pressure and temperature. The obtained results indicate that the electrical potential is proportional to the angular velocity.

关键词： functionally graded piezoelectric (FgP) material sensor rotating cylinder angular velocity pressure temperature

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Collapse assessment of steel moment frames using endurance time method

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Earthquake Engineering and Engineering Vibration 2015年第2期14卷 347-360页

作者： E.rahimi h.E.Estekanchi Department of Civil Engineering Sharif University of Technology (SUT)

In endurance time(ET) method structures are subjected to a set of predesigned intensifying excitations. These excitations are produced in a way that their response spectrum, while complying with a specifi ed spectrum, intensifi es with time so they can be used approximately to simulate the average effects of several ground motions scaled to different intensities. In this paper applicability of the ET method for evaluating collapse potential of buildings is investigated. A set of four steel moment frames is used for collapse assessment. The process of using ET method in collapse evaluation is explained and the results are compared with incremental dynamic analysis(IDA) results. It is shown that although the computational effort using the ET method is much less than the IDA analysis, the results of both methods are consistent. Finally collapse fragility curves using ET and IDA methods are produced and it is shown that the probabilities of collapse in different hazard levels are also consistent.

关键词： endurance time method collapse analysis incrementa

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Mixing and segregation of solid particles in a conical spouted bed： Effect of particle size and density

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Particuology 2017年第3期15卷 132-140页

作者： M. Kiani M.R. rahimi S.h. hosseini g. Ahmadi Department of Chemical Engineering Faculty of Engineering Yasouj University Yasouj lran Department of Chemical Engineering Faculty of Engineering llam University Ilam 69715-516 Iran Department of Mechanical and Aeronautical Engineering Clarkson University Potsdam NY 13699-5725 USA

In this work, the mixing and segregation of binary mixtures of particles with different sizes and densities in a pseudo-2D spouted bed were studied experimentally. A binary mixture of solid particles including sand, gypsum, and polyurethane was used. To determine the particles mass fraction, and their mixing and segregation in the bed, an image-processing technique was developed and used. Important hydrodynamic parameters, such as the axial and radial segregation profiles of the solid particles, were measured. The effects of air velocity, particle size, and particle mass fraction were also evaluated. The flow regime in the spouted bed and the time required for reaching the equilibrium state of the solid particles were discussed. The results showed that the segregation of solid particles and the time to equilibrium both decreased when the air velocity increased to much larger than the minimum spouting velocity. The axia! segregation increased with the diameter ratio of the particles. Upon completion of the test, coarse particles were concentrated mainly in the spout region, while fine particles were aggregated in the annulus region. Examination of the flow pattern in the spouted bed showed that the particles near the wall had longer flow paths, while those near the spout region had shorter flow paths.

关键词： Experimental Segregation Binary particles 2D spouted bed

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Sensing the heavy water concentration in an h_(2)O-D_(2)O mixture by solid-solid phononic crystals

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Chinese Physics B 2024年第4期33卷 493-498页

作者： Mohammadreza rahimi Ali Bahrami Optoelectronic and Nanophotonics Research Laboratory(ONRL) Faculty of Electrical EngineeringSahand University of TechnologyTabrizIran

A new method based on phononic crystals is presented to detect the concentration of heavy water(D_(2)O)in an h_(2)O-D_(2)O *** have been obtained and analyzed in the concentration range of 0%-10%and 90%-100%D_(2)O.A proposed structure of tungsten scatterers in an aluminum host is *** order to detect the target material,a cavity region is considered as a sound wave resonator in which the target material with different concentrations of D_(2)O is *** changing the concentration of D_(2)O in the h_(2)O-D_(2)O mixture,the resonance frequency undergoes a frequency *** 1%change in D_(2)O concentration in the h_(2)O-D_(2)O mixture causes a frequency change of about 120 *** finite element method is used as the numerical method to calculate and analyze the natural frequencies and transmission spectra of the proposed *** performance evaluation index shows a high Q factor up to 1475758 and a high sensitivity up to 13075,which are acceptable values for sensing *** other figures of merit related to the detection performance also indicate high-quality performance of the designed sensor.

关键词： phononic crystals sensor h_(2)O-D_(2)O mixture cavity

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Plant-pollinator metanetworks in fragmented landscapes:a simulation study

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Ecological Processes 2023年第1期12卷 415-424页

作者： Ehsan rahimi Chuleui Jung Agricultural Science and Technology Institute Andong National UniversityAndong City 36729Republic of Korea Department of Plant Medicals Andong National UniversityAndong CityRepublic of Korea

Background The topology of the plant-pollinator network can be explained by the species’abundance and their random ***-pollinator networks can be studied in the context of a landscape,because each patch can accommodate a certain local *** populations of pollinators in the landscape can be connected through migration and then constitute a metanetwork that is known as a combination of spatial and ecological *** this regard,habitat fragmentation can affect the topology of plant-pollinator metanetworks through changes in the species abundance and limiting their ***,it is not clear what pattern(fragmented or aggregated)of the landscape structure can accommodate networks with a higher degree of *** we created simulated landscapes with different forest proportions scenarios(from 5%to 50%of the total landscape)and degrees of ***,for each landscape,we limited the proportion of pollinators to the forest *** assumed that plants and pollinators are randomly distributed around the landscape and interact *** used landscape metrics to measure different aspects of landscape structure and bipartite metrics for calculating the degree of specialization in plant-pollinator *** The statistical relationship between bipartite and landscape metrics showed that the relationship between the topology of plant-pollinator networks and the landscape structure is affected by the forest amount in the landscape and the degree of forest *** also found that according to the nestedness and h2(a measure of specialization)metrics,fragmented landscapes contain more general plant-pollinator *** Our findings suggest that fragmented landscapes,characterized by scattered forest patches,can promote higher levels of interaction between limited pollinators and diverse flowers,leading to more general plant-pollinator networks.

关键词： Plant–pollinator metanetwork habitat fragmentation Simulated landscape Landscape metrics Bipartite metrics

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Microstructure characterization and electrochemical corrosion behavior of Zn and Zn/Mg alloys in h_2SO_4 solution

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Journal of Central South University 2015年第6期22卷 2007-2013页

作者： S.h.Ettefagh Far A.rahimi M.Chaghazardi A.Davoodi Young Researchers and Elites Club North Tehran Branch Islamic Azad University Electrochemistry and Inhibitors group Environmental Protection DepartmentResearch Institute of Petroleum Industry Materials and Polymers Engineering Department Faculty of Engineering Hakim Sabzevari University

The three systems of pure Zn, Zn-0.10% Mg(mass fraction), and Zn-0.15% Mg(mass fraction) were cast under controlled atmosphere and their microstructures were characterized by SEM/EDS analysis. The electrochemical corrosion behavior of these three samples was examined in the very aggressive solution of 50% h2SO4(mass fraction) using electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization measurements. The results show that magnesium improves in some extent the corrosion resistance of pure Zn in 50% h2SO4(mass fraction) confirmed by EIS test. Results of polarization measurment also demonstrate that small amount of Mg significantly improves the passivation of Zn in the test solution. Results of surface morphology of the samples and EDS analysis reveal that Mg reduced the corrosion attacks to pure Zn.

关键词： composites corrosion zinc-magnesium alloys potentiodynamic polarization electrochemical impedance spectroscopy

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