Journal of Applied and Computational MechanicsJournal of Applied and Computational Mechanics
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Feed provided by Journal of Applied and Computational Mechanics. Click to visit.Buckling Analysis of a Micro Composite Plate with Nano Coating Based on the Modified Couple ...
http://jacm.scu.ac.ir/article_12863_1659.html
The present study investigates the buckling of a thick sandwich plate under the biaxial non-uniform compression using the modified couple stress theory with various boundary conditions. For this purpose, the top and bottom faces are orthotropic graphene sheets and for the central core the isotropic soft materials are investigated. The simplified first order shear deformation theory (S-FSDT) is employed and the governing differential equations are obtained using the Hamilton’s principle by considering the Von-Karman’s nonlinear strains. An analytical approach is applied to obtain exact results with different boundary conditions. Due to the fact that there is no research on the stability of micro/nano sandwich plates based on S-FSDT including the couple stress effect, the obtained results are compared with the FSDT studies which use the Eringen nonlocal elasticity.Sun, 31 Dec 2017 20:30:00 +0100Ritz Method Application to Bending, Buckling and Vibration Analyses of Timoshenko Beams via ...
http://jacm.scu.ac.ir/article_13028_1659.html
Bending, buckling and vibration behaviors of nonlocal Timoshenko beams are investigated in this research using a variational approach. At first, the governing equations of the nonlocal Timoshenko beams are obtained, and then the weak form of these equations is outlined in this paper. The Ritz technique is selected to investigate the behavior of nonlocal beams with arbitrary boundary conditions along them. To find the equilibrium equations of bending, buckling, and vibration of these structures, an analytical procedure is followed. In order to verify the proposed formulation, the results for the nonlocal Timoshenko beams with four classical boundary conditions are computed and compared wherever possible. Since the Ritz technique can efficiently model the nano-sized structures with arbitrary boundary conditions, two types of beams with general boundary conditions are selected, and new results are obtained.Sun, 31 Dec 2017 20:30:00 +0100Quasi-Static Transient Thermal Stresses in an Elliptical Plate due to Sectional Heat Supply on ...
http://jacm.scu.ac.ir/article_13045_1659.html
This paper is an attempt to determine quasi-static thermal stresses in a thin elliptical plate which is subjected to transient temperature on the top face with zero temperature on the lower face and the homogeneous boundary condition of the third kind on the fixed elliptical curved surface. The solution to conductivity equation is elucidated by employing a classical method. The solution of stress components is achieved by using Goodier’s and Airy’s potential function involving the Mathieu and modified functions and their derivatives. The obtained numerical results are accurate enough for practical purposes, better understanding of the underlying elliptic object, and better estimates of the thermal effect on the thermoelastic problem. The conclusions emphasize the importance of better understanding of the underlying elliptic structure, improved understanding of its relationship to circular object profile, and better estimates of the thermal effect on the thermoelastic problem.Sun, 31 Dec 2017 20:30:00 +0100Buckling and Vibration Analysis of Tapered Circular Nano Plate
http://jacm.scu.ac.ir/article_13035_1659.html
In this paper, buckling and free vibration analysis of a circular tapered nanoplate subjected to in-plane forces were studied. The linear variation of the plate thickness was considered in radial direction. Nonlocal elasticity theory was employed to capture size-dependent effects. The Raleigh-Ritz method and differential transform method were utilized to obtain the frequency equations for simply supported and clamped boundary conditions. To verify the accuracy of the Ritz method, the differential transform method (DTM) was also used to drive the size-dependent natural frequencies of circular nanoplates. Both methods reported good results. The validity of solutions was performed by comparing the present results with those of the literature for both classical plate and nanoplate. The effects of nonlocal parameter, mode number, and taper parameter on the natural frequency were investigated. The results showed that increasing the taper parameter causes increasing of buckling load and natural frequencies, and its effects on the clamped boundary condition is more than the simply support.Sun, 31 Dec 2017 20:30:00 +0100Reducing Retrieval Time in Automated Storage and Retrieval System with a Gravitational Conveyor ...
http://jacm.scu.ac.ir/article_13038_1659.html
The main objective of this study is to reduce the retrieval time of a list of products by choosing the best combination of storage and retrieval rules at any time. This is why we start by implementing some storage rules in an Automated Storage/Retrieval System (Automated Storage and Retrieval System: AS/RS) fitted with a gravity conveyor while some of these rules are dedicated to storage and others to retrieval. The system is seen as a Multi-Agent System (MAS) where the produced agents are reactive agents that can interact to achieve a behavior (organizing the store). Our MAS is characterized by a decentralized control, which means that there is no preset plan. The produced agents exchange information such as their color, their distance from the output station, etc. Each product merely applies a set of behavioral rules. The aim is to choose the best product to be retrieved in the shortest possible time. The product-type agents have no cognitive ability, but still perform complex tasks.Sun, 31 Dec 2017 20:30:00 +0100Experimental Investigation on Radial Ball Bearing Parameters Using Taguchi Method
http://jacm.scu.ac.ir/article_12993_1659.html
In this work, characteristics of various ball bearing parameters are studied under different loads and rotational speeds. By using Dimensional Analysis (DA), dimensionless parameters are computed which provides solution for a group of parameters. This analysis can be accomplished by using the Buckingham π-theorem. DA leads to reduction of the number of independent parameters involved in a problem. These independent parameters get expressed as dimensionless groups. These dimensionless groups are always ratios of important physical quantities involved in the problem of interest. In modeling and experimentation, its main function is to reduce the amount of independent variables, simplify the solution, and generalize the results. It becomes an effective method, especially if a complete mathematical model of the investigated process is not known. Moreover, in the present work the Buckingham π-theorem is applied to find the influencing parameter π5 by using the Taguchi method.Sun, 31 Dec 2017 20:30:00 +0100Vibration Analysis of Material Size-Dependent CNTs Using Energy Equivalent Model
http://jacm.scu.ac.ir/article_13086_0.html
This study presents a modified continuum model to investigate the vibration behavior of single and multi-carbon nanotubes (CNTs). Two parameters are exploited to consider size dependence; one derived from the energy equivalent model and the other from the modified couple stress theory. The energy equivalent model, derived from the basis of molecular mechanics, is exploited to describe size-dependent material properties such as Young and shear moduli for both zigzag and armchair CNT structures. A modified couple stress theory is proposed to capture the microstructure size effect by assisting material length scale. A modified kinematic Timoshenko nano-beam including shear deformation and rotary inertia effects is developed. The analytical solution is shown and verified with previously published works. Moreover, parametric studies are performed to illustrate the influence of the length scale parameter, translation indices of the chiral vector, and orientation of CNTs on the vibration behaviors. The effect of the number of tube layers on the fundamental frequency of CNTs is also presented. These findings are helpful in mechanical design of high-precision measurement nano-devices manufactured from CNTs.Tue, 01 Aug 2017 19:30:00 +0100Thermal Analysis of Convective-Radiative Fin with Temperature-Dependent Thermal Conductivity ...
http://jacm.scu.ac.ir/article_13087_0.html
In this paper, the Chebychev spectral collocation method is applied for the thermal analysis of convective-radiative straight fins with the temperature-dependent thermal conductivity. The developed heat transfer model was used to analyse the thermal performance, establish the optimum thermal design parameters, and also, investigate the effects of thermo-geometric parameters and thermal conductivity (nonlinear) parameters on the thermal performance of the fin. The results of this study reveal that the rate of heat transfer from the fin increases as convective, radioactive, and magnetic parameters increase. This study finds good agreements between the obtained results using the Chebychev spectral collocation method and the results obtained using the Runge-Kutta method along with shooting, homotopy perturbation, and Adomian decomposition methods.Thu, 03 Aug 2017 19:30:00 +0100Study of Parameters Affecting Separation Bubble Size in High Speed Flows using k-ω Turbulence Model
http://jacm.scu.ac.ir/article_13088_0.html
Shock waves generated at different parts of vehicle interact with the boundary layer over the surface at high Mach flows. The adverse pressure gradient across strong shock wave causes the flow to separate and peak loads are generated at separation and reattachment points. The size of separation bubble in the shock boundary layer interaction flows depends on various parameters. Reynolds-averaged Navier-Stokes equations using the standard two-equation k-ω turbulence model is used in simulations for hypersonic flows over compression corner. Different deflection angles, including q ranging from 15o to 38o, are simulated at Mach 9.22 to study its effect on separated flow. This is followed by a variation in the Reynolds number based on the boundary layer thickness, Red from 1x105 to 4x105. Simulations at different constant wall conditions Tw of cool, adiabatic, and hot are also performed. Finally, the effect of free stream Mach numbers M∞, ranging from 5 to 9, on interaction region is studied. It is observed that an increase in parameters, q, Red, and Tw results in an increase in the separation bubble length, Ls, and an increase in M∞ results in the decrease in Ls. Mon, 14 Aug 2017 19:30:00 +0100Transient Natural Convection in an Enclosure with Variable Thermal Expansion Coefficient and ...
http://jacm.scu.ac.ir/article_13099_0.html
Transient natural convection is numerically investigated in an enclosure using variable thermal conductivity, viscosity, and the thermal expansion coefficient of Al2O3-water nanofluid. The study has been conducted for a wide range of Rayleigh numbers (103≤ Ra ≤ 106), concentrations of nanoparticles (0% ≤ ϕ ≤ 7%), the enclosure aspect ratio (AR =1), and temperature differences between the cold and hot walls (∆T= 30). Transient parameters such as development time and time-average Nusselt number along the cold wall are also presented as a non-dimensional form. Increasing the Rayleigh number shortens the non-dimensional time of the initializing stage. By increasing the volume fraction of nanoparticles, the flow development time shows different behaviors for various Rayleigh numbers. The non-dimensional development time decreases by enhancing the concentration of nanoparticles.Sat, 19 Aug 2017 19:30:00 +0100Bending Response of Nanobeams Resting on Elastic Foundation
http://jacm.scu.ac.ir/article_13100_0.html
In the present study, the finite element method is developed for the static analysis of nano-beams under the Winkler foundation and the uniform load. The small scale effect along with Eringen's nonlocal elasticity theory is taken into account. The governing equations are derived based on the minimum potential energy principle. Galerkin weighted residual method is used to obtain the finite element equations. The validity and novelty of the results for bending are tested and comparative results are presented. Deflections according to different Winkler foundation parameters and small scale parameters are tabulated and plotted. As it can be seen clearly from figures and tables, for simply-supported boundary conditions, the effect of small scale parameter is very high when the Winkler foundation parameter is smaller. On the other hand, for clamped-clamped boundary conditions, the effect of small scale parameter is higher when the Winkler foundation parameter is high. Although the effect of the small scale parameter is adverse on deflection for simply-supported and clamped-clamped boundary conditions.Mon, 21 Aug 2017 19:30:00 +0100Buckling Behaviors of Symmetric and Antisymmetric Functionally Graded Beams
http://jacm.scu.ac.ir/article_13109_0.html
The present study investigates buckling characteristics of both nonlinear symmetric power and sigmoid functionally graded (FG) beams. The volume fractions of metal and ceramic are assumed to be distributed through a beam thickness by the sigmoid-law distribution (S-FGM), and the symmetric power function (SP-FGM). These functions have smooth variation of properties across the boundary rather than the classical power law distribution which permits gradually variation of stresses at the surface boundary and eliminates delamination. The Voigt model is proposed to homogenize micromechanical properties and to derive the effective material properties. The Euler-Bernoulli beam theory is selected to describe Kinematic relations. A finite element model is exploited to form stiffness and buckling matrices and solve the problem of eignivalue numerically. Numerical results present the effect of material graduations and elasticity ratios on the buckling behavior of FG beams. The proposed model is helpful in stability of mechanical systems manufactured from FGMs.Sun, 27 Aug 2017 19:30:00 +0100Finite Element Solutions of Cantilever and Fixed Actuator Beams using Augmented Lagrangian Methods
http://jacm.scu.ac.ir/article_13110_0.html
In this paper we develop a numerical procedure using finite element and augmented Lagrangian meth-ods that simulates electro-mechanical pull-in states of both cantilever and fixed beams in microelectromechanical systems (MEMS) switches. We devise the augmented Lagrangian methods for the well-known Euler-Bernoulli beam equation which also takes into consideration of the fringing effect of electric field to allow a smooth transi-tion of the electric field between center of a beam and edges of the beam. The numerical results obtained by the procedure are tabulated and compared with some existing results for beams in MEMS switches in literature. This procedure produces stable and accurate numerical results for simulation of these MEMS beams and can be a useful and efficient alternative for design and determining onset of pull-in for such devices.Thu, 31 Aug 2017 19:30:00 +0100Buckling analysis of embedded nanosize FG beams based on a refined hyperbolic shear deformation ...
http://jacm.scu.ac.ir/article_13152_0.html
In this paper, mechanical buckling response of refined hyperbolic shear deformable (FG) functionally graded nanobeams embedded in an elastic foundation is studied base on refined hyperbolic shear deformation theory. Material properties of FG nanobeam change continuously in thickness direction based on power-law model. To capture small size effects, Eringen’s nonlocal elasticity theory is adopted. Employing Hamilton’s principle, the nonlocal governing equations of FG nanobeams embedded in elastic foundation are obtained. To predict buckling behavior of embedded FGP nanobeams, the Navier-type analytical solution is applied to solve the governing equations. Numerical results demonstrate the influences of various parameters such as elastic foundation, power-law index, nonlocal parameter and slenderness ratio on the buckling loads of size dependent FG nanobeams.Wed, 20 Sep 2017 19:30:00 +0100Inherent irreversibility of exothermic chemical reactive third-grade poiseuille flow of a ...
http://jacm.scu.ac.ir/article_13194_0.html
In this study, the analysis of inherent irreversibility of chemical reactive third-gradepoiseuille flow of a variable viscosity with convective cooling is investigated. The dissipative heat in a reactive exothermic chemical moves over liquid in an irreversible wayand entropy is produced unceasingly in the system within the fixed walls. The heat convective exchange with the surrounding temperature at the plate surface follows Newtonslaw of cooling. The solutions of the dimensionless nonlinear equations are obtained usingweighted residual method (WRM). The solutions are used to get the Bejan number andentropy generation rate for the system. The influence of some pertinent parameters onthe entropy generation and Bejan number are illustrated graphically and discussed withrespect to the parameters.Tue, 26 Sep 2017 20:30:00 +0100MOVING MESH NON-STANDARD FINITE DIFFERENCE METHOD FOR NON-LINEAR HEAT TRANSFER IN A THIN FINITE ROD
http://jacm.scu.ac.ir/article_13202_0.html
In this paper, a moving mesh technique and a non-standard finite difference method are combined, and a moving mesh non-standard finite difference(MMNSFD) method is developed to solve an initial boundary value problem involving a quartic nonlinearity that arises in heat transfer with thermal radiation. In this method the moving spatial grid is obtained by a simple geometric adaptive algorithm for preserving stability. Also it uses variable time steps for protecting the positivity condition of solution. We compare the results of our computational technique against the corresponding uniform mesh non-standard finite difference scheme. Our simulations show that the presented method is efficient and applicable and approximates well the solutions, while corresponding uniform mesh non-standard finite difference because of producing unreal solution, fails.Sat, 30 Sep 2017 20:30:00 +0100Semi-analytical solution for vibration of nonlocal piezoelectric Kirchhoff plates resting on ...
http://jacm.scu.ac.ir/article_13203_0.html
ABSTRACT: Semi-analytical solutions for vibration analysis of nonlocal piezoelectric Kirchhoff plates resting on viscoelastic foundation with arbitrary boundary conditions are derived by developing the Galerkin strip distributed transfer function method. Based on the nonlocal elasticity theory for piezoelectric materials and Hamilton's principle, the governing equations of motion and boundary conditions are first obtained, where external electric voltage, viscoelastic foundation, piezoelectric effect and nonlocal effect are considered simultaneously. Subsequently, the Galerkin strip distributed transfer function method is developed to solve the governing equations for the semi-analytical solutions of natural frequencies. Numerical results from the model are also presented to show the effects of nonlocal parameter, external electric voltages, boundary conditions, viscoelastic foundation and geometric dimensions on vibration responses of the plate. The results demonstrate the efficiency of the proposed methods for vibration analysis of nonlocal piezoelectric Kirchhoff plates resting on viscoelastic foundation.Sat, 30 Sep 2017 20:30:00 +0100Modelling of crack growth using a new fracture criteria based peridynamics
http://jacm.scu.ac.ir/article_13213_0.html
Peridynamics (PD) is a nonlocal continuum theory based on integro-differential equations without spatial derivatives. The elongation fracture criterion is implicitly incorporated in the PD theory and fracture is a natural outcome of the simulation. On the other hand, a new fracture criterion based on the crack opening displacement combine with peridynamic (PD-COD) is proposed. When the relative deformation of the PD bond between two particles reach the critical crack tip opening displacement of the fracture mechanics, we assume that the bond force vanishes. The new damage rule of fracture criteria similar to the local damage rule in conventional PD is introduced to simulate fracture. In this paper, a comparative study between XFEM and PD is presented at first. Then , four examples, i.e. a bilateral crack problem, double parallel crack, monoclinic crack and the double inclined crack are given to demonstrate the effectiveness of the new criterion.Mon, 02 Oct 2017 20:30:00 +0100Bending of Shear Deformable Plates Resting on Winkler Foundations According to Trigonometric ...
http://jacm.scu.ac.ir/article_13234_0.html
In this paper, a trigonometric plate theory is evaluated for the bending analysis of plates resting on Winkler elastic foundation. The theory is taking into account effects of transverse shear deformation as well as transverse normal strain. The theory accounts for realistic variation of the transverse shear stress through the thickness and satisfies the traction free conditions at the top and bottom surfaces of the plate without using shear correction factors. Governing equations of equilibrium and associated boundary conditions of the theory are obtained using the principle of virtual work. A closed-form solution is obtained using double trigonometric series. The numerical results are obtained for flexure of simply supported plates subjected to various static loadings. The displacements and stresses are obtained for three different values of foundation modulus. The numerical results are also generated using higher order shear deformation theory of Reddy, first order shear deformation theory of Mindlin and classical plate theory for the comparison of present results.Wed, 18 Oct 2017 20:30:00 +0100Differential quadrature method for dynamic buckling of graphene sheet coupled by a viscoelastic ...
http://jacm.scu.ac.ir/article_13235_0.html
The dynamic buckling of graphene sheet coupled by a viscoelastic matrix has been studied in the paper. In light of the simplicity of Eringen's non-local continuum theory to considering the nanoscale influences, the theory has been employed. Equations of motion and boundary conditions were obtained using Mindlin plate theory by taking into account nonlinear strains of von Kármán and Hamilton's principle. A viscoelastic matrix was modeled as a three-parameter foundation. Furthermore, differential quadrature method was applied by which critical load has been obtained. Finally, in order to compare the results, since, there are no researches available for dynamic buckling of a nanoplate, the static buckling has been considered. The outcomes will be carried out to explain some significant and novel findings. One of these harvests shows that for greater values of nanoscale parameter, the small scale has further impacted on the dynamic buckling.Sat, 21 Oct 2017 20:30:00 +0100Exact Radial Free Vibration Frequencies of Power-Law Graded Spheres
http://jacm.scu.ac.ir/article_13243_0.html
This work concentrates on the free pure radial vibrations of hollow spheres made of hypothetically functionally simple power rule graded materials having identical inhomogeneity indexes for both Young’s modulus and the density in an analytical manner. After offering the exact elements of the free vibration coefficient matrices for free-free, free-fixed, and fixed-fixed restraints, a parametric study is fulfilled to study the effects of both the aspect ratio and the inhomogeneity parameters on the natural frequencies. The outcomes are presented in both graphical and tabular forms. It was seen that the fundamental frequency is principally affected from the inhomogeneity parameters than the higher ones. However, the natural frequencies except the fundamental ones are dramatically affected from the thickness of the sphere. It is also revealed that, there is a linear relationship between the fundamental frequency and others in higher modes of the same sphere under all boundary conditions.Sat, 28 Oct 2017 20:30:00 +0100Verification of Meshfree Numerical Schemes with Approximation of Spatial Derivatives
http://jacm.scu.ac.ir/article_13292_0.html
In order to improve the approximation of spatial derivatives without meshes, a set of meshfree numerical schemes for derivative terms is developed, which is compatible with the coordinates of Cartesian, cylindrical and spherical. Based on the comparisons between numerical and theoretical solutions, errors and convergences are assessed by a posteriori methods, which show the approximations for functions and derivatives are of the second accuracy order, and the scale of the support domain has some influences on numerical errors but not on accuracy orders. With a discrete scale h=0.01, the relative errors of the numerical simulation for the selected functions and their derivatives are within 0.65%.Mon, 27 Nov 2017 20:30:00 +0100The Complementary Functions Method (CFM) Solution to the Elastic Analysis of Polar Orthotropic ...
http://jacm.scu.ac.ir/article_13293_0.html
This study primarily deals with introducing an efficient numerical technique called the Complementary Functions Method (CFM) for the initial value problem solutions to the linear elastic analysis of anisotropic rotating uniform discs. To bring the performance of the method to light, closed form formulas are derived for such discs in the first place. The governing equation of the problem at stake is solved analytically with the help of Euler Cauchy technique under three types of boundary conditions namely free-free, fixed-free, and fixed-guided constraints. In the second place, the CFM is applied to the same problem. It was seen that both numerical and analytical results coincide with each other up to a desired numerical accuracy. After verifying the results with the literature, in the third place, a parametric study with CFM on the elastic behavior of discs made of five different materials which physically exist is performed. And finally, by using hypothetically chosen anisotropy degrees from 0.3 through 5, effects of the anisotropy on the elastic response of such structures are investigated analytically. Useful graphs are provided for readers.Mon, 27 Nov 2017 20:30:00 +0100