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.Vibration Analysis of Material Size-Dependent CNTs Using Energy Equivalent Model
http://jacm.scu.ac.ir/article_13086_1659.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.Sat, 31 Mar 2018 19:30:00 +0100Thermal Analysis of Convective-Radiative Fin with Temperature-Dependent Thermal Conductivity ...
http://jacm.scu.ac.ir/article_13087_1659.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.Sat, 31 Mar 2018 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_1659.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. Sat, 31 Mar 2018 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_1659.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.Sat, 31 Mar 2018 19:30:00 +0100Buckling Behaviors of Symmetric and Antisymmetric Functionally Graded Beams
http://jacm.scu.ac.ir/article_13109_1659.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.Sat, 31 Mar 2018 19:30:00 +0100Finite Element Solutions of Cantilever and Fixed Actuator Beams Using Augmented Lagrangian Methods
http://jacm.scu.ac.ir/article_13110_1659.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.Sat, 31 Mar 2018 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 +0100Stability of a Strongly Displacement Time-Delayed Duffing Oscillator by the ...
http://jacm.scu.ac.ir/article_13341_0.html
In the current work, some perturbation methods are applied to Duffing equation having a displacement time-delayed variable to study the stability of such systems. Two approaches are considered to analyze Duffing oscillator having a strong delayed variable. The homotopy perturbation method has been applied through the frequency analysis. Nonlinear frequency is formulated as a function of all the problem’s parameters. Based on the multiple scales-homotopy-perturbation method, a uniform second-order periodic solution having a damping part has been formulated. Comparing these two approaches reveals the accuracy of using the second approaches further allowing studying the stability behavior. Numerical simulations are carried out to validate the analytical finding.Thu, 14 Dec 2017 20:30:00 +0100Cyclic and monotonic behavior of strengthened and unstrengthened square reinforced concrete columns
http://jacm.scu.ac.ir/article_13349_0.html
The use of composite materials is an effective technique to enhance the capacity of reinforced concrete columns subjected to seismic loading due to their high tensile strength. In this paper, numerical models were developed in order to predict the experimental behavior of square reinforced concrete columns strengthened with glass fiber reinforced polymer and steel bars and unstrengthened column under cyclic and monotonic loadings, respectively. Two columns were modeled in the present work. The first concerns the column without strengthening subjected to lateral monotonic loading, and the second concerns the column strengthened with glass fiber reinforced polymer and steel bars subjected to lateral cyclic loading. Comparison of the numerical modeling and the experimental laboratory tests results were performed and discussed. Good accordance between the numerical and experimental force-displacement responses was obtained. Improvement of the strength of the reinforced concrete column subjected to cyclic loading was described with comparison of the behavior of the strengthened column with the unstrengthened reference column. The results show a good improvement in the load carrying capacity and ductility of the column. The main objectives of this numerical modeling are to contribute to the comprehension of the monotonic and cyclic behavior of the square reinforced concrete columns and to compare the numerical results with the experimental ones.Wed, 20 Dec 2017 20:30:00 +0100ON THE SLIP EFFECTS FOR SQUEEZING MHD FLOW OF A CASSON FLUID BETWEEN PARALLEL DISKS
http://jacm.scu.ac.ir/article_13350_0.html
This paper considers the effects of squeezing electrically conducting Casson fluid, flowing through parallel disk under slip condition. The Nonlinear model describing the transport phenomena of the Casson fluid is analyzed adopting the homotopy perturbation method (HPM). Solutions generated from higher order non-linear equations arising from the mechanics of the fluid utilsing the HPM are used to investigate effects of rheological parameters such as squeeze and slip on fluid flow for cases of plates moving apart and coming together. Results reveal increasing velocity profile due to quantitative increase of slip parameter when plates are receding as well as collapsing, with effect more pronounced towards the upper plate. This present study provides good insights to applications such as hydraulic lifts, electric motors, nasogastric tube and syringe flow amongst other application.Wed, 20 Dec 2017 20:30:00 +0100Modeling of Self-Healing Concrete: A Review
http://jacm.scu.ac.ir/article_13355_0.html
Self-healing concrete (SHC) has received a tremendous attention due to its advanced ability of automatic crack detection and crack repairing compared to standard concrete. Two main approaches considered to-date of self-healing mechanism are autogenous and autonomous healing. In the past several years, the effort of the research has been focused on experimental works instead of numerical models to simulate the healing process. The purpose of this review is to provide comprehensive comparison from different self-healing concrete (cement based masterials) modeling approaches which are available. In this review, special attention is given to the autonomous healing model and a few of recent works of autogenous healing model are also revealed. Moreover, this review covers both of analytical and numerical simulation method of self-healing concrete model.Thu, 28 Dec 2017 20:30:00 +0100Nonlinear Dynamic Response of Functional Graded Porous Plates on Elastic Foundation Subjected ...
http://jacm.scu.ac.ir/article_13360_0.html
In this paper, the first-order shear deformation theory is used to derive theoretical formulations illustrating the nonlinear dynamic response of functionally graded porous plates under thermal and mechanical loading supported by Pasternak’s model of the elastic foundation. Two types of porosity, namely evenly distributed porosities (Porosity-I) and unevenly distributed porosities (Porosity-II), are assumed influencing effective properties of FGM plates such as Young’s modulus, the coefficient of thermal expansion and density. The strain-displacement formulations admitted Von Karman geometrical nonlinearity and general Hooke’s law are used to obtain constitutive relations. Airy stress functions with full motion equations are employed to shorten the number of governing equations, accompanying with the boundary and initial conditions lead to a system of differential equations of the nonlinear dynamic response of porous FGM plates. Considering linear parts of these equations, natural frequencies of porous FGM plates could be determined. Numerical results employed Runge-Kutta method illustrate the influence of geometrical configurations, volume faction index, porosity, elastic foundations, mechanical and thermal loads on the nonlinear dynamic response of the plates. Good agreements are obtained in comparison with other results in the literature.Sat, 06 Jan 2018 20:30:00 +0100Evaluation of fracture parameters by coupling the edge based smoothed finite element method and ...
http://jacm.scu.ac.ir/article_13372_0.html
This paper presents a technique to evaluate the fracture parameters by combining the edge based smoothed finite element method (ESFEM) and the scaled boundary finite element method (SBFEM). A semi-analytical solution is sought in the region close to the vicinity of the crack tip using the SBFEM, whilst, the ESFEM is used for the rest of the domain. As both the methods satisfy the partition of unity and the compatibility condition, the stiffness matrices obtained from both the methods can be assembled as in the conventional finite element method. The stress intensity factors (SIFs) are computed directly from their definition. Numerical examples of linear elastic bodies with cracks are solved without requiring additional post-processing technique. The SIFs computed using the proposed technique are in good agreement with the reference solutions. Crack propagation study is also carried out with minimal remeshing locally, to show the robustness of the proposed technique. The maximum circumferential stress criterion is used to predict the direction of propagation.Thu, 18 Jan 2018 20:30:00 +0100An analysis of thermal-bending stresses in a simply supported thin elliptical plate
http://jacm.scu.ac.ir/article_13400_0.html
In this paper, we consider a transient thermal stress investigation on a simply supported thin elliptical plate during sectional heating with time-dependent temperature supply. The solution of heat conduction equation with the corresponding initial and boundary conditions is obtained by employing an integral transform approach. The governing equation solution for small deflection theory is obtained and utilized to preserve the intensities of thermal bending moments, involving the Mathieu and modified functions and its derivatives. It was established that the deflection result proximately accedes with the previously given result. It is also exhibited that the temperature field in a circular solution could be resulting as a particular case from the present mathematical solution. The numerical results obtained utilizing computational implements was precise enough for practical purposes.Fri, 26 Jan 2018 20:30:00 +0100On the geometrically nonlinear analysis of composite axisymmetric shells
http://jacm.scu.ac.ir/article_13401_0.html
Composite axisymmetric shells have numerous applications; many researchers have taken advantage of the general shell element or semi-analytical formulation to analyze these structures. The present study is devoted to the nonlinear analysis of composite axisymmetric shells by using a 1D three nodded axisymmetric shell element. Both the low and higher-order shear deformations are included in the formulation. The displacement field is considered to be nonlinear function of the nodal rotations. This assumption eliminates the restriction of small rotations between two successive increments. Both Total Lagrangian Formulation and the Generalized Displacement Control Method are employed for analyzing the shells. Several numerical tests are performed to corroborate the accuracy and efficiency of the suggested approach.Fri, 26 Jan 2018 20:30:00 +0100DETERMINATION OF THE OPTIMAL REDUCTION RATIO FOR LEAST SPRINGBACK DURING COLD DRAWING OF ...
http://jacm.scu.ac.ir/article_13433_0.html
Cold drawing process is one of the most used metals forming process in industries for forming of seamless tubes. This process of plastic deformation of metals occurs below the recrystallization temperature and is generally performed at room temperature. When metal is cold worked, upon release of forming force, springback occurs. In this paper the springback effect of seamless tube that has undergone cold drawing has been studied for three different reduction ratios viz.10-15 %,15-20 % and 20-25 % with the aim to reduce it. Experiments are conducted under different reduction ratios with working conditions of die semi angles of 10 and 15 degree, die land width of 5 mm and 10 mm as well as drawing speed of 4, 6 and 8 m/min for C-45 tube material. Optimum reduction ratio is finalized using Statistical Package for Social Science (SPSS) software of data analysis using statistical tests like Kruskal-Wallis, ANOVA, Post-hoc etc. Metallurgical analysis through microstructural investigation, XRD and mechanical testing through cold draw load, hardness testing for different reduction ratios are also studied for validation purpose. The result of this research is that 10-15 % reduction ratio yields minimum springback. This can be used to help in design of tools in the metal forming industry to minimize springback and to improve the quality of the product.Wed, 07 Feb 2018 20:30:00 +0100Mixed Strong Form Representation Particle Method for Solids and Structures
http://jacm.scu.ac.ir/article_13434_0.html
In this paper, a generalized particle system (GPS) method, a general method to describe multiple strong form representation based particle methods is described. Gradient, divergence, and Laplacian operators used in various strong form based particle method such as moving particle semi-implicit (MPS) method, smooth particle hydrodynamics (SPH), and peridynamics, can be described by the GPS method with proper selection of parameters. In addition, the application of mixed formulation representation to the GPS method is described. Based on Hu-Washizu principle and Hellinger-Reissner principle, the mixed form refers to the method solving multiple primary variables such as displacement, strain and stress, simultaneously in the FEM method; however for convenience in employing FEM with particle methods, a simple representation in construction only is shown. It is usually applied to finite element method (FEM) to overcome numerical errors including locking issues. While the locking issues do not arise in strong form based particle methods, the mixed form representation in construction only concept applied to GPS method can be the first step for fostering coupling of multi-domain problems, coupling mixed form FEM andmixed form representation GPS method; however it is to be noted that the standard GPS particle method and the mixed for representation construction GPS particle method are equivalent. Two dimensional simple bar and beam problems are presented and the results from mixed form GPS method is comparable to the mixed form FEM results.Wed, 07 Feb 2018 20:30:00 +0100Further Study on Thermal Performance analysis of Porous Fin with Temperature-Dependent Thermal ...
http://jacm.scu.ac.ir/article_13473_0.html
In this present study, thermal performance analysis of porous fin with temperature-dependent thermal conductivity and internal heat generation is carried out using Galerkin’s method of weighted residual. The results of the Galerkin’s method of weighted residual show excellent agreement with the results of numerical method using shooting method coupled with Runge-Kutta method and also with the results of homotopy perturbation method. Thereafter, the developed analytical solutions are used to investigate the influences of the thermal model parameters on the thermal performance of the porous fin. It is found as the with the other model parameters that as the convective parameter increases, the rate of heat transfer from the base of the fin increases and consequently, the porous fin efficiency improves. However, increase in the nonlinear thermal conductivity parameter decreases the temperature distribution in the fin. Based on the high accuracy of the Galerkin’s method of weighted residual as displayed in this work, it is hoped that the simple analytical solutions given by the approximate analytical method will enhance the analysis of extended surfaces and also assist the designers.Sun, 18 Feb 2018 20:30:00 +0100Free convection flow of an electrically-conducting micropolar fluid between parallel porous ...
http://jacm.scu.ac.ir/article_13474_0.html
In this work, effect of temperature dependent heat sources on the fully developed free convection electrically conducting micropolar fluid between two parallel porous vertical plates in a strong cross magnetic field is analyzed. The micropolar fluid fills the space inside the porous plates when the rate of suction at one boundary is equal to the rate of injection at the other boundary. The coupled nonlinear governing differential equations are solved using differential transform method (DTM). Also the Runge-Kutta shooting method (RKSM) which is a numerical method is used for the validity of the DTM method and excellent agreement is observed between the solutions of DTM and RKSM. Trusting this validity, the effects of Hartmann number, Reynolds number, micropolar parameter and applied electric field load parameter are discussed on the velocity, microrotation velocity and temperature. The skin friction, couple stress and Nusselt numbers at the plates are shown in graphs. It is observed that the Hartmann number and micropolar parameter decreases the skin friction and couple stress at both the plates for suction and injection.Mon, 19 Feb 2018 20:30:00 +0100Evaluation of new best cross ply laminated plate theories through the axiomatic/asymptotic approach
http://jacm.scu.ac.ir/article_13516_0.html
This paper presents Best Theory Diagrams (BTDs) constructed from various non-polynomial theories for the static analysis of thick and thin symmetric and asymmetric cross ply laminated plates. The BTD is a curve that provides the minimum number of unknown variables necessary for a fixed error or vice versa. The plate theories that belong to the BTD have been obtained by means of the Axiomatic/Asymptotic Method (AAM). The different plate theories reported are implemented by using the Carrera Unified Formulation (CUF). Navier-type solutions have been obtained for the case of simply supported plates loaded by a bisinuisoidal transverse pressure with different length-to-thickness ratios. The BTDs build from non-polynomials functions are compared with BTDs using Maclaurin expansion. The results suggest that the plate models obtained from the BTD using non-polynomial terms can improve the accuracy obtained from Maclaurin expansions for a given number of unknown variables of the displacement field.Thu, 15 Mar 2018 20:30:00 +0100Study of Model Separation Flow Behaviour At High Angles of Attack Aerodynamics
http://jacm.scu.ac.ir/article_13517_0.html
This paper analyzed the aerodynamic performance and flow separation characteristics on the rectangular wing for varying Reynolds numbers. The mechanism of separation and its effect over the rectangular wing is simulated in ANSYS FLUENT using K-ω SST turbulence model. The detail analysis was performed to discuss the lift and drag force of the wing surface, surface pressure distribution around the wing surface, flow separation characteristics for different angles of attack, velocity profiles at different sections of the wing surface along the chord length, effect of wing tip vortices, etc. The simulation results show that with the increase in angles of attack, separation point moves towards the leading edge and on set of stalling it is very much closer to the leading edge. The experimental and numerical results also indicated that NACA4415 airfoil has enhanced coefficient of lift to coefficient of drag ratio at the ranges of angles of attack (AoA) 4◦-6◦ which are distinctively advantageous for the better performance of small scale wind turbine rotors. The experimental and computational results are analyzed in the context of effective change in stalling characteristics at different Reynolds numbers.Fri, 16 Mar 2018 20:30:00 +0100Extension Ability of Reduced Order Model of the Unsteady Incompressible Flows Using Combination ...
http://jacm.scu.ac.ir/article_13518_0.html
In this article, a new low-dimensional modelling approach, based on the proper orthogonal decomposition (POD) method, is presented. After projecting the governing equations of flow dynamics along POD modes, a dynamical system is obtained. Normally, the classical reduced order models do not predict accurate time variations of flow variables due to some reasons. To improve the response of the dynamical system a calibration method based on a least square optimization process, was used. The calibration polynomial can be assumed as the pressure correction term which is vanished in projecting the Navier-Stokes equations along the POD modes. The above least square procedure is a combination of POD method with solution of an optimization problem and the obtained model can predict accurate time variations of flow field with high speed. For the long time periods, the calibration term is computed using a combined form of POD and Fourier modes. This extension is a totally new extension to this procedure which has been proposed by the authors recently. The results obtained from the calibrated low-dimensional model show close agreements to the benchmark DNS data and proving high accuracy of our model.Sun, 18 Mar 2018 20:30:00 +0100Free Convection Flow and Heat Transfer of Nanofluids of Different Shapes of Nano-size particles ...
http://jacm.scu.ac.ir/article_13519_0.html
In this paper, free convection flow and heat transfer of nanofluids of different shapes nano-size particles over a vertical plate at very low and high Prandtl number are analyzed. The governing systems of nonlinear partial differential equations of the flow and heat transfer processes are converted to systems of nonlinear ordinary differential equation through similarity transformations. The resulting systems of fully coupled nonlinear ordinary differential equations are solved using differential transformation method-Padé approximant technique. The accuracies of the developed analytical methods are verified by comparing their results with the results of past works as presented in literature. Thereafter, the analytical solutions are used to investigate the effects of Prandtl number, nanoparticles volume-fraction, shape and type on the flow and heat transfer behaviour of various nanofluids over the flat plate. It is observed that the velocity and temperature of the nanofluid decreases and increases, respectively as the Prandtl number and volume-fraction of the nanoparticles in the basefluid increase. Also, the maximum decrease in velocity and maximum increase in temperature are caused lamina shaped nanoparticle and followed by platelets, cylinder, bricks and sphere shaped nanoparticles, respectively. Using a common basefluid to all the nanoparticle type, it was established that the maximum decrease in velocity and maximum increase in temperature are caused by TiO2 and followed by CuO, Al2O3 and SWCNTs nanoparticles, in that order. It is hoped that the present study will enhance the understanding of free convection boundary-layer problems as applied in various engineering processes.Mon, 19 Mar 2018 20:30:00 +0100A Comparative Analysis of TLCD Equipped Shear Buildings Under Dynamic Loads
http://jacm.scu.ac.ir/article_13520_0.html
This study targets the behavior of shear buildings equipped with tuned liquid column dampers (TLCD) which attenuates dynamic load induced vibration. TLCDs are a passive damping system used in tall buildings. This kind of damper has proven to be very efficient, being an excellent alternative to mass dampers. A dynamic analysis of the structure-damper system is made using the software DynaPy, developed in the research process. The software solves the equations of motion through numeric integration using the central differences method. The simulations results obtained with DynaPy showed that the use of TLCD can reduce the dynamic response significantly for both harmonic excitations and random excitations.Tue, 20 Mar 2018 20:30:00 +0100Free vibration analysis of quintic nonlinear beams by using the equivalent linearization method ...
http://jacm.scu.ac.ir/article_13523_0.html
In this paper, the equivalent linearization method with a weighted averaging proposed by Anh (2015) is applied to analyse the transverse vibration of quintic nonlinear Euler-Bernoulli beams subjected to the axial loads. The proposed method does not require small parameter in the equation which is difficult to be found for nonlinear problems. The approximate solutions are harmonic oscillations, which are compared with the previous analytical solutions and the exact solutions. Comparisons show the accuracy of the present solutions. The impact of nonlinear terms on dynamical behavior of beams and the effect of the initial amplitude on frequencies of beams are investigated. Futhermore, the effect of the axial force and the length of beams on frequencies are studied.Thu, 05 Apr 2018 19:30:00 +0100Wave motion and stop-bands in pipes with helical characteristics using Wave Finite Element analysis
http://jacm.scu.ac.ir/article_13555_0.html
Pipes are widely used in many industrial and mechanical applications and devices. Although there are many different constructions according to the specific application and device, these can show helical pattern, such as spiral pipes, wire-reinforced pipes/shells, spring-suspension and so on. Theoretical modelling of wave propagation provides a prediction about the dynamic behaviour, andit is fundamental in the design process of these structures/devices and in structural health monitoring techniques. However, standard approaches have limitations in terms of difficulties in modelling and impossible computational cost at higher frequencies. In this paper wave characteristics in waveguides with helical patterns are obtained using a Wave Finite Element (WFE) method. The method is described for a 1D and 2D waveguide with helical properties and it is illustrated by numerical examples. These include the optimisation of stop-bands for a fluid-filled pipe with concentrated masses and a cylindrical structure with helical orthotropy.Mon, 23 Apr 2018 19:30:00 +0100