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.Modelling 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 combined with peridynamic (PD-COD) is proposed. When the relative deformation of the PD bond between two particles reaches 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 the fracture. In this paper, first, a comparative study between XFEM and PD is presented. 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.Sat, 02 Dec 2017 20:30:00 +0100Extension Ability of Reduced Order Model of Unsteady Incompressible Flows Using a Combination ...
http://jacm.scu.ac.ir/article_13518_1754.html
In this article, an improved reduced order modelling approach, based on the proper orthogonal decomposition (POD) method, is presented. After projecting the governing equations of flow dynamics along the POD modes, a dynamical system was obtained. Normally, the classical reduced order models do not predict accurate time variations of flow variables due to some reasons. The response of the dynamical system was improved using a calibration method based on a least-square optimization process. 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 and the solution of an optimization problem. The obtained model can predict accurate time variations of flow field with high speed. For long time periods, the calibration term can be computed using a combined form of POD and Fourier modes. This extension is a totally new extension to this procedure which has recently been proposed by the authors. The results obtained from the calibrated reduced order model show close agreements to the benchmark DNS data, proving high accuracy of our model.Mon, 31 Dec 2018 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 the seismic loading due to their high tensile strength. In this paper, numerical models are developed in order to predict the experimental behavior of square reinforced concrete columns strengthened by glass fiber reinforced polymer and steel bars and unstrengthened column under cyclic and monotonic loadings, respectively. Two columns are modeled in the present work. The first one corresponds to the column without strengthening subjected to lateral monotonic loading, and the second one corresponds to the column strengthened by glass fiber reinforced polymer and steel bars subjected to lateral cyclic loading. Comparison of the numerical modeling and the experimental laboratory test results are performed and discussed. A good agreement between the numerical and experimental force-displacement responses is obtained. Moreover, improvements in the strength of the reinforced concrete column subjected to the cyclic loading along with the comparison of the behavior of the strengthened column with the unstrengthened reference column are discussed. 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 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 +0100Free Convection Flow and Heat Transfer of Nanofluids of Different Shapes of Nano-Sized ...
http://jacm.scu.ac.ir/article_13519_1754.html
In this paper, free convection flow and heat transfer of nanofluids of differently-shaped nano-sized particles over a vertical plate at very low and high Prandtl numbers 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 a differential transformation method - Padé approximant technique. The accuracy of the developed approximate analytical methods is verified by comparing the results of the differential transformation method - Padé approximant technique with those of previous works as presented in the literature. Thereafter, the analytical solutions are used to investigate the effects of the Prandtl number, the nanoparticles volume-fraction, the shape and the type on the flow and heat transfer behaviour of various nanofluids over the flat plate. It is observed that as the Prandtl number and volume-fraction of the nanoparticles in the basefluid increase, the velocity of the nanofluid decreases while the temperature increases. Also, the maximum decrease in velocity and the maximum increase in temperature are recorded in lamina-shaped nanoparticles, followed by platelets, cylinders, bricks, and sphere-shaped nanoparticles, respectively. Using a common basefluid for all nanoparticle types, it is established that the maximum decrease in velocity and the maximum increase in temperature are recorded in TiO2 followed by CuO, Al2O3 and SWCNTs nanoparticles, respectively. It is hoped that the present study will enhance the understanding of free convection boundary-layer problems as applied in various industrial, biological and engineering processes.Mon, 31 Dec 2018 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 the standard concrete. Two main approaches which considered as to-date self-healing mechanisms 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 study is to provide a comprehensive comparison of different self-healing concrete (cement based materials) modeling approaches which are available. In this review, special attention is given to the autonomous healing model and a few of recent works related to the autogenous healing model are also investigated. Moreover, this review covers both analytical and numerical simulation methods of self-healing concrete model.Thu, 28 Dec 2017 20:30:00 +0100A Comparative Analysis of TLCD-Equipped Shear Buildings under Dynamic Loads
http://jacm.scu.ac.ir/article_13520_1754.html
This study targets the behavior of shear buildings equipped with tuned liquid column dampers (TLCD) which attenuate dynamic load-induced vibrations. 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 was 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.Mon, 31 Dec 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 methods satisfy the partition of unity and the compatibility condition, the stiffness matrices obtained from both 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 techniques. The SIFs computed using the proposed technique are in a good agreement with the reference solutions. A crack propagation study is also carried out with minimal local remeshing 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 +0100Free Vibration Analysis of Quintic Nonlinear Beams using Equivalent Linearization Method with a ...
http://jacm.scu.ac.ir/article_13523_1754.html
In this paper, the equivalent linearization method with a weighted averaging proposed by Anh (2015) is applied to analyze the transverse vibration of quintic nonlinear Euler-Bernoulli beams subjected to 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 the dynamical behavior of beams and the effect of the initial amplitude on frequencies of beams are investigated. Furthermore, the effect of the axial force and the length of beams on frequencies are studied.Mon, 31 Dec 2018 20:30:00 +0100Some New Existence, Uniqueness and Convergence Results for Fractional Volterra-Fredholm ...
http://jacm.scu.ac.ir/article_13592_1754.html
This paper demonstrates a study on some significant latest innovations in the approximated techniques to find the approximate solutions of Caputo fractional Volterra-Fredholm integro-differential equations. To this aim, the study uses the modified Adomian decomposition method (MADM) and the modified variational iteration method (MVIM). A wider applicability of these techniques are based on their reliability and reduction in the size of the computational work. This study provides an analytical approximate to determine the behavior of the solution. It proves the existence and uniqueness results and convergence of the solution. In addition, it brings an example to examine the validity and applicability of the proposed techniques.Mon, 31 Dec 2018 20:30:00 +0100Numerical Investigation of the Effect of Bubble-Bubble Interaction on the Power of Propagated ...
http://jacm.scu.ac.ir/article_13672_0.html
The study of bubble dynamics, especially the interaction of bubbles, has drawn considerable attention due to its various applications in engineering and science. Meanwhile, the study of the oscillation effect of a bubble on the emitted pressure wave of another bubble in an acoustic field which has less been investigated. This issue is investigated in the present study using the coupling of Keller-Miksis and Gilmore models. The ordinary differential equations are solved using MATLAB software and Runge-Kutta forth order method with the adaptive step size control. The results show the dependence of bubbles behavior and the strength of their pressure waves on two parameters of the initial radius and the bubbles center-to-center distance. As the initial radius of the adjacent bubble grows, its effect on the other bubble increases and causes a reduction in the other bubble maximum radius, wall velocity, internal pressure, and emitted pressure wave intensity. However, increasing the initial distance of the bubbles reduces the effect of the bubbles on each other and causes their behaviors become closer to the single-bubble oscillation mode.Wed, 27 Jun 2018 19:30:00 +0100A Numerical Simulation of Inspiratory Airflow in Human Airways during Exercise at Sea Level and ...
http://jacm.scu.ac.ir/article_13586_1754.html
At high altitudes, the air pressure is much lower than it is at sea level and contains fewer oxygen molecules and less oxygen is taken in at each breath. This requires deeper and rapid breathing to get the same amount of oxygen into the blood stream compared to breathing in air at sea level. Exercises increase the oxygen demand and make breathing more difficult at high altitude. In this study, a numerical simulation of inspiratory airflow in a three-dimensional bifurcating human airways model (third to sixth generation) during exercise at sea level and at high altitude was performed. The computational fluid dynamics (CFD) solver FLUENT was used to solve the governing equations for unsteady airflow in the model. Flow velocity, pressure, and wall shear stress were obtained from the simulations with the two breathing conditions. The result of this study quantitatively showed that performing exercise with a given work rate at high altitude increased inspiratory airflow velocity, pressure, and wall shear stress more than that at sea level in the airway model. The ranges of the airflow fields were also higher at high altitude than sea level. The simulation results showed that there were no significant differences in flowing pattern for the two breathing conditions.Mon, 31 Dec 2018 20:30:00 +0100A Novel Approach for Korteweg-de Vries Equation of Fractional Order
http://jacm.scu.ac.ir/article_13674_0.html
In this study, the localfractional variational iterationmethod (LFVIM) and the localfractional series expansion method (LFSEM) are utilized to obtain approximate solutions for Korteweg-de Vries equation (KdVE) within local fractionalderivative operators (LFDOs). The efficiency of the considered methods is illustrated by some examples. The results reveal that the suggested algorithms are very effective and simple and can be applied for linear and nonlinear problems in mathematical physics.Mon, 02 Jul 2018 19:30:00 +0100Study on Free Vibration and Wave Power Reflection in Functionally Graded Rectangular Plates ...
http://jacm.scu.ac.ir/article_13595_1754.html
In this paper, the wave propagation approach is presented to analyze the vibration and wave power reflection in FG rectangular plates based on the first order shear deformation plate theory. The wave propagation is one of the useful methods for analyzing the vibration of structures. This method gives the reflection and propagation matrices that are valuable for the analysis of mechanical energy transmission in devices. It is assumed that the plate has two opposite edges simply supported while the other two edges may be simply supported or clamped. It is the first time that the wave propagation method is used for functionally graded plates. In this study, firstly, the matrices of reflection and propagation are derived. Second, these matrices are combined to provide an exact method for obtaining the natural frequencies. It is observed that the obtained results of the wave propagation method are in a good agreement with the obtained values in literature. At the end, the behavior of reflection coefficients for FG plates are studied for the first time.Mon, 31 Dec 2018 20:30:00 +0100Experimental Study of the Residual Stresses in Girth Weld of Natural Gas Transmission Pipeline
http://jacm.scu.ac.ir/article_13695_0.html
In order to achieve integrated condition in the girth welding of high pressure natural gas transmission pipelines, the weld zones and its surrounding area should have good mechanical properties. Residual stresses are an important defect especially in the girth welding of the pipeline. In this study, two API X70 steel pipes (with spiral seam weld) of 56 inches outside diameter and 0.780 inch wall thickness were girth welded first. The hole drilling tests were conducted for residual stress measurement on the surfaces of the pipes. The hoop tensile residual stress on the external surface of the pipe with the maximum value equal to 318-MPa was measured on the weld centerline. Hoop residual stress distributions in the internal and external surfaces of the pipe were approximately similar. The maximum axial residual stress was observed in the heat affected zone (a distance of approximately 30 mm from the weld centerline). The maximum axial residual stress on the external surface of the pipe was tensile, equal to 137 MPa, and on the internal surface of the pipe was compressive, equal to 135-MPa. Axial residual stress magnitudes in the weld centerline on the internal and external surfaces of the pipe were close together. Away from the weld centerline, axial residual stresses on the internal and external surfaces showed the opposite behavior. Therefore, in the girth welding of natural gas transmission pipelines, the peripheral direction on the internal surface of the pipe is the critical zone and have the highest tensile residual stresses.Thu, 12 Jul 2018 19:30:00 +0100High Order Compact Finite Difference Schemes for Solving Bratu-Type Equations
http://jacm.scu.ac.ir/article_13596_1754.html
In the present study, high order compact finite difference methods is used to solve one-dimensional Bratu-type equations numerically. The convergence analysis of the methods is discussed and it is shown that the theoretical order of the method is consistent with its numerical rate of convergence. The maximum absolute errors in the solution at grid points are calculated and it is shown that the presented methods are efficient and applicable for lower and upper solutions.Mon, 31 Dec 2018 20:30:00 +0100Effect of Thermal Conductivity and Emissivity of Solid Walls on Time-Dependent Turbulent ...
http://jacm.scu.ac.ir/article_13714_0.html
In the present study, the conjugate turbulent free convection with the thermal surface radiation in a rectangular enclosure bounded by walls with different thermophysical characteristics in the presence of a local heater is numerically studied. The effects of surface emissivity and wall materials on the air flow and the heat transfer characteristics are the main focus of the present investigation. The conjugate convective heat transfer for the fluid (air), described in terms of linear momentum, continuity, and energy equations combined with k-ε turbulence model, is predicted by using the finite difference method. The results for the isotherms, streamlines, and average Nusselt numbers along the heat source are presented. The numerical experiments show that an increase in thermal conductivity of solid walls illustrates the enhancement of heat transfer. Eventually, the main result obtained in this work provides a good technical support for the development and research of energy-efficient building materials.Fri, 27 Jul 2018 19:30:00 +0100On the Buckling Response of Axially Pressurized Nanotubes Based on a Novel Nonlocal Beam Theory
http://jacm.scu.ac.ir/article_13600_1754.html
In the present study, the buckling analysis of single-walled carbon nanotubes (SWCNT) on the basis of a new refined beam theory is analyzed. The SWCNT is modeled as an elastic beam subjected to unidirectional compressive loads. To achieve this aim, the new proposed beam theory has only one unknown variable which leads to one equation similar to Euler beam theory and is also free from any shear correction factors. The equilibrium equation is formulated by the nonlocal elasticity theory in order to predict small-scale effects. The equation is solved by Navier’s approach by which critical buckling loads are obtained for simple boundary conditions. Finally, to approve the results of the new beam theory, some available well-known references are compared.Mon, 31 Dec 2018 20:30:00 +0100NURBS-Based Isogeometric Analysis Method Application to Mixed-Mode Computational Fracture Mechanics
http://jacm.scu.ac.ir/article_13715_0.html
An interaction integral method for evaluating mixed-mode stress intensity factors (SIFs) for two dimensional crack problems using NURBS-based isogeometric analysis method is investigated. The interaction integral method is based on the path independent J-integral. By introducing a known auxiliary field solution, the mixed-mode SIFs are calculated simultaneously. Among features of B-spline basis functions, the possibility of enhancing a B-spline basis with discontinuities by means of knot insertion makes isogeometric analysis method a suitable candidate for modelling discrete cracks. Moreover, the repetition of two different control points between two patches can create a discontinuity and also demonstrates a singularity in the stiffness matrix. In the case of a pre-defined interface, non-uniform rational B-splines are used to obtain an efficient discretization. Various numerical simulations for edge and center cracks demonstrate the suitability of the isogeometric analysis approach to fracture mechanics.Fri, 27 Jul 2018 19:30:00 +0100Topology Optimization of the Thickness Profile of Bimorph Piezoelectric Energy Harvesting Devices
http://jacm.scu.ac.ir/article_13608_1754.html
Due to developments in additive manufacturing, the production of piezoelectric materials with complex geometries is becoming viable and enabling the manufacturing of thicker harvesters. Therefore, in this study a piezoelectric harvesting device is modelled as a bimorph cantilever beam with a series connection and an intermediate metallic substrate using the plain strain hypothesis. On the other hand, the thickness of the harvester’s piezoelectric material is structurally optimized using a discrete topology optimization method. Moreover, different optimization parameters are varied to investigate the algorithm’s convergence. The results of the optimization are presented and analyzed to examine the influence of the harvester's geometry and its different substrate materials on the harvester’s energy conversion efficiency.Mon, 31 Dec 2018 20:30:00 +0100Analysis of Fluid Dynamics and Heat Transfer in a Rectangular Duct with Staggered Baffles
http://jacm.scu.ac.ir/article_13717_0.html
This computational fluid dynamic analysis attempts to simulate the incompressible steady fluid flow and heat transfer in a solar air channel with wall-mounted baffles. Two ꞌSꞌ-shaped baffles, having different orientations, i.e., ꞌSꞌ-upstream and ꞌSꞌ-downstream, were inserted into the channel and fixed to the top and bottom walls of the channel in a periodically staggered manner to develop vortices to improve the mixing and consequently the heat transfer. The analyses are conducted with the Commercial CFD software FLUENT using the finite volume method for Reynolds number varying from 12,000 to 32,000. The numerical results are presented in terms of streamlines, velocity-magnitude, x-velocity, y-velocity, dynamic pressure coefficient, turbulent kinetic energy, turbulent viscosity, turbulent intensity, temperature field, coefficient and factor of normalized skin friction, local and average numbers of normalized Nusselt, and thermal performance factor. The insertion of the S-shaped baffles in the channel not only causes a much high friction loss, f/f0 = 3.319 - 32.336, but also provides a considerable augmentation in the thermal transfer rate in the channel, Nu/Nu0 = 1.939 - 4.582, depending on the S-baffle orientations and the Reynolds number. The S-upstream baffle provides higher friction loss and heat transfer rate than the S-Downstream around 56.443 %, 55.700 %, 54.972 %, 54.289 % and 53.660 %; and 25.011 %, 23.455 %, 21.977 %, 20.626 %, and 19.414 % for Re = 12,000, 17,000, 22,000, 27,000, and 32,000, respectively. In addition, the result analysis shows that the optimum thermal performance factor is around 1.513 at the highest Reynolds number and S-downstream.Mon, 31 Dec 2018 20:30:00 +0100Buckling and Postbuckling of Concentrically Stiffened Piezo-Composite Plates on Elastic Foundations
http://jacm.scu.ac.ir/article_13630_1754.html
This research presents the modeling and analysis for the buckling and postbuckling behavior of sandwich plates under thermal and mechanical loads. The lay-up configurations of plates are laminated composite with concentric stiffener and surface mounted piezoelectric actuators. The plates are in contact with a three-parameter elastic foundation including softening and/or hardening nonlinearity. Several types of grid shapes of stiffeners are studied such as ortho grid, angle grid, iso grid, and orthotropic grid. The equations of structures are formulated based on the classical lamination theory incorporating nonlinear von-Karman relationships. The stress function and Galerkin procedure are applied to derive explicit formulations of the equilibrium paths. New results are introduced to give the influences of voltage through the thickness of piezoelectric actuators, different stiffeners, and nonlinear elastic foundations.Mon, 31 Dec 2018 20:30:00 +0100Experimental Study on the Surface Modification by Electrical Discharge Process
http://jacm.scu.ac.ir/article_13732_0.html
The creation of modified layer on metal surfaces using new methods is one of the procedures in surface engineering which can improve the surface mechanical properties. The electrical discharge process is a new method that can form a modified layer on the metal surfaces. This study aims to improve of pure aluminum surface properties through Electrical Discharge process with Monel 400 electrode. In order to design the experiments, the pulse on time and the pulse current were considered as input parameters. The SEM images indicated that the increase in the pulse on time and the pulse current can increase the thickness of the modified layer. Based on the obtained results, the thickness of improved layer varied between 35 to 75 microns. The results of the EDX analysis showed the diffusion of the copper and nickel to the aluminum surface. Moreover, the results of microhardness testing of the surface layer showed that after Electrical discharge process, the surface hardness has increased and the surface hardness as 35 Vickers has reached more than 400 Vickers.Thu, 06 Sep 2018 19:30:00 +0100Generalized 2-Unknown’s HSDT to Study Isotropic and Orthotropic Composite Plates
http://jacm.scu.ac.ir/article_13649_1754.html
The present study introduces a generalized 2-unknown’s higher order shear deformation theory (HSDT) for isotropic and orthotropic plates. The well-known Shimpi’s two-unknown's HSDT is reproduced as a special case. Reddy’s shear strain shape function (SSSF) is also adapted to the present generalized theory. The results show that both Shimpi and the adapted Reddy’ HSDT are essentially the same, i.e., both present the same static results. This is due to the fact that both theories use polynomial SSSFs. This study presents a new optimized cotangential SSSF. The generalized governing equation obtained from the principle of virtual displacement is solved via the Navier closed-form solution. Results show that transverse shear stresses can be improved substantially when non-polynomial SSSFs are utilized. Finally, this theory is attractive and has the potential to study other mechanical problems such as bending in nanoplates due to its reduced number of unknown’s variables.Mon, 31 Dec 2018 20:30:00 +0100Accuracy Assessment of Ultrasonic C-scan and X-ray Radiography Methods for Impact Damage ...
http://jacm.scu.ac.ir/article_13731_0.html
The present study introduces two quantitative parameters to compare the accuracy of ultrasonic C-scan testing and X-ray radiography methods in the damaged area detection under low-velocity impact in polymer-based composites. For this purpose, the hand lay-up technique of composite processing was employed to prepare the composite specimen. A composite specimen consisting of the glass fiber reinforced with the unsaturated polyester resin was considered for this investigation. The impact tests at different energy levels were carried out to create three damaged areas in this composite specimen. Because the glass/polyester specimen had a transparent surface, a digital scanner was used to obtain an ideal image of specimen representing the region and edge of the impacted areas. Two image quality factors were introduced as quantitative parameters to compare the ultrasonic C-scan and X-ray radiography results with those of an ideal image. The results of this study showed that the ultrasonic C-scan is a more accurate method for inspection of the GFRP specimen.Thu, 06 Sep 2018 19:30:00 +0100Magnetohydrodynamic Free Convection Flows with Thermal Memory over a Moving Vertical Plate in ...
http://jacm.scu.ac.ir/article_13666_1754.html
The unsteady hydro-magnetic free convection flow with heat transfer of a linearly viscous, incompressible, electrically conducting fluid near a moving vertical plate with the constant heat is investigated. The flow domain is the porous half-space and a magnetic field of a variable direction is applied. The Caputo time-fractional derivative is employed in order to introduce a thermal flux constitutive equation with a weakly memory. The exact solutions for the fractional governing differential equations for fluid temperature, Nusselt number, velocity field, and skin friction are obtained by using the Laplace transform method. The numerical calculations are carried out and the results are presented in graphical illustrations. The influence of the memory parameter (the fractional order of the time-derivative) on the temperature and velocity fields is analyzed and a comparison between the fluid with the thermal memory and the ordinary fluid is made. It was observed that due to evolution in the time of the Caputo power-law kernel, the memory effects are stronger for the small values of the time t. Moreover, it is found that the fluid flow is accelerated / retarded by varying the inclination angle of the magnetic field direction.Mon, 31 Dec 2018 20:30:00 +0100Fractional Thermoelasticity Model of a 2D Problem of Mode-I Crack in a Fibre-Reinforced Thermal ...
http://jacm.scu.ac.ir/article_13730_0.html
A model of fractional-order of thermoelasticity is applied to study a 2D problem of mode-I crack in a fibre-reinforced thermal environment. The crack is under prescribed distributions of heat and pressure. The normal mode analysis is applied to deduce exact formulae for displacements, stresses, and temperature. Variations of field quantities with the axial direction are illustrated graphically. The results regarding the presence and absence of fiber reinforcement and fractional parameters are compared. Some particular cases are also investigated via the generalized thermoelastic theory. The presented results can be applied to design different fibre-reinforced isotropic thermoelastic elements subjected to the thermal load in order to meet special technical requirements.Thu, 06 Sep 2018 19:30:00 +0100Elastic-Plastic Analysis of Bending Moment – Axial Force Interaction in Metallic Beam of T-Section
http://jacm.scu.ac.ir/article_13667_1754.html
This study derives kinematic admissible bending moment – axial force (M-P) interaction relations for mild steel by considering elastic-plastic idealizations. The interaction relations can predict strains, which is not possible in a rigid perfectly plastic idealization. The relations are obtained for all possible cases pertaining to the locations of neutral axis. One commercial rolled steel T-section is considered for studying the characteristics of interaction curves for different models. On the basis of these interaction curves, most significant cases for the position of neutral axis which are enough for the establishment of interaction relations are suggested.Mon, 31 Dec 2018 20:30:00 +0100Bending and Free Vibration Analysis of Functionally Graded Plates via Optimized Non-polynomial ...
http://jacm.scu.ac.ir/article_13739_0.html
Optimization concept in the context of shear deformation theories was born for the development of accurate models to study the bending problem of structures. The present study seeks to extend such an approach to the dynamic analysis of plates. A compact and unified formulation with non-polynomial shear strain shape functions (SSSFs) is employed to develop a static and free vibration analysis of simply supported functionally graded plates. In this context, three new non-polynomial displacement fields are proposed using trigonometric and hyperbolic SSSFs. Then, the non-polynomial SSSFs are optimized by varying the arguments of the trigonometric and hyperbolic functions. Additionally, the Mori-Tanaka approach is used to estimate the effective properties of the functionally graded plates. The Principle of Virtual Displacement (PVD) and the Hamilton’s Principle along with the Navier closed-form solution technique are used to obtain exact results. The obtained numerical results are in a good agreement with 3D and 2D higher order shear deformation theory solutions available in the literature.Thu, 13 Sep 2018 19:30:00 +0100A Note on Free Vibration of a Double-beam System with Nonlinear Elastic Inner Layer
http://jacm.scu.ac.ir/article_13566_1754.html
In this note, small amplitude free vibration of a double-beam system in presence of inner layer nonlinearity is investigated. The nonlinearity is due to inner layer material and is not related to large amplitude vibration. At first, frequencies of a double-beam system with linear inner layer are studied and categorized as synchronous and asynchronous frequencies. It is revealed that the inner layer does not affect higher modes significantly and mainly affects the first frequency. Then, equation of motion in the presence of cubic nonlinearity in the inner layer is derived and transformed to the form of Duffing equation. Using an analytical solution, the effect of nonlinearity on the frequency for simply-supported and clamped boundary conditions is analyzed. Results show that the nonlinearity effect is not significant and, in small amplitude free vibration analysis of a double-beam system, the material nonlinearity of the inner layer could be neglected.Mon, 31 Dec 2018 20:30:00 +0100Thermoelastic Vibration of Temperature-Dependent Nanobeams Due to Rectified Sine Wave ...
http://jacm.scu.ac.ir/article_13733_0.html
In this study, the second type of Green and Naghdi's thermoelasticity theory is applied to present the vibration of a nanobeam subjected to rectified sine wave heating based upon the nonlocal thermoelasticity theory. Both Young's modulus and thermal conductivity are considered to be linear functions of the temperature. The Laplace transform domain is adopted to solve the governing partial differential equations using the state space approach. Numerical computations are carried out using the inverse of Laplace transforms. The effects of nonlocal parameter and angular frequency on the thermal vibration quantities are discussed. The results of all quantities are illustrated graphically and investigated.Sun, 09 Sep 2018 19:30:00 +0100A New Quasi-3D Model for Functionally Graded Plates
http://jacm.scu.ac.ir/article_13807_0.html
This article investigates the static behaviour of functionally graded plate under mechanical loads using a new quasi 3D model. The theory is designated as fifth-order shear and normal deformation theory (FOSNDT). Properties of functionally graded material are graded across the transverse direction using rule of mixture i.e. power law. The effect of thickness stretching is considered to develop the present theory. In this theory, axial and transverse displacement components involve fifth-order and fourth order shape functions respectively to evaluate shear and normal strains. The theory involves nine unknowns. Zero transverse shear stress conditions are satisfied using constitutive relations. Analytical solutions are obtained using double Fourier series technique. The results predicted by the FOSNDT are compared with existing results. It is pointed out that the present theory is helpful for accurate structural analysis of isotropic and functionally graded plates compared to other plate models.Sun, 30 Sep 2018 20:30:00 +0100On The Use of Acoustic Emission and Digital Image Correlation for Welded Joints Damage ...
http://jacm.scu.ac.ir/article_13822_0.html
A series of tests has been conducted to investigate fatigue damage characterisation in corroded welded steel plates using structural health monitoring (SHM) techniques. AE is a non-destructive testing (NDT) technique with potential applications for locating and monitoring fatigue cracks in service. In the present work, AE was used to characterise damage during crack evolution based on the relationship between RA value (the rise time divided by the amplitude) and the average frequency of the recorded data. Results were confirmed by visual observation of the crack geometry at the end of the test and by Digital Image Correlation (DIC) measurements. The results obtained allowed a more detailed understanding of such damage mechanisms, enabling an early warning against final failure and hence ensuring the safety and integrity of the structures.Sat, 06 Oct 2018 20:30:00 +0100Effect of exponentially variable viscosity and permeability on Blasius flow of Carreu nanofluid ...
http://jacm.scu.ac.ir/article_13834_0.html
The present investigation brings attention regarding the effect of exponential variable viscosity modeled by Vogel and variable permeability on stagnation point flow of Carreu nanofluid over an electromagnetic plate through a porous medium. Brownian motion and thermophoretic diffusion mechanism are taken into consideration. An efficient fourth order R K method along with shooting technique is used to obtain the required solution of the non-dimensional modeled equations. The contribution of the present study is that augmented electromagnetic field strength due to suitable arrangement of the plate and that of porosity parameter yield an accelerated motion while that of viscosity parameter produces retarded motion of shear thickening fluid, however, contrary to shear thinning fluid. At the same time it brings about an outcome that inclusion of porous matrix controls the thermal as well as concentration boundary layers while enhanced Brownian motion exhibits diametrically opposite trend for them in response to shear thickening fluid.Sun, 07 Oct 2018 20:30:00 +0100ISOGEOMETRIC TOPOLOGY OPTIMISATION OF CONTINUUM STRUCTURES USING EVOLUTIONARY ALGORITHM
http://jacm.scu.ac.ir/article_13835_0.html
Topology optimization has been an interesting area of research in the recent years. The main focus of this paper is to use evolutionary swarm intelligence algorithm to perform Isogeometric Topology optimization of continuum structures. A two dimensional plate is analysed statically and the nodal displacements are calculated. The nodal displacements using Isogeometric analysis were found to be in good agreement with the nodal displacements obtained using standard finite element analysis. The sizing optimization of the beam is then performed. The formulation to determine the stress at any point in the beam is presented. The optimal cross section dimensions by performing Isogeometric analysis are obtained and verified with the cross section dimensions obtained by using bending stress and shear stress criteria as well. The topology optimization of a two dimensional simply supported plate continuum and a problem on three dimensional continuum are optimized and presented. The results show that the minimum weight obtained by applying Isogeometric topology optimization gives better results over traditional finite element analysis.Sun, 07 Oct 2018 20:30:00 +0100Electro-magneto-hydrodynamics flows of Burgers fluids in cylindrical domains with time ...
http://jacm.scu.ac.ir/article_13836_0.html
This paper investigates the axial unsteady flow of a generalized Burgers’ fluid with fractional constitutive equation in a circular micro-tube, in presence of a time-dependent pressure gradient and an electric field parallel to flow direction and a magnetic field perpendicular on the flow direction. The mathematical model used in this work is based on a time-nonlocal constitutive equation for shear stress with time-fractional Caputo-Fabrizio derivatives; therefore, the histories of the velocity gradient will influence the shear stress and fluid motion. Thermal transport is considered in the hypothesis that the temperature of the cylindrical surface is constant. Analytical solutions for the fractional differential momentum equation and energy equation are obtained by employing the Laplace transform with respect to the time variable t and the finite Hankel transform with respect to the radial coordinate r. It is important to note that the analytical solutions for many particular models such as, ordinary/fractional Burgers fluids, ordinary/fractional Oldryd-B fluids, ordinary/fractional Maxwell fluids and Newtonian fluids, can be obtained from the solutions for the generalized fractional Burgers' fluid by particularizing the material coefficients and fractional parameters. By using the obtained analytical solutions and the Mathcad software, we have carried out numerical calculations in order to analyze the influence of the memory parameters and magnetic parameter on the fluid velocity and temperature. Numerical results are presented in graphical illustrations. It is found that ordinary generalized Burgers’ fluids flow faster than the fractional generalized Burgers’ fluids.Thu, 11 Oct 2018 20:30:00 +0100Transient MHD convective flow of fractional nanofluid between vertical plates
http://jacm.scu.ac.ir/article_13837_0.html
Effects of the uniform transverse magnetic field on the transient free convective flowsof a nanofluid with generalized thermal transport between two vertical parallel plates have beenanalyzed. The fluid temperature is described by a time-fractional differential equation withCaputo derivatives. Closed form of the temperature field is obtained by using the Laplacetransform and fractional derivatives of the Wright’s functions. A semi-analytical solution for thevelocity field is obtained by using the Laplace transform coupled with the numerical algorithmsfor the inverse Laplace transform elaborated by Stehfest and Tzou. Effects of the derivativefractional order and physical parameters on the nanofluid flow and heat transfer are graphicallyinvestigated.Thu, 11 Oct 2018 20:30:00 +0100Residual power series method for solving time-fractional model of vibration equation of large ...
http://jacm.scu.ac.ir/article_13838_0.html
The primary aim of this manuscript is to present the approximate analytical solutions of the time fractional order Vibration Equation (VE) of large membranes with the use of aniterative technique namely Residual Power Series Method (RPSM). The fractional derivative isdefined in Caputo sense. Example problems have been solved to demonstrate the efficacy of the present method and the results obtained are verified graphically. The convergence analysis of the proposed method has also been included in this article. It is seen that the present method is found to be reliable, very effective and easy to implement for various kinds of fractional differential equations used in science and engineering.Thu, 11 Oct 2018 20:30:00 +0100The solar air channels: Comparative analysis, introduction of arc-shaped fins to improve the ...
http://jacm.scu.ac.ir/article_13839_0.html
The problem under investigation contains a computational simulation of a specific heat exchanger with complex geometry fins. The problem solved is potentially interesting for researchers and engineers working on solar collectors and aerospace industry. It is known that heat transfer enhancement can be achieved by creating longitudinal vortices in the flow. These vortices can be generated by arc-shaped fins, and a computational analysis of such solar air channels is not a simple task. Therefore, we used a present-day commercial CFD code to solve the problem. The mathematical problem including the main equations and their explanation, as well as the numerical procedure was presented. The impact of arc-fins’ spacings on streamlines and temperature distributions was completely investigated, as well as the heat transfer rate, pressure drop and thermal enhancement factor. The Nusselt number (Nu) and friction loss (f) values of the solar air channel at AR = 1.321 (aspect ratio of channel width-to-height) and S = Pi/2 are found to be around 11.963 % and 26.006 %; 21.645 % and 40.789 %; 26.196 % and 50.314 %; and 30.322 % and 58.355 % higher than that with S = 3Pi/4, Pi, 5Pi/4 and 3Pi/2, respectively. Importantly, the arc-fins with Re = 12,000 at S = Pi/2 showed higher thermal enhancement performance than the one at S = 3Pi/4, Pi, 5Pi/4 and 3Pi/2 around 2.530 %, 6.576 %, 6.615 % and 6.762 %, respectively. This study contains the information which seems to be important for practical engineers.Thu, 11 Oct 2018 20:30:00 +0100Modified multi-level residue harmonic balance method for solving nonlinear vibration problem of ...
http://jacm.scu.ac.ir/article_13841_0.html
Nonlinear vibration behavior of beam is an important issue of structural engineering. In this study, a mathematical modeling of a forced nonlinear vibration of Euler-Bernoulli beam rest on nonlinear elastic foundation is presented and the nonlinear vibration behavior of the beam is investigated by using a modified multi-level residue harmonic balance method. The main advantage of the method is that only one nonlinear algebraic equation is generated at each solution level. The computational time of using the new method is much less than that spent on solving the set nonlinear algebraic equations generated in the classical harmonic balance method. Besides the new method can generate higher-level nonlinear solutions neglected by previous multi-level residue harmonic balance methods. The results obtained from the proposed method compared with the results obtained by a classical harmonic balance method to verify the accuracy of the method which shows good agreement between the proposed and classical harmonic balance method. Besides, the effect of various parameters such as excitation magnitude, linear and nonlinear foundation stiffness, shearing stiffness etc. on the nonlinear vibration behaviors are examined.Sat, 13 Oct 2018 20:30:00 +0100Traveling Waves of Some Symmetric Planar Flows of Non-Newtonian Fluids
http://jacm.scu.ac.ir/article_13842_0.html
We present some variants of Burgers-type equations for incompressible and isothermal planar flow of viscous non-Newtonian fluids based on the Cross, the Carreau, the Power-law rheology models, and a symmetry assumption on the flow. We numerically solve the associated traveling wave equations by using industrial data and prove existence and uniqueness of solutions to the equations for validation of the models. We also provide numerical estimates of the shock thickness as well as maximum strain associated with the traveling waves.Sat, 13 Oct 2018 20:30:00 +0100Axial and torsional free vibrations of elastic nano-beams by stress-driven two-phase elasticity
http://jacm.scu.ac.ir/article_13843_0.html
Size-dependent longitudinal and torsional vibrations of nano-beams are examined by two-phase mixture integral elasticity. A new and efficient elastodynamic model is conceived by convexly combining the local phase with strain- and stress-driven purely nonlocal phases. The proposed stress-driven nonlocal integral mixture leads to well-posed structural problems for any value of the scale parameter. Effectiveness of stress-driven mixture is illustrated by analyzing axial and torsional free vibrations of cantilever and doubly clamped nano-beams. The local/nonlocal integral mixture is conveniently replaced with an equivalent differential law equipped with higher-order constitutive boundary conditions. Exact solutions of fundamental natural frequencies associated with strain- and stress-driven mixtures are evaluated and compared with counterpart results obtained by strain gradient elasticity theory. The provided new numerical benchmarks can be effectively employed for modelling and design of Nano-Electro-Mechanical-Systems (NEMS).Mon, 15 Oct 2018 20:30:00 +0100Scalings of inverse energy transfer and energy decay in 3-D decaying isotropic turbulence with ...
http://jacm.scu.ac.ir/article_13845_0.html
Energy development of decaying isotropic turbulence in a 3-D periodic cube with non-rotating or rotating frames of reference is studied through direct numerical simulation using GPU accelerated lattice Boltzmann method. The initial turbulence is isotropic, generated in spectral space with prescribed energy spectrum E(κ)~κm in a range between κmin and κmax. The Taylor microscale Reynolds number Reλ and Rossby number Ro are introduced to characterize the inertial, viscous, and rotational attributes of the system. The focus of this study is on the scalings of early inverse energy transfer and late energy decay in the development of turbulent energy under various conditions through combinations of m, κmin, κmax, Reλ and Ro. First, we demonstrate the validity of the simulation by confirming the quantitative dependence of the decay exponent n on the initial energy spectrum exponent m, at Reλ =255 and Ro=∞, varying the values of m, κmin and κmax. Second, at relatively low Reλ, the decay exponent for different initial spectra statistically fall in respective ranges, all of which agree well with the corresponding analytical predictions. Third, we quantitatively investigate the 3-D inverse energy transfer. Our findings include (i) the exponent of inverse energy transfer spectrum E(κ)~κσ depends on the initial spectrum exponent E(κ) ~ κm: if mWed, 24 Oct 2018 20:30:00 +0100Failure Procedure in Adhesive Composite Joints under Different types of Loading
http://jacm.scu.ac.ir/article_13878_0.html
In this paper, we have used numerical simulation to study failure of adhesive joints in composite plates. To determine the failure load, adhesive joints are subjected to different types of loading and gradual failure of the joint is studied using the finite element method. The composite material failure theory is implemented into the FEM software. Also different geometries for the joint edge are considered and effect of these geometries and fillet chamfer angle on the failure load are investigated.Sun, 04 Nov 2018 20:30:00 +0100Impact of magnetic field on convective flow of a micropolar fluid with two parallel heat sources
http://jacm.scu.ac.ir/article_13902_0.html
A numerical study is performed to analyze the buoyancy convection induced by the combinedeffect of temperature and species gradients inside an inclined square cavity. The two side walls of the cavity are maintained at a constant temperature. A uniformly thin heated plate is placed at the center of the cavity. The horizontal top and bottom walls are adiabatic. Numerical solutions of governing equations are obtained using the finite volume method coupled with the upwind and central difference technique. Numerical results of the two-dimensional flow field governed by the Navier-Stokes equations are obtained over a wide range of physical parameters, namely the Rayleigh number, the Hartmann number, the inclined angle of the magnetic parameter and vortex viscosity parameter. It is observed from the results, the heat transfer rate is reduced when increasing Hartmann number, inclination angle and vortex viscosity parameter. The higher heat transfer rate is obtained based on the Newtonian fluid as compared to the micropolar fluid.Wed, 14 Nov 2018 20:30:00 +0100Hygro-Thermal Nonlinear Analysis of a Functionally Graded Beam
http://jacm.scu.ac.ir/article_13909_0.html
Nonlinear behaviour of a functionally graded cantilever beam is analyzed under non-uniform hygro-thermal effect. In the solution of problem, finite element method is used within plane solid continua. Total Lagrangian approach is used in the nonlinear kinematic relations. In nonlinear solution, Newton-Raphson method is used with incremental displacement. Comparison study is performed. Effects of material distribution, temperature and moisture changes on nonlinear deflections of the functionally graded beam are presented and discussed.Sun, 18 Nov 2018 20:30:00 +0100An efficient numerical method to solve the boundary layer flow of an Eyring-Powell ...
http://jacm.scu.ac.ir/article_13915_0.html
In this paper, the boundary layer flow of an Eyring-Powell non-Newtonian fluid over a linearly stretching sheet is solved using the combination of the quasilinearization method and the Fractional order of Rational Chebyshev function (FRC) collocation method on a semi-infinite domain. The quasilinearization method converts the equation into a sequence of linear equations and then using the FRC collocation method, these linear equations are solved. The governing nonlinear partial differential equations are reduced to the nonlinear ordinary differential equation by similarity transformations. The physical significance of the various parameters of the velocity profile is investigated through graphical figures. We have obtained a very good approximation solution and the convergence of numerical results is shown.Sat, 24 Nov 2018 20:30:00 +0100Scale-Dependent Dynamic Behavior of Nanowire-Based Sensor in Accelerating Field
http://jacm.scu.ac.ir/article_13918_0.html
The accelerating fields (e. g. centrifugal acceleration and constant acceleration) can change the physical performance of nano-sensors significantly. Herein, a new size-dependent model is developed to investigate the scale-dependent dynamic behavior of nanowire-fabricated sensor operated in an accelerating field. The scale-dependent equation of motion is developed by employing a consolidation of the strain gradient elasticity (SGE) and the Gurtin–Murdoch theory (GMT). A semi-analytical solution is extracted for calculating the stability parameters. Effects of different phenomena including centrifugal force, microstructure dependency, surface layer, length-scale-parameter, dispersion forces, squeezed film damping on the dynamic stability parameters are demonstrated.Sun, 02 Dec 2018 20:30:00 +0100Cracking elements method for simulating complex crack growth
http://jacm.scu.ac.ir/article_13932_0.html
The cracking elements method (CEM) is a recently proposed numerical approach for simulating fracture of quasi-brittle materials. This method is built in the framework of conventional finite element method (FEM) based on standard Galerkin approximation, which models the cracks with disconnected cracking segments. The orientation of propagating cracks is determined by local criteria and no explicit or implicit representations of the crack's topology are needed. Moreover, CEM does not need remeshing technique, cover algorithm, nodal enrichment or specific crack tracking strategies. The crack opening is condensed in local element, greatly reducing the coding efforts and simplifying the numerical procedure. This paper presents numerical simulations with CEM regarding several benchmark tests, the results of which further indicate the capability of CEM in capturing complex crack growths.Sat, 08 Dec 2018 20:30:00 +0100Fluid Flow and Heat Transfer Over Staggered ꞌ+ꞌ Shaped Obstacles
http://jacm.scu.ac.ir/article_13989_0.html
The inclusion of complex obstacles within solar channels is the aim of our study. Two obstacles of the form ꞌ+ꞌ interlaced within a two-dimensional and rectangular channel are the subject of our study. Fluid is Newtonian, turbulent, non-compressible and has constant properties. The number of Reynolds varies from 12,000 to 32,000 with a constant temperature along the upper surface of the channel. The thermal and dynamic analysis of the channel's internal structure has been carefully processed. Different fields of speed and heat, with various profiles of frictions and heat exchange coefficients have been included in this research. Future work will involve more complex geometries and using nanofluids to assess the optimum conditions for heat transfer enhancements.Fri, 14 Dec 2018 20:30:00 +0100A Review of Recent Studies on Simulations for Flow around High-Speed Trains
http://jacm.scu.ac.ir/article_14005_0.html
Fluid flow around bluff bodies occurs in numerous fields of science and engineering. For example, flows pass vehicles, cables, towers, bridges etc. These flows have been studied experimentally and numerically for the last several decades. The investigation of flow over high-speed train is an important application of bluff bodies. Fluid flow, aerodynamic forces and moments, separation and wake region have been studied for the last several decades. This paper brings together the comprehensive review of the research on air flow around the high-speed trains and its impacts.Sun, 16 Dec 2018 20:30:00 +0100Variable thermal conductivity and thermal radiation effect on the motion of a micro polar fluid ...
http://jacm.scu.ac.ir/article_14030_0.html
The intent of this analysis is to explore the influence of thermal radiation paired with variable thermal conductivity on MHD micropolar fluid flow over an upper surface. The novelty of present model is to consider the fluid flow along an upper horizontal surface of a paraboloid of revolution (uhspr) with the porous medium. This physical phenomenon is described by a set of coupled non-linear ODEs by using suitable scaling analysis. The ODEs along with the boundary conditions are solved numerically. Influence of various flow parameters on momentum, thermal and concentration boundary layers is discussed graphically. It is noticed that the variable thickness of surface has a leading consequence on the boundary layer progression along the surface. More over, the results of this study are not only useful for industrial applications but also present a basic understanding of the physical model.Fri, 21 Dec 2018 20:30:00 +0100Effects of Thermal Diffusion and Radiation on Magnetohydrodynamic (MHD) chemically reacting ...
http://jacm.scu.ac.ir/article_14040_0.html
An analysis has been conceded to study the effects of Soret and thermal radiation effects on magnetohydrodynamic convective flow of a viscous, incompressible, electrically conducting fluid with heat and mass transfer over a plate with time dependent suction velocity in a slip flow regime in the presence of first order chemical reaction. The slip conditions at the boundaries for the governing flow are taken for the velocity and temperature distributions and a uniform magnetic field of strength is applied normal to the flow direction. The free stream velocity is assumed to be subject to follow an exponentially small perturbation law. Analytical solutions are obtained for velocity, temperature and concentration fields for the governing partial differential equations depending on slip flow boundary circumstances by using the traditional perturbation method.Wed, 26 Dec 2018 20:30:00 +0100Elastic behavior of functionally graded two tangled circles chamber
http://jacm.scu.ac.ir/article_14043_0.html
This paper presents the numerical elastic solution for a real problem, functionally graded chamber of hydraulic gear pumps under internal pressure. Because of the similarity and complexity for the considering geometry, a bipolar cylindrical coordinate system is used for extract the governing equations. The material properties are considered to vary along the two tangled circles with a power-law function. The two coupled governing equations solved by the differential quadrature method. The results are presented for various material index and show that the complexity in considering geometry and material inhomogeneity can change the stress and displacements value through the geometry efficiently. The results and presented method in this paper for extracting and solving the problem can be used for designing similar geometry more accurate. The results of this research are compared with those reported in the previous work.Fri, 04 Jan 2019 20:30:00 +0100Introduction to the slide modeling method for the efficient solution of heat conduction calculations
http://jacm.scu.ac.ir/article_14053_0.html
Determination of the maximum temperature and its location is the matter of the greatest importance in many technological and scientific engineering applications. In terms of numerical calculations of the heat conduction equation by using uniform mesh increments in space, sometime large computational cost is countered. However, adaptive grid refinement method could be computationally efficient both in terms of accuracy and execution time. In this work, the numerical solution of the heat conduction equation based on the slide modeling method (SMM) is introduced. This method is based on a pre-determined mesh density approach which divides each homogeneous region into different slides and then assigns higher mesh point densities to slides of interest regarding their relative importance by performing some mathematical calculations. The importance of each region is determined by some formulated weighting factors which rely on the estimation of temperature profiles in all regions and slides. To investigate the accuracy and efficiency of the proposed method, a number of different case studies have been considered. The results all revealed the strength of the proposed SMM in comparison with the conventional method (based on uniform mesh point distribution).Fri, 11 Jan 2019 20:30:00 +0100Melting heat transfer and radiation effects on Jeffrey fluid flow over a continuously moving ...
http://jacm.scu.ac.ir/article_14059_0.html
This article is proposed to address the melting heat transfer of a Jeffrey fluid in Blasius and Sakiadis flow caused due to a moving surface. Thermal radiation and a constant free stream is considered in this mathematical model. The non-linear coupled dimensionless equations from the governing equations are attained by employing appropriate similarity transformations. Finally, the resulting dimensionless equations are solved computationally by implementing RKF method. The impact of sundry emerging parameters on different flow fields are interpreted with the help of figures and tables. For augmented values of Deborah number, the velocity profile diminishes in the case of Blasius flow and reverse behavior in Sakiadis flow is observed. Moreover, the velocity of non-Newtonian liquid in case of Blasius flow is superior to that of Sakiadis flow. The outcomes of the present work are authenticated by matching with the computational results in the literature and found to be outstanding agreement.Mon, 14 Jan 2019 20:30:00 +0100The Urban Path Routing Adjustable Optimization by Means of Wavelet Transform and Multistage ...
http://jacm.scu.ac.ir/article_14070_0.html
The present paper introduces the optimization algorithm to improve search rate in urban path routing problems using viral infection and local search in urban environment. This algorithm operates based on two different approaches including wavelet transform and genetic algorithm. The variables proposed by driver such as degree of difficulty and difficulty traffic are of the essence in this technique. Wavelet transform as the first part of proposed algorithm derives edges risk; finally multistage genetic algorithm operates to find the optimal solution which is defined as the shortest path. The proposed algorithm is applied to the case study; its performance is efficiency individually investigated and it is compared with other algorithms.Tue, 15 Jan 2019 20:30:00 +0100Evaluation of turbulence on the dynamics of monopile offshore wind turbine under the wave and ...
http://jacm.scu.ac.ir/article_14071_0.html
In recent years, the use of offshore wind turbines has been considered on the agenda of the countries which have a significant maritime boundary due to more speed and stability of wind at sea. The aim of this study is to investigate the effect of wind turbulence on the aero-hydrodynamic behavior of offshore wind turbines with a monopile platform. Since in the sea, the wind turbine structures are under water and structures interactions, the dynamic analysis has been conducted under combined wind and wave loading. The offshore wind turbines have been investigated under two models of normal and severe wind turbulence, and the results of this study show that the amplitude of fluctuation of dynamic response of structures is increased with increasing the amount of wind turbulence, and this increase is not necessarily observed in the mean values of responses. Therefore, conducting the dynamic analysis is inevitable in order to observe the effect of wind turbulence on the structures response.Wed, 16 Jan 2019 20:30:00 +0100Dynamic response analysis of fractionally damped beams subjected to external loads using ...
http://jacm.scu.ac.ir/article_14072_0.html
This manuscript examines the solution of a damped beam equation whose damping characteristics are well-defined by the fractional derivative (FD). Homotopy Analysis Method (HAM) is applied for calculating the dynamic response (DR). Unit step and unit impulse functions are deliberated for this analysis. Acquired results are illustrated to show the movement of the beam under various sets of parameters with different orders of the FDs. Here FD is defined in the Caputo sense. Obtained results have been compared with the solutions achieved by Adomian decomposition method (ADM) to show the efficiency and powerfulness of the present method.Thu, 17 Jan 2019 20:30:00 +0100Viscous dissipation impact on free convection flow of Cu-water nanofluid in a circular ...
http://jacm.scu.ac.ir/article_14076_0.html
In this work, free convection of Cu-water nanofluid in an enclosure by considering internally heat generated in the porous circular cavity and the impacts of viscous dissipation are numerically evaluated by control volume finite element method (CVFEM). We maintain the outer and inner sides of the circular porous enclosure at a fixed temperature while insulating the other two walls. We examined the impacts of diverse effective parameters including the Rayleigh number, viscous dissipation, and nanofluid concentration on features of heat transfer and fluid flow. Also, a new correlation for average Nusselt number is developed according to the study’s active parameters. It can be deduced by the results that the maximum value of the temperature is proportional to viscous dissipation parameter.Sun, 20 Jan 2019 20:30:00 +0100Correlation between the weld residual stresses and it’s tensile and impact strength
http://jacm.scu.ac.ir/article_14093_0.html
The tensile strength, impact strength and the hardness of the weld were determined. A criteria was proposed for describing the effect of residual stress on the weld mechanical properties. Dimensionless parameters Rya (the average of residual stress over the material yield strength), Rym (the maximum residual stress over the material yield strength), Ru2 (the difference of residual stress over the material ultimate strength) and Ru3 (the difference ratio between the maximum and minimum of three-dimensional residual stresses over the material ultimate strength) were presented to describe the influence of residual stresses on the actual mechanical behavior of the welded pipe. Maximum Rya criterion and lowest strength were obtained at the weld gap center on the external surface of the pipe. The sharp decline in Ru2 criteria is in consistent with the sever reduction in impact strength perpendicular to the weld gap.Sat, 02 Feb 2019 20:30:00 +0100Estimating the mode shapes of a bridge using short time transmissibility measurement from a ...
http://jacm.scu.ac.ir/article_14113_0.html
This paper reports on the analysis of the signals sent by accelerometers fixed on the axles of a vehicle which passes over a bridge. The length of the bridge is divided into some parts and the transmissibility measurement is applied to the signals recorded by two following instrumented axles. As the transmissibility procedure is performed on the divided signals, the method is called Short Time Transmissibility Measurement. Afterwards, a rescaling process is accomplished in order to estimate the bridge mode shapes. The numerical results indicate that the method can calculate the mode shapes of the bridge accurately. It is demonstrated that short time transmissibility method does not depend on the excitation characteristics contrary to the other related methods which assume that the excitation should be white noise. Generally, the bridge mode shapes may be invisible due to the excitation exerted by the road profile. This issue is also resolved by subtracting the signals from the successive axles. Finally, the signals are contaminated with noise and the robustness of the method is investigated.Thu, 07 Feb 2019 20:30:00 +0100Numerical Modeling and Multi Objective Optimization of Face Milling of AISI 304 Steel
http://jacm.scu.ac.ir/article_14114_0.html
There is a requirement to find accurate parameters to accomplish precise dimensional accuracy, excellent surface integrity and maximum MRR. This work studies the influence of various cutting parameters on output parameters like Cutting force, Surface roughness, Flatness, and Material removal rate while face milling. A detailed finite element model was developed to simulate the face milling process. The material constitutive behavior is described by Johnson-Cook material model and the damage criteria is established by Johnson-Cook damage model. The result indicate significant effects of all three cutting parameters on MRR, both feed rate and depth of cut have significant effect on cutting force. Also, feed rate has significant effect on PEEQ and none of the parameters have effect on flatness.Thu, 07 Feb 2019 20:30:00 +0100Study of MHD second grade flow through a porous microchannel under the Dual-Phase-Lag heat and ...
http://jacm.scu.ac.ir/article_14115_0.html
A semi-analytical investigation has been carried out to analyze unsteady MHD second grade flow under the Dual-Phase-Lag (DPL) heat and mass transfer model in a vertical microchannel filled with porous material. Diffusion thermo (Dufour) effects and homogenous chemical reaction are considered as well. The governing partial differential equations are solved by using Laplace transform method while its inversion is done numerically using INVLAP subroutine of MATLAB. The numerical values of fluid velocity, fluid temperature and species concentration are demonstrated through graphs while the numerical values of skin friction, heat transfer rate and mass transfer rate presented in tabular form for different values of parameters that govern the flow. For the first time, a comparison of heat transfer utilizing the classical Fourier’s heat conduction model, hyperbolic heat conduction Cattaneo-Vernotte (CV) model and the DPL model is carried out for the flow of a second grade fluid. It is found that the differences between them vanish at dimensionless time t=0.4 (for temperature) and at t=0.5 (for velocity) i.e. at a time where the system reaches steady state. The influence of phase lag parameters in both thermal and solutal transport on the fluid flow characteristics have been deciphered and analyzed. The results conveyed through this article would help researchers to understand non-Fourier heat and mass transfer in the flow of second grade fluids which may play a vital role in the design of systems in polymer industries.Thu, 07 Feb 2019 20:30:00 +0100Transient electro-osmotic slip flow of an Oldroyd-B fluid with time-fractional Caputo-Fabrizio ...
http://jacm.scu.ac.ir/article_14128_0.html
In this article, we study the electro-osmotic flow of an Oldroyd-B fluid a with slip condition on the boundary in a circular micro-channel by using a newly definedtime-fractional Caputo-Fabrizio derivative without singular kernel. Closed form solutions for the velocity field is acquired by means of Laplace and finite Hankel transforms.In addition, Stehfest’s algorithm is used for inverse Laplace transform. The solutions for fractional Maxwell, ordinary Maxwell, fractional Newtonian and ordinary Newtonian fluids are obtained as limiting cases of our solution. Finally, the influences of fractional and some important physical parameters on the fluid flow are spotlighted graphically.Tue, 12 Feb 2019 20:30:00 +0100Irreversibility analysis of MHD Buoyancy-Driven Variable Viscosity Liquid Film Along and ...
http://jacm.scu.ac.ir/article_14130_0.html
Analysis of intrinsic irreversibility and heat transfer in a buoyancy-driven changeable viscosity liquid along an incline heated wall with convective cooling putting into consideration the heated isothermal and isoflux wall is investigated. By Newton’s law of cooling, we assumed the free surface exchange heat with environment and fluid viscosity is exponentially dependent on temperature. Appropriate governing model equations for momentum and energy balance with volumetric entropy generation expression are obtained and then transformed using dimensionless variables to form set of nonlinear boundary valued problem. Using shooting method with Runge-Kutta-Fehlberg integration scheme, the model is numerically tackled. Pertinent results for the fluid velocity, temperature, skin friction, Nusselt number, entropy generation rate and Bejan number are obtained and discussedTue, 12 Feb 2019 20:30:00 +0100